Sulfur and peroxide vulcanization of the blends based on styrene–butadiene rubber, ethylene–propylene–diene monomer rubber and their combinations

Ci a ion: K uželák, J.; K asniˇcáko á, A.; Džugano á, M.; Hanzlik, J.; Bedna ik, M.; Chodák, I.; Hudec, I. Sul u and Pe oxide Vulcaniza ion o he Blends Based on S y ene–Bu adiene Rubbe , E hylene–P opylene–Diene Monome Rubbe and Thei Combina ions. Ma e ials 2024,17, 2718. h ps://doi.o g/10.3390/ma17112718 Academic Edi o s: Naozumi Te amo o and Klaus We ne S öckelhube Recei ed: 7 Ma ch 2024 Re ised: 2 Ap il 2024 Accep ed: 29 May 2024 Published: 3 June 2024 Copy igh : © 2024 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). ma e ials A icle Sul u and Pe oxide Vulcaniza ion o he Blends Based on S y ene–Bu adiene Rubbe , E hylene–P opylene–Diene Monome Rubbe and Thei Combina ions Ján K uželák1,* , And ea K asniˇcáko á1, Michaela Džugano á1, Jan Hanzlik 2, Ma in Bedna ik 2, I an Chodák3and I an Hudec 1 1Depa men o Plas ics, Rubbe and Fib es, Facul y o Chemical and Food Technology, Slo ak Uni e si y o Technology in B a isla a, Radlinského 9, 812 37 B a isla a, Slo akia; [email p o ec ed] (A.K.); [email p o ec ed] (M.D.); [email p o ec ed] (I.H.) 2Facul y o Technology, Tomas Ba a Uni e si y in Zlin, Va ecko a 5669, 760 01 Zlin, Czech Republic; [email p o ec ed] (J.H.); [email p o ec ed] (M.B.) 3Polyme Ins i u e, Slo ak Academy o Sciences, Dúb a skáces a 9, 845 41 B a isla a, Slo akia; [email p o ec ed] *Co espondence: jan.k [email p o ec ed] Abs ac : Rubbe blends based on s y ene–bu adiene ubbe , e hylene–p opylene–diene monome ubbe and a combina ion o bo h ubbe s we e cu ed wi h di e en sul u and pe oxide cu ing sys ems. In sul u cu ing sys ems, wo ype o accele a o s, namely e ame hyl hiu am disul ide, N-cyclohexyl-2-benzo hiazole sul enamide, and combina ions o bo h accele a o s we e used. In pe oxide cu ing sys ems, dicumyl pe oxide, and a combina ion o dicumyl pe oxide wi h zinc diac yla e o zinc dime hac yla e, espec i ely, we e applied. The wo k was aimed a in es iga ing he e ec o cu ing sys ems composi ion as well as he ype o ubbe o ubbe combina ions on he cu ing p ocess, c oss-link densi y and physical–mechanical p ope ies o ulcaniza es. The dynamic mechanical p ope ies o he selec ed ulcaniza es we e examined oo. The esul s e ealed a co ela ion be ween he c oss-link densi y and physical–mechanical p ope ies. Simila ly, he e was a ce ain co ela ion be ween he c oss-linking deg ee and glass ansi ion empe a u e. The ensile s eng h o ulcaniza es based on ubbe combina ions was highe when compa ed o ha based on pu e ubbe s, which poin s ou he ac ha in ubbe combina ions, no only a e he ea u es o bo h elas ome s combined, bu imp o emen in he ensile cha ac e is ics can also be achie ed. When compa ed o ulcaniza es cu ed wi h dicumyl pe oxide, ma e ials cu ed wi h a sul u sys em exhibi ed highe ensile s eng h. Wi h he applica ion o co-agen s in pe oxide ulcaniza ion, he ensile s eng h o e came he ensile beha io o sul u -cu ed ulcaniza es. Keywo ds: ubbe blends; sul u cu ing sys ems; pe oxide cu ing sys ems; c oss-linking; p ope ies 1. In oduc ion S y ene–bu adiene ubbe (SBR) is gene al-pu pose ubbe wi h an unsa u a ed poly- me backbone. I is he mos widely used ubbe in ubbe echnologies, applied in he p oduc ion o i es, con eyo bel s, hoses, ubbe ca pe ing, shoe soles and in o he ap- plica ions. The p ope ies o SBR a e highly dependen on he p opo ion a io be ween bu adiene and s y ene uni s. Inc easing he amoun o s y ene leads o highe ensile and ea s eng h, highe ha dness, highe ab asion esis ance and highe p ocessabili y. On he o he hand, he elas ici y dec eases wi h an inc ease in s y ene con en . Due o a high deg ee o unsa u a ion, SBR exhibi s limi ed esis ance o deg ada ion ac o s, like oxygen and ozone, and low esis ance o sol en s and chemicals [1,2]. E hylene–p opylene–diene monome ubbe EPDM is one o he mos e sa ile spe- cial y ype ubbe s, wi h excellen elec o-insula ing p ope ies, which a e e ained in high- humidi y en i onmen s and inc eased empe a u es [ 3 ]. I also exhibi s e y good elas ic Ma e ials 2024,17, 2718. h ps://doi.o g/10.3390/ma17112718 h ps://www.mdpi.com/jou nal/ma e ials Ma e ials 2024,17, 2718 2 o 25 p ope ies a low empe a u es, a low comp ession se and good esis ance agains ab asion and ac u ing. The double bonds a e si ua ed only in side g oups o non-conjuga ed diene, meaning ha he main polyme chain is sa u a ed. EPDM hus demons a es good esis ance o he mo-oxida i e and ozone ageing [ 4 ]. I has also good esis ance o pola sol en s, wa e , and s eam. EPDM is widely used o manu ac u ing o con eyo bel s, hy- d aulic and indus ial hoses, sealan s, cable shee ing, connec o s, oo memb anes, asphal modi ica ions, e c. As he concen a ion o double bonds in EPDM is low, his ubbe has a low p opensi y o ulcaniza ion wi h sul u cu ing sys ems. As each ubbe has some ad an ages as well as d awbacks, he main aim o ubbe combina ions is o p o ide he bene i s o one ubbe o o supp ess he disad an ages o ano he one in hei mu ual combina ion. The combina ion o SBR wi h EPDM leads o highe esis ance o he compounds agains he mo-oxida i e and ozone ageing and o chemical a acks. Ab asion esis ance o he compounds is also imp o ed. Vulcaniza ion, o en e e ed o as cu ing is a e y impo an p ocess in ubbe echnol- ogy leading o he o ma ion o a h ee-dimensional c oss-linked ne wo k s uc u e wi hin he ubbe ma ix. This ne wo k inc eases physical–mechanical p ope ies and elas ici y, while educing hys e esis and plas ici y. Di e en ulcaniza ion sys ems can be used o c oss-linking ubbe ma ices. The selec ion o a cu ing sys em usually depends on he ype o ubbe o ubbe s in he compound and on he p ope ies o he inal ma e ials oo. Sul u ulcaniza ion is he mos equen ly used me hod o c oss-linking ubbe compounds, accoun ing a ound 90% o p oduc s. I is e y complex p ocess, gene ally unning in se e al s ages. Sul u ulcaniza ion sys ems gene ally consis o ac i a o s, accele a o s, and sul u . Ac i a o s and accele a o s a e e y impo an pa s o sul u ulcaniza ion sys ems; hey inc ease eac ion speed, dec ease he ulcaniza ion empe a u e, and inc ease he e iciency o sul u o o m c oss-links be ween ubbe chain segmen s. The mos common ac i a o s o sul u ulcaniza ion a e zinc oxide in combina ion wi h a y acid, like s ea ic acid o palmi ic acid. A lo o accele a o s ha e been used in sul u cu ing sys ems; hey a e o ganic subs ances, mos ly con aining sul u and ni ogen in hei s uc u es. They di e in hei chemical s uc u e and ac i i y in he ulcaniza ion p ocess. Du ing sul u ulcaniza ion, ac i a o s oge he wi h accele a o s o m a sal ha eac s wi h sul u o gene a e an ac i e sul u a ing agen . A p ima y ulcanizing ne wo k wi h dominan polysul idic c oss-links is o med in he second s age. The es uc u ing o polysul idic c oss-links in o di- and monosul ic c oss-links and he modi ica ions o ubbe chains occu in he inal s age, which leads o he gene a ion o a inal h ee-dimensional c oss-linked ne wo k [ 5 – 7 ]. Th ough he sul u cu ing p ocess, ubbe chain segmen s a e c oss-linked wi h sul idic c oss-links wi h a di e en numbe o sul u a oms in sul u b idges (namely mono-, di- and polysul idic c oss-links) [8,9]. O ganic pe oxides a e mainly used o c oss-linking compounds based on sa u a ed elas ome s, which canno be cu ed wi h sul u . Al hough, hey a e also e ec i e o c oss- linking o unsa u a ed ubbe s. Du ing he pe oxide cu ing p ocess, o ganic pe oxide i s unde goes homoly ic dissocia ion by he clea age o an oxygen–oxygen bond [10,11]. This leads o he o ma ion o p ima y pe oxide adicals, which can be decomposed in o seconda y adical agmen s. Bo h ypes o adicals a e ac i e in ulcaniza ion p ocess. Pe oxide adicals can eac wi h ubbe chains by adding o he double bonds o by hyd o- gen abs ac ion. Bo h eac ion mechanisms lead o he o ma ion o ubbe adicals, which unde go ecombina ion o o m ca bon–ca bon bonds be ween he chain segmen s [ 12 – 14 ]. C-C c oss-links ha e highe bonding ene gy when compa ed o sul idic c oss-links (C—S x —C < 252 kJ · mol −1 ; C—S 2 —C < 268 kJ · mol −1 ; C—S—C < 285 kJ · mol −1 ; C—C < 352 kJ · mol −1 ), and hus he main ea u e o pe oxide-cu ed ulcaniza es a e good hea ageing s abili y, good esis ance o he mo-oxida i e ageing, and a low comp ession se [ 15 , 16 ]. Howe e , when compa ed o sul u -cu ed ulcaniza es, hey ha e wo se physical–mechanical p ope ies, like poo e ensile and ea s eng h and wo se dynamic p ope ies [17]. To inc ease he c oss-linking e iciency o ubbe compounds wi h o ganic pe oxides, low molecula o ganic compounds wi h ac i a ed double bonds, he so-called co-agen s, a e Ma e ials 2024,17, 2718 3 o 25 o en applied [ 18 , 19 ]. Co-agen s can boos he pe oxide ulcaniza ion p ocess by supp essing side eac ions like chain scission o disp opo iona ion. Bu he main eason o hei posi i e e ec on he cu ing p ocess is ha hey ac i ely pa icipa e in he o ma ion o ex a c oss-links. This subsequen ly leads no only o he inc ease in c oss-link densi y, bu he s uc u e and he quali y o he o med c oss-links is changed oo. This con ibu es o imp o emen s in he physical–mechanical p ope ies o pe oxide-cu ed ulcaniza es [20–23]. Bo h SBR and EPDM can be cu ed wi h pe oxide as well as sul u cu ing sys ems. The eac ion mechanisms o sul u and pe oxide cu ing o bo h ubbe s ha e been desc ibed in se e al scien i ic s udies, o example, e s. [ 24 – 27 ]. The cu en s udy deals wi h he in es iga ion o se e al sul u and pe oxide cu ing sys ems on pu e SBR and EPDM ubbe s, as well as hei mu ual combina ions. This s udy in es iga es he in luence o cu ing sys em composi ions on he ulcaniza ion p ocess, c oss-link densi y, physical–mechanical, and dynamic–mechanical p ope ies. The ela ion be ween he c oss-link densi y and he s uc u e o he o med c oss-links in ela ion o he es ed p ope ies is ou lined. Pe oxide cu ing sys ems ha e ne e been epo ed o ha e been applied o c oss- linking o ubbe blends based on SBR and EPDM combina ions. Thus, his wo k is ocused on compa ing he c oss-linking p ocess o pe oxide- and sul u -based cu ing sys ems o SBR and EPDM blends in ela ion o hei physical– and dynamical–mechanical p ope ies. 2. Expe imen al 2.1. Ma e ials S y ene–bu adiene ubbe (SBR, K alex 1502, s y ene con en —23.5 w .%) p epa ed by cold emulsion polyme iza ion was supplied om Syn hos K alupy, a.s. K alupy nad Vl a ou, Czech Republic. E hylene–p opylene–diene monome ubbe (EPDM, ype KEP 570F, e hylene con en —70 w .%, non-conjuga ed 5-e hylidene-2-no bo nene monome (ENB) con en —4.5 w .%) was p o ided by Kumho Polychem Co., L d., Seoul, Republic o Ko ea. Sul u cu ing sys em consis ed o ac i a o s (s ea ic acid and zinc oxide), accele a o s (N-cyclohexyl-2-benzo hiazole sul enamide (CBS), e ame hyl hiu am disul ide (TMTD)) and sul u . The chemicals o he sul u cu ing sys em we e p o ided by Vegum a.s., Dolné Ves enice, Slo ak Republic). Dicumyl pe oxide (DCP) wi h 99% pu i y was used as a pe oxide cu ing agen . Zinc diac yla e (ZDA) and dime hac yla e (ZDMA) we e used as co-agen s in pe oxide ulcaniza ion. The chemicals o he pe oxide cu ing sys em we e supplied om Sigma-Ald ich, Bu ling on, MA, USA. 2.2. Me hods 2.2.1. P epa a ion and Cu ing o Rubbe Compounds Fi e ypes o ubbe o mula ions based on SBR and EPDM we e ab ica ed. The i s ubbe blend was based on SBR, while he las was based on EPDM. In he o he h ee ypes o ubbe o mula ions, he mu ual a io o bo h ubbe s was changed. The c oss-linking o ubbe blends was pe o med using sul u o pe oxide cu ing sys ems. The amoun o ac i a o s and sul u was kep cons an in all ubbe o mula ions. The ubbe composi ions di e ed depending on he ype o accele a o . In he i s se ies o ubbe blends, N-cyclohexyl-2-benzo hiazole sul enamide was used in an amoun 1.5 ph . Simila ly, in he second se ies, e ame hyl hiu am disul ide was applied in he same amoun , 1.5 ph . In he hi d se ies, a combina ion o bo h accele a o s in a a io o 1 ph o 1 ph was used. The composi ion o ubbe blends wi h he sul u cu ing sys em is summa ized in Tables 1and 2. In he i s se ies o ubbe blends cu ed wi h pe oxide sys ems, dicumyl pe oxide was exclusi ely used o c oss-linking he ubbe blends (Table 3). In nex wo se ies, dicumyl pe oxide in combina ion wi h zinc diac yla e o zinc dime hac yla e, espec i ely, was used (Table 4). Ma e ials 2024,17, 2718 4 o 25 Table 1. Composi ion and designa ion o sul u -cu ed ubbe blends in he p esence o CBS o TMTD ( he amoun o addi i es is in ph ). S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 SBR 100 75 50 25 0 EPDM 0 25 50 75 100 ZnO 3 3 3 3 3 S ea ic acid 2 2 2 2 2 Sul u 1.5 1.5 1.5 1.5 1.5 CBS o TMTD 1.5 1.5 1.5 1.5 1.5 Table 2. Composi ion and designa ion o sul u -cu ed ubbe blends in he p esence o a combina ion CBS wi h TMTD ( he amoun o addi i es is in ph ). S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 SBR 100 75 50 25 0 EPDM 0 25 50 75 100 ZnO 3 3 3 3 3 S ea ic acid 2 2 2 2 2 Sul u 1.5 1.5 1.5 1.5 1.5 CBS 1 1 1 1 1 TMTD 1 1 1 1 1 Table 3. Composi ion and designa ion o ubbe blends cu ed wi h DCP ( he amoun o addi i es is in ph ). S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 SBR 100 75 50 25 0 EPDM 0 25 50 75 100 DCP 1 1 1 1 1 Table 4. Composi ion and designa ion o ubbe blends cu ed wi h DCP in combina ion wi h ZDA o ZDMA ( he amoun o addi i es is in ph ). S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 SBR 100 75 50 25 0 EPDM 0 25 50 75 100 DCP 1 1 1 1 1 ZDA o ZDMA 5 5 5 5 5 The ab ica ion o ubbe blends was pe o med in a labo a o y kneading machine B abende (B abende GmbH & Co. KG, Duisbu g, Ge many) in wo mixing s eps. The o e all mixing ime was 11 min a a empe a u e o 90 ◦ C a 50 pm. The ubbe o ubbe s we e i s pu in o he chambe and we e plas ica ed o 2.5 min. Then, zinc oxide and s ea ic acid we e added, and he ubbe blends we e mixed o 4.5 min a 90 ◦ C and 50 pm. The ubbe blends we e aken ou om he chambe , cooled down, and homogenized using a wo- oll mill. In he second s ep, sul u and he accele a o o a combina ion o accele a o s we e in oduced, and he ubbe sys ems we e compounded o 4 min a 90 ◦ C. A e mixing, he ubbe compounds we e shee ed in a wo- oll mill. The compounding p ocess o he ubbe o mula ions wi h a pe oxide cu ing sys em was e y simila . In he i s s ep, only he ubbe o ubbe s in hei mu ual combina ions we e mixed and plas ica ed. In he second s ep, DCP o a combina ion o DCP wi h a co-agen (ZDA o ZDMA) was applied, and he ubbe blends we e mixed o 4 min a 90 ◦ C and 50 pm. The inal s ep was homogeniza ion and shee ing o he compounds using he wo- oll mill. Ma e ials 2024,17, 2718 5 o 25 The ulcaniza ion p ocess was pe o med a 160 ◦ C and a p essu e o 15 MPa in a hy- d aulic p ess Fon ijne (Fon ijne, Vlaa dingen, The Ne he lands). The ime o ulcaniza ion was iden ical wi h he op imum cu e ime o each ubbe blend, which was de e mined om co esponding cu ing iso he ms. A e cu ing, hin shee s wi h dimensions 15 ×15 cm and hickness 2 mm we e ob ained. 2.2.2. De e mina ion o Cu ing Cha ac e is ics Cu ing cha ac e is ics o he blends we e de e mined om co esponding cu ing iso he ms, which we e in es iga ed using an oscilla o y heome e MDR 2000 (Alpha Technologies, Ak on, OH, USA). The in es iga ed cu ing pa ame e s we e as ollows: ∆M(dN·m)— o que di e ence, he di e ence be ween he maximum and minimum o que (∆M=MH−ML). c90 (min)—op imum cu ing ime. s1(min)—sco ch ime. R(dN·m·min−1)—cu ing a e, de ined as: R= Mc90 −Ms1 c90 − s1 Mc90— o que a c90. Ms1— o que a s1. 2.2.3. De e mina ion o C oss-Link Densi y The c oss-link densi y ν was de e mined based on he equilib ium swelling o ulcan- iza es in xylene. The weigh ed d ied samples we e placed in o xylene in which hey swelled wi hin ime. The weigh o samples was measu ed e e y hou un il equilib ium swelling was eached. Du ing he measu emen , he sol en di used in o he ubbe and dis up ed almos all physical in e ac ions wi hin he ubbe ma ix. The esul was he de e mina ion o chemical c oss-link densi y, i.e., he concen a ion o chemical c oss-links wi hin he ubbe compounds. The expe imen s we e ca ied ou a a labo a o y empe a u e, and he swelling ime was equal o 30 h. The Flo y–Rehne equa ion [ 28 ] was hen used o calcula e he c oss-link densi y based upon he equilib ium swelling s a e. 2.2.4. In es iga ion o Physical–Mechanical Cha ac e is ics Zwick Roell/Z 2.5 appliance (Zwick GmbH & Co. KG, Ulm, Ge many) was used o e alua e ensile p ope ies o ulcaniza es. The es s we e pe o med in acco dance wi h he alid in e na ional echnical s anda ds (ISO 37) and he c oss-head speed o he measu ing de ice was se up o 500 mm.min −1 . Dumbbell-shaped es samples (wid h 6.4 mm, leng h 80 mm, hickness 2 mm) we e used o measu emen s. The ha dness was measu ed by using du ome e and was exp essed in Sho e A. 2.2.5. De e mina ion o Dynamical–Mechanical P ope ies The dynamical–mechanical pe o mances o ulcaniza es we e ob ained using a dynamical-mechanical analyze DMTA MkIII, y Rheome ic Scien i ic (Pisca away, NJ, USA), ollowing he in e na ional s anda d ISO 6721-11:2019. The samples we e analyzed in ensile mode a a equency o 10 Hz, an ampli ude o dynamic de o ma ion o 64 µ m, and a s a ic o ce o 0.2 N in a empe a u e ange o − 60 ◦ C o 80 ◦ C. The hea ing a e was 2◦C pe min. 3. Resul s and Discussion 3.1. Vulcaniza ion P ocess and Physical–Mechanical P ope ies o Sul u -Cu ed Rubbe Compounds The in luence o cu ing sys em composi ions on he ulcaniza ion cha ac e is ics o ubbe o mula ions was examined h ough he de e mina ion o sco ch ime s1 , op imum Ma e ials 2024,17, 2718 6 o 25 cu e ime c90 , cu ing a e R, and he di e ence be ween he maximum and minimum o que ∆ M. As seen in Figu e 1, he highes sco ch ime was ha o ubbe blends cu ed in he p esence o a CBS accele a o . On he o he hand, he lowes s1 was ha o he ubbe o mula ions cu ed wi h TMTD. I can be s a ed ha he sco ch ime showed a sligh inc easing end wi h an inc easing a io o EPDM in ubbe combina ions, and he highes sco ch ime was ha o ubbe o mula ions based on EPDM (S0–E100). Looking a Figu e 2, one can see e y simila dependences o op imum cu e ime on he used accele a o s. The highes op imum cu e ime was ha o ubbe blends cu ed in he p esence o CBS. F om Figu e 2, i also becomes appa en ha he op imum cu e ime o CBS-based o mula ions inc eased wi h an inc easing a io o EPDM. When compa ed o ubbe blends based on SBR (S100–E0), he c90 o he blend based on EPDM (S0–E100) was p olonged by mo e han 10 min ( om 16 min o mo e han 26 min). The ubbe blends cu ed in he p esence o TMTD o he combina ion CBS-TMTD equi ed an almos iden ical amoun o ime o hei op imum c oss-linking. Again, he highes c90 was exhibi ed by he S0–E100 blends. Ma e ials 2024, 17, x FOR PEER REVIEW 7 o 25 Figu e 1. Sco ch ime s1 ubbe blends cu ed wi h sul u sys ems. Figu e 2. Op imum cu e ime c90 o ubbe blends cu ed wi h sul u sys ems. The diffe ence be ween he maximum and minimum o que usually ela es wi h he numbe o c oss-links o med wi hin he ubbe ma ix and exp esses he deg ee o ans- o ma ion o uncu ed ubbe compound in o ulcaniza e. Gene ally speaking, he highe he o que diffe ence, he highe he c oss-link densi y. Howe e , his is alid mainly o un illed ubbe compounds. As seen in Figu e 3, he bigges diffe ence be ween he max- imum and minimum o que was exhibi ed by ubbe blends based on EPDM (S0–E100). The diffe ences in he ΔM alues o he dependence on he ype o accele a o o accele - a o s combina ions we e minimal. Looking a Figu e 4, one can see a ce ain co ela ion be ween c oss-link densi y and o que diffe ence. This means ha he highes o que di - e ence in he blends designa ed S0–E100 was e lec ed in hei highes c oss-linking de- g ee. I is in e es ing ha he c oss-link densi y o he ma e ials wi h CBS showed an in- c easing end wi h an inc easing a io o EPDM in ubbe combina ions. On he o he hand, he c oss-link densi y o ulcaniza es cu ed in he p esence o TMTD and he com- bina ion CBS-TMTD ended o dec ease wi h an inc easing a io o EPDM up o he com- posi ion S25–E75. Then, a signi ican inc ease in he deg ee o c oss-linking occu ed o he ulcaniza e S0–E100. When compa ing he cu ing sys ems, he highes c oss-link den- si y was exhibi ed by ubbe blends cu ed wi h he CBS-TMTD combina ion. TMTD ac s Figu e 1. Sco ch ime s1 ubbe blends cu ed wi h sul u sys ems. Ma e ials 2024, 17, x FOR PEER REVIEW 7 o 25 Figu e 1. Sco ch ime s1 ubbe blends cu ed wi h sul u sys ems. Figu e 2. Op imum cu e ime c90 o ubbe blends cu ed wi h sul u sys ems. The diffe ence be ween he maximum and minimum o que usually ela es wi h he numbe o c oss-links o med wi hin he ubbe ma ix and exp esses he deg ee o ans- o ma ion o uncu ed ubbe compound in o ulcaniza e. Gene ally speaking, he highe he o que diffe ence, he highe he c oss-link densi y. Howe e , his is alid mainly o un illed ubbe compounds. As seen in Figu e 3, he bigges diffe ence be ween he max- imum and minimum o que was exhibi ed by ubbe blends based on EPDM (S0–E100). The diffe ences in he ΔM alues o he dependence on he ype o accele a o o accele - a o s combina ions we e minimal. Looking a Figu e 4, one can see a ce ain co ela ion be ween c oss-link densi y and o que diffe ence. This means ha he highes o que di - e ence in he blends designa ed S0–E100 was e lec ed in hei highes c oss-linking de- g ee. I is in e es ing ha he c oss-link densi y o he ma e ials wi h CBS showed an in- c easing end wi h an inc easing a io o EPDM in ubbe combina ions. On he o he hand, he c oss-link densi y o ulcaniza es cu ed in he p esence o TMTD and he com- bina ion CBS-TMTD ended o dec ease wi h an inc easing a io o EPDM up o he com- posi ion S25–E75. Then, a signi ican inc ease in he deg ee o c oss-linking occu ed o he ulcaniza e S0–E100. When compa ing he cu ing sys ems, he highes c oss-link den- si y was exhibi ed by ubbe blends cu ed wi h he CBS-TMTD combina ion. TMTD ac s Figu e 2. Op imum cu e ime c90 o ubbe blends cu ed wi h sul u sys ems. The dependencies o he op imum cu e ime as well as he sco ch ime on he ype o accele a o used ela e wi h he cha ac e and s uc u e o he accele a o s. CBS belongs Ma e ials 2024,17, 2718 7 o 25 o he class o as accele a o s o he sul enamide ype ha a e cha ac e ized by a long induc ion pe iod (delayed ac ion accele a o s). Thus, he blends cu ed wi h CBS exhibi ed he longes sco ch ime. TMTD is om a g oup o e y as accele a o s, which indica es ha he cu ing p ocess o ubbe o mula ions p oceeds as e . This co esponds wi h a sho e sco ch ime and op imum cu e ime o he co esponding blends. When combining bo h CBS and TMTD, he op imum cu e ime was no changed, while sligh p olonga ion o he sco ch ime was eco ded in compa ison wi h he equi alen TMTD-cu ed ubbe blends. Al hough he p olonga ion o sco ch ime was no e y signi ican , i is a posi i e aspec ega ding he sa e p ocessabili y o ubbe blends in o inal c oss-linked ma e ials. The sco ch ime o induc ion pe iod ep esen s he ime du ing which he c oss-linking does no occu ye . The mu ual in e ac ions among he addi i es o he cu ing sys em occu , and he ma e ials mus be hea ed uni o mly in i s en i e olume. This is a e y impo an ac o o achie ing homogenous dis ibu ion o he o med c oss-links wi hin he ubbe ma ix and hus o ming a spa ially uni o m, h ee-dimensional c oss-linked s uc u e. When his is achie ed, he ollowing ulcaniza ion can p oceed quickly, esul ing in ime and economic bene i s. The sho op imum ulcaniza ion ime o ubbe blends wi h a combina ion o accele a o s (CBS-TMTD) can be a ibu ed o he p esence o a e y as accele a o (TMTD) on one hand, and o he inc ease in he o e all accele a o con en (2 ph ) on he o he hand. In gene al, he mo e ac i i y he e is and he highe he amoun o accele a o s, he as e he ulcaniza ion p ocess [13]. I was eco ded ha he cu ing p ocess o he ma e ials based on EPDM was longe han ha o he co esponding blends based on SBR. Conside ing ha SBR is highly un- sa u a ed ubbe , he concen a ion o double bonds in i s s uc u e is much highe when compa ed o EPDM ( he double bonds a e si ua ed only in non-conjuga ed ENB monome uni s, he concen a ion o which is only 4.5 w .% in EPDM). O e all, he lowe he concen- a ion o he double bonds in he ubbe s uc u e, he slowe he ulcaniza ion p ocess. The di e ence be ween he maximum and minimum o que usually ela es wi h he numbe o c oss-links o med wi hin he ubbe ma ix and exp esses he deg ee o ans o ma ion o uncu ed ubbe compound in o ulcaniza e. Gene ally speaking, he highe he o que di e ence, he highe he c oss-link densi y. Howe e , his is alid mainly o un illed ubbe compounds. As seen in Figu e 3, he bigges di e ence be ween he maximum and minimum o que was exhibi ed by ubbe blends based on EPDM (S0–E100). The di e ences in he ∆ M alues o he dependence on he ype o accele a o o accele a o s combina ions we e minimal. Looking a Figu e 4, one can see a ce ain co ela ion be ween c oss-link densi y and o que di e ence. This means ha he highes o que di e ence in he blends designa ed S0–E100 was e lec ed in hei highes c oss-linking deg ee. I is in e es ing ha he c oss-link densi y o he ma e ials wi h CBS showed an inc easing end wi h an inc easing a io o EPDM in ubbe combina ions. On he o he hand, he c oss-link densi y o ulcaniza es cu ed in he p esence o TMTD and he combina ion CBS-TMTD ended o dec ease wi h an inc easing a io o EPDM up o he composi ion S25–E75. Then, a signi ican inc ease in he deg ee o c oss-linking occu ed o he ulcaniza e S0–E100. When compa ing he cu ing sys ems, he highes c oss-link densi y was exhibi ed by ubbe blends cu ed wi h he CBS-TMTD combina ion. TMTD ac s no only as accele a o , bu also as a sul u dono due o sul u b idges in i s s uc u e and, hus, i con ibu es o he c oss- links o ma ion. The highes c oss-link densi y o ulcaniza es based on EPDM seems o be su p ising, as EPDM has a low alue o unsa u a ion and, he e o e, he c oss-link densi y was expec ed o be lowe when compa ed o ulcaniza es based on highly unsa u a ed SBR. A possible explana ion could be ha he EPDM migh ha e a highly b anched s uc u e and he physical en anglemen s linked wi h chemical linkages can ac as addi ional c oss-links. Ma e ials 2024,17, 2718 8 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 8 o 25 no only as accele a o , bu also as a sul u dono due o sul u b idges in i s s uc u e and, hus, i con ibu es o he c oss-links o ma ion. The highes c oss-link densi y o ulcani- za es based on EPDM seems o be su p ising, as EPDM has a low alue o unsa u a ion and, he e o e, he c oss-link densi y was expec ed o be lowe when compa ed o ulcan- iza es based on highly unsa u a ed SBR. A possible explana ion could be ha he EPDM migh ha e a highly b anched s uc u e and he physical en anglemen s linked wi h chemical linkages can ac as addi ional c oss-links. Figu e 3. The diffe ence be ween he maximum and minimum o que ΔM o ubbe blends cu ed wi h sul u sys ems. Figu e 4. C oss-link densi y ν o ulcaniza es cu ed wi h sul u sys ems. F om Figu e 5, i becomes appa en ha he lowes cu ing a e was exhibi ed by o - mula ions cu ed wi h CBS wi h almos no dependence on he ype o ubbe o hei com- bina ions. The applica ion o TMTD esul ed in a highe cu ing a e, which was ound o sligh ly dec ease wi h an inc easing a io o EPDM in ubbe combina ions. The highes cu ing a e was demons a ed by he ma e ials cu ed wi h he CBS-TMTD combina ion wi h he highes in luence on he ype o ubbe o ubbe combina ions. The cu e a e accoun s o no only he diffe ences be ween he op imum cu e ime and sco ch ime, bu Figu e 3. The di e ence be ween he maximum and minimum o que ∆ Mo ubbe blends cu ed wi h sul u sys ems. Ma e ials 2024, 17, x FOR PEER REVIEW 8 o 25 no only as accele a o , bu also as a sul u dono due o sul u b idges in i s s uc u e and, hus, i con ibu es o he c oss-links o ma ion. The highes c oss-link densi y o ulcani- za es based on EPDM seems o be su p ising, as EPDM has a low alue o unsa u a ion and, he e o e, he c oss-link densi y was expec ed o be lowe when compa ed o ulcan- iza es based on highly unsa u a ed SBR. A possible explana ion could be ha he EPDM migh ha e a highly b anched s uc u e and he physical en anglemen s linked wi h chemical linkages can ac as addi ional c oss-links. Figu e 3. The diffe ence be ween he maximum and minimum o que ΔM o ubbe blends cu ed wi h sul u sys ems. Figu e 4. C oss-link densi y ν o ulcaniza es cu ed wi h sul u sys ems. F om Figu e 5, i becomes appa en ha he lowes cu ing a e was exhibi ed by o - mula ions cu ed wi h CBS wi h almos no dependence on he ype o ubbe o hei com- bina ions. The applica ion o TMTD esul ed in a highe cu ing a e, which was ound o sligh ly dec ease wi h an inc easing a io o EPDM in ubbe combina ions. The highes cu ing a e was demons a ed by he ma e ials cu ed wi h he CBS-TMTD combina ion wi h he highes in luence on he ype o ubbe o ubbe combina ions. The cu e a e accoun s o no only he diffe ences be ween he op imum cu e ime and sco ch ime, bu Figu e 4. C oss-link densi y νo ulcaniza es cu ed wi h sul u sys ems. F om Figu e 5, i becomes appa en ha he lowes cu ing a e was exhibi ed by o mula ions cu ed wi h CBS wi h almos no dependence on he ype o ubbe o hei combina ions. The applica ion o TMTD esul ed in a highe cu ing a e, which was ound o sligh ly dec ease wi h an inc easing a io o EPDM in ubbe combina ions. The highes cu ing a e was demons a ed by he ma e ials cu ed wi h he CBS-TMTD combina ion wi h he highes in luence on he ype o ubbe o ubbe combina ions. The cu e a e accoun s o no only he di e ences be ween he op imum cu e ime and sco ch ime, bu also he di e ences be ween he o que a he op imum cu e ime and sco ch ime; hus, i demons a es he change p ocess o an uncu ed blend in o a ulcaniza e. The highes cu ing a e was ha o he blends based on SBR (S100–E0), which sugges s ha he cu ing p ocess o equi alen ubbe blends p oceeded he as es . Ma e ials 2024,17, 2718 9 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 9 o 25 also he diffe ences be ween he o que a he op imum cu e ime and sco ch ime; hus, i demons a es he change p ocess o an uncu ed blend in o a ulcaniza e. The highes cu - ing a e was ha o he blends based on SBR (S100–E0), which sugges s ha he cu ing p ocess o equi alen ubbe blends p oceeded he as es . Figu e 5. Cu ing a e R o ubbe blends cu ed wi h sul u sys ems. The physical–mechanical p ope ies o sul u -cu ed ulcaniza es a e depic ed in Fig- u es 6–9. The elonga ion a he b eak o ulcaniza es co ela es, o ce ain ex en , wi h he c oss-link densi y. As he ubbe compounds cu ed in he p esence o CBS (S100–E0, S75– E25, S50–E50) exhibi ed he lowes c oss-link densi y, hose ulcaniza es we e ound o ha e he highes elonga ion a b eak (Figu e 6). Also, as he c oss-link densi y o ulcani- za es cu ed in he p esence o TMTD and he CBS-TMTD combina ion showed a dec eas- ing end wi h an inc easing a io o EPDM up o he composi ion o S25–E75, he elonga- ion a b eak inc eased in he same di ec ion. The lowes elonga ion a b eak was exhibi ed by ulcaniza es based on EPDM wi h he highes deg ee o c oss-linking. The inc easing deg ee o c oss-linking leads o he es ic ion o he elas ici y and mobili y o ubbe chains, and as a esul o which, he elonga ion a b eak dec eases. The lowes c oss-link densi y o ulcaniza es cu ed in he p esence o CBS was e- lec ed in hei lowes modulus (Figu e 7). Wi h he applica ion o TMTD and he CBS- TMTD combina ion, he c oss-link densi y inc eased, which esul ed in an inc ease in he modulus. In Figu e 8, i is shown ha he lowes ha dness was exhibi ed by he ulcani- za es based on SBR (S100–E0), ollowed by he ulcaniza es based on EPDM (S0–E100). The ha dness o ma e ials based on ubbe combina ions (S75–E25, S50–E50, S25–E75) was sligh ly highe . The highe c oss-link densi y o ulcaniza es cu ed in he p esence o TMTD and he CBS-TMTD combina ion was esponsible o he highe ha dness o equi - alen ulcaniza es. The lowes ensile s eng h was exhibi ed by ulcaniza es based on EPDM (S0–E100) wi h no signi ican in luence on he ype o accele a o used. The ensile s eng h o ulcaniza es wi h a designa ion o S100–E0 was highe . Again, no appa en in luence o he accele a o composi ion on ensile s eng h was eco ded. As shown in Figu e 9, in he case o ulcaniza es based on ubbe s combina ions, he ensile s eng h showed an inc easing end wi h an inc easing a io o EPDM. Conside ing he ype o accele a o , he highes con ibu ion o he ensile s eng h was eco ded o TMTD. The highes ensile s eng h was mani es ed by he ulcaniza es wi h composi ions o 25 ph SBR and 75 ph EPDM. The ensile s eng h o he sample S25–E75 cu ed wi h TMTD eached mo e han 9 MPa, which ep esen s a mo e han h ee old o ou old inc ease in Figu e 5. Cu ing a e Ro ubbe blends cu ed wi h sul u sys ems. The physical–mechanical p ope ies o sul u -cu ed ulcaniza es a e depic ed in Figu es 6–9. The elonga ion a he b eak o ulcaniza es co ela es, o ce ain ex en , wi h he c oss-link densi y. As he ubbe compounds cu ed in he p esence o CBS ( S100–E0 , S75–E25, S50–E50) exhibi ed he lowes c oss-link densi y, hose ulcaniza es we e ound o ha e he highes elonga ion a b eak (Figu e 6). Also, as he c oss-link densi y o ulcan- iza es cu ed in he p esence o TMTD and he CBS-TMTD combina ion showed a dec easing end wi h an inc easing a io o EPDM up o he composi ion o S25–E75, he elonga ion a b eak inc eased in he same di ec ion. The lowes elonga ion a b eak was exhibi ed by ulcaniza es based on EPDM wi h he highes deg ee o c oss-linking. The inc easing deg ee o c oss-linking leads o he es ic ion o he elas ici y and mobili y o ubbe chains, and as a esul o which, he elonga ion a b eak dec eases. Ma e ials 2024, 17, x FOR PEER REVIEW 10 o 25 ensile s eng h in compa ison wi h equi alen ulcaniza es based on SBR o EPDM, e- spec i ely. The highes ensile s eng h o ulcaniza es cu ed wi h TMTD can be a ibu ed o he change in he sul idic c oss-links o med wi hin he ubbe ma ices. As TMTD ac s as a sul u dono , i can be deduced ha mo e disul idic and polysul idic c oss-links a e gene a ed. In gene al, he ulcaniza es wi h dominan polysul idic linkages a e cha ac e - ized by highe ensile beha io when compa ed o ulcaniza es in which he chain seg- men s a e linked wi h monosul idic and disul idic c oss-links. Longe and mo e lexible polysul idic c oss-links enable highe mobili y and elas ici y o ubbe chains, which con- ibu es o be e edis ibu ion o he de o ma ion s ains wi hin he ubbe ma ix [29]. This co esponds wi h be e de o ma ion beha io and highe ensile cha ac e is ics o ulcaniza es. Figu e 6. Elonga ion a b eak o ulcaniza es cu ed wi h sul u sys ems. Figu e 7. Modulus M100 o ulcaniza es cu ed wi h sul u sys ems. Figu e 6. Elonga ion a b eak o ulcaniza es cu ed wi h sul u sys ems. Ma e ials 2024,17, 2718 16 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 16 o 25 Figu e 17. Elonga ion a b eak o ulcaniza es cu ed wi h pe oxide sys ems. The ype and s uc u e o ubbe as well as he s uc u e o he o med c oss-links a e key ac o s in luencing he ensile s eng h o un illed ulcaniza es. F om Figu e 18 i be- comes appa en ha he lowes ensile s eng h exhibi ed ulcaniza es based on e e ence SBR and EPDM ubbe s (S100–E0 and S0–E100) cu ed wi h DCP. While he e was almos no in luence o co-agen s on he ensile s eng h o he ulcaniza e S100–E0, he applica- ion o ZDA and ZDMA caused an enhancemen in he ensile beha io o he EPDM- based ulcaniza e (S0–E100). The ensile s eng h o ulcaniza es based on ubbe combi- na ions (S75–E25, S50–E50, S25–E75) was highe and, as in he case o ulcaniza es cu ed wi h a sul u sys em, showed an inc easing end wi h an inc easing a io o EPDM. When combining SBR and EPDM in 25 ph o 75 ph , he ensile s eng h o DCP-cu ed ulcan- iza e achie ed almos 9 MPa, which was mo e han 7 MPa highe han ha o he ulcan- iza es S100–E0 and S0–E100 (bo h ulcaniza es exhibi ed a ensile s eng h equi alen o only 2 MPa). The u iliza ion o co-agen s con ibu ed o he o ma ion o mo e complex c oss-linked s uc u es wi hin he ubbe ma ices h ough he o ma ion o mul i unc- ional c oss-links, which con ibu ed o imp o emen s in he ensile beha io o ulcani- za es. Again, he highes ensile s eng h ( ema kable 13 MPa) was mani es ed by he ul- caniza es S25–E75 cu ed wi h DCP and bo h co-agen ypes. When compa ing he ensile s eng h o sul u -cu ed ulcaniza es (including all ac- cele a o sys ems) and ulcaniza es cu ed wi h DCP, i is shown ha highe ensile s eng h was exhibi ed by ulcaniza es cu ed wi h a sul u sys em. This is in line wi h gene al knowledge demons a ing ha sul u -cu ed ulcaniza es a e cha ac e ized by highe ensile beha io compa ed o pe oxide-cu ed ulcaniza es. This can be a ibu ed o he s uc u e o he o med c oss-links. Longe and mo e lexible sul idic c oss-links make ubbe chain segmen s mo e lexible and elas ic. Highe elas ici y and mobili y o ubbe chains leads o be e , mo e uni o m edis ibu ion o applied de o ma ion s ains on o he ubbe ma ix, which can bea mo e s ain load wi hou ha ing a nega i e impac on ensile beha io . On he o he hand, sho and igid ca bon–ca bon bonds es ic he mobili y and elas ici y o ubbe chains. Highly c oss-linked ubbe si es can ac as s ess concen a o s upon applied de o ma ion s ains, which can mo e easily lead o c acks g owing and hei p opaga ion. This co esponds o he lowe ensile s eng h o pe ox- ide-cu ed ulcaniza es. Al hough, wi h he applica ion o bo h co-agen ypes, he ensile s eng h inc eased and o e came he ensile s eng h o sul u -cu ed ulcaniza es. So, i can be s a ed ha wi h he p ope selec ion o co-agen s, i is possible o ab ica e pe ox- ide-cu ed ma e ials wi h applicable physical–mechanical p ope ies. Figu e 17. Elonga ion a b eak o ulcaniza es cu ed wi h pe oxide sys ems. Ma e ials 2024, 17, x FOR PEER REVIEW 17 o 25 Figu e 18. Tensile s eng h o ulcaniza es cu ed wi h pe oxide sys ems. I can also be s a ed ha o bo h sul u - and pe oxide-cu ed ulcaniza es, he ma e- ials based on ubbe combina ions exhibi ed highe ensile s eng h when compa ed o he equi alen ulcaniza es based on SBR o EPDM. The highes ensile s eng h was demons a ed by ulcaniza es wi h composi ions o 25 ph SBR and 75 ph EPDM. This is a e y posi i e aspec , sugges ing ha wi h he combina ion o ubbe s, no only can he ad an ages o bo h ubbe s be combined, bu imp o ed ensile beha io can also be achie ed. 3.3. Dynamical–Mechanical Analysis Dynamic–mechanical analysis o ulcaniza es was pe o med o in es iga e he in- luence o ubbe combina ions and cu ing sys em composi ion on he isco-elas ic p op- e ies o ulcaniza es. Fo his pu pose, ulcaniza es cu ed wi h a sul u sys em in he p esence o TMTD and ulcaniza es cu ed wi h a combina ion o DCP and ZDMA we e chosen. Those ulcaniza es we e selec ed due o hei highes ensile cha ac e is ics. The dynamic s o age moduli exhibi no able a ia ions in bo h magni ude and cha - ac e is ics due o he in e play o in e molecula and in amolecula in e ac ions wi hin he polyme sys em. Figu e 19 illus a es he impac o a blend a io on he s o age mod- ulus (E′) o sul u -cu ed ulcaniza es. A lowe empe a u es below he glass ansi ion empe a u e (Tg), pu e SBR (S100–E0) demons a es he highes E′, while pu e EPDM (S0– E100) exhibi s he lowes E′, e lec ing he dis inc s uc u al a ibu es o each polyme . SBR is a copolyme o s y ene and bu adiene, which esul s in a mo e densely packed polyme s uc u e compa ed o he e polyme s uc u e o EPDM, which includes e h- ylene, p opylene, and diene monome s. The mo e compac s uc u e o SBR gene ally leads o highe s iffness and a highe s o age modulus. A simila end is obse ed in Fig- u e 20, whe e a pe oxide cu ing sys em was employed, albei wi h gene ally highe mod- ulus alues in he glassy egion. This phenomenon is asc ibed o he g ea e igidi y con- e ed by co alen C-C c osslinks compa ed o mo e lexible polysul idic c osslinks. All samples display single ansi ions, indica i e o phase miscibili y, ye he cu es o EPDM- con aining samples ea u e a less p onounced slope, po en ially a ibu able o he p es- ence o c ys alline egions. Upon su passing he glass ansi ion empe a u e (Tg), he ub- be unde goes a ansi ion om a glassy o a ubbe y s a e, p ecipi a ing a dec ease in hei s o age moduli. Loga i hmic ep esen a ion o empe a u e dependence o s o age moduli, depic ed in Figu es 21 and 22, becomes impe a i e due o he sub le diffe ences Figu e 18. Tensile s eng h o ulcaniza es cu ed wi h pe oxide sys ems. When compa ing he ensile s eng h o sul u -cu ed ulcaniza es (including all accel- e a o sys ems) and ulcaniza es cu ed wi h DCP, i is shown ha highe ensile s eng h was exhibi ed by ulcaniza es cu ed wi h a sul u sys em. This is in line wi h gene al knowledge demons a ing ha sul u -cu ed ulcaniza es a e cha ac e ized by highe en- sile beha io compa ed o pe oxide-cu ed ulcaniza es. This can be a ibu ed o he s uc u e o he o med c oss-links. Longe and mo e lexible sul idic c oss-links make ubbe chain segmen s mo e lexible and elas ic. Highe elas ici y and mobili y o ubbe chains leads o be e , mo e uni o m edis ibu ion o applied de o ma ion s ains on o he ubbe ma ix, which can bea mo e s ain load wi hou ha ing a nega i e impac on ensile beha io . On he o he hand, sho and igid ca bon–ca bon bonds es ic he mobili y and elas ici y o ubbe chains. Highly c oss-linked ubbe si es can ac as s ess concen a o s upon applied de o ma ion s ains, which can mo e easily lead o c acks g owing and hei p opaga ion. This co esponds o he lowe ensile s eng h o pe oxide-cu ed ulcaniza es. Al hough, wi h he applica ion o bo h co-agen ypes, he ensile s eng h inc eased and Ma e ials 2024,17, 2718 17 o 25 o e came he ensile s eng h o sul u -cu ed ulcaniza es. So, i can be s a ed ha wi h he p ope selec ion o co-agen s, i is possible o ab ica e pe oxide-cu ed ma e ials wi h applicable physical–mechanical p ope ies. I can also be s a ed ha o bo h sul u - and pe oxide-cu ed ulcaniza es, he ma- e ials based on ubbe combina ions exhibi ed highe ensile s eng h when compa ed o he equi alen ulcaniza es based on SBR o EPDM. The highes ensile s eng h was demons a ed by ulcaniza es wi h composi ions o 25 ph SBR and 75 ph EPDM. This is a e y posi i e aspec , sugges ing ha wi h he combina ion o ubbe s, no only can he ad an ages o bo h ubbe s be combined, bu imp o ed ensile beha io can also be achie ed. 3.3. Dynamical–Mechanical Analysis Dynamic–mechanical analysis o ulcaniza es was pe o med o in es iga e he in lu- ence o ubbe combina ions and cu ing sys em composi ion on he isco-elas ic p ope ies o ulcaniza es. Fo his pu pose, ulcaniza es cu ed wi h a sul u sys em in he p esence o TMTD and ulcaniza es cu ed wi h a combina ion o DCP and ZDMA we e chosen. Those ulcaniza es we e selec ed due o hei highes ensile cha ac e is ics. The dynamic s o age moduli exhibi no able a ia ions in bo h magni ude and cha ac- e is ics due o he in e play o in e molecula and in amolecula in e ac ions wi hin he polyme sys em. Figu e 19 illus a es he impac o a blend a io on he s o age modulus (E ′ ) o sul u -cu ed ulcaniza es. A lowe empe a u es below he glass ansi ion empe a u e (Tg), pu e SBR (S100–E0) demons a es he highes E ′ , while pu e EPDM (S0–E100) exhibi s he lowes E ′ , e lec ing he dis inc s uc u al a ibu es o each polyme . SBR is a copoly- me o s y ene and bu adiene, which esul s in a mo e densely packed polyme s uc u e compa ed o he e polyme s uc u e o EPDM, which includes e hylene, p opylene, and diene monome s. The mo e compac s uc u e o SBR gene ally leads o highe s i ness and a highe s o age modulus. A simila end is obse ed in Figu e 20, whe e a pe oxide cu ing sys em was employed, albei wi h gene ally highe modulus alues in he glassy egion. This phenomenon is asc ibed o he g ea e igidi y con e ed by co alen C-C c osslinks compa ed o mo e lexible polysul idic c osslinks. All samples display single ansi ions, indica i e o phase miscibili y, ye he cu es o EPDM-con aining samples ea u e a less p onounced slope, po en ially a ibu able o he p esence o c ys alline egions. Upon su passing he glass ansi ion empe a u e (Tg), he ubbe unde goes a ansi ion om a glassy o a ubbe y s a e, p ecipi a ing a dec ease in hei s o age moduli. Loga i hmic ep esen a ion o empe a u e dependence o s o age moduli, depic ed in Figu es 21 and 22, becomes impe a i e due o he sub le di e ences in p e ious igu es. I becomes appa en om hese igu es ha i espec i e o he ulcaniza ion sys em used, he lowes s o age moduli in he ubbe y egion pe ain o pu e SBR. This phenomenon in he ubbe y egion can be asc ibed o he mac omolecules’ abili y o impede in amolecula slippage. Despi e he expec ed end o E ′ lying be ween he alues o pu e SBR and EPDM, as e iden in Figu es 21 and 22, his is no he case. In e ac ions be ween SBR and EPDM, including in e molecula bonding, may culmina e in a mo e homogeneous blend, he eby yielding a s i e sample wi h ele a ed E′ alues in he ubbe y s a e. The loss modulus E ′′ quan i ies he ene gy dissipa ion pe cycle o de o ma ion du ing mechanical es ing, p o iding c ucial insigh s in o he iscoelas ic beha io o ma e ials. In bo h Figu es 23 and 24, singula glass- ansi ion peaks a e e iden , indica ing he p esence o a homogeneous phase wi hin he s udied polyme blends. No ably, he peaks o S75–E25 blends a e ma ginally shi ed o highe empe a u es ac oss bo h cu ing sys ems employed. This phenomenon may s em om EPDM being dispe sed wi hin a con inuous SBR phase, po en ially impeding molecula mo ion and necessi a ing inc eased ene gy o o e come molecula in e ac ions. The a ea unde he peak o he loss modulus cu e o pu e SBR is obse ed o be he highes ac oss bo h ulcaniza ion sys ems u ilized. This obse a ion sugges s ha SBR exhibi s g ea e iscoelas ici y compa ed o EPDM, enabling i o abso b mo e ene gy du ing de o ma ion. Abo e he glass ansi ion empe a u e, Ma e ials 2024,17, 2718 18 o 25 he loss modulus e lec s heigh ened molecula mobili y, culmina ing in inc eased ene gy dissipa ion du ing de o ma ion ela i e o he glassy s a e. As depic ed in Figu es 25 and 26, pe oxide ulcaniza ion appea s o induce limi ed chain mobili y, esul ing in a highe loss modulus a ele a ed empe a u es compa ed o sul u ulcaniza ion. Ma e ials 2024, 17, x FOR PEER REVIEW 18 o 25 in p e ious igu es. I becomes appa en om hese igu es ha i espec i e o he ulcan- iza ion sys em used, he lowes s o age moduli in he ubbe y egion pe ain o pu e SBR. This phenomenon in he ubbe y egion can be asc ibed o he mac omolecules’ abili y o impede in amolecula slippage. Despi e he expec ed end o E′ lying be ween he alues o pu e SBR and EPDM, as e iden in Figu es 21 and 22, his is no he case. In e ac ions be ween SBR and EPDM, including in e molecula bonding, may culmina e in a mo e ho- mogeneous blend, he eby yielding a s iffe sample wi h ele a ed E′ alues in he ubbe y s a e. Figu e 19. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h sul u sys- em. Figu e 20. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h pe oxide sys em. Figu e 19. Tempe a u e dependences o s o age modulus E ′ o ulcaniza es cu ed wi h sul u sys em. Ma e ials 2024, 17, x FOR PEER REVIEW 18 o 25 in p e ious igu es. I becomes appa en om hese igu es ha i espec i e o he ulcan- iza ion sys em used, he lowes s o age moduli in he ubbe y egion pe ain o pu e SBR. This phenomenon in he ubbe y egion can be asc ibed o he mac omolecules’ abili y o impede in amolecula slippage. Despi e he expec ed end o E′ lying be ween he alues o pu e SBR and EPDM, as e iden in Figu es 21 and 22, his is no he case. In e ac ions be ween SBR and EPDM, including in e molecula bonding, may culmina e in a mo e ho- mogeneous blend, he eby yielding a s iffe sample wi h ele a ed E′ alues in he ubbe y s a e. Figu e 19. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h sul u sys- em. Figu e 20. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h pe oxide sys em. Figu e 20. Tempe a u e dependences o s o age modulus E ′ o ulcaniza es cu ed wi h pe oxide sys em. Ma e ials 2024,17, 2718 19 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 19 o 25 Figu e 21. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h sul u sys- em ( om 0 °C). Figu e 22. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h pe oxide sys em ( om 0 °C). The loss modulus E″ quan i ies he ene gy dissipa ion pe cycle o de o ma ion du - ing mechanical es ing, p o iding c ucial insigh s in o he iscoelas ic beha io o ma e i- als. In bo h Figu es 23 and 24, singula glass- ansi ion peaks a e e iden , indica ing he p esence o a homogeneous phase wi hin he s udied polyme blends. No ably, he peaks o S75–E25 blends a e ma ginally shi ed o highe empe a u es ac oss bo h cu ing sys- ems employed. This phenomenon may s em om EPDM being dispe sed wi hin a con- inuous SBR phase, po en ially impeding molecula mo ion and necessi a ing inc eased ene gy o o e come molecula in e ac ions. The a ea unde he peak o he loss modulus cu e o pu e SBR is obse ed o be he highes ac oss bo h ulcaniza ion sys ems u ilized. This obse a ion sugges s ha SBR exhibi s g ea e iscoelas ici y compa ed o EPDM, Figu e 21. Tempe a u e dependences o s o age modulus E ′ o ulcaniza es cu ed wi h sul u sys em ( om 0 ◦C). Ma e ials 2024, 17, x FOR PEER REVIEW 19 o 25 Figu e 21. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h sul u sys- em ( om 0 °C). Figu e 22. Tempe a u e dependences o s o age modulus E′ o ulcaniza es cu ed wi h pe oxide sys em ( om 0 °C). The loss modulus E″ quan i ies he ene gy dissipa ion pe cycle o de o ma ion du - ing mechanical es ing, p o iding c ucial insigh s in o he iscoelas ic beha io o ma e i- als. In bo h Figu es 23 and 24, singula glass- ansi ion peaks a e e iden , indica ing he p esence o a homogeneous phase wi hin he s udied polyme blends. No ably, he peaks o S75–E25 blends a e ma ginally shi ed o highe empe a u es ac oss bo h cu ing sys- ems employed. This phenomenon may s em om EPDM being dispe sed wi hin a con- inuous SBR phase, po en ially impeding molecula mo ion and necessi a ing inc eased ene gy o o e come molecula in e ac ions. The a ea unde he peak o he loss modulus cu e o pu e SBR is obse ed o be he highes ac oss bo h ulcaniza ion sys ems u ilized. This obse a ion sugges s ha SBR exhibi s g ea e iscoelas ici y compa ed o EPDM, Figu e 22. Tempe a u e dependences o s o age modulus E ′ o ulcaniza es cu ed wi h pe oxide sys em ( om 0 ◦C). Ma e ials 2024,17, 2718 20 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 20 o 25 enabling i o abso b mo e ene gy du ing de o ma ion. Abo e he glass ansi ion empe - a u e, he loss modulus e lec s heigh ened molecula mobili y, culmina ing in inc eased ene gy dissipa ion du ing de o ma ion ela i e o he glassy s a e. As depic ed in Figu es 25 and 26, pe oxide ulcaniza ion appea s o induce limi ed chain mobili y, esul ing in a highe loss modulus a ele a ed empe a u es compa ed o sul u ulcaniza ion. Figu e 23. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h sul u sys em. Figu e 24. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h pe oxide sys- em. Figu e 23. Tempe a u e dependences o loss modulus E ′′ o ulcaniza es cu ed wi h sul u sys em. Ma e ials 2024, 17, x FOR PEER REVIEW 20 o 25 enabling i o abso b mo e ene gy du ing de o ma ion. Abo e he glass ansi ion empe - a u e, he loss modulus e lec s heigh ened molecula mobili y, culmina ing in inc eased ene gy dissipa ion du ing de o ma ion ela i e o he glassy s a e. As depic ed in Figu es 25 and 26, pe oxide ulcaniza ion appea s o induce limi ed chain mobili y, esul ing in a highe loss modulus a ele a ed empe a u es compa ed o sul u ulcaniza ion. Figu e 23. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h sul u sys em. Figu e 24. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h pe oxide sys- em. Figu e 24. Tempe a u e dependences o loss modulus E ′′ o ulcaniza es cu ed wi h pe oxide sys em. Ma e ials 2024,17, 2718 21 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 21 o 25 Figu e 25. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h sul u sys em ( om 0 °C). Figu e 26. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h pe oxide sys- em ( om 0 °C). Tan δ se es as he a io o he loss modulus (E″) o he s o age modulus (E′), com- monly employed o measu e ene gy dissipa ion wi hin a ma e ial. Wi h a ising empe a- u e, damping peaks wi hin he ansi ion egion be o e dec easing wi hin he ubbe y egion. Below Tg, damping emains minimal as chain segmen s a e immobilized, yielding p ima ily elas ic de o ma ions wi h limi ed molecula mo ion conduci e o iscous low. Abo e Tg, damping likewise diminishes as molecula segmen s gain eedom o mo e- men , encoun e ing minimal esis ance o low. The ansi ion egion wi nesses heigh - ened damping due o he incep ion o mic o-B ownian mo ion among mac omolecules and hei ensuing s ess elaxa ion, al hough no all segmen s concu en ly pa ake in such elaxa ion. The ele a ed a ea unde he peak o an δ deno es augmen ed ene gy dissipa- ion, simila o E″ elabo a ed ea lie . The empe a u e dependencies o he loss ac o an Figu e 25. Tempe a u e dependences o loss modulus E ′′ o ulcaniza es cu ed wi h sul u sys em ( om 0 ◦C). Ma e ials 2024, 17, x FOR PEER REVIEW 21 o 25 Figu e 25. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h sul u sys em ( om 0 °C). Figu e 26. Tempe a u e dependences o loss modulus E″ o ulcaniza es cu ed wi h pe oxide sys- em ( om 0 °C). Tan δ se es as he a io o he loss modulus (E″) o he s o age modulus (E′), com- monly employed o measu e ene gy dissipa ion wi hin a ma e ial. Wi h a ising empe a- u e, damping peaks wi hin he ansi ion egion be o e dec easing wi hin he ubbe y egion. Below Tg, damping emains minimal as chain segmen s a e immobilized, yielding p ima ily elas ic de o ma ions wi h limi ed molecula mo ion conduci e o iscous low. Abo e Tg, damping likewise diminishes as molecula segmen s gain eedom o mo e- men , encoun e ing minimal esis ance o low. The ansi ion egion wi nesses heigh - ened damping due o he incep ion o mic o-B ownian mo ion among mac omolecules and hei ensuing s ess elaxa ion, al hough no all segmen s concu en ly pa ake in such elaxa ion. The ele a ed a ea unde he peak o an δ deno es augmen ed ene gy dissipa- ion, simila o E″ elabo a ed ea lie . The empe a u e dependencies o he loss ac o an Figu e 26. Tempe a u e dependences o loss modulus E ′′ o ulcaniza es cu ed wi h pe oxide sys em ( om 0 ◦C). Tan δ se es as he a io o he loss modulus (E ′′ ) o he s o age modulus (E ′ ), com- monly employed o measu e ene gy dissipa ion wi hin a ma e ial. Wi h a ising empe - a u e, damping peaks wi hin he ansi ion egion be o e dec easing wi hin he ubbe y egion. Below Tg, damping emains minimal as chain segmen s a e immobilized, yielding p ima ily elas ic de o ma ions wi h limi ed molecula mo ion conduci e o iscous low. Abo e Tg, damping likewise diminishes as molecula segmen s gain eedom o mo e- men , encoun e ing minimal esis ance o low. The ansi ion egion wi nesses heigh ened damping due o he incep ion o mic o-B ownian mo ion among mac omolecules and hei ensuing s ess elaxa ion, al hough no all segmen s concu en ly pa ake in such elaxa ion. The ele a ed a ea unde he peak o an δ deno es augmen ed ene gy dissipa ion, simila o E ′′ elabo a ed ea lie . The empe a u e dependencies o he loss ac o an δ o bo h ulcaniza e ypes a e delinea ed in Figu es 27 and 28. Peak maxima in an δ empe a u e Ma e ials 2024,17, 2718 22 o 25 dependencies co espond o he glass ansi ion empe a u e (Tg) o ulcaniza es, wi h sum- ma ized alues p o ided in Table 5. No ably, i gin SBR mani es s lowe Tg han EPDM. The c oss-linking o ubbe ma ices ele a es he glass ansi ion empe a u e ela i e o i gin ubbe s. Speci ically, ulcaniza es based on SBR cu ed wi h a sul u sys em (S100–E0) exhibi lowe Tg han hei EPDM-based coun e pa s (S0–E100). Con e sely, ulcaniza es designa ed as S100–E0 and S0–E100, cu ed wi h a pe oxide sys em, demons a e p ac ically iden ical Tg alues. This can be a ibu ed o he nea ly wo old highe c oss-link densi y o SBR-based ulcaniza es compa ed o hose based on EPDM, whe eby inc eased c oss-link densi y es ic s ubbe chain mobili y and elas ici y, hus ele a ing Tg. Fo bo h ulcan- iza e ypes, hose based on an equi alen a io o bo h ubbe s (S50–E50) exhibi he highes Tg, while hose designa ed as S25–E75 showcase he lowes and nea ly iden ical Tg alues (a ound − 29 ◦ C). Figu e 27 e eals ha he sul u -cu ed ulcaniza e S25–E75 exhibi s wo peaks on loss ac o empe a u e dependencies, wi h he second peak occu ing a − 6 ◦ C. Gi en ha he occu ence o wo ansi ion peaks is ypical o block copolyme s, i may be in e ed ha he composi ion o bo h ubbe s a his a io p ecipi a es he o ma ion o some block copolyme s. Mo eo e , Figu e 28 illus a es ha an δ is highe abo e Tg, sugges ing ha he pe oxide ulcaniza ion sys em engende s c oss-links be ween SBR and EPDM ha impede segmen mobili y e en abo e Tg. Ma e ials 2024, 17, x FOR PEER REVIEW 22 o 25 δ o bo h ulcaniza e ypes a e delinea ed in Figu es 27 and 28. Peak maxima in an δ empe a u e dependencies co espond o he glass ansi ion empe a u e (Tg) o ulcan- iza es, wi h summa ized alues p o ided in Table 5. No ably, i gin SBR mani es s lowe Tg han EPDM. The c oss-linking o ubbe ma ices ele a es he glass ansi ion empe - a u e ela i e o i gin ubbe s. Speci ically, ulcaniza es based on SBR cu ed wi h a sul u sys em (S100–E0) exhibi lowe Tg han hei EPDM-based coun e pa s (S0–E100). Con- e sely, ulcaniza es designa ed as S100–E0 and S0–E100, cu ed wi h a pe oxide sys em, demons a e p ac ically iden ical Tg alues. This can be a ibu ed o he nea ly wo old highe c oss-link densi y o SBR-based ulcaniza es compa ed o hose based on EPDM, whe eby inc eased c oss-link densi y es ic s ubbe chain mobili y and elas ici y, hus ele a ing Tg. Fo bo h ulcaniza e ypes, hose based on an equi alen a io o bo h ub- be s (S50–E50) exhibi he highes Tg, while hose designa ed as S25–E75 showcase he lowes and nea ly iden ical Tg alues (a ound −29 °C). Figu e 27 e eals ha he sul u - cu ed ulcaniza e S25–E75 exhibi s wo peaks on loss ac o empe a u e dependencies, wi h he second peak occu ing a −6 °C. Gi en ha he occu ence o wo ansi ion peaks is ypical o block copolyme s, i may be in e ed ha he composi ion o bo h ubbe s a his a io p ecipi a es he o ma ion o some block copolyme s. Mo eo e , Figu e 28 illus- a es ha an δ is highe abo e Tg, sugges ing ha he pe oxide ulcaniza ion sys em engende s c oss-links be ween SBR and EPDM ha impede segmen mobili y e en abo e Tg. Table 5. Glass ansi ion empe a u e Tg and c oss-link densi y ν o ulcaniza es cu ed wi h sul u and pe oxide sys ems. S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 Tg o i gin ubbe s (°C) −34.7 −29.6 Tg o ulcaniza es wi h sul u sys em (°C) −28.5 −25.4 −23.3 −29.2 (−6.2) −24.9 Tg o ulcaniza es wi h pe oxide sys em (°C) −26.4 −23.5 −19.8 −29.9 −27 C oss-link densi y o ulcaniza es wi h sul u sys em ν·104 (mol·cm−3) 1.59 1.47 1.20 0.98 2.95 C oss-link densi y o ulcaniza es wi h pe oxide sys em ν·104 (mol·cm−3) 4.02 3.68 3.56 3.66 1.90 Figu e 27. Tempe a u e dependences o loss ac o an δ o ulcaniza es cu ed wi h sul u sys em. Figu e 27. Tempe a u e dependences o loss ac o an δ o ulcaniza es cu ed wi h sul u sys em. Table 5. Glass ansi ion empe a u e Tg and c oss-link densi y ν o ulcaniza es cu ed wi h sul u and pe oxide sys ems. S100–E0 S75–E25 S50–E50 S25–E75 S0–E100 Tg o i gin ubbe s (◦C) −34.7 −29.6 Tg o ulcaniza es wi h sul u sys em (◦C) −28.5 −25.4 −23.3 −29.2 (−6.2) −24.9 Tg o ulcaniza es wi h pe oxide sys em (◦C) −26.4 −23.5 −19.8 −29.9 −27 C oss-link densi y o ulcaniza es wi h sul u sys em ν·104(mol·cm−3)1.59 1.47 1.20 0.98 2.95 C oss-link densi y o ulcaniza es wi h pe oxide sys em ν·104(mol·cm−3)4.02 3.68 3.56 3.66 1.90 Ma e ials 2024,17, 2718 23 o 25 Ma e ials 2024, 17, x FOR PEER REVIEW 23 o 25 Figu e 28. Tempe a u e dependences o loss ac o an δ o ulcaniza es cu ed wi h pe oxide sys- em. 4. Conclusions In his wo k, ubbe blends based on SBR, EPDM, and hei mu ual combina ions we e cu ed wi h sul u as well as pe oxide ulcaniza ion sys ems. When conside ing sul u cu ing sys ems, he longes sco ch ime as well as he op i- mum cu e ime we e exhibi ed by ubbe o mula ions cu ed wi h CBS. On he o he hand, he highes cu e a e and c oss-link densi y was demons a ed by ulcaniza es cu ed wi h a CBS-TMTD combina ion. The modulus, ha dness, and elonga ion a b eak we e o a ce - ain ex en dependen on c oss-link densi y, sugges ing ha highe c oss-link densi y o ulcaniza es cu ed wi h TMTD and he CBS-TMTD combina ion was e lec ed in highe modulus and ha dness and lowe elonga ion a b eak o he equi alen ulcaniza es. The ensile s eng h o ulcaniza es based on ubbe combina ions was highe when compa ed o ulcaniza es based on pu e SBR and EPDM. The applica ion o TMTD con ibu ed o he highes inc ease in ensile s eng h, a guably due o he change in he s uc u e o he o med c oss-links. The highes ensile s eng h was exhibi ed by he ulcaniza e wi h a composi ion o 25 ph SBR and 75 ph o EPDM, eaching mo e han 9 MPa. Simila ly, pe oxide-cu ed ulcaniza es based on ubbe combina ions eached a highe ensile s eng h when compa ed o ulcaniza es based on SBR and EPDM. The applica ion o co- agen s esul ed in an inc ease in ensile s eng h due o he o ma ion o mul i unc ional c oss-links wi hin he ubbe ma ices. The applica ion o co-agen s led o he inc ease in he modulus and ha dness o ulcaniza es due o he inc ease in hei c oss-linking de- g ee. A high c oss-link densi y was esponsible o lowe elonga ion a b eak o he ul- caniza es cu ed wi h DCP and co-agen s. No signi ican changes in cu ing cha ac e is ics we e eco ded depending on he pe oxide cu ing sys em composi ion. Au ho Con ibu ions: Concep ualiza ion, J.K.; Valida ion, I.H.; Fo mal analysis, M.D.; In es iga- ion, A.K. and I.C.; Resou ces, A.K.; Da a cu a ion, M.D.; W i ing—o iginal d a , J.H. and M.B.; W i ing— e iew & edi ing, J.K.; Supe ision, I.H. All au ho s ha e ead and ag eed o he published e sion o he manusc ip . Funding: This wo k was suppo ed by he Slo ak Resea ch and De elopmen Agency unde he con ac No. APVV-19-0091, APVV-22-0011 and by g an agency VEGA unde he con ac No. 1/0056/24. Ins i u ional Re iew Boa d S a emen : No applicable. Figu e 28. Tempe a u e dependences o loss ac o an δ o ulcaniza es cu ed wi h pe oxide sys em. 4. Conclusions In his wo k, ubbe blends based on SBR, EPDM, and hei mu ual combina ions we e cu ed wi h sul u as well as pe oxide ulcaniza ion sys ems. When conside ing sul u cu ing sys ems, he longes sco ch ime as well as he op- imum cu e ime we e exhibi ed by ubbe o mula ions cu ed wi h CBS. On he o he hand, he highes cu e a e and c oss-link densi y was demons a ed by ulcaniza es cu ed wi h a CBS-TMTD combina ion. The modulus, ha dness, and elonga ion a b eak we e o a ce ain ex en dependen on c oss-link densi y, sugges ing ha highe c oss-link densi y o ulcaniza es cu ed wi h TMTD and he CBS-TMTD combina ion was e lec ed in highe modulus and ha dness and lowe elonga ion a b eak o he equi alen ulcaniza es. The ensile s eng h o ulcaniza es based on ubbe combina ions was highe when compa ed o ulcaniza es based on pu e SBR and EPDM. The applica ion o TMTD con ibu ed o he highes inc ease in ensile s eng h, a guably due o he change in he s uc u e o he o med c oss-links. The highes ensile s eng h was exhibi ed by he ulcaniza e wi h a composi ion o 25 ph SBR and 75 ph o EPDM, eaching mo e han 9 MPa. Simila ly, pe oxide-cu ed ulcaniza es based on ubbe combina ions eached a highe ensile s eng h when compa ed o ulcaniza es based on SBR and EPDM. The applica ion o co-agen s esul ed in an inc ease in ensile s eng h due o he o ma ion o mul i unc ional c oss-links wi hin he ubbe ma ices. The applica ion o co-agen s led o he inc ease in he modulus and ha dness o ulcaniza es due o he inc ease in hei c oss-linking deg ee. A high c oss-link densi y was esponsible o lowe elonga ion a b eak o he ulcaniza es cu ed wi h DCP and co-agen s. No signi ican changes in cu ing cha ac e is ics we e eco ded depending on he pe oxide cu ing sys em composi ion. Au ho Con ibu ions: Concep ualiza ion, J.K.; Valida ion, I.H.; Fo mal analysis, M.D.; In es iga ion, A.K. and I.C.; Resou ces, A.K.; Da a cu a ion, M.D.; W i ing—o iginal d a , J.H. and M.B.; W i ing— e iew & edi ing, J.K.; Supe ision, I.H. All au ho s ha e ead and ag eed o he published e sion o he manusc ip . Funding: This wo k was suppo ed by he Slo ak Resea ch and De elopmen Agency unde he con ac No. APVV-19-0091, APVV-22-0011 and by g an agency VEGA unde he con ac No. 1/0056/24. Ins i u ional Re iew Boa d S a emen : No applicable. In o med Consen S a emen : No applicable. Ma e ials 2024,17, 2718 24 o 25 Da a A ailabili y S a emen : The o iginal con ibu ions p esen ed in he s udy a e included in he a icle, u he inqui ies can be di ec ed o he co esponding au ho . Con lic s o In e es : The au ho s decla e no con lic o in e es . Re e ences 1. Wang, L.; Luo, Z.; Yang, L.; Wang, H.; Zhong, J. E ec o s y ene con en on mechanical and heological beha io o s y ene bu adiene ubbe . Ma e . Res. Exp ess 2021,8, 015302. [C ossRe ] 2. Gaca, M.; Vaulo , C.; Maciejewska, M.; Lipi´nska, M. P epa a ion and p ope ies o SBR composi es con aining g aphene nanopla ele s modi ied wi h py idinium de i a i e. Ma e ials 2020,13, 5407. [C ossRe ] [PubMed] 3. S elescu, M.D.; Ai inei, A.; Ba gan, A.; Fi e e, N.; Geo gescu, M.; Sonmez, M.; Ni uica, M.; Alexand escu, L.; S e an, A. Mechanical p ope ies and equilib ium swelling cha ac e is ics o some polyme composi es based on e hylene p opylene diene e polyme (EPDM) ein o ced wi h hemp ibe s. Ma e ials 2022,15, 6838. [C ossRe ] [PubMed] 4. Ba osik, D.; Szadkowski, B.; Ku´smie ek, M.; Rybi´nski, P.; Mi khodzhae , U.; Ma zec, A. Ad anced e hylene-p opylene-diene (EPDM) ubbe composi es illed wi h aw silicon ca bide o hyb id sys ems wi h di e en con en ional ille s. Polyme s 2022,14, 1383. [C ossRe ] [PubMed] 5. Dondi, D.; Bu a a a, A.; Ze i o, A.; Palamini, C.; Los i o, A.; Giannini, L.; Fauci ano, A. The mechanisms o he sulphu -only and ca aly ic ulcaniza ion o polybu adiene: An EPR and DFT s udy. Eu . Polym. J. 2015,62, 222–235. [C ossRe ] 6. Lian, Q.; Li, Y.; Li, K.; Cheng, J.; Zhang, J. Insigh s in o he ulcaniza ion mechanism h ough a simple and acile app oach o he sul u clea age beha io . Mac omolecules 2017,50, 803–810. [C ossRe ] 7. Milani, G.; Milani, F. Fas and eliable me a-da a model o he mechanis ic analysis o NR ulcanized wi h sulphu . Polym. Tes . 2014,33, 64–78. [C ossRe ] 8. Na delli, F.; Calucci, L.; Ca ignani, E.; Bo sacchi, S.; Ce olin, M.; A imondi, M.; Giannini, L.; Geppi, M.; Ma ini, F. In luence o sul u -cu ing condi ions on he dynamics and c osslinking o ubbe ne wo ks: A ime-domain NMR s udy. Polyme s 2022,14, 767. [C ossRe ] [PubMed] 9. Rabiei, S.; Shojaei, A. Vulcaniza ion kine ics and e e sion beha io o na u al ubbe /s y ene-bu adiene ubbe blend illed wi h nanodiamond—The ole o sul u cu ing sys em. Eu . Polym. J. 2016,81, 98–113. [C ossRe ] 10. Gao, Y.; Xue, Y.; Lü, Z.G.; Wang, Z.; Chen, Q.; Shi, N.; Sun, F. Sel -accele a ing decomposi ion empe a u e and quan i a i e s uc u e-p ope y ela ionship o o ganic pe oxides. P ocess Sa . En i on. P o . 2015,94, 322–328. [C ossRe ] 11. P ana, V.; Ro u eau, P.; Faye , G.; And é, D.; Hub, S.; Vico , P.; Rao, L.; Adamo, C. P edic ion o he he mal decomposi ion o o ganic pe oxides by alida ed QSPR models. J. Haza d. Ma e . 2014,276, 216–224. [C ossRe ] [PubMed] 12. Aze edo, M.; Monks, A.M.; Ke schbaume , R.C.; Schlögl, S.; Holze , C. Pe oxide-based c osslinking o solid silicone ubbe , Pa I: Insigh s in o he in luence o dicumylpe oxide concen a ion on he cu ing kine ics and he modynamics de e mined by a heological app oach. Polyme s 2022,14, 4404. [C ossRe ] [PubMed] 13. K uželák, J.; Sýko a, R.; Hudec, I. Sulphu and pe oxide ulcanisa ion o ubbe compounds–o e iew. Chem. Pap. 2016,70, 1533–1555. [C ossRe ] 14. Posadas, P.; Fe nández-To es, A.; Chamo o, C.; Mo a-Ba an es, I.; Rod íguez, A.; González, L.; Valen ín, J.L. S udy on pe oxide ulcaniza ion he modynamics o e hylene– inyl ace a e copolyme ubbe using 2,2,6,6,- e ame hylpipe idinyloxyl ni oxide. Polym. In . 2013,62, 909–918. [C ossRe ] 15. Cong, C.; Liu, Q.; Li, J.; Meng, X.; Zhou, Q. The e ec o pe oxide c osslinking on he syne gis ic c osslink o double bond and ni ile g oup o ni ile ubbe in H2S en i onmen . Polym. Tes . 2019,76, 298–304. [C ossRe ] 16. Wang, J.; Pan, S.; Zhang, Y.; Guo, S. C osslink ne wo k e olu ion o BIIR/EPDM blends du ing pe oxide ulcaniza ion. Polym. Tes . 2017,59, 253–261. [C ossRe ] 17. Zedle , L.; Colom, X.; Cana a e, J.; Reza Saeb, M.; Haponiuk, J.T.; Fo mela, K. In es iga ing he impac o cu ing sys em on s uc u e-p ope y ela ionship o na u al ubbe modi ied wi h b ewe y by-p oduc and g ound i e ubbe . Polyme s 2020,12, 545. [C ossRe ] [PubMed] 18. Zhao, X.; Co nish, K.; Vodo o z, Y. Syne gis ic mechanisms unde lie he pe oxide and coagen imp o emen o na u al- ubbe - oughened poly(3-hyd oxybu y a e-co-3-hyd oxy ale a e) mechanical pe o mance. Polyme s 2019,11, 565. [C ossRe ] [PubMed] 19. Laing, B.; De Keyze , J.; Se eno, D.; Van Bael, A. E ec o co-agen s on adhesion be ween pe oxide cu ed e hylene–p opylene– diene monome and he moplas ics in wo-componen injec ion molding. J. Appl. Polym. Sci. 2020,137, 48414. [C ossRe ] 20. Lee, Y.S.; Ha, K.R. E ec s o co-agen ype and con en on cu ing cha ac e is ics and mechanical p ope ies o HNBR composi e. Elas om. Compos. 2020,55, 95–102. 21. K uželák, J.; K asniˇcáko á, A.; Hložeko á, K.; Hudec, I. In luence o dicumyl pe oxide and Type I and II co-agen s on c oss-linking and physical-mechanical p op ies o ubbe compounds based on NBR. Plas . Rubbe Compos. 2020,49, 307–320. [C ossRe ] 22. S ohmeie , L.; Balasoo iya, W.; Sch i esse , B.; an Duin, M.; Schlögl, S. Hyb id in si u ein o cemen o EPDM ubbe compounds based on phenolic no olac esin and ionic coagen . Appl. Sci. 2022,12, 2432. [C ossRe ] 23. Rim, K.; Pa k, J. O ganic co-agen s o main aining mechanical p ope ies o ubbe elas ome s a high p ocessing empe a u es. Ko ean J. Chem. Eng. 2023,40, 2565–2571. [C ossRe ] Ma e ials 2024,17, 2718 25 o 25 24. K uželák, J.; Hakošo á, S.; K asniˇcáko á, A.; Hudec, I. Dicumyl pe oxide used as cu ing agen o di e en ypes o ubbe ma ices. Pa I: E ec o empe a u e. Kau sch. Gummi Kuns s . 2020,10, 36–42. 25. Nah, C.; Kim, S.G.; Shibulal, G.S.; Yoo, Y.H.; Mensah, B.; Jeong, B.H.; Hong, B.K.; Ahn, J.H. E ec s o cu ing sys ems on he mechanical and chemical ageing esis ance p ope ies o gaske compounds based on e hylene-p opylene-diene e monome ubbe in a simula ed uel cell en i onmen . In . J. Hyd ogen Ene gy 2015,40, 10627–10635. [C ossRe ] 26. K uželák, J.; K asniˇcáko á, A.; Hudec, I. Pe oxide cu ing sys ems applied o c oss-linking o ubbe compounds based on SBR. Ad . Ind. Eng. Polym. Res. 2020,3, 120–128. [C ossRe ] 27. Pie zak, D.; Bieli´nski, D.M.; Henneicke, D. S udies o con en ional sul u ulcaniza ion o SBR ubbe : Analysing he eac ion p oduc s om he mal deg ada ion o he accele a o by means o MCC-IMS echnique. Polym. Tes . 2020,90, 106715. [C ossRe ] 28. K aus, G. Swelling o ille - ein o ced ulcaniza es. J. Appl. Polym. Sci. 1963,7, 861–871. [C ossRe ] 29. Maciejewska, M.; Siwek, M. The in luence o cu ing sys ems on he cu e cha ac e is ics and physical p ope ies o s y ene– bu adiene elas ome . Ma e ials 2020,13, 5329. [C ossRe ] 30. K uželák, J.; Sýko a, R.; Hudec, I. Vulcaniza ion o ubbe compounds wi h pe oxide cu ing sys ems. Rubbe Chem. Technol. 2017, 90, 60–88. [C ossRe ] 31. Wang, H.; Ding, Y.; Zhao, S. E ec s o co-agen s on he p ope ies o pe oxide-cu ed e hylene-p opylene diene ubbe (EPDM). J. Mac omol. Sci. B 2016,55, 433–444. [C ossRe ] 32. Bha acha ya, A.B.; Gopalan, A.M.; Cha e jee, T.; Vennemann, N.; Naska , K. Explo ing he he momechanical p ope ies o pe oxide/co-agen assis ed he moplas ic ulcaniza es h ough empe a u e scanning s ess elaxa ion measu emen s. Polym. Eng. Sci. 2021,61, 2466–2476. [C ossRe ] 33. Li, C.; Yuan, Z.; Ye, L. Facile cons uc ion o enhanced mul iple in e acial in e ac ions in EPDM/zinc dime hac yla e (ZDMA) ubbe composi es: Highly ein o cing e ec and imp o emen mechanism o sealing esilience. Compos. Pa A Appl. Sci. 2019, 126, 105580. [C ossRe ] 34. K uželák, J.; Ka líko á, V.; Dosoudil, R.; Tomano á, K.; Hudec, I. Rein o cemen o ubbe magne ic composi es wi h zinc sal s o ac ylic and me hac ylic acids. Ma e ials 2018,11, 2161. [C ossRe ] [PubMed] Disclaime /Publishe ’s No e: The s a emen s, opinions and da a con ained in all publica ions a e solely hose o he indi idual au ho (s) and con ibu o (s) and no o MDPI and/o he edi o (s). 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