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 .
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