The influence of Titanium Dioxide (TiO2) particle size and crystalline form on the microstructure and UV protection factor of polyester substrates

Ci a ion: Co , M.; Mijas, G.; P ie o-Fuen es, R.; Riba-Moline , M.; Cayuela, D. The In luence o Ti anium Dioxide (TiO2) Pa icle Size and C ys alline Fo m on he Mic os uc u e and UV P o ec ion Fac o o Polyes e Subs a es. Polyme s 2024,16, 475. h ps:// doi.o g/10.3390/polym16040475 Academic Edi o : Ya osla O. Mezhue Recei ed: 17 Decembe 2023 Re ised: 19 Janua y 2024 Accep ed: 2 Feb ua y 2024 Published: 8 Feb ua y 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/). polyme s A icle The In luence o Ti anium Dioxide (TiO2) Pa icle Size and C ys alline Fo m on he Mic os uc u e and UV P o ec ion Fac o o Polyes e Subs a es Ma ía Co 1, Gab iela Mijas 1,2,3 , Remedios P ie o-Fuen es 1, Ma a Riba-Moline 1,2 and Diana Cayuela 1,2,* 1Te assa Ins i u e o Tex ile Resea ch and Indus ial Coope a ion (INTEXTER), Uni e si a Poli ècnica de Ca alunya (UPC), 08222 Te assa, Spain 2Depa men o Ma e ials Science and Enginee ing (CEM), Uni e si a Poli ècnica de Ca alunya (UPC), 08222 Te assa, Spain 3Fundación Asociación de Beca ios Re o nados EC (ABREC), Qui o 170518, Ecuado *Co espondence: [email p o ec ed] Abs ac : The inclusion o pa icles in a polyme ic subs a e o achie e ce ain p ope ies is a well- known p ac ice. In he case o ex ile subs a es, his p ac ice may deeply a ec he s uc u e o he p oduced ya ns, as e en a ilamen wi h no ex ile applica ions can be ob ained. In his manusc ip , i anium dioxide (TiO 2 ) pa icles we e inco po a ed in o polyes e (PET) chips and he in luence o hese ille s on he p ope ies o ya n and ab ic, and he ul a iole p o ec ion ac o (UPF) was assessed. Fo his pu pose, u ile and ana ase c ys alline o ms o TiO 2 , as well as he size o he pa icles, we e e alua ed. Mo eo e , pa ame e s such as mechanical p ope ies, o ien a ion o he mac omolecules and he mal beha io we e analyzed o ensu e ha he ex ile g ade is main ained h oughou he p oduc ion p ocess. The esul s showed ha he inclusion o mic o- and nanopa icles o TiO 2 dec eases he molecula weigh and enaci y o PET. Also, al hough o ien a ion and c ys allini y a ied du ing he ex ile p ocess, he esul ing hea se ab ics did no p esen impo an di e ences in hose pa ame e s. Finally, he a ainmen o ex ile-g ade PET-TiO 2 ab ics wi h UPF indexes o 50+ wi h bo h u ile and ana ase and mic o- and nano-sized TiO2 o ms was demons a ed. Keywo ds: ul a iole p o ec ion ac o (UPF); i anium dioxide (TiO 2 ); ana ase; u ile; polye hylene e eph hala e (PET); POY mul i ilamen ; di e en ial scanning calo ime e (DSC); c ys allini y; kni ed ab ic 1. In oduc ion In ecen yea s, he e has been a signi ican su ge in he applica ion o nano echnology wi hin he ex ile indus y, pa icula ly in he ealm o inco po a ing subs ances o enhance unc ionali y [ 1 ]. Fo example, sil e nanopa icles ha e been used o p o ide an ibac e ial p ope ies [ 2 ], i anium dioxide (TiO 2 ) o block UV ays [ 3 ], and zinc oxide (ZnO) o sel -cleaning [ 4 ]. The con en ional me hods used o apply hese subs ances ha e been su ace ea men s, which p o ide ab ics wi h di e en p ope ies in a sa is ac o y mode bu , occasionally, hey do no ha e pe manen e ec s, and he subs a es lose hei unc ion a e washing o a ce ain usage ime. In mos cases, nanopa icles ha e been added as a inishing p ocess in he ex ile chain, al hough a emp s ha e been made o inco po a e hem in ea lie s ages, such as spinning, using he wis ing o ibe s in he ya n o e ain he nanopa icles inside. Va ious publica ions ha e discussed he applica ion o nanopa icles by deposi ing hem on he su ace o ibe s o modi y some o hei p ope ies [ 5 – 9 ]. The inclusion o ille s du ing he p oduc ion o polye hylene e eph hala e (PET) ya n by a mel spinning p ocess imp o es he quali y o he composi e, wi h he possibili y o p o iding mo e pe manen mul i unc ional p ope ies o ex ile ma e ials. The size o hose pa icles is a c ucial pa ame e ha de e mines he inal p ope ies o he sys em. As he size o Polyme s 2024,16, 475. h ps://doi.o g/10.3390/polym16040475 h ps://www.mdpi.com/jou nal/polyme s Polyme s 2024,16, 475 2 o 13 he pa icles dec eases, he e is a g ea e endency o agglome a ion and, simul aneously, an inc ease in speci ic su ace a ea, leading o he modynamic ins abili y [ 10 ]. To achie e uni o m dispe sions and a oid agg ega ion, i is essen ial o egula e hese pa ame e s when inco po a ing pa icles in o a polyme ic ma ix. The use o dispe sing agen s is c ucial in ensu ing homogenei y h oughou he p ocess [11,12]. Mos o he applica ions discussed in he li e a u e ocus on he u iliza ion o ce amic nanopa icles in polyme ic ma ices, ypically in he o m o ilms o subs a es p oduced h ough injec ion o molding p ocesses. The p oduc ion o ilamen -shaped composi es, which exhibi unique s uc u es and p ope ies, is limi ed [ 4 , 13 – 15 ]. Ne e heless, he p og ess in unc ional ibe de elopmen plays a pi o al ole in he ad ancemen o ex iles o echnical applica ions. Ti anium dioxide (TiO 2 ) is an ino ganic, non- oxic compound, chemically s able agains exposu e o bo h ele a ed empe a u es and UV ays, abundan , and ela i ely cheap [ 16 , 17 ]. Addi ionally, TiO 2 can be ob ained in a ious c ys alline o ms, such as u ile, ana ase and b ooki e, wi h he i s wo being he mos widely used a he indus ial le el. Mo eo e , he ca aly ic ac i i y o TiO 2 is g ea ly enhanced when he pa icle size is lowe han 20 nm. Un o una ely, ew syn hesis echniques allow o he p oduc ion o such small sizes (mainly pa icles < 10 nm) in a ep oducible way, limi ing he ange o he pa icles cu en ly s udied [17,18]. P e ious s udies ha e p ima ily ocused on explo ing he dispe sion, he mal p ope ies, mechanical p ope ies, ul a iole p o ec ion, an ibac e ial p ope ies, and o he ele an ac o s associa ed wi h he inclusion o TiO 2 pa icles du ing he mel spinning o PET [13–15] . Howe e , i is impo an o e alua e he in luence o pa icle size and polymo phism on he a o emen ioned p ope ies. On an indus ial scale, he esul s o his s udy a e ele an because TiO2is used as a ma ing agen in he syn hesis o plas ics and ex ile ibe s [16]. In his s udy, TiO 2 was applied o ex ile ibe s o p oduce PET ab ics ha block UV ays, hus ob aining adia ion-p o ec i e ex iles ac oss a wide ange o wa eleng hs. Fo his, TiO 2 was inco po a ed du ing PET spinning and he c ys alline o ms o u ile and ana ase we e conside ed o s udy he e ec o polymo phism, ollowed by he e alua ion o size e ec using mic o- and nano-sized pa icles. The mechanical p ope ies, o ien a ion, c ys allini y, and he mal beha io o he ya ns p oduced we e e alua ed. Finally, kni ed ab ics we e p oduced and he UPF and UPF index we e analyzed. 2. Expe imen al Sec ion 2.1. Ma e ials Ti anium dioxide (TiO 2 ) pa icles, la e inco po a ed in he spinning o POY PET ya ns, we e u ile and ana ase c ys alline o ms in mic o- and nanome ic sizes supplied by Zeus Química, S.A. (Ba celona, Spain). The cha ac e is ics o he pa icles, as p o ided by he manu ac u e s [ 19 – 22 ], a e shown in Table 1and TEM images a e a ailable in a p e ious wo k [23]. Table 1. Cha ac e is ics o TiO2pa icles. RN RM AN AM Comme cial e e ence MT-500HD Tayca Co po a ion KRONOS 2360 AMT-600 Tayca Co po a ion KRONOS 1071 Pa icle size (nm) 30 190 30 220 C ys alline o m Ru ile Ru ile Ana ase Ana ase Speci ic su ace a ea (m 2 /g) 48 13–17 52 9–11 Composi ion (%) TiO2: 85 Al2O3: 1–15 Z O2: 1–10 TiO2≥92 Al2O3: 3–3.8 SiO2: 2.4–3 C: 0.18–0.2 TiO2: 80–98 TiO2≥96 Al2O3: 1–1.2 SiO2: 0.5–0.7 P2O5: 0.3–0.4 C: 0.15–0.25 Polyme s 2024,16, 475 3 o 13 The dispe sing agen used was LICOWAX E (Cla ian )( (San Joan Despí, Spain), an es e o mon anic acids wi h mul i unc ional alcohols (MAWMA), which was ound o be sui able o dispe sing TiO2pa icles in a PET ma ix in a p e ious wo k (Table 2) [24,25]. Table 2. Cha ac e is ics o MAWMA dispe sing agen . Cha ac e is ics Value Appea ance Pale yellow pelle s Acid Index (mg KOH/g) 15–20 Saponi ica ion index (mg KOH/g) 140–160 Viscosi y (mPa·s) ~20 Densi y (23 ◦C) (g/cm3)~1.02 Pa ially o ien ed ya ns (POY) o PET mul i ilamen (48 ilamen s) con aining TiO 2 pa icles we e manu ac u ed by IQAP Mas e ba ch G oup S.L. (Masies de Roda, Spain) by mel spinning using an ex usion empe a u e o 295 ◦ C, a p essu e o 80 ba , and a winde collec ion speed o 3000 m/min. The composi ion o hese POY including TiO 2 pa icles is p esen ed in Table 3. In a p e ious s udy, a discon inui y in he ex usion ou low o some mix u es wi h concen a ions o 3% TiO 2 was ound o be caused by a dec ease in iscosi y, which p e en ed he spinning o he ya ns. Consequen ly, he p epa a ion o he ya ns had a maximum concen a ion limi o 2% TiO 2 [ 26 ]. I should be no ed ha he concen a ion o TiO 2 nanopa icles in he ya n con aining RN pa icles is lowe compa ed o ha o he o he ya ns. This is due o he ac ha hese pa icles caused a dec ease in he iscosi y o he PET ma ix. Consequen ly, he quan i y o nanopa icles had o be sligh ly educed in o de o main ain he app op ia e low o polyme and ensu e he con inui y equi ed o ya n p oduc ion. Table 3. P ope ies o manu ac u ed POY PET ya ns. Sample TiO2(%) Dispe sing Agen (%) Linea Densi y o Non-D awn Ya n ( ex) Linea Densi y o D awn Ya n ( ex) RN 1.8 1.8 26.9 17.6 RM 2 2 23.7 14.1 AN 2 2 27.4 18.3 AM 2 2 27.7 17.0 PET -- -- 28.9 15.8 2.2. T ea men s A e spinning, he ya ns we e d awn wi h a s e ch a io o 1:2 a 190 ◦ C. This pos -spinning s e ching was applied o o ien a e he ilamen s in he di ec ion o he ibe axis and o gi e a p ope c ys allini y, making he ya ns sui able o use as ex ile ibe s. A e wa ds, plain kni ed ab ics we e p oduced using a ci cula kni ing machine (90 mm and 167 needles). The a e aged cha ac e is ics o he p oduced ab ics we e as ollows: s i ch leng h 3.23 mm/s i ch; hickness 2.24 ± 0.011 mm, 16.1 ± 1.0 cou ses/cm, 10.8 ±0.58 wales/cm, and 0.89 ±0.01 g/m2. Finally, he ab ics we e hea se o he mally s abilize he subs a e. The p ocess was pe o med in a s en e E ns Benz AG (Zü ich, Swi ze land). The hea se ing condi ions we e a empe a u e o 190 ◦C o 1 min wi hou ension. Polyme s 2024,16, 475 4 o 13 2.3. Cha ac e iza ion Scanning Elec on Mic oscopy (SEM) Mic og aphs o he ya ns we e ob ained wi h aPhenomWo ld (Eindho en, The Ne he lands ) 800-03103-02 scanning elec on mic oscope. Samples we e p e iously Au/Pd coa ed. Molecula weigh de e mina ion The de e mina ion o he molecula weigh was pe o med by gel pe mea ion ch o- ma og aphy (GPC) on a Pe kin Elme (No walk, CN, USA) 200 High Pe o mance Liquid Ch oma og aph equipped wi h an Agilen PLgel 5 µ m Mixed-D column 300 × 7.5 mm p eceded by an Agilen (S ockpo , UK) Oligopo e column 6 µ m 300 × 7.5 mm. The sys em was calib a ed wi h Wa e s (Mil o d, CN, USA) polys y ene s anda ds, wi h an a e age molecula weigh in he ange o 2350–200,000 g/mol. Then, 3 mg o washed ya n we e placed in a es ube wi h 0.2 mL o o-chlo ophenol (>99%, Sigma-Ald ich, S einheim, Ge many). A e dissol ing he ya n and cooling he ubes, 1.8 mL o chlo o o m (HPLC g ade, s abilized wi h amylene, app ox. 150 ppm, Scha lau, Ba celona, Spain) was added and he mix u e was s i ed. The esul ing solu ion was hen il e ed (PTFE il e , 0.45 µ m) and ans e ed o a ial. Analyses we e conduc ed a 40 ◦ C wi h chlo o o m (HPLC g ade, Scha lau, Ba celona, Spain) as he mobile phase a a low a e o 1 mL/min. The To alCh om Na iga o –Tu boSEC . 6.3.1.0504 so wa e (Pe kin Elme , No walk, CN, USA) was used o calcula e he molecula weigh in numbe , he molecula weigh in weigh , and polydispe si y. Ya ns and ab ic pa ame e s P e ious o cha ac e iza ion, he samples we e condi ioned o 48 h a 20 ± 2 ◦ C and ela i e humidi y 65 ±4% acco ding o he ISO 139:2005 s anda d [27]. The linea densi y o he ya ns was de e mined acco ding o he ISO 2060:1996 s an- da d [ 28 ], he su ace mass was ob ained acco ding o he UNE-EN 12127:1998 s anda d [ 29 ], and he hickness was calcula ed acco ding o he ISO 5084:1997 s anda d [ 30 ] using a p essu e o 100 g/cm 2 in an Adamel Lhoma gy C euso -Loi e (Le C euso , F ance) com- p ession me e . Dynamome ic es s we e ca ied ou in a Us e (Us e , Swi ze land) TensoKid au o- ma ic PE 4056 equipmen , ollowing he ISO 2062:2010 s anda d [ 31 ] wi h a gauge leng h o 250 mm, a es speed o 250 mm/min, p e ension o 0.5 CN/ ex, a b eaking s eng h o 80%, and 50 samples pe ya n. De e mina ion o he o ien a ion o he molecules (sonic modulus) Sonic modulus de e mines he molecula o ien a ion along he ibe axis. By measu ing he speed o sound a eling longi udinally h ough he ibe , and, la e , by calcula ing he sound modulus be o e and a e d awing he ya ns, he inc ease in molecula o ien a ion along he ibe axis was de e mined [ 32 ]. A HM Mo gan Co., Inc. (Camb idge, MA, USA) Dynamic Modulus Tes e PPM–5R was used o ha pu pose. Di e en ial Scanning Calo ime y (DSC) The DSC echnique was employed o de e mine he c ys allini y o he samples. A Pe kin Elme (No walk, CN, USA) DSC7/TAC7 calo ime e was used, and he condi ions o he expe imen we e as ollows: holding a 40 ◦ C o 5 min, i s hea ing om 40 ◦ C o 300 ◦ C a 20 ◦ C/min, holding a 300 ◦ C o 5 min, and cooling om 300 ◦ C o 40 ◦ C a 20 ◦C/min. Ni ogen (2 kg/cm2) was used as he pu ge gas. In he DSC s eps, he i s hea ing was used o e alua e he mic os uc u e o he non-d awn and d awn ya ns and o he hea se ab ics, and o de e mine he c ys allini y om he mel ing en halpies o he samples. This i s hea ing was also used o elimina e he he mal his o y o he polyme and, so, he s udy o he c ys alliza ion p ocess, which solely depended on he blend and no he s uc u e, was conduc ed by ob aining cooling he mog ams in all ins ances. To calcula e he o al mel ing en halpies ( ∆HT) and a oid baseline e o s, he me hodology de ailed by Cayuela e al. [ 33 ] was applied. A pu e PET Polyme s 2024,16, 475 5 o 13 he mog am was sub ac ed om he he mog am ob ained om each o he samples con- aining pa icles and he esul ing he mog am was analyzed. Subsequen ly, he calcula ed en halpy was added o he en halpy o he pu e polyes e subs a e in o de o ob ain he o al mel ing en halpy ( ∆HT ). Fu he mo e, he c ys allini y o ya ns was calcula ed ollowing Equa ion (1). α(%) = ∆HT 117.6·100 (1) whe e 117.6 J/g is he en halpy o a pe ec polyes e c ys al. In all cases, he pe cen age o polyes e in each blend was conside ed. UPF de e mina ion The UPF (UV p o ec ion ac o ) o he ab ics was measu ed on a Labsphe e (No h Su on, NH, USA) UV T ansmi ance Analyze (UPF) and e alua ed wi h he speci ic p og am o UV-1000F ab ics, acco ding o he AS/NZS 4399:1996 s anda d [ 34 ]. The spec al ange o he ins umen was se om 250 o 450 nm wi h a 10 mm iewing beam diame e . The e e ence o he sola spec um used was he spec al i adiance acco ding o CIE No. 85 measu ed in Albuque que a noon on 3 July. 3. Resul s and Discussion Ini ially, mic og aphs o he d awn ya ns we e cap u ed o de e mine whe he any a ia ions could be iden i ied among he samples (Figu e 1). Polyme s 2024, 16, x FOR PEER REVIEW 5 o 13 calcula ed en halpy was added o he en halpy o he pu e polyes e subs a e in o de o ob ain he o al mel ing en halpy (∆𝐻). Fu he mo e, he c ys allini y o ya ns was calcu- la ed ollowing Equa ion (1). 𝛼 (%) = ∆𝐻 117.6 · 100 (1) whe e 117.6 J/g is he en halpy o a pe ec polyes e c ys al. In all cases, he pe cen age o polyes e in each blend was conside ed. UPF de e mina ion The UPF (UV p o ec ion ac o ) o he ab ics was measu ed on a Labsphe e (No h Su on, NH, USA) UV T ansmi ance Analyze (UPF) and e alua ed wi h he speci ic p o- g am o UV-1000F ab ics, acco ding o he AS/NZS 4399:1996 s anda d [34]. The spec al ange o he ins umen was se om 250 o 450 nm wi h a 10 mm iewing beam diame e . The e e ence o he sola spec um used was he spec al i adiance acco ding o CIE No. 85 measu ed in Albuque que a noon on July 3. 3. Resul s and Discussion Ini ially, mic og aphs o he d awn ya ns we e cap u ed o de e mine whe he any a ia ions could be iden i ied among he samples (Figu e 1). Figu e 1. SEM images o (a) PET, (b) PET-RN, (c) PET-RM, (d) PET-AN, and (e) PET-AM. No no iceable a ia ions we e obse ed be ween he plain polyes e and he polyes e con aining TiO2 pa icles. This sugges s ha he pa icles we e e enly dis ibu ed wi hin he ibe , indica ing he effec i e ole o he MAWMA dispe sing agen . Con e sely, he a e age molecula weigh in numbe (𝑀     ), in weigh ( 𝑀     ), and he polydispe si y (𝑀     /𝑀     ) o he ya ns we e measu ed o assess any changes in he polyme ic subs a e (Table 4). Table 4. Values o 𝑴𝒏     , 𝑴𝒘      and polydispe si y o he ya ns. Sample 𝑴𝒏     (kg/mol) 𝑴𝒘      (kg/mol) Polydispe si y (𝑴𝒘      /𝑴𝒏     ) PET-RN 21.0 42.9 2.0 PET-RM 23.0 45.1 2.0 Figu e 1. SEM images o (a) PET, (b) PET-RN, (c) PET-RM, (d) PET-AN, and (e) PET-AM. No no iceable a ia ions we e obse ed be ween he plain polyes e and he polyes e con aining TiO 2 pa icles. This sugges s ha he pa icles we e e enly dis ibu ed wi hin he ibe , indica ing he e ec i e ole o he MAWMA dispe sing agen . Con e sely, he a e age molecula weigh in numbe ( Mn , in weigh ( Mw ), and he polydispe si y ( Mw / Mn ) o he ya ns we e measu ed o assess any changes in he polyme ic subs a e (Table 4). The esul s showed ha he inco po a ion o ce amic pa icles caused a dec ease in he molecula weigh o he subs a e. Fo he same manu ac u ing p ocess, PET nanocom- posi es show a educ ion in hei in insic iscosi y and, consequen ly, in hei molecula weigh compa ed o he pu e polyme , which means ha hese ma e ials a e mo e sensi i e o deg ada ion as a esul o hea ing, high shea a es and esidence imes du ing he ex usion p ocess [ 35 , 36 ]. Compa ing he TiO 2 -con aining ya ns, PET-RM, PET-AM and Polyme s 2024,16, 475 6 o 13 PET-AN exhibi ed e y simila Mn alues. In con as , he PET-RN sample had he lowes alues o Mn and Mw . Du ing he p oduc ion o he composi es, a dec ease in iscosi y was obse ed, leading o a necessa y dec ease in he concen a ion o u ile- ype nanopa icles in he mix u e. The polydispe si y alues o all samples we e ound o be 2.0, which is in acco dance wi h he in o ma ion a ailable in he bibliog aphy [35,37]. Table 4. Values o Mn,Mwand polydispe si y o he ya ns. Sample Mn (kg/mol) Mw (kg/mol) Polydispe si y (Mw/Mn) PET-RN 21.0 42.9 2.0 PET-RM 23.0 45.1 2.0 PET-AN 23.3 46.7 2.0 PET-AM 23.2 44.4 2.0 PET 27.6 51.5 2.0 The he mal beha io o he samples was assessed using he Di e en ial Scanning Calo ime y (DSC) echnique. This analysis is c ucial in es ablishing he e ec i e empe - a u e ange o p ocessing pu poses. By examining he he mog ams ob ained om all samples, he empe a u e o c ys alliza ion (T c ) and he en halpy o c ys alliza ion ( ∆ H c ) we e de e mined using he me hodology de eloped by Cayuela e al. [33] (Table 5). Table 5. Tempe a u e and en halpy o c ys alliza ion om mel ing o mix u es. Sample Tc (◦C) ∆Hc (J/g) PET-RN 202.8 −52.4 ±0.2 PET-RM 205.3 −52.7 ±1.2 PET-AN 206.3 −52.9 ±0.4 PET-AM 206.3 −54.7 ±0.4 PET 200.3 −48.4 ±0.3 Many impo an p ope ies o polyes e s depend on he nuclea ion p ocess, in which he p ima y nuclei o he c ys al a e o med. This phenomenon can be homogeneous i he molecula mo emen s o he polyme in he mol en s a e cause he alignmen o a su icien numbe o segmen s o he chain o ollow a mo e s able o m; o he e ogeneous i he nuclei a e o med om he simple con ac o he subs ance wi h he con aine o om insoluble mic oscopic pa icles andomly dis ibu ed in he ma e ial [ 38 ]. In he p esen case, TiO 2 pa icles ac ed as he e ogeneous c ys alliza ion nuclei, shi ing he c ys alliza ion empe a u e owa ds highe alues. In his con ex , he ana ase o m showed a highe c ys alliza ion empe a u e, which mean a g ea e nuclea ion powe compa ed o he u ile o m. Conc e ely, PET-AM was he sample wi h he highes alue, wi h a c ys alliza ion empe a u e o 206.3 ◦C and a c ys alliza ion en halpy o −54.7 ±0.4 J/g. The mechanical p ope ies equi ed o a ibe o ha e ex ile quali ies a e achie ed h ough he d awing p ocess. Hence, dynamome ic es s we e conduc ed on he ya ns be o e and a e his p ocess (Table 6). In all ins ances, a educ ion in he alues o lineal densi y was obse ed a e he d awing p ocess. Ne e heless, no co ela ion could be es ablished among he size, he polymo phism o he pa icles and he men ioned pa ame e , p obably due o he e ec o he dispe sing agen , which p o ides a plas icizing e ec o he mac omolecula chains. In gene al, he enaci y and elonga ion sligh ly dec eased a e he inco po a ion o pa icles. A mo e comp ehensi e unde s anding o hese changes was ob ained by examining he s ess–s ain cu es (Figu e 2). Polyme s 2024,16, 475 7 o 13 Table 6. Lineal densi y and enaci y alues o non-d awn and d awn ya ns. Sample Lineal Densi y ( ex) Tenaci y (cN/d ex) Elonga ion (%) Non-D awn D awn Non-D awn D awn Non-D awn D awn PET-RN 26.9 17.6 1.14 ±0.12 1.4 ±0.2 150.9 ±9.2 20.6 ±3.9 PET-RM 23.7 14.1 1.25 ±0.11 2.8 ±0.2 140.1 ±7.2 17.5 ±2.4 PET-AN 27.4 18.3 1.32 ±0.12 1.8 ±0.3 148.7 ±6.1 27.2 ±4.7 PET-AM 27.7 17.0 1.18 ±0.10 2.6 ±0.2 140.3 ±6.2 21.5 ±2.1 PET 28.9 15.8 1.73 ±0.11 3.5 ±0.1 149.5 ±8.2 27.6 ±2.3 Polyme s 2024, 16, x FOR PEER REVIEW 7 o 13 PET 28.9 15.8 1.73 ± 0.11 3.5 ± 0.1 149.5 ± 8.2 27.6 ± 2.3 In all ins ances, a educ ion in he alues o lineal densi y was obse ed a e he d awing p ocess. Ne e heless, no co ela ion could be es ablished among he size, he polymo phism o he pa icles and he men ioned pa ame e , p obably due o he effec o he dispe sing agen , which p o ides a plas icizing effec o he mac omolecula chains. In gene al, he enaci y and elonga ion sligh ly dec eased a e he inco po a ion o pa i- cles. A mo e comp ehensi e unde s anding o hese changes was ob ained by examining he s ess–s ain cu es (Figu e 2). Figu e 2. S ess–s ain cu es o (a) non-d awn and (b) d awn ya ns. When compa ed o he es , he ya n wi hou pa icles exhibi ed a highe modulus and g ea e ensile s eng h. The inclusion o he pa icles dec eased he esis ance o he ya n, al hough he elonga ion was almos he same. Fu he mo e, i was obse ed ha ya ns wi h ana ase TiO2 had be e esis ance p ope ies han ya ns wi h u ile pa icles. The ya ns subjec ed o he d awing p ocess dec eased in esis ance wi h espec o he non-d awn ya ns. The dec ease in magni ude was mo e signi ican when nano-sized pa - icles we e p esen a he han mic o-sized pa icles ega dless o he c ys alline o m. In addi ion, he p esence o nanopa icles esul ed in a highe elonga ion a b eak. This can be a ibu ed o he smalle sizes o hese pa icles, which caused a educed obs acle effec compa ed o he mic opa icles. In gene al, he enaci y o he ya ns wi h pa icles was ound o be lowe compa ed o he enaci y o pu e PET ya n. P e ious in es iga ions ha e indica ed ha when he quan i y o ce amic pa icles, speci ically TiO2, in Nylon ya ns exceeds 0.33%, he e is a dec ease in he ensile s eng h. This educ ion can be a ibu ed o he p esence o high pa icle concen a ions, in his case anging om 1.8 w .% o 2 w .%, which could lead o in e ac ions and agglome a ions. Consequen ly, he con ac su ace be ween he pa icles and he ma ix is educed. Fu he mo e, hese pa icles can also se e as si es o s ess concen a ion. As a esul , when he ma e ial is subjec ed o ensile de o ma ion, he la ge pa icles induce highe s ess concen a ions in he ma ix, leading o a dec ease in impac ene gy. This ul ima ely causes he ma e ial o b eak ea lie han expec ed [39–41]. The enaci y alues o he ya ns wi h mic opa icles we e highe han hose o ya ns wi h nanopa icles, wi h hese diffe ences being mo e e iden a e d awing. This inding was co ela ed wi h he p e iously obse ed dec ease in molecula weigh alues in he p esence o pa icles. Despi e he dec ease in he mechanical p ope ies, he enaci y al- ues we e s ill sui able o ex ile applica ions. The ya ns con aining mic opa icles exhibi ed g ea e enaci y alues in compa ison o he ya ns con aining nanopa icles. The dispa i ies be ween hese wo ypes o ya ns became mo e appa en a e unde going he d awing p ocess. This ou come can be Figu e 2. S ess–s ain cu es o (a) non-d awn and (b) d awn ya ns. When compa ed o he es , he ya n wi hou pa icles exhibi ed a highe modulus and g ea e ensile s eng h. The inclusion o he pa icles dec eased he esis ance o he ya n, al hough he elonga ion was almos he same. Fu he mo e, i was obse ed ha ya ns wi h ana ase TiO 2 had be e esis ance p ope ies han ya ns wi h u ile pa icles. The ya ns subjec ed o he d awing p ocess dec eased in esis ance wi h espec o he non-d awn ya ns. The dec ease in magni ude was mo e signi ican when nano-sized pa icles we e p esen a he han mic o-sized pa icles ega dless o he c ys alline o m. In addi ion, he p esence o nanopa icles esul ed in a highe elonga ion a b eak. This can be a ibu ed o he smalle sizes o hese pa icles, which caused a educed obs acle e ec compa ed o he mic opa icles. In gene al, he enaci y o he ya ns wi h pa icles was ound o be lowe compa ed o he enaci y o pu e PET ya n. P e ious in es iga ions ha e indica ed ha when he quan i y o ce amic pa icles, speci ically TiO 2 , in Nylon ya ns exceeds 0.33%, he e is a dec ease in he ensile s eng h. This educ ion can be a ibu ed o he p esence o high pa icle concen a ions, in his case anging om 1.8 w .% o 2 w .%, which could lead o in e ac ions and agglome a ions. Consequen ly, he con ac su ace be ween he pa icles and he ma ix is educed. Fu he mo e, hese pa icles can also se e as si es o s ess concen a ion. As a esul , when he ma e ial is subjec ed o ensile de o ma ion, he la ge pa icles induce highe s ess concen a ions in he ma ix, leading o a dec ease in impac ene gy. This ul ima ely causes he ma e ial o b eak ea lie han expec ed [39–41]. The enaci y alues o he ya ns wi h mic opa icles we e highe han hose o ya ns wi h nanopa icles, wi h hese di e ences being mo e e iden a e d awing. This inding was co ela ed wi h he p e iously obse ed dec ease in molecula weigh alues in he p esence o pa icles. Despi e he dec ease in he mechanical p ope ies, he enaci y alues we e s ill sui able o ex ile applica ions. The ya ns con aining mic opa icles exhibi ed g ea e enaci y alues in compa ison o he ya ns con aining nanopa icles. The dispa i ies be ween hese wo ypes o ya ns be- Polyme s 2024,16, 475 8 o 13 came mo e appa en a e unde going he d awing p ocess. This ou come can be a ibu ed o he dec ease in molecula weigh alues ha we e p e iously obse ed when pa icles we e p esen . Despi e he decline in mechanical p ope ies, he enaci y alues emained sui able o use in ex ile applica ions. The sonic module echnique enables he de e mina ion o he speed a which sound o a pulse passes longi udinally h ough a ibe . This is use ul o de e mine he o ien a ion o molecules since a highe speed co esponds o a g ea e o ien a ion and alue o he sonic module (Table 7). Table 7. Sonic modulus and c ys allini y o s udied ya ns. Sample Sonic Modulus C ys allini y (%) Non-D awn D awn Non-D awn D awn Hea se Fab ic PET-RN 28.4 ±0.2 86.2 ±0.5 6.5 50.9 52.0 PET-RM 27.4 ±1.5 106.6 ±6.7 6.0 47.4 51.0 PET-AN 28.0 ±2.0 91.0 ±4.6 7.7 51.0 52.0 PET-AM 28.1 ±0.8 106.7 ±7.2 11.7 49.7 54.9 PET 26.1 ±0.7 106.2 ±6.1 8.0 47.1 53.5 The esul s indica ed ha ega dless o he p esence and ype o pa icles, he non- d awn ya ns exhibi ed simila o ien a ion alues. Ne e heless, he d awn ya ns demon- s a ed wo dis inc beha io s: he o iginal PET and he mic opa icle-con aining ya ns displayed simila o ien a ion alues, which we e highe han hose o he nano-sized coun e pa s. These indings can be linked o he alues ob ained om he dynamome ic assay, pa icula ly he g ea e elonga ion esponse obse ed in ya ns con aining nano- sized pa icles. The nanome ic size o he pa icles po en ially led o a highe deg ee o in e locking wi hin he polyme ic ma ix, consequen ly hinde ing he o ien a ion o molecules o a g ea e ex en . Mo eo e , his esul was consis en wi h he obse ed enaci y, indica ing ha ya ns wi h mic opa icles exhibi ed highe enaci y compa ed o ya ns wi h nanopa icles. Rega ding he c ys allini y o non-d awn ya ns (Table 7), no ably, all he subs a es ex- amined showed no signi ican a ia ions, excep o he PET-AM sample, which displayed a highe le el o c ys allini y. I is wo h no ing ha he mog ams o und awn ibe s gene - ally exhibi ed dis inc he mal ansi ions. The i s ansi ion is cha ac e ized by a change in hea lux (hea capaci y, c p ) co esponding o he glass ansi ion (Tg) egion. This egion is associa ed wi h he empe a u e a which he mobili y o he polyme mac omolecules begins in he amo phous zone o he ibe . This ansi ion co esponds o he amo phous ac ion in a iphasic model o he ibe . Subsequen ly, an exo he mic peak is obse ed, indica ing cold c ys alliza ion. This peak is ela ed o he mesophase o he model, which ep esen s he ac ion o mac omolecules ha a e o de ed. By applying ene gy in he o m o empe a u e, hese mac omolecules can c ys allize due o hei mo emen caused by he mal agi a ion. Finally, he mel ing endo he m obse ed in he non-d awn polyes e he mog ams indica es he mel ing o bo h he o iginal c ys alli es and hose o med du ing he cold c ys alliza ion ansi ion. The he mog ams o he d awn samples did no display any dis inc egions co e- sponding o he glass ansi ion empe a u e (Tg) o cold c ys alliza ion (Figu e 3). The p ocess o d awing he ibe leads o he alignmen o mac omolecules along he ibe axis, he eby inducing a c ys alliza ion p ocess. As a esul , he in ensi y o he mal ansi- ions associa ed wi h he amo phous po ion o he polyme dec eases. Addi ionally, his alignmen o mac omolecules in an ex ended s a e may acili a e he app oxima ion o in e - mac omolecula chains and he o ma ion o bonds be ween g oups. Consequen ly, he d awn ya ns exhibi signi ican ly highe c ys allini y ( i e o eigh imes highe , depending Polyme s 2024,16, 475 9 o 13 on he case) compa ed o hei p ecu so s, in acco dance wi h he inc eased o ien a ion indica ed by he sonic modulus esul s. Polyme s 2024, 16, x. h ps://doi.o g/10.3390/xxxxx www.mdpi.com/jou nal/polyme s Figu e 3. The mog ams co esponding o (le ) he mal ansi ions o und awn ibe s and ( igh ) d awn ibe s. Once he p oduc ion p ocess was comple ed, he kni ed ab ics unde wen hea se (Figu e 4). The e alua ion o he impac o hea se ing on c ys allini y (Table 7) indica ed no signi ican a ia ions among he di e en samples. This sugges s ha he he mome- chanical ea men s applied o he ibe s, such as sh inkage and hea se ing, in o de o con e ex ile p ope ies o he TiO 2 -con aining ya ns, esul ed in a inal p oduc wi h equi alen ex ile p ope ies. Consequen ly, he inclusion o TiO 2 pa icles du ing he spinning p ocess al e ed he mic os uc u e o he ini ial ya ns, bu hese di e ences we e elimina ed du ing subsequen p oduc ion p ocesses, leading o he a ainmen o ab ics wi h compa able s uc u es ha can be dyed and inished unde s anda d condi ions o con en ional polyes e . Polyme s 2024, 16, x FOR PEER REVIEW 9 o 13 Figu e 3. The mog ams co esponding o (le ) he mal ansi ions o und awn ibe s and ( igh ) d awn ibe s. Once he p oduc ion p ocess was comple ed, he kni ed ab ics unde wen hea se (Figu e 4). The e alua ion o he impac o hea se ing on c ys allini y (Table 7) indica ed no signi ican a ia ions among he diffe en samples. This sugges s ha he he mome- chanical ea men s applied o he ibe s, such as sh inkage and hea se ing, in o de o con e ex ile p ope ies o he TiO2-con aining ya ns, esul ed in a inal p oduc wi h equi alen ex ile p ope ies. Consequen ly, he inclusion o TiO2 pa icles du ing he spinning p ocess al e ed he mic os uc u e o he ini ial ya ns, bu hese diffe ences we e elimina ed du ing subsequen p oduc ion p ocesses, leading o he a ainmen o ab ics wi h compa able s uc u es ha can be dyed and inished unde s anda d condi ions o con en ional polyes e . Figu e 4. Kni ed ab ics a he en ance o he s en e . The UPF and UPF index o kni ed ab ic we e de e mined, and he co esponding esul s a e p esen ed in Table 8. Table 8. UPF alues o he hea se ab ics. Fab ic UPF UPF Index PET-RN 108 50+ PET-RM 165 50+ PET-AN 66 50+ PET-AM 105 50+ PET 33 30 All ab ics wi h pa icles exhibi ed a signi ican imp o emen in he UPF alue com- pa ed o he alue o pu e PET ab ic. I was ound ha he ab ic wi h PET-RM had he highes UPF alue, sugges ing ha he u ile o m had a g ea e p o ec i e effec han he Figu e 4. Kni ed ab ics a he en ance o he s en e . The UPF and UPF index o kni ed ab ic we e de e mined, and he co esponding esul s a e p esen ed in Table 8. Table 8. UPF alues o he hea se ab ics. Fab ic UPF UPF Index PET-RN 108 50+ PET-RM 165 50+ PET-AN 66 50+ PET-AM 105 50+ PET 33 30