Novel Thermoplastic Vulcanizates Prepared by Dynamic Vulcanization: Undergraduate Experiments for Polymers

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1 Americn Journl of Polymer Science 2018, 8(1): 1- DOI: /j.jps Novel Thermoplstic Vulcniztes Prepred y Dynmic Vulcniztion: Undergrdute Experiments for Polymers Zhoo Wng *, Boxing Wng, Zhiyn Guo, Tong Liu, Ylong Sho, Fnglin Du College of Mterils Science & Engineering, Qingdo University of Science & Technology, Qingdo, Chin Astrct Novel thermoplstic vulcniztes (TPVs) sed on high impct polystyrene (HIPS)/high vinyl polyutdiene ruer (HVPBR) lends were prepred y dynmic vulcniztion where styrene-utdiene-styrene (SBS) lock copolymer ws used s comptiilizer. The effect of SBS dosge on the mechnicl properties of the TPVs ws investigted. Compred with those of HIPS/HVPBR lends, the tensile strength, elongtion t rek nd tering strength of HIPS/HVPBR lend with 12 phr SBS incorportion were improved remrkly. The morphologicl evolution during the dynmic vulcniztion ws oserved y field-emission scnning electron microscopy (FE-SEM). Energy dispersive X-ry micronlysis system (EDX) ws used to confirm tht the protruding prticles in the etched TPV surfce were the vulcnized HVPBR prticles. Keywords Thermoplstic vulcnizte, Dynmic vulcniztion, Morphologicl evolution, Comptiility 1. Introduction Thermoplstic vulcniztes (TPVs), s specil cse of thermoplstic elstomers (TPEs), re produced vi dynmic vulcniztion of lends of ruer nd thermoplstic polymer in the presence of vulcnizing system. [1-8] TPVs hve the processing ehvior of thermoplstics in molten stte ut ruery ehvior t ordinry tempertures similr to ruer vulcniztes. Morphologiclly, the resulting TPVs re chrcteristic of finely dispersed, micrometersized, crosslinked ruer prticles distriuted in continuous thermoplstic mtrix. [9] Compred with those lends comprising of uncured or slightly crosslinked components, dynmic vulcniztion possesses significntly improved mechnicl properties tht cn e ttriuted to the stilized morphology of ruer prticles resulting from crosslinking. Becuse thermoplstic nd ruer re usully incomptile, this will inevitly result in poor mechnicl properties due to the gross phse seprtion nd poor interfcil interction. However, the further improvement of TPV properties cn e chieved y the ddition of comptiility components, which cn effectively enhnce the interfcil interction. [10-1] The work presented here ims t the development of n integrted reserch-eduction ctivity on novel TPVs. Becuse of their unique chrcteristics, TPVs ply very importnt role in the pplictions of utomotives, uildings, * Corresponding uthor: wngzh.cn@gmil.com (Zhoo Wng) Pulished online t Copyright 2018 Scientific & Acdemic Pulishing. All Rights Reserved constructions, wires nd cles, etc. In recent yers, there hs een gret interest nd significnt progress in the preprtion of vrious TPVs sed on novel thermoplstic resin/ruer lends. Therefore, novel TPVs ecome n ctive reserch suject in some importnt fields. The determintion of n optiml preprtion condition of novel TPVs is descried elow. This esy nd convenient method uses two-roll mill nd Brender Plsticorder, which cn e crried out in the polymer processing lortory, nd requires thermoplstic resin, ruer mterils nd relted dditives used in the crosslinking recipe. The chrcteriztion of the novel TPVs y moving die rheometer, universl testing mchine, field-emission scnning electron microscopy (FE-SEM) nd energy dispersive X-ry micronlysis system (EDX) enefits the students y exposing them to few importnt instruments tht will e widely used in the future cdemic reserch or industril work. 2. Experiment Description 2.1. Mterils HVPBR ruer (with the mss frction of vinyl content 8.5%, ML 1+ (100 C) =50 nd M n =1.5*10 ) ws supplied y the Key Lortory of Ruer-Plstics (Qingdo University of Science & Technology), Ministry of Eduction, Chin. HIPS resin ws the product of Shnghi SECCO Petrochemicl Co., Ltd., Chin. The HIPS ws injection grde 22P with melt flow index (MFI) of

2 2 Zhoo Wng et l.: Novel Thermoplstic Vulcniztes Prepred y Dynmic Vulcniztion: Undergrdute Experiments for Polymers.8 g 10min -1 (200 C/5.0 kg). The polyutdiene content in the grft copolymer ws 7.5 wt.%. SBS, grde YH-792, ws produced y the Yueyng Petrochemicl Co., Ltd., Chin. It ws liner SBS with totl polystyrene lock percentge of 0 wt.%. Sulfur, used s vulcnizing gent, ws otined from Hengye Zhongyun Chemicl Co., Ltd., Chin. N-cyclohexyl-2-enzothizole sulfenmide (CZ) nd tetrmethylthiurm disulfide (TMTD), used s ccelertors, were mnufctured y Northest Auxiliry Chemicl Industry Co., Chin. Zinc oxide (ZnO) ws used s n ctivtor nd otined from NewLe Qinshi Zinc Co., Ltd., Chin. Steric cid ws used s n ctivtor nd otined from Wnyou Co., Ltd., Chin. N-phenyl-N -cyclohexyl-p-phenylenedimine (Antioxidnt 010) nd N-phenyl-2-nphthlmine (Antioxidnt D) were used s n ntioxidnt nd otined from Shengo Chemicl Co., Ltd., Chin Instruments nd Chrcteriztion HVPBR nd crosslinking ingredients were compounded in two-roll mill (X(S) K-10, Shnghi Qunyi Ruer & Plstic Mchinery Co., Ltd., Shnghi, Chin) t room temperture. The vulcniztion cure of the HVPBR sed prelend ws determined y using moving die rheometer (GT-M2000, GoTech Testing Mchines Co., Ltd., Tiwn, Chin) t 15 C nd virtion ngel ws ±1. TPV compounds were prepred y melt-mixing using Brender PLE 1 Plsticorder (Brender Gmh, Duisurg, Germny). For the mesurement of tensile properties, dumell-shpe specimens were prepred ccording to ASTM D12. The tering strength ws tested ccording to ASTM D2 using unnotched 90 ngle test pieces. Both tensile nd tering tests were performed on universl testing mchine (TCS-2000, GoTech Testing Mchines Inc., Chin) t crosshed speed of 500 mm/min. The Shore A hrdness ws determined using hnd-held Shore A Durometer (LX-A, Shnghi Liu Ling Instrument Fctory, Chin) ccording to ASTM D220. All tests were crried out t 2 C. The verge vlue of tensile strength ws clculted for 5 test specimens nd those of tering strength nd Shore A hrdness were clculted for test specimens. Morphologicl study ws crried out using field-emission scnning electron microscopy (FE-SEM, JEOL-700F, Jpn Electron Co., Ltd., Jpn). For the etched specimens, the HIPS phse ws extrcted y immersing the dynmiclly vulcnized lends into xylene for 0 min t 80 C. Then, the smples were dried t room temperture. The etched surfces of the specimens were sputtered with thin lyers of gold nd imged using FE-SEM. Elementl nlysis on the etched surfce of the specimens ws mesured using n energy dispersive X-ry micronlysis system (EDX, Oxford Instrument Co., UK) with em size of elow 1 nm.. Experimentl Procedure.1. Preprtion of Dynmiclly Vulcnized HIPS/HVPBR nd HIPS/SBS/HVPBR Blends.1.1. Preprtion of HVPBR Prelends The concentrtions for crosslinking the HVPBR re expressed in prts per hundred HVPBR ruer y weight (phr). The sulfur-contining ccelerting system recipe for crosslinking the HVPBR is consisted of the following ingredients: 100 phr HVPBR, 1.0 phr sulfur, 1.2 phr CZ, 0. phr TMTD, 5.0 phr ZnO, 2.0 phr steric cid, 1.5 phr Antioxidnt D nd 0.5 phr Antioxidnt 010. The prelends contining HVPBR nd the crosslinking ingredients were compounded in two-roll mill t room temperture. After min of mixing time, the prelends were removed from the mixer Curing Chrcteristic of HVPBR Bsed Prelend Elstic torque, N m 12 9 t 10 t Cure time, min Figure 1. Vulcniztion curve of HVPBR sed prelend t 15 C The vulcniztion curve of the HVPBR prelend is illustrted in Figure 1. As oserved in Figure 1, the cure chrcteristic ws shown n ovious plteu curing, indicting the reltively high therml stility of the HVPBR prelend; moreover, it ws fvourle for controlling the lter melt mixing of dynmic vulcniztion. The t 10 nd t 90, which re defined s the scorch time nd the optimum cure time, were 2.5 nd.2 min respectively. According to the nlysis of the vulcniztion curve, the proper dynmic vulcniztion time should e min or so..1.. Preprtion of Dynmiclly Vulcnized Blends The TPV compounds were prepred y melt-mixing the HVPBR prelends with HIPS resins using Brender Plsticorder. The mixing temperture ws kept t 15 C with constnt rotor (cm type) speed of 80 rpm. The HIPS/HVPBR lending rtio ws vried from 20/80 to 0/0. For the comptiilized TPVs, the HIPS/HVPBR lending rtio ws fixed t 0/70 nd the SBS mount ws vried from 0 to 15 phr. During the dynmic vulcniztion, the requisite

3 Americn Journl of Polymer Science 2018, 8(1): 1- quntities of HIPS resin nd SBS were chrged into the mixer nd llowed to melt. After min, the HVPBR sed prelend ws dded. The mixing ws continued for nother.2 min to llow the dynmic vulcniztion. Finlly, the compound ws removed from the mixer nd pssed through cold two-roll mill in the molten stte to otin sheet. The sheet, out 2 mm thick, ws compression-molded under pressure of 15 MP t 180 C for min, followed y cold compression in nother molding mchine for 8 min t room temperture. Test specimens were die-cut from the compression-molded sheet nd used for testing fter 2 h..2. Mechnicl Properties of the Dynmiclly Vulcnized HIPS/HVPBR Blends nd HIPS/SBS/HVPBR Blends.2.1. Mechnicl Properties of the Dynmiclly Vulcnized HIPS/HVPBR Blends Figure 2 illustrtes the stress-strin ehviors of the dynmiclly vulcnized HIPS/HVPBR lends with different weight rtios. As shown in Figure 2, the stress-strin curves of dynmiclly vulcnized lends present chrcter of eing reltively soft when the HIPS content ws less thn 0 phr. Incresing HIPS content, the stress-strin curves showed quick increse in tensile stress nd modulus. Unfortuntely, the elongtion t rek of the dynmiclly vulcnized HIPS/HVPBR lends ws lower thn 100%, ccording to ASTM D15-11, the HIPS/HVPBR lends should not e considered to e TPEs. However, the mechnicl properties of the dynmiclly vulcnized HIPS/HVPBR lends were expected to e improved y modifiction of the interfce interction. Stress, MP : HIPS/HVPBR=20/80 2: HIPS/HVPBR=0/70 : HIPS/HVPBR=0/0 : HIPS/HVPBR=50/50 5: HIPS/HVPBR=0/ Strin, % Figure 2. Stress-strin curves of dynmiclly vulcnized HIPS/HVPBR lends Influence of SBS on the Mechnicl Properties of the Dynmiclly Vulcnized HIPS/HVPBR Blends Figure shows the stress strin ehviors of the dynmiclly vulcnized HIPS/HVPBR lends comptiilized y different SBS dosges. As shown in Figure, the stress-strin curves of HIPS/SBS/HVPBR TPVs were similr in the shpe. Initilly, n ovious increse in tensile stress nd modulus could e oserved (for 10% strin). Upon further deformtion, the slope of the curves decresed with the stress incresing lmost linerly until frcture occurred. All the stress strin curves showed the representtive elstomeric chrcter of eing soft nd tough. It cn lso e seen from Figure tht the tensile strength nd the elongtion t rek of the HIPS/HVPBR lends were improved gretly with the incorportion of SBS. Stress, MP :HIPS/SBS/HVPBR=0/0/70 1 2:HIPS/SBS/HVPBR=0/1/70 :HIPS/SBS/HVPBR=0//70 :HIPS/SBS/HVPBR=0//70 5:HIPS/SBS/HVPBR=0/9/70 :HIPS/SBS/HVPBR=0/12/70 0 7:HIPS/SBS/HVPBR=0/15/ Strin,% Figure. Stress-strin curves of dynmiclly vulcnized HIPS/HVPBR lends comptiilized y SBS The mechnicl properties results of the series HIPS/SBS/HVPBR TPVs t vrious lend rtios re presented in Tle 1. From Tle 1, we cn find tht incresing SBS loding in the HIPS/HVPBR lends, the tensile strength nd tering strength were improved significntly nd reched mximum vlue t 12 phr SBS incorportion; however, the SBS loding hd little influence on the Shore A hrdness. Incresing the SBS dosge, the elongtion t rek ws lso sustntilly improved, nd ws higher thn 100% t only 1 phr SBS incorportion; moreover, the lrger elongtion t rek led to the reltively lrger tensile set t rek. However, ll the tensile set t rek vlues in Tle 1 were much lower thn 50%, indicting tht the dynmic vulcnized HIPS/SBS/HVPBR lends cn e descried s elstomers. 5 7

4 Zhoo Wng et l.: Novel Thermoplstic Vulcniztes Prepred y Dynmic Vulcniztion: Undergrdute Experiments for Polymers Tle 1. Mechnicl properties of dynmiclly vulcnized HIPS/SBS/HVPBR lends HIPS/SBS/HVPBR (weigh rtio) Tensile Strength /MP Elongtion t rek /% Tensile set t rek /% Tering strength/kn/m Shore A hrdness 0/0/ /1/ // // /9/ /12/ /15/ Morphologicl Reserch of HIPS/HVPBR TPVs..1. Morphologicl Evolution of SBS Comptiilized HIPS/HVPBR TPV c d prelend egn to enter the crosslinking rection, leding to drmtic incresing viscosity of HIPS/SBS/HVPBR lends; s result, the crosslinking HVPBR prelend ws grdully torn into prticles nd dispersed in the HIPS mtrix under the strong sher force in the mixer. At this moment, the ovious two-phse microstructure could e oserved, nd the size of the vulcnized HVPBR prticles ws out 10 μm, s shown in Figure. Incresing dynmic vulcniztion time to 5 min, under the effect of the continuous sher force, the crosslinking HVPBR prticles were torn into smller prticles with the more uniform morphologies, nd the size of the HVPBR prticles ws - μm, s shown in Figure c. When the dynmic vulcniztion time ws min, the vulcnized HVPBR prticles were continued to e torn into smller prticles with the size of -5 μm nd uniformly dispersed in the etched TPV surfce. Figure. Morphologicl evolution of HIPS/SBS/HVPBR TPV (weight rtio=0/12/70): () 1 min, () min, (c) 5 min, (d) min Figure shows the morphologicl evolution of HIPS/SBS/HVPBR (weight rtio 0/12/70) TPV vrying with the dynmic vulcniztion time. For these TPV specimens otined t specific dynmic vulcniztion time, they were etched in xylene fter molded into sheets; therefore, the thermoplstic HIPS mtrix in the TPV surfce could e selectively etched, nd the vulcnized HVPBR prticles were prominent nd could e found clerly in the etched surfces, s shown in Figure. During the erly stge of dynmic vulcniztion, the HVPBR prelend ws still in the scorch stge without ovious crosslinking, nd the HVPBR prelend nd HIPS were melt-compounded fully in the mixer. Both the HIPS nd the HVPBR prelend could e etched in the xylene, so there ws no ovious two-phse microstructure which could e oserved clerly in the surfce of the etched specimen, s shown in Figure. With prolongting dynmic vulcniztion time, the pre-vulcniztion stge ws strted nd the HVPBR Figure 5. EDX testing re in the etched HIPS/SBS/HVPBR (0/12/70) TPV surfce: () the dispersed prticle re, () the lnk re Tle 2. EDX testing dt of the selected re in the etched HIPS/SBS/HVPBR (0/12/70) TPV surfce Percentge of elements (wt.%) Cron Oxygen Zinc Sulfur In order to further confirm whether the protruding prticles in the etched TPV surfce were the vulcnized HVPBR prticles or not, EDX ws used to nlyze the element content of the selected re in the FE-SEM vision. Since the zinc oxide ws used s n ctivtor in the HVPBR prelend, the dispersed ruer prticles nd the continuous mtrix in the TPVs could e distinguished ccording to the differences in zinc content. Figure 5 shows the selected res

5 Americn Journl of Polymer Science 2018, 8(1): 1-5 used for EDX testing nd the relted results were shown in Tle 2. It cn e seen from Tle 2 tht the zinc content in the prticle re selected in Figure 5 is 7.87%, which ws much higher thn tht in the lnk re (1.1%), indicting tht the protruding prticles were vulcnized HVPBR prticles nd the lnk re should e mtrix phse. Although no zinc oxide ws mixed in the mtrix resin, Tle 2 detected the wek zinc signl in the lnk re of Figure 5. On the one hnd, smll mount of zinc oxide could e migrted from the HVPBR prelend into the HIPS mtrix under the strong sher force during dynmic vulcniztion; on the other hnd, usully the EDX detection hs certin depth, the dispersed HVPBR phse under the mtrix might lso e detected, leding to the wek zinc signl in the lnk re of the etched TPVs...2. Influence of SBS Comptiilizer on the Morphology of Dynmic Vulcnized HIPS/SBS/HVPBR Blends During the dynmic vulcniztion, the viscosity of the HVPBR prelend ws incresed quickly due to the initition of the crosslinking rection nd then the HVPBR phse ws grdully roken down into dispersed prticles under the strong sher force. The etched surfces of the dynmiclly vulcnized HIPS/HVPBR nd HIPS/SBS/HVPBR lends re shown in Figure. As it cn e seen from Figure, the crosslinked HVPBR prticles, with irregulr morphologies, were dispersed evenly in the thermoplstic mtrix. The dimensions of the discrete HVPBR prticles in Figure were in the rnge of 5-8 µm. It should e noted tht the presence of comptiilizer SBS in the mtrix decresed the verge size of the HVPBR prticles considerly, s shown in Figure. hnd, the existence of the SBS hindered the ggregting nd merging etween the crosslinked HVPBR prticles, leding to the decresing dimension of the dispersed HVPBR prticles; on the other hnd, the incresing of the interfce viscosity inevitly incresed the sher force t the interfce during the dynmic vulcniztion, nd the crosslinking HVPBR phse ws roken down into smller dispersed prticles with smll dimension nd rough surfce, which is lso helpful for the improvement of the interfce interction nd the mechnicl properties of HIPS/HVPBR TPVs, s shown in Tle 1.. Appliction of the Otined TPVs These prepred HIPS/SBS/HVPBR TPVs cn e further used s the rw mterils for polymer physics experiments, the preprtion of functionl TPVs nd polymer processing, etc. There experiments re performed t tmospheric pressure conveniently nd mking them suitle for mterils physics nd mterils chemistry lortories. ACKNOWLEDGEMENTS This work ws finncilly supported y Shndong Provincil Nturl Science Foundtion, Chin (ZR2017MEM021), Upgrded Project of Shndong Province for Guidnce Aility of Grdute Tutors (SDYY170), nd Ntionl Trining Progrms of Innovtion nd Entrepreneurship for Undergrdutes, Chin ( ). Figure. FE-SEM imges of etched HIPS/HVPBR nd HIPS/SBS/HVPBR TPVs: () HIPS/HVPBR (0/70), () HIPS/SBS/HVPBR (0/12/70) REFERENCES [1] Corn, A. Y., Ptel, R. P., nd Willims, D., 1982, Ruer-thermoplstic compositions. Prt V. Selecting polymers for thermoplstic vulcniztes., Ruer Chem. Technol., 55(1), [2] Gohrpey, F., Kt, A. A., nd Nzockdst, H., 2001, Mechnism of morphology development in dynmiclly cured EPDM/PP TPEs. I. Effects of stte of cure., J. Appl. Polym. Sci., 81(10), Usully, in the presence of comptiilizer t the interfce of TPVs, the ruer phse cn e finely dispersed nd the interfce interction cn e enhnced oviously. [15] During the dynmic vulcniztion, the comptiilizer in the lends tent to e distriuted t the interfce etween the ruer phse nd the thermoplstic phse, leding to the incresing interfce viscosity remrkly; moreover, the contcting nd the susequent ggregting etween the dispersed phses were prevented effectively. [1] Compring Figure with Figure, we cn know tht the existence of the SBS in the dynmiclly vulcnized HISP/HVPBR lends influenced the microstructure of the prepred TPVs gretly. On the one [] Kim, J. K., Lee, S. H., nd Hwng, S. H., 200, Study on the thermoplstic vulcnizte using ultrsoniclly treted ruer powder., J. Appl. Polym. Sci., 90(9), [] Hung, H., Liu, X., Ikehr, T., nd Nishi, T., 200, Investigtion of crystlliztion ehvior in dynmiclly vulcnized EPDM-nylon copolymer lends., J. Appl. Polym. Sci., 90(), [5] Chtterjee, K., nd Nskr, K., 2008, Study on chrcteriztion nd properties of nnosilic-filled thermoplstic vulcniztes., Polym. Eng. Sci., 8(), [] Wng, Z. B., Yu, W. J., nd Cheng, X. K., 2011, Mechnicl

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