The comparative characteristics of the properties of petroleum-based and biobased EPDM rubbers

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1 Kuchuk i Rezin, No. 5, 2014, pp The comprtive chrcteristics of the properties of petroleum-bsed nd biobsed EPDM rubbers M.A. Grim, P. Hough, D. Tylor, nd M.V. Urk LANXESS, Cologne, Germny Selected from Interntionl Polymer Science nd Technology, 42, No. 1, 2014, reference KR 14/05/08; trnsl. seril no Trnslted by P. Curtis The trditionl method for producing copolymers of ethylene, propylene, nd diene monomer EPDM (SKEPT in Russi) implies the use of ethylene nd propylene bsed on petroleum derivtives s the feedstock. However, to synthesise SKEPT of grde Eco (LANXESS, Cologne, Germny), use is mde of ethylene lone, produced by the dehydrogention of ethnol from renewble source sugr cne. This solution ws dopted in light of the worldwide trend towrds replcing non-renewble minerl resources s the min rw mteril for the production of synthetic polymers with renewble resources. The first stndrd production of biobsed SKEPT worldwide ws begun by LANXESS t the end of 2011 nd becme n importnt lndmrk in the history of synthetic elstomers. Brzilin sugr cne is one of the most ecologiclly efficient lterntive products for the polymer industry. Corn, cerels, nd sugr beet do not possess such high potentil for reducing the emission of greenhouse gses into the tmosphere s sugr cne (90% reduction in emissions by comprison with petroleum derivtives). This huge green potentil is possessed by sugr cne owing to its fvourble energy blnce nd high efficiency ; ccording to dt of the Brzilin Sugr Cne Industry Assocition (UNICA), it is possible to produce 7000 L ethnol/h sugr cne. With the introduction of cellulose hydrolysis, it will become possible to increse the yield to L ethnol/ h. This will be the second genertion of biofeedstock. Furthermore, the decision in fvour of sugr cne does not plce n excessive lod on the Brzilin griculturl sector, s its cultivtion requires less thn 1% of the totl re of the country nd 1.5% of cultivted res in ll. Bioethylene is supplied by pipeline from the compny Brskem S.A. to the existing fctory for SKEPT production in Triunfo, Brzil. The qulity indices of Eco SKEPT re s high s other rubbers of the series. Furthermore, Eco leves considerbly lower crbon nd energy footprint, nd lso mkes it possible to reduce the consumption of non-renewble minerl resources. Eco rubber is suitble for the production of sections, hosing, sels, dditives for plstics, etc. Furthermore, it cn be checked nd certified tht the crbon in Eco psses into it from sugr cne, which hs been demonstrted by mesuring the content of rdioctive isotope 14 C in the mteril in ccordnce with the ASTM D6866 test stndrds [1]. In this pper, the chemicl, processing, nd service properties of trditionl rubbers nd Eco rubbers, both in pure form nd in the form of composites, re compred. The results of the work should be importnt for producers of mechnicl rubber goods tht hve decided to use the more eco-friendly Eco insted of the trditionl rubber. SKEPT specimens used in the present reserch were produced t the LANXESS Elstomer Fctory in Triunfo (Brzil) by solution polymeristion using Ziegler Ntt ctlyst. ws synthesised from ethylene bsed on petroleum feedstock, while Eco ws synthesised from ethylene on the bsis of biofeedstock supplied by Brskem S.A. To estblish the properties of the two rubbers, full nlysis ws crried out. The Mooney viscosity [ML (1 + 4) t 100 or 125 C] ws mesured in ccordnce with the ISO 289 stndrd in Mooney units. To determine the 2015 Smithers Informtion Ltd. T/1

2 chemicl composition of the polymers, use ws mde of infrred spectroscopy (IRS) with Fourier trnsformtion (FTIR). The moleculr weight distribution (MWD) ws determined by gel permetion chromtogrphy (GPC) using universl clibrtion. The therml chrcteristics were determined on differentil scnning clorimeter (DSC) by the following schedule: heting to 200 C nd subsequent cooling to 70 C t rte of 10 C/min. The so-clled Dδ prmeter, which ws used s mesure of the non-newtonin viscoelstic behviour of SKEPT, nd lso for nominl ssessment of the degree of long-chin brnching, ws mesured using dynmic mechnicl spectrometry (DMS) (t 125 C nd 20% strin). Prmeter Dδ is defined s the difference between the mechnicl loss ngles (δ) t frequencies of 10 1 nd 10 2 rd/s, or s derivtive of the frequency of scnning of sections obtined during DMS [2]. The mount of biocrbon in the polymer ws mesured using rdiocrbon nlysis [2]. nd Eco were lso compred under conditions of stndrd sulphur vulcnistion of mix obtined by extrusion [nominl formultion 70/40/70, where the numbers denote the content (in prts) of crbon blck N550, crbon blck N772, nd prffin oils respectively]. The mix hs reltively low degree of filling (high rubber content) (Tble 1) nd consequently is extremely sensitive to smll chnges in the properties of the rubber. The rubbers were lso compred in composite (nominlly, service composite) comprising mix intended for solid motor vehicle sels with Shore A hrdness of 70 (Tble 2). For subsequent comprison, one other version of this mix ws chosen, in which furnce crbon blck of petroleum origin (FEF N550) ws replced with crbon blck produced by tyre pyrolysis (BBC 500). Mixing, vulcnistion, nd testing of the composites were conducted in LANXESS s Elstomer Lbortory in Geleen (The Netherlnds). Mixing of ll formultions ws conducted in Shw K-1 intermixer with loding fctor of 54%. After mixing, the btches were chrged into Troester WNU-5 tworoll mill, where, t temperture of 60 C, vulcnising gents were dded to the composites. Their Mooney viscosity [ML (1 + 4) t 100 C] ws mesured. The behviour of the 70/40/70 composites ws studied during test extrusion with Grvey extrusion hed t 50 rev/min. The vulcnistion kinetics of ll the composites ws ssessed on Monsnto MDR 2000 rheometer in ccordnce with ISO 6502 t 180 C for 20 min. During this mesurement, the scorch time (t s2 ), the vulcnistion time (t 90 ), nd the difference between the mximum nd minimum rheometer torques (M H M L ), s nominl mesure of crosslink density, were determined. The Mooney viscosity of the 70/40/70 composites ws mesured t 125 C. Tble 1. The composition of extruded composites of SKEPT nd Eco (70/40/70) Ingredient Content (prts) SKEPT 100 Active zinc oxide 5 Steric cid 1 Crbon blck N Crbon blck N Prffin oils 70 MBTS ZBEC ZDBP Vulklent E/C 0.5 S Totl number of prts Tble 2. The composition of service composites of SKEPT Eco/N550 nd Eco/BBC 500 of industril designtion Ingredient Eco/N550 (prts) Eco/BBC 500 (prts) SKEPT Crbon blck N Crbon blck BBC Whiting Prffin oils Active zinc oxide 5 5 Steric cid 1 1 Polyethylene glycol CO CBS TMTD ZDMC ZDBC S Totl number of prts To determine the mechnicl properties of the composites, two sheets of 2 nd 6 mm thickness were pressed t pressure of 40 br nd temperture of 180 C. The sheets of 2 mm thickness were vulcnised for time equl to (t %) min, nd the sheets of 6 mm thickness for time equl to (t %) min. The initil hrdness (in reltive interntionl units of rubber hrdness IRHD or METP) nd the hrdness fter het geing (for 168 h t temperture of 100 C) were mesured in ccordnce with DIN The tensile properties (tensile strength, elongtion t brek, stress under 100 nd 300% elongtion) before nd fter het geing by the regime indicted bove were determined on dumbbell No. 2 T/2 Interntionl Polymer Science nd Technology, Vol. 42, No. 6, 2015

3 testpieces in ccordnce with ISO 37. The tensile strength of so-clled Delft specimens before nd fter het geing ws mesured for 70/40/70 composites in ccordnce with ISO 188. The compression set (ISO stndrd, type B) of specimens of 70/40/70 composites ws mesured fter 24 h tests t temperture of 70 C nd fter 24 h t 100 C, while the compression set of service formultions ws mesured only fter 24 h t 100 C. The rebound resilience ws mesured for service formultions in ccordnce with ISO Sttisticl processing of the results of the experiment consisted in determining the rithmetic men vlues of ech index of the physicomechnicl properties of Eco nd nd of composites bsed on them (see Tble 1), nd lso their stndrd devition for the purposes of estimting the degree of error of tests. Tble 3. Comprtive chrcteristics of SKEPT nd Eco Eco Mooney viscosity (t 125 C) D (reltive units) Molr concentrtion of crbon (%) Ethylidene norbornene concentrtion (%) Crystllistion temperture T cr ( C) Het of crystllistion dh cr (J/g) MWD chrcteristics Molr concentrtion of biobsed crbon (%) 70 THE PROPERTIES OF SKEPT The polymeristion of Eco ws conducted under the sme synthesis conditions s those trditionlly used for. The im ws to produce rubber possessing the sme properties s the existing, with the one exception of different feedstock source for ethylene (biologicl rther thn petroleum). To demonstrte their similrity, the moleculr nd supermoleculr chrcteristics of the two rubbers were determined nd compred. From the dt in Tble 3 it cn be seen tht the Mooney viscosity indices of the two investigted SKEPT rubbers re very similr nd lie within the stndrd rnge for (55 ± 4). The vlues of Dδ re prcticlly identicl, which mens tht the two rubbers hve equivlent levels of brnching in their structures. Furthermore, the chemicl composition of the polymers, the crystllinity chrcteristics (see lso Figure 1), nd the moleculr weight distribution (Figure 2) re identicl. The results of rdiocrbon nlysis confirmed tht the only difference to be expected is tht the molr crbon concentrtion in Eco, mounting to 70%, is of vegetble origin. Figure 1. DSC curves of specimens of nd Eco during initil heting (1), cooling (2), nd reheting (3) THE PROPERTIES OF EXTRUDED SKEPT COMPOSITES From Figure 3 it cn be seen tht the mixing curves of extruded composites of nd Eco (their formultions with reltively high rubber content re given in Tble 1) prcticlly merge with ech other, which indictes their identicl behviour during mixing. This conclusion is confirmed by the dt given in Tble 4. Furthermore, the two composites hve very similr Mooney viscosity indices nd re prcticlly identicl Figure 2. MMW curves of nd Eco: moleculr weight; log reltive distribution density extrusion chrcteristics, s indicted by the results of test extrusion with Grvey hed (see Tble 4). Thus, it cn be concluded tht, during mixing nd extrusion, these two composites behve identiclly. The chrcteristics of the composite during vulcnistion were ssessed on the bsis of rheometry dt (Figure 4 nd Tble 5). These dt were lso used 2015 Smithers Informtion Ltd. T/3

4 Tble 4. The chrcteristics of the processes of mixing nd extrusion of extruded composites of nd Eco Eco Mixing Mixing time (s) Mximum power expended on mixing (kw) Temperture t exit ( C) Mooney viscosity (t 100 C) Extrusion (Grvey extrusion hed, 50 rev min 1 ) Mss throughput (g/min) Coefficient of swelling of extrudte (%) Pressure in hed (br) Qulity expert ssessment of the ppernce, swelling, nd porosity of the extrudtes recorded no differences between the nd Eco composites re identicl or similr not only in their initil stte but lso fter het geing, nd their smll differences lie within the limits of test error. The fct tht the two rubbers exhibit similr behviour in these composites demonstrtes tht Eco rubbers re prcticlly equivlent to 540, the only difference being the source of the monomer (ethylene) biofeedstock or petroleum. Tble 5. The chrcteristics of processes of vulcnistion nd scorching of extruded nd Eco composites Chrcteristics Eco M H M L (dn m) t s2 (min) t 90 (min) Mooney viscosity t t t t M H M L difference between the mximum nd minimum rheometer torques; t s2 scorch time; t 90 vulcnistion time; t 0, t 2, t 5, t 35 initil Mooney viscosity nd Mooney viscosity fter 2, 5, nd 35 min respectively Figure 3. Mixing curves of extruded composites of nd Eco: N power expended on mixing; t mixing time Figure 4. Rheometry dt of extruded composites of nd Eco: M t rheometer torque; t time to ssess the crosslink density (nominlly defined s the difference in the mximum nd minimum rheometer torques M H M L ). Tble 5 lso shows the results of ssessing the Mooney scorch rte. From Figures 4 nd 5 it cn be seen tht the behviour nd chrcteristics of the two polymers during scorching nd vulcnistion, including the crosslink density, re prcticlly identicl. As most physicomechnicl properties correlte with the crosslink density, it could be nticipted tht the two composites, which in this cse hve n identicl degree of crystllinity, will lso hve very similr mechnicl properties, which ws confirmed by subsequent tests (Tble 6). It should be emphsised tht the vlues of the properties of the two composites tht re given in Tble 6 Figure 5. Mixing curves of service composites of SKEPT: N power expended on mixing; t mixing time T/4 Interntionl Polymer Science nd Technology, Vol. 42, No. 6, 2015

5 Tble 6. The mechnicl properties of extruded nd Eco composites Eco METP hrdness b 68/71 68/70 Tensile strength (MP) 15/15 15/15 Stress under 100% elongtion 2.8/ /3.5 (MP) Stress under 300% elongtion 10/12 9/12 (MP) Elongtion t brek (%) 486/ /409 Tensile strength of Delft specimens 51/51 49/51 (N) Compression set fter 24 h t 70 C 9 9 (%) Compression set fter 24 h t 100 C (%) Numertors initil vlue of the property; denomintors fter het geing for 168 h t 100 C b METP mximum expected tubing pressure The chrcteristics of these two composites during vulcnistion, given for comprison in Figure 6 nd in Tble 8, demonstrte tht, when crbon N550 is replced with BBC 500, the scorch nd vulcnistion time increses, lthough ultimtely commensurte finl crosslink density is chieved. From the dt given in Tble 9 it cn be concluded tht composite contining BBC 500, produced by Blckber Crbon, possesses properties tht re comprble with the properties of Eco composite contining N550 crbon blck, which demonstrtes the possibility of developing more eco-friendly composites. Results obtined by Blckber indicte reduction in CO 2 emissions of t/t produced crbon blck by comprison with norml furnce blck, nd reduction of 3.9 t/t produced green ethylene by comprison with ethylene bsed on petroleum feedstock. The properties of Eco service composites Although the min im of the present work ws to show the technicl interchngebility of Eco nd, ttention must be drwn to the fct tht Eco offers the formultion developer polymeric bse for the cretion of green composites with the use of ingredients produced from renewble resources. To demonstrte this, Eco ws used, s indicted bove, in stndrd solid motor vehicle sels. The formultion contined crbon blck obtined from petroleum (furnce blck N550) nd crbon blck obtined by the pyrolysis of tyres (BBC 500) nd supplied by BlckBer Crbon BV (Eindhoven, The Netherlnds). In ccordnce with supplier instructions, the content of BBC 500 ws incresed by 12.5 wt% by comprison with N550 to chieve the sme mechnicl properties. The mixing curves indicte tht, for composites using crbon blck N550, considerbly less time is required for mixing by comprison with composite with BBC 500 (Figure 5). This is due to the fct tht BBC 500 is supplied in non-grnulr form nd consequently possesses n extremely low bulk density; therefore, in the process of mixing, it ws necessry to dd it 3 times, s result of which much more time ws needed for mixing. However, it ws noted tht, when the entire volume of BBC 500 hd been dded, mixing proceeded rpidly. Consequently, it cn be nticipted tht the grnulr form of BBC 500 will be introduced nd mixed in the sme mnner s norml furnce blck N550. Tble 7 gives the mixing chrcteristics nd shows the Mooney viscosity of these composites. Figure 6. MWD curves of nd Eco: M moleculr weight; log M reltive distribution density Tble 7. The mixing chrcteristics of SKEPT service composites Eco/N550 Eco/ BBC 500 Mixing time (s) Mximum power (kw) Temperture t exit ( C) Mooney viscosity (t 100 C) Tble 8. The chrcteristics of the vulcnistion of SKEPT service composites (ccording to rheometry dt) Chrcteristics Eco/N550 Eco/BBC 500 M H M L (dn m) t s2 (min) t 90 (min) M H M L the difference between the mximum nd minimum rheometer torques; t s2 scorch time; t 90 scorch time 2015 Smithers Informtion Ltd. T/5

6 Tble 9. The mechnicl properties of service composites of Eco eco/n550 eco/bbc 500 Shore A hrdness (reltive units) 68/78 68/78 Tensile strength (MP) 11/11 10/11 Stress under 100% elongtion (MP) 2.8/ /5.4 Stress under 300% elongtion (MP) 7.9/0 6.2/0 Elongtion t brek (%) 440/ /207 Schob rebound resilience (%) Compression set fter 24 h t 100 C (%) Numertors the initil vlue of the property; denomintors the vlue fter het geing for 168 h t 100 C Using these dt, it cn be estimted tht the production of Eco using biobsed ethylene leds to reduction in CO 2 emissions of 2.7 t/t produced SKEPT by comprison with stndrd. It cn lso be estimted tht the totl reduction in CO 2 emissions is of the order of 5 t/t service-designtion composite in this cse. Thus, the complex ssessment of Eco nd, conducted by compring their chemicl, rheologicl, nd moleculr chrcteristics, showed tht these rubbers re prcticlly identicl. The only obvious nd expected difference ws found by rdiocrbon nlysis, which confirmed tht rubber Eco contins 70% biobsed crbon, which corresponds to the mount of biobsed ethylene in the moleculr composition of Eco. Subsequent ssessments of the two polymers in composites with low degree of filling lso confirmed tht Eco nd exhibit identicl chrcteristics during processing, nd likewise identicl mechnicl properties, both before nd fter het geing, nd ny differences in properties lie within the limits of experimentl error. Finlly, it hs been shown tht Eco is high-qulity rubber, nd composites bsed on it possess improved chrcteristics for the production of eco-friendly products. As result of using Eco combined with crbon blck produced by tyre pyrolysis, composite hs been produced tht possesses vulcnistion chrcteristics prcticlly coinciding with the chrcteristics of equivlent composites produced using the norml furnce blck, but with considerbly less crbon. This mens tht Eco offers rubber mix developers rel solution to the problem of producing more eco-friendly products. REFERENCES 1. ASTM D Booij H.C., Kutschuk, Gummi, Kunststoffe, 44:128 (1991). Received T/6 Interntionl Polymer Science nd Technology, Vol. 42, No. 6, 2015