Mechanical Properties and Recyclability of Ionic Thermoplastic Rubber Based on Citraconated Ethylene Propylene Diene Monomer

Abstract

The mechanical properties and recyclability of novel ionomers based on citraconated ethylene propylene diene monomer (EPDM) were examined. Citraconated EPDM (CCA-g-EPDM) was synthesized using a melt grafting technique from citraconic acid (CCA)/EPDM/free radical initiator [2,5-dimethyl-2,5-di(tert-butyl peroxy) hexane: L-101]. Ionomers (IZnO(5), IZnO(10), IZnSt.( 5), IZnSt.(10), IZnO(5)/ZnSt.( 5)) based on citraconated EPDM were prepared by melt mixing from CCA-g-EPDM and zinc oxide and/or zinc stearate using a Haake Rheocorder. This study compared the mechanical properties of pristine EPDM, CCA-g-EPDM and pristine/recycled ionomers. The density, tensile strength, elongation at break, modulus and tear strength increased in the order, ionomers > CCA-g-EPDM > pristine EPDM, whereas the compression set was in the opposite order. The ionomer, IZnO(5)/ZnSt.( 5), exhibited the highest mechanical properties and showed no significant change in the mechanical properties and compression set with successive recycling. These results suggest that the recyclable ionomers based on citraconated EPDM prepared in this study have high potential as new high performance thermoplastic elastomers.

Preparation and properties of high‐performance recyclable ethylene propylene diene rubber

“…Citraconated EPDM (EPDM‐g‐CCA) was prepared by melt grafting from citraconic acid (CCA)/EPDM/free radical initiator [2,5‐dimethyl‐2,5‐di(tert‐butyl peroxy) hexane: L‐101] using Haake Rheocorder (Rheocord 9000, Haake Co., Germany) under 50 rpm, at 160°C for 15 min. The EPDM‐g‐CCA with 1.78% of percent grafting and 18.0% of gel content was prepared by free radical melt graft copolymerization of pristine EPDM (100 g) with citraconic acid (CCA, 2 g)/initiator (L‐101, 0.04 g) . Percent grafting (%) of EPDM‐g‐CCA was determined by the following equation: where the dry weights of EPDM‐g‐CCA extracted in acetone at 40°C for 48 h and pristine EPDM are W g and W o , respectively.…”

“…Therefore, understanding the effect of melt processing/recycling on the properties of citraconated EPDM‐based ionomers is very important for reusing. Our previous study examined citraconated EPDM (EPDM‐g‐CCA) and mechanical properties and recyclability of EPDM‐g‐CCA ionomers . We found that the mechanical properties and compression set (CS) resistance increased in the order of EPDM‐g‐CCA ionomers > EPDM‐g‐CCA > pristine EPDM.…”