The Preparation Of NR/EPDM Elastomer And Its Heat Aging Resistance

With the development of science and technology,the requirements of rubber products in aerospace,automobile,chemical industry and other fields of high temperature resistance and high performance are more and more high than a single general rubber.Natural rubber(NR)has excellent physical and mechanical properties such as resilience,electrical insulation,bending fatigue resistance,etc.EPDM has excellent heat and oxygen aging resistance,insulation,water resistance and corrosion resistance.Nowadays,more attention has been on the combination of NR and EPDM which obtain excellent comprehensive properties has attracted the attention of researchers.Because of the large unsaturation of NR and the high speed of vulcanization,the main chain of EPDM is completely saturated,only a small amount of double bonds exist in the side chain,the unsaturation is low and the speed of vulcanization is slow,so it is difficult to realize the co vulcanization of NR and EPDM.The main materials natural rubber STR10 CV from Malaysia and EPDM with three different third monomer content made by LANXESS chemical.The effects of the third monomer ENB content(4.2%,6.5%,9.0%)and different curing systems on the co vulcanization of NR and EPDM were studied.It was found that the higher the ENB content,the faster the vulcanization rate and the better the mechanical properties.When the ENB content was 9.0%(EPDM 6950c),the positive curing time T90 was 14.18 min,and the tensile strength of EPDM vulcanizate reached 18.4 MPa.Compared with the T90 with 4.2% ENB(EPDM 2470s),it was 6.35 min shorter and 73% higher in tensile strength.When S/CZ/TRA/MBT/ZBPD and S/TDEC/TRA/CZ/TMTD were used in the low-speed vulcanization system of NR and EPDM 6950 C,the positive vulcanization time was 3.43 min and 4.11 min respectively,and the tensile strength of the alloy elastomer increased from 9.8 MPa to 15.8 MPa,which could realize the good co vulcanization of NR and EPDM 6950C(60:40).The retention rate of tensile strength and elongation at break increased from 57% to 72% and 44% to 71% respectively.The effects of NR/EPDM blending ratio,mixing process,ZDMA and antioxidant on the properties of NR/EPDM alloy elastomer were investigated,and characterized by RPA,SEM,TEM and DMA.The results show that with the increase of EPDM content,the tensile strength and elongation at break of the alloy elastomer decrease first and then increase,while the hardness increases gradually.The results of DMA and TEM showed that the compatibility of NR/EPDM was better when the ratio of NR/EPDM was 60/40.Four different mixing processes were used to prepare NR/EPDM alloy elastomers.The results showed that the properties of the elastomer prepared by mixing NR and its additives separately from EPDM and its additives before mixing were better than those of other preparation processes.ZDMA was an unsaturated carboxylate,haved a good effect on strengthening and toughening of NR/EPDM alloy elastomers,as well as heat and oxygen aging.When ZDMA content was 2 phr,the tensile strength of NR/EPDM elastomer increased from 15.8 MPa to 16.5 MPa,and the elongation at break increased from 285% to 315%.The tensile strength retention rate of 100 ? and 72 h aging test increased from 71% to 76%.The results of thermal oxygen aging test show that the antioxidant system(A/B/C)with high quinoline polymer content can make NR/EPDM alloy elastomer obtain good thermal aging properties.The antioxidant STMQ was used to replace the antioxidant RD,and the tensile strength retention rate of NR/EPDM(60/40)alloy elastomer was increased from 76% to 80% and the elongation at break retention rate was increased from 74% to 81% after 100 ? and 72 h heat-resistant oxygen aging test;the antioxidant 4010 NA was replaced by amine compound antioxidant,and 100 ? & 72 h was used The retention rate of tensile strength and elongation at break increased from 76% to 84% and 74% to 80% respectively.TG analysis showed that the thermal stability of NR/EPDM alloy elastomer with STMQ/4010 NA anti-aging system and amine compound anti-aging agent/4010 NA anti-aging system was improved.