Preparation And Properties Of Green Crosslinked EPDM

Rubber is widely used in many important fields due to its unique entropy elasticity.However,the traditional vulcanization method widely used in the rubber industry has a variety of problems,including the use of toxic vulcanizing agents,the release of toxic and smelly volatile organic compounds（VOCs）,and the difficulty of recycling waste rubber.Therefore,in order to solve the inherent problems in the traditional vulcanization process of elastomer materials.This paper constructed a new green crosslinking system by functionalizing the double bonds on the rubber molecular chain,introducing functional groups as crosslinking sites,and using bio-based small molecules as green crosslinking agents to replace sulfur or peroxides.The main research contents are as follows:（1）Firstly,epoxidation modification of EPDM was carried out through"formic acid-hydrogen peroxide"in situ epoxidation technology to obtain epoxidized EPDM（EEPDM）.Then,based on the reaction between epoxy and carboxylic acid groups,the bio-based dicarboxylic acid was used as the green crosslinking agent to construct the crosslinked network structure containing"ester bond"and"ether bond".At the same time,the effects of different dicarboxylic acids（sebacic acid,iconic acid and maleic acid）on the crosslinking and mechanical properties of EEPDM were systematically studied and revealed.It was found that the efficiency and rate of crosslinking reaction of EEPDM were positively correlated with the acidity of dicarboxylic acid.At the same time,the mechanism of crosslinking EEPDM with iconic acid was studied.The results showed that the epoxy groups in EEPDM would react with carboxyl groups to produceβ-hydroxy ester bonds.In addition,the ether bonds can also be produced by self-polymerization under the initiation of carboxyl group.Finally,an efficient green crosslinking method with adjustable crosslinking mechanics was established for EPDM,and EPDM composites with excellent mechanical properties,heat and oxygen aging resistance and compression permanent deformation performance were prepared.（2）Firstly,carboxylated EPDM（XEPDM）was successfully synthesized by"Thiol-ene"Click Reaction,and the effects of the ratio of double bonds,3-sulfhydryl-propionic acid and initiator on the reaction rate,grafting rate and side reactions were systematically studied.Then,the bio-based epoxy soybean oil（ESO）was used as the green crosslinking agent.Based on the reaction between epoxy and carboxylic acid,a crosslinking network structure containing"ester bonds"was constructed to realize the simple,efficient and green crosslinking of XEPDM.In addition,the addition of zinc oxide（Zn O）can activate the epoxy groups of ESO and catalyze the cross-linking reaction between epoxy and carboxyl groups.A small amount of Zn O can significantly improve the cross-linking efficiency and cross-linking density of XEPDM.At the same time,the ion pairs or ion clusters formed by Zn²⁺and carboxylic acid were used as physical strengthening points,which greatly increased the mechanical properties of XEPDM/ESO system as a whole.（3）Firstly,keto-functionalized EPDM（OEPDM）was successfully prepared by continuous epoxidation and oxidative chain scission of EPDM with 5-Ethylidene-2-norbornene（ENB）as the third monomer.The carbonyl group in OEPDM was used as the crosslinking site and p-phenylenediamine was used as the crosslinking agent.Based on the reaction between the ketone group and the amino group,a cross-linking network containing’imine bond’was constructed without catalyst.In addition,the epoxidation of EPDM with dicyclopentadiene（DCPD）as the third monomer was more difficult to break the chain reaction and synthesize aldehyde functionalized EPDM.