| Moisture crosslink has attracted the attention from researchers in many countries due to its advantages such as convenient and safe processing and low cost.Nowadays,the moisture crosslinking polyolefin has become mature,but its application in the rubber field is rarely reported.The matrix material selected in this paper,ethylene-vinyl acetate-glycidyl methacrylate elastomer(EVM-GMA),is obtained by chemical modification of ethylene-vinyl acetate rubber(EVM).Compared with EVM,glycidyl methacrylate(GMA)is introduced into EVM-GMA.The highly active epoxy group was contained in it,which is easy to react with amino group or carboxyl group.Based on this property,γ-aminopropyltriethoxysilane(APTES)was selected as the novel crosslinking agent of EVM-GMA.The feasibility of moisture crosslink on EVM-GMA was investigated by means of rotorless vulcanizer(MDR),fourier transform infrared spectroscopy(FTIR),and universal electronic tensile machine.In the meanwhile,it was probed to the effect of different APTES content on the basic properties of moisture crosslinked EVMGMA.Then,maleic anhydride(MAH)grafted rubber was also used to improve the utilization rate of APTES monomers and thereby increase the degree of moisture crosslink.Besides,rubber foaming materials were studied to broaden the application of this technique.This work aims to explore the new crosslinking method of rubber,optimize the processing method of EVM,and provide references for promoting green processing in rubber industry.First,γ-aminopropyltriethoxysilane(APTES)amino-functionalized groups was selected as the grafting monomer,then the amino-silane grafting reaction was completed by melt blending without grafting initiator to prepare EVM-GMA-gAPTES grafting copolymer.Subsequently,the copolymer was mixed with catalyst dibutyltin dilaurate(DBTL)and formed by compression molding.The molded samples were kept at 90 ℃ in a constant temperature water bath for 2 hours to obtain the moisture crosslinked EVM-GMA-g-APTES.The results showed that the silane grafting rate and branching degree of EVM-GMA-g-APTES gradually increased with the increasing APTES(1.5 phr to 5.5 phr)content.The tensile strength and modulus of the moisture crosslinked samples also showed a law of increasing with the number of APTES.Even after hot air aging,the moisture crosslinked EVMGMA-g-APTES still showed continued crosslinking behaviour.Compared with the peroxide crosslinked sample with similar crosslinking density,it was found that the tensile strength of moisture crosslinked EVM-GMA-g-APTES was greater than that of the peroxide crosslink system,although the modulus of the two kinds of sample was similar.It was indicated that the moisture crosslinked network was more outgoing on physical and mechanical properties.Secondly,in order to improve the grafting rate of APTES,after the successful preparation of the graft copolymer EVM-GMA-g-APTES in the first stage,a fixed ratio of dicumyl peroxide(DCP)and maleic anhydride(MAH)was used to initiate the grafting of MAH onto the rubber molecule backbone of EVM-GMA.Herein,the anhydride group of MAH reacted with the residual APTES monomer from the previous stage,thereby increasing the silane grafting amount of APTES on the rubber matrix and providing more reactive sites for subsequent moisture crosslinking reaction.The results showed that the crosslink density of moisture crosslinked EVM-GMA-g-APTES/MAH was significantly higher than that of nongrafting MAH.Although it is inevitable to produce a small amount of peroxide crosslink,it was still dominated by moisture crosslink.The comprehensive mechanical performance of moisture crosslinked EVM-GMA-g-APTES/MAH were significantly improved compared with those of non-grafted MAH samples.Finally,in order to broaden the application of moisture crosslink in rubber industry.This work combined moisture crosslinking with peroxide crosslinking to investigate the chemical foaming of EVM-GMA.The dual crosslinked EVM-GMAg-APTES foams were prepared with azodicarbonamide(AC)as the foaming agent.It was found that the expansion ratio and pore size of the double crosslinked EVMGMA-g-APTES foaming materials tended to decrease with the increasing DCP content.Among them,the dual crosslinked foam containing 0.15 phr DCP was the most uniform with the narrowest size distribution,showing good foaming behaviour.It was showed that the foaming material with 0.25 phr DCP had superior energy absorption effect,which is suitable for use as damping materials. |
