| Moisture crosslinking of polyolefins has attracted more and more attention because of its high efficiency,low cost and easy processing.In recent years,the research on moisture crosslinked polyethylene resin has become mature,but few publications focus on moisture crosslinked ethylene-propylene-diene terpolymer(EPDM).And the unsaturated third monomer can make the grafting process of EPDM complicated.In this paper,EPDM was selected as the research matrix.The rheological response of rubber compound,Fourier transform infrared spectroscopy(FTIR),differential scanning calorimeter(DSC)and moving die rheometer(MDR)were used to study the influence of vinyl triethoxysilane(VTES)content on the silane graft ratio,moisture crosslinking and basic properties of the specimens.The moisture crosslinking of EPDM was optimized by combining with chemical foaming and using2,2,6,6-tetramethyl-1-piperinedinyloxy(TEMPO)as radical scavenger so as to provide scientific guidance for the development of EPDM technology.Firstly,in the paper,the ethylene-propylene-diene terpolymer grafted with silane of vinyl triethoxysilane(EPDM-g-VTES)was prepared by melt grafting with dicumyl peroxide(DCP)as initiator.And the EPDM-g-VTES was immersed in water bath to achieve moisture crosslinking with dibutyl tin dilaurate(DBTL)as the catalyst.The results showed that the VTES graft ratio and the branching degree of EPDM-g-VTES compounds increased with VTES content.The moisture crosslinking achieved successfully in the water bath of 90 ?×2 h.The degree of DCP pre-crosslinking(scorch)increased with the increase of VTES content,but the moisture crosslinking was still dominant in the EPDM-g-VTES vulcanizates.The tensile strength and elongation at break of EPDM-g-VTES were improved by moisture cure.The mechanical performance of moisture crosslink system was better than that of peroxide crosslink system at the similar crosslink density.Secondly,in order to broaden the application of moisture crosslinking,a new chemical foaming process combined with moisture crosslinking was used to prepare moisture cured EPDM-g-VTES foams in this paper.The results showed that the EPDM-g-VTES compounds with azodicarbonamide(AC)formed good cell morphology by making use of DCP pre-crosslinking in compression mould.And the crosslink network formed by moisture could improve the size uniformity and dispersity of cells.The tensile strength and elongation at break of EPDM-g-VTES foams were improved by moisture cure.The moisture cured foam with 4 phr AC had about 3 times expansion ratio,which could bear large deformation and showed high energy absorption effect.Finally,in order to further improve the moisture crosslinking,TEMPO was added as radical scavenger in the silane grafting based on the previous study.The results showed that due to the addition of TEMPO during the VTES grafting,the degree of DCP pre-crosslinking was effectively reduced,but the VTES grafting ratio decreased.The EPDM-g-VTES compound with 5 phr VTES and 0.1 phr TEMPO had little peroxide pre-crosslinking and showed a high silane grafting ratio.The moisture cured EPDM-g-VTES with 5 phr VTES and 0.1 phr TEMPO showed a high elongation at break,tensile strength and a low tensile modulus,which was good for the rubber nanocomposite. |
PDF Full Text Request