Study On Graft Modification Of Polyolefin And Toughening Effect Of Its Product On SAN Resin

EPM-g-MAN, synthesized by suspension grafting copolymerization of methyl methacrylate and acrylonitrile （MMA-AN） from ethylene-propylene bipolymer （EPM）, was blended with styrene-acrylonitrile copolymer （SAN） to prepare a high impact plastic AEMS. POE-g-MAN, synthesized by suspension grafting copolymerization of methyl methacrylate and acrylonitrile from polyethylene-octene copolymer （POE）, was blended with styrene-acrylonitrile copolymer （SAN） to prepare a high impact plastic AOMS. AEMS and AOMS are characterized by excellent weatherability and yellow discoloration resistivity because of no double bond in molecule chain of polyolefin elastomer （ES）: EPM and POE. AEMS and AOMS are potential engineering plastic,will substitute ABS if it can be in industrial production.The effect of f_AN (f_AN was equal to AN/MMA-AN), f_ES (f_ES was equal to ES/（ES+MMA-AN）, content of initiator BPO, content of solvent toluene, main dispersant PVA,assistant dispersant, water/oil ratio, reactive temperature and reactive time on the monomer conversion ratio （CR）, average grafting ratio （GR） and grafting efficiency （GE） of copolymerization and the notched impact strength of grafting copolymer/SAN resin blends were investigated systematically. EPM-g-MAN and POE-g-MAN synthesize by optimized condition were blended with SAN resin respectively to prepare AEMS and AOMS.Contemporary analysis methods were used to investigate grafting copolymer and blends systematically. The components of the grafted copolymer were separated by different solvent and were qualitative/quantitative analyzed using Fourier transform infrared spectroscopy （FTIR）. The results showed that, the main elementary reactions in EPM/MMA-AN grafting reaction system were graft copolymerization of EPM/MMA-AN, graft polymerization of EPM/MMA, copolymerization of MMA and AN, homopolymerization of MMA, crosslinking reaction of EPM, and there were no grafting polymerization of EPM/AN and homopolymerization of AN. The main elementary reactions in POE/MMA-AN grafting reaction system were graft copolymerization of POE/MMA-AN, graft polymerization of POE/MMA, copolymerization of MMA and AN, homopolymerization of MMA, and there were no grafting polymerization of POE/AN, homopolymerization of AN and crosslinking reaction of POE. DSC analysis indicated that the graft branches affected the crystallization of POE chains and made the melt temperature and the fusion heat be lower. For EPM/MMA-AN system, the quantitative relationship of f_AN on AN unit-to-MMA unit weight ratio in g-MAN chains/non-grafted components had been established by using FTIR quantitative analysis method, and it was found that the average weight fraction of AN unit in g-MAN （FAN-1） was less than f_AN. EPM-g-MAN had a best toughening effect on SAN resin while FAN-1 was 13.9wt%. TEM and SEM analysis showed that the phase structure of AEMS and AOMS were co-continue structure and the toughening machenism was severe shear yielding when the blends reached their highest notched Izod impact strength. DMA analysis showed that the miscibility between grafting copolymer and SAN resin was good. TG/DTG analysis showed that thermal stability of AEMS and AOMS increased with increasing f_AN. The melt flow rate（MFR） of AEMS decreased as EPM increasing. The less EPM content in the blends was, the better rheological and processing properties were.With research on the effect of reaction time on CR, GR, and GE of PEB/MMA-AN suspension system, POE/MMA-AN suspension system, EPM/MMA-AN suspension system and EPDM/St-AN solution system, the grafting copolymerization mechanism was investigated. The grafting polymerization product was characterized by GPC and FTIR analysis, the grafting copolymerization mechanism was investigated and the formula of calculating molecular weight of grafted chain was established. The results showed that, firstly the polymerization was mainly forming non-grafted copolymer with low molecular weight （MANL） of the transferring terminating polymerization of chain propagating free radicals and forming the grafted chains （g-MAN） of the transferring graft polymerization, and then the polymerization was mainly forming non-grafted copolymer with high molecular weight （MANH） of bimolecular terminating polymerization of chain propagating free radicals; molecular weight of MANL was less than that of g-MAN and molecular weight of g-MAN was less than that of MANH. The effects of reaction time on rubber’s grafting ratio of the four system were investigated. The results showed that the reaction mechanism after grafting copolymerization could be divided into two kinds. The one was that there existed chain scission and random regrafting of the backbone of ES-g-M and ungrafted ES which resulted in the production of multi-block polymer of ES and ES-g-M during the grafting copolymerization after transferring grafting polymerization, such as PEB and POE. The other was that the crosslinking reaction between grafted and ungrafted ES which resulted in the production of crosslinked polymer, such as EPDM and EPM. The same point of the two reaction was that the more ungrafted ES joined, the better toughening effect of the product on SAN resin.For PEB/MMA-AN system, toughening effect of different components on SAN resin was studied. The results showed that, grafted PEB （PEB-g-MAN） was the effective component that had toughening effect, non-grafted copolymer （MAN） was synergistic agent between PEB-g-MAN and SAN resin, and ungrafted PEB decreased the toughening effect. The thermal oxidative aging and accelerated weather aging results showed that the aging property of the blends of EPDM-g-SAN/SAN, EPDM-g-MAN/SAN and EPM-g-MAN/SAN was better than ABS. The aging mechanism was mainly the decrease of -CH2, -C≡N and benzene ring and firstly the increase and then the decrease of -OH of the blends during aging process.