Synthesis Of Suspension Grafting Poe-g-san And Its Toughening Effect On San Resin

POE-g-SAN, synthesized by suspension grafting copolymerization of styrene(St) and acrylonitrile(AN) onto polyethylene-octene elastomer (POE), was blended with styrene-acrylonitrile copolymer (SAN) to prepare a high impact plastic AOS. AOS is characterized by excellent weatherability and yellow discoloration resistivity because of no double bond in molecule chain of POE. AOS is a potential engineering plastic,will substitute ABS if it can be in industrial production and this high performance plastic hasn't been reported yet.The effect of fAN(fAN was equal to AN/St-AN), fPOE(fPOE was equal to POE/(POE+St-AN)),content of initiator BPO,content of solvent toluene, main dispersant PVA,assistant dispersant, water/oil ratio, reactive temperature, reactive time and content of additional monomer styrene on the monomer conversion ratio (CR), average grafting ratio (GR), grafting efficiency (GE), rubber's grafting ratio(GRR), ture grafting ratio(GRT) of copolymerization and the notched impact strength of AOS were investigated systematically. The best synthetic conditions which made the notched impact strength of AOS to reach the highest level were obtained by optimizing grafting reaction condition. The results showed that fAN,GRR were the key factors influencing on the toughening effect of POE-g-SAN on SAN resin. The notched impact strength of AOS was 45.1 kJ/m2 with POE-g-SAN synthesize by optimized condition and CR, GR, GE, GRR, GRT of the POE-g-SAN was 92.1%, 26.7%, 42.4%, 30.9%, 70.1% respectively.GPC analysis showed that molecular weight increased with the increase fAN,first increased and decreasing after with fPOE.It had the best toughened effect when POE-g-SAN had the molecular weight of the Mn being 8.6×104and the Mw being 21.8×104. The components of the grafted copolymer were separated by different solvent and it was found that the first stage of polymerization was mainly graft reaction generating graft copolymer, the second stage of polymerization was competitive reaction between graft copolymerization and copolymerization , and the third stage of polymerization was mainly copolymerization.TEM and SEM analysis showed that main factors influencing on phase struture and toughening mechanism of AOS were the polarity of graft chain g-SAN and GRR. POE-g-SAN had a highest GRR and a proper polarity graft chain when fAN was 35wt%, fPOE was 60%, and the phase structure of AOS with this POE-g-SAN was co-continue structure with occlusion structure (POE occluded plastic particle), the toughening machenism was severe shear yielding. When the POE content was low, the toughening mechanism of the blends was branch and termination of crack with slight cavitations, then changed into extensive cavitations,severe shear yielding , and finally changed into shear yielding accompanied by cavitations as POE increasing.DMA analysis showed that POE was compatible with SAN resin. TG and DTG analysis showed that thermal stability of AOS resin was between SAN resin and POE.