Study On The Structure And Properties Of PP/EVA Blends

Firstly,the propylene/ethylene-vinyl acetate copolymer(PP/EVA)blends with different EVA contant was prepared.And the mechanical property,processability and morphology of PP/EVA blends were studied systematically.The results showed that the addition of EVA improved the impact strength and melt flowability of PP.when the EVA/PP proportion was 20/80,the PP/EVA blend showed best combination propery.And the impact strength of which was 16.1KJ/m2,it was 66.0%higher than that of pure PP.when the EVA/PP proportion was 25/75,the EVA phase began to form a conninous phase.The melt of PP/EVA blend was pseudoplastic fluid.EVA distributed as dispersed phase in PP matrix,and it increased the degree of crystallinity of PP.Secondly,PP/EVA dynamically vulcanized blend was prepared by using vulcanizing systems that were made up of peroxide andauxiliary curing agent(S).Bis[1-(tert-butylperoxy)-1-methylethyl]benzene(BIPB)and Dicumyl peroxide(DCP)were two kind of peroxide which were investigated separately for their effect on the property of PP/EVA dynamically vulcanized blends,and the optimum vulcanizing system was screened out.The results showed that the BIPB-S vulcanizing system was relatively more suitable for preparing high-performance PP/EVA dynamically vulcanized blends.When the dosage of BIPB was 0.4phr and S was 0.12phr,PP/EVA dynamically vulcanized blend showed best combination property.The impact strength of PP/EVA dynamically vulcanized blend was 70.2 KJ/m2 with 20/80 EVA/PP proportion.The dynamical vulcanization of PP/EVA blend contained a series of complex chemical reaction,including the crosslinking of both EVA and PP and the formation of PP-g-EVA.In PP/EVA blend,EVA was the dispersed phase,and PP was the continous phase.Dynamical vulcanization reduced the critical matrix ligament thickness of PP/EVA blend and improved the compatibility between PP and EVA.The melt of PP/EVA dynamically vulcanized blend was pseudoplastic fluid.Dynamical vulcanization increased the degree of crystallinity of PP,and it readuced the size of PP spherulite.Lastly,saponified EVA(EVAL)was prepared by melt saponification,and EVAL was used for toughing PP by dynamical vulcanization.The results showed that the saponification degree of EVAL can be dominated by controlling the mixing temperature,mixing time and sodium hydroxide dosage.When the saponification degree of EVA was 49.5%and the proportion of PP/EVAL/PP-g-MAH was 80/20/8,PP/EVAL dynamically vulcanized blends showed best combination property,and its impact shtrength was 74.1KJ/m,which was 663.9%higher than that of pure PP.In PP/EVAL dynamically vulcanized blend,EVA was the dispersed phase,and PP was the continous phase.PP-g-MAH improve the compatibility between PP and EVA and it prompted the formation of a crystallization and β crystallization of PP in the PP/EVAL dynamically vulcanized blend,thus promoting the toughness and rigidity of the blend.