Study On Toughening Modification Of Polyamides With Maleic Anhydride Grafted Ethylene Propylene Rubber

The toughening and compatibilizing effects of maleic anhydride graftedethylene propylene rubber (EPM-g-MAH) on Polyamide (PA) and PA/ethylenepropylene rubber (EPM) blends were studied in this paper. Both thePA/EPM-g-MAH binary blends and PA/EPM/EPM-g-MAH ternary blends wereprepared in a twin screw extruder and the mechanical properties、thermal properties、fracture morphology and dispersed particle size were investigated. The Molau testwas adopted to confirm the formation of a grafting copolymer between PA and EPM;rheological properties also indicated the grafting reaction. The n optimized toughenedsystems were obtained.Three kinds of EPM-g-MAH (2708、2608、2715) with different grafting de greewere used to toughen and compatibilize PA6. The results showed that the tougheningefficiency of EPM-g-MAH (2715) with higher grafting degree was better than theothers. Scanning electron microscopy (SEM) and differential scanning calorimetry(DSC) were employed to obtain some detailed quantitative analyses of themorphology of the elastomer particles and the melting and crystallization behavior.The crystallinity decreased with the incorporation of elastomers. That means theaddition of elastomers decreased the melting enthalpy and prevented the crystalgrowth. The structure of morphology was greatly improved with the increasing ofgrafting elastomer content, especially when the ratio of PA6/EPM-g-MAH (2715)was80/20, and the dimension of dispersed particle size was even and the impactstrength was reached to56.7kJ/m~2, which was increased by28.4times as comparedto that of net PA6(2.0kJ/m~2).Compared with the effects of EPM-g-MAH toughening and compatibilizingtwo kinds of PA6, the fracture morphology and mechanical properties were investigated. The results showed that the effects of EPM-g-MAH toughened PA6(L)were better than PA6(M) because the molecular weight of PA (L) was lower. When20wt%was chosen as the overall dispersed phase concentration, with the ratio ofPA6(M)/EPM/EPM-g-MAH was80/10/10, the blends had the optimizedcomprehensive mechanical properties, and the impact strength reached to47kJ/m~2,which was increased by8times as compared to that of net PA6(M). However, theoptimized impact strength of PA6(L)/EPM/EPM-g-MAH blends was49.3kJ/m~2when the ratio of80/0/20. Thus EPM-g-MAH could be an effective reactivecompatibilizer of PA6(M)/EPM blends, and the moderate EPM-g-MAH additionimproved the compatibility of PA6(M) and EPM, as well as reduced the costs. Fromthe analysis of dispersed phase morphology and particle size, EPM-g-MAH coulddecrease the particle size of dispersion phase. The optimal size range of elastomerparticles was0.2~1μm when PA6were toughened by EPM and EPM-g-MAH. Withthe increasing of EPM-g-MAH, the crystallinity of PA6(M)/elastomer blends wasincreased, while PA6(L)/elastomer blends was decreased. A typical double meltingbehavior presented in PA6(M)/elastomer blends.Afterwards, the toughening and the compatibilizing effects of EPM-g-MAH onPA66and PA66/EPM blends, as well as fracture morphology and crystallizingbehavior, were also studied. In PA66/EPM-g-MAH binary blends, the increasing ofEPM-g-MAH content resulted in a quickly increase of the impact strength,especially when the dispersed phase mass fraction was10to20wt%, and it gave63kJ/m~2when the concentration of EPM-g-MAH was20wt%, which was increased by12.6times as compared to that of net PA66(5.1kJ/m~2).20wt%was also chosen asthe overall dispersed phase concentration of PA66/EPM/EPM-g-MAH blends. Withthe addition of EPM-g-MAH content within the dispersed phase, the impact strengthwas increased rapidly. The particle size of dispersed phase was decreased greatlywith an increase in EPM-g-MAH content in the blend. The crystallinity ofPA66/EPM blend was the low est, and with the increase of EPM-g-MAH in theblends the crystallinity was increased gradually. The crystallinity ofPA66/EPM-g-MAH blend was almost as the same as the crystallinity of net PA66.