Preparation Of Maleated Low Molecular Weight Polybutadiene Functionalized PP And Its PA6Alloys

Although Polyamide6(PA6) has been widely-used in the world as electrical connectors, gears, rollers and so on because of its good mechanical and chemical resistance properties, its quite low impact strength still limits its application, especially at low temperature or in dry state. Rubber has been commonly employed to toughen PA6. Good toughness can be achieved when the rubber phase forms a submicron-sized dispersion. However, the addition of rubber might induce a substantial loss in elastic modulus and increase the cost. Recently, some studies have shown that the core shell particles with hard core and soft shell structure are effective in toughening and can avoid the elastic modulus and tensile strength loss.LDPE/PB-g-MAH core/shell rubbers toughening PA6blends exhibit excellent impact properties,but their elastic modulus and tensile yield stress are still low. The main reason is associated with the low modulus (<0.4GPa) and yield strength (～25MPa) of the LDPE core material. In this study, we have redressed this problem by replacing the LDPE core with a PP core, which has both higher elastic modulus and yield strength and which can be grafted with varying amounts of PB-g-MAH, forming new core/shell (PP/PB-g-MAH) rubbers.The experimental results showed PB-g-MAH was grafted onto PP molecular chain. The formation of core-shell structure (PP core and rubber shell) particles in the system has been proven by the TEM micrograph, which have good toughening effect in PA6alloys. When the core/shell rubber containing5wt%PB-g-MAH is blended with PA6, the Izod impact strengths can reach480J/m, and the modulus and yield strength are2.13GPa and54MPa, respectively,(which represent15%loss of modulus and13%in yield strength relative to neat PA6).Through the contrast of morphology and mechanical properties of core/shell toughened PA6blends with PP or LDPE core,we can know, increasing the modulus and yield strength of the core material will increase the elastic modulus and tensile yield stress of the blends.The cavitation and fibrillation of the rubber shell is the key process for toughening. However, the stability of the rubber fibrils of PP/PA6toughened blends will decrease, resulting in lower toughness of the blends. Nonetheless, increasing the elastic modulus and yield strength of the core material in the rigid core/soft shell rubber is an effective way to obtain PP/PA6blends with a good balance of elastic modulus, tensile yield strength and impact strength.