Synergistic effect of beta-nucleating agent and layered double hydroxide on high toughness of polypropylene composites

The crystalline behaviors and micromorphology of polymers have a large impact on the physical and mechanical properties, especially for polypropylene (PP) composites with toughening effect. In this work, the changes of the content ratio for layered double hydroxide (LDH) and beta-nucleating agent (CaHA), mechanical properties, and crystallization behaviors of PP/ethylene vinyl acetate copolymer (EVA)/LDH ternary composites are investigated by differential scanning calorimeter (DSC), polarizing optical microscopy (POM), scanning electron microscopy (SEM), and notched impact strength testing. The CaHA is used for synergistic toughening with LDH, and the highest notched impact strength is achieved in the 6PEL2 sample with CaHA of 0.03 phr and LDH of 5.70 phr, which is about 100% higher than that of pure PP. It is found from the crystallization behaviors and SEM images of the composites that 6PEL2 has the highest relative content of beta-crystals and the appearance of rougher interface and deformation pullout of the EVA phase in 6PEL2 because of dislocations in the beta-crystals and the formation of a large number of cavities absorbing the impact energy.