Effect of rare earth nucleating agent on supercritical CO2 foaming behavior of block copolymerized polypropylene

The rare earth nucleating agent was used to modify block copolymerized polypropylene (PPB) in foaming process. The results show that the crystallization of PPB and the melting temperature of beta-crystal increased gradually with increased beta-crystal nucleating agent content. The total crystallinity decreased with amount of addition increasing, and the relative content of beta-crystal increased first and then decreased. When beta-crystal nucleating agent content was 0.4 wt%, the relative beta-crystal content reached the maximum value of 95.27%, and the final crystal grain refinement significantly. The addition of rare earth beta-crystal nucleating agent has a good effect on improving the uniformity of foam cells. Under the same content of beta-crystal nucleating agent and pressure, the average cell diameter and expansion ratio increased with the saturation temperature increasing. After the foaming temperature reaches 155 degrees C, the expansion ratio began to decrease, which was also consistent with the changed trend of relative beta-crystal content. At the same content of temperature and relative beta-crystal, as the foaming pressure increased, the cell diameter decreased gradually, and the expansion ratio increased first, and then decreased.