Effect of Nucleating Agent Concentration on Non-Isothermal Melt Crystallization Kinetics of b-Nucleated Impact Polypropylene Copolymer

Hypothesis: 

b-Nucleation in synergy to rubbery phase of impact polypropylene copolymer (b-IPC) leads to enhanced impact strength at low temperature. The extent of crystallinity is a major factor affecting the mechanical performance and impact strength. An important step to develop the application of this polymer on industrial scale is to study its crystallization kinetics especially in non-isothermal mode which is more closely related to industrial processes. For this purpose, the effect of beta nucleating agent concentration on the non-isothermal crystallization kinetics of µ-IPC has been investigated in this article by theoretical models.

Non-isothermal melt crystallization kinetics of b-IPC samples with two different amounts of calcium pimelate as the beta nucleating agent, prepared in solution blending method, was investigated at various heating rates of 1, 10 and
25°C/min using differential scanning calorimetry.

The results showed that the total crystallinity improved by increasing the content of b-nucleating agent (b-NA). Also, increasing the cooling rate and increasing the concentration of the nucleating agent were in favor of beta crystal formation. On the other hand, the results of calculating the half-time for crystallization, changes in conversion rate with relative crystallization, Mo's analysis and the evaluated activation energy based on Kissinger method showed that the higher the share of beta crystal and the lower the share of alpha, the crystallization kinetics of b-IPC slowed down. Therefore, increasing the concentration of beta nucleating agent reduces the rate of crystallization of b-IPC. The Ozawa model was not accurate enough due to the presence of secondary crystallization, while the Mo's analysis was well able to elucidate the effect of the concentration of the nucleating agent on the crystallization kinetics.