Comparative study on quiescent crystallization kinetics of isotactic polyolefins

Abstract

Quiescent melt crystallization rates of various polyolefins including high density polyethylene (PE), isotactic form of polypropylene (PP), polybutene-1 (PB1), and poly(4-methyl pentene-1) (P4MP1) were investigated under both isothermal and nonisothermal conditions using differential scanning calorimetry (DSC). The order of overall crystallization rates under quiescent conditions from fast to slow was found to be: PE, P4MP1, PP and PB1. The Avrami equation was used to analyze isothermal and nonisothermal crystallization processes, respectively. In order to compare relative crystallization rates of these polymers, continuous cooling transformation curves for each polymer under nonisothermal condition as well as the plot of crystallization half-time as a function of crystallization temperature under isothermal conditions were constructed. Comparisons were made of the relative rate of crystallization of the different isotactic polyolefins with each other and with reports in the literature. Isotactic polyolefins with linear side groups crystallize increasingly more slowly as the side group lengthens with polypentene-1 (PPT1) and polyhexene-1 (PH1) crystallizing even more slowly than PB1. It is notable that P4MP1, which has isobutyl as a bulky side group, and apparently poly(3-methyl butene-1) (P3MB1) showed fairly high crystallization rates.

The effect of poly(4‐methyl‐1‐pentene) on the nonisothermal crystallization kinetics of polypropylene

“…These results mean that crystallization proceeds during quenching, even at the previous cooling rate of 10 000 K s −1 . It is also clear that the crystallization rate of PMP is faster than that of PP, and this trend coincides with the literature examined by conventional DSC . For PP/PMP blends (Figure C), the thermal signals of PP (below 160°C) and PMP (above 160°C) are separated into different temperature regions.…”

“…It is also clear that the crystallization rate of PMP is faster than that of PP, and this trend coincides with the literature examined by conventional DSC. [12] For PP/PMP blends ( Figure 6C), the thermal signals of PP (below 160 C) and PMP (above 160 C) are separated into different temperature regions. Below 160 C, the shape of FSC curves of PP/PMP blends agreed with that of the PP homopolymer.…”

“…Form V also transforms into form I by annealing at 90°C. The crystallization rate from the melt tends to be in the following order: PP < PMP < PE . The typical sample of PP shows morphology of spherulites sized sub‐mm diameter (observed by polarized optical microscopy [POM]).…”

Crystallization and compatibility of poly(4-methyl-1-pentene) and polypropylene in their blends

“…The values of ÁH f * for PMP and PP are 117.2 and 209.00 J/g, respectively. 21,22 The calculated data are listed in Table 1. It showed that the crystallinity of PMP (X c, PMP ) did not show significant variation with the increase in the amount of PP in the blends until the amount of PP of the blend reached 80 wt%.…”