Thermal properties and isothermal crystallization of syndiotactic polypropylenes: Differential scanning calorimetry and overall crystallization kinetics

✍ Scribed by Pitt Supaphol; Joseph E. Spruiell

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 265 KB
• Volume: 75
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(20000103)75:1<44::aid-app6>3.0.co;2-1

✦ Synopsis

Isothermal crystallization and subsequent melting behavior of five samples of syndiotactic polypropylene are presented. Crystallization studies were carried out in the temperature range of 60°C to 97.5°C using a differential scanning calorimeter (DSC). Subsequent DSC scans of isothermally crystallized samples exhibited double melting endotherms. The high melting peak was concluded to be the result of the melting of crystals formed by recrystallization during the reheating process. Overall crystallization kinetics was studied based on the traditional Avrami analysis. Analysis of crystallization times based on the modified growth rate theory suggested that, within the crystallization temperature range studied, the syndiotactic polypropylenes crystallize in regime III. Kinetic crystallizability parameters also were evaluated, and were found to be in the range of 0.41°C s Ϫ1 to 2.14°C s Ϫ1 .