Mechanical properties of polypivalolactone: Effects of thermal history and solvent exposure

摘要

AbstractThe mechanical properties and solvent resistance of polypivalolactone (PPL) were determined as part of our study of PPL composites. High elongation (30) films were obtained when moldings were cooled slowly and annealed for 15 min at 200°C prior to testing. The ductility fell when samples were held at 71°C for 2 weeks either dry or more so when exposed to water. Molecular weight degradation is believed to be responsible. This conditioning, however, raised the modulus of the sample by up to 32 in the vicinity of the conditioning temperature. It is speculated that this is due to densification in some of the stressed amorphous regions. The high crystallinity of PPL makes it insoluble in all common organic solvents. However, it swells and softens considerably when immersed in methylene chloride or methyl ethyl keton