THERMAL-PROPERTIES OF POLY(PIVALOLACTONE)

Polypivalolactone (PPVL) is a highly crystalline polyester formed eith er by nucleophilic or electrophilic ring-opening polymerization of 2,2 -dimethyl-beta-propiolactone, commonly known as pivalolactone (PVL). T he thermal properties and crystallization kinetics of the polymer form ed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential sca nning calorimetry (DSC), and Avrami theory was used to interpret the b ulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, wh ich is of lower molecular weight, has similar crystallization rates co mpared to the higher molecular weight commercial material. The kinetic s data also indicate the rate of crystallization is relatively rapid o verall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous thermogravimet ric analysis/differential scanning calorimetry (TGA/DSC). Thermal anal ysis showed a clear difference in melting behavior between high and lo w molecular weight material, possibly a reflection of the presence of the alpha and gamma-crystal forms of the polymer.