Influence of chain extenders on the melt strength and thermal stability of polyglycolic acid

摘要

Biodegradable polyglycolic acid (PGA) has been attracting much attention recently. However, poor melt strength and thermal stability limit the processing of PGA by methods such as film blowing and injection molding. To improve melt strength and thermal stability, two reactive chain extenders, styrene-acrylonitrile-glycidyl methacrylate terpolymer (poly(St-AN-GMA)) and 4, 4 '-methylenebis(phenyl isocyanate) (MDI), were incorporated respectively into PGA using twin-screw extrusion. MDI was found to be more effective in chain extension and enhancing thermal stability than poly(St-AN-GMA). The T-5% (the temperature where the remaining weight percentage is 95%) of PGA modified with 3 wt% MDI increased to 334.5 degrees C from 310.8 degrees C for pure PGA. Melt flow rate for the same materials decreased from 47.2 g/10 min to 13 g/10 min. The activation energy of thermal degradations for MDI-modified PGA was twice that of the unmodified PGA as evaluated by the Flynn-Wall-Ozawa method.