Effect of Chain Extenders on Thermal Degradation and Rheological Properties of Polylactic acid (PLA)

The control of thermal degradation of polylactic acid (PLA) during processing is still a challenge for the industry. In this work, two different chain extenders: Lauroyl peroxide (LP) and Tris (nonyl phenyl) Phosphite (TNPP) were incorporated into PLA in an effort to control thermal degradation of molecular structure. The thermal and rheological properties of the PLA with and without chain extenders (CA) were investigated. Gel permeation chromatography revealed that adding TNPP to PLA increased the weight average molecular weight. Thermogravimetric analysis showed an increase up to 17 ˚C in the onset temperature for thermal degradation after incorporation of 0.6 wt% TNPP. The rheological results revealed that the addition of such a concentration of chain extender had a profound effect on the low frequency storage modulus (G’) and causes non-terminal behavior. The mechanism of stabilization is most likely chain extension that results in the formation of longer linear chains in the TNPP-modified samples, and a long chain branched (LCB) structure in LP-based samples

Keywords:

Polylactic acid , Thermal degradation , Rheological properties , Molecular weight , Chain extender