Thermo-mechanical degradation and VOC emission of unstabilized and stabilized polypropylene copolymer during multiple Extrusions

Abstract

The thermo-mechanical degradation during the multi-extrusion of unstabilized and stabilized polypropylene copolymer (cPP) was analyzed using the Chain Scission Distribution Function (CSDF) method. During the first extrusion of unstabilized cPP almost 60% of the initial polymeric chains were submitted to chain scission. The calculations using CSDF show a random chain scission process of chains with molecular weight below 100 kg.mol-1, and above that a preferential chain scission process. When stabilized the cPP molecular weight is kept constant, even after four extrusions, independently of the stabilizers concentration used. Its chain scission is greatly reduced, only being noteworthy at high values of molecular weight, presenting in this case a preferential chain scission process. During extrusion the unstabilized cPP evolves Volatile Organic Compounds (VOC) due to the volatilization of low molecular weight oxidized chain segments. VOC's emissions are greatly reduced during the melt processing of stabilized cPP, even after multiple extrusions.

Keywords

• extrusion
• thermo-mechanical degradation
• polypropylene copolymer
• VOC