Comparison of volatile emissions and structural changes of melt reprocessed polypropylene resins

Document Type

Article

Publication Date

12-1-2002

Abstract

Polypropylene (PP), as a commodity recyclable thermoplastic, was studied in this research to evaluate the potential environmental impact resulting from volatile organic compounds (VOCs) emitted during multiple melt reprocessing. Unstabilized PP (U-PP) and stabilized PP (S-PP) resins, simulating recycled materials prone to degradation, were evaluated for total VOC emissions generated during multiple melt reprocessing by injection molding and extrusion, respectively. Results show that the maximum amount of total VOCs from each cycle (up to six cycles for extrusion and up to ten for injection molding) did not significantly change, while the cumulative VOCs increased with increasing processing cycle for both materials. A good correlation between cumulative VOC increases and melt flow index increase for the U-PP and weight-average molecular weight Mw decrease for the S-PP were obtained. Reprocessing in all cases was accompanied by decreases in Mw and melt viscosity as a result of thermooxidative degradation. FTIR data considering increases in carbonyl content and degree of unsaturation suggest that at equivalent cycle numbers, degradation appears to be more severe for the extruded material in spite of the longer oxidative induction time of the "as received" pellets used in extrusion. The onset and type of structural changes are shown to depend on cycle number and reprocessing method.

Identifier

0036889197 (Scopus)

Publication Title

Advances in Polymer Technology

External Full Text Location

https://doi.org/10.1002/adv.10027

ISSN

07306679

First Page

235

Last Page

242

Issue

4

Volume

21

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