03/27/2025
By Danielle Fretwell
The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation defense by Mansour Alotaibi on: "The Impact of Compounding Systems and Parameters on Polymer Degradation."
Date: Friday, April 4, 2025
Time: 1 - 3 p.m.
Location: Ball 201A
Committee:
Advisor: Carol Barry, D.Eng., Professor & Chair, Plastics Engineering, UMass Lowell
Committee Members*
Amir Ameli, Ph.D., Associate Professor, Plastics Engineering, UMass Lowell
Akshay Kokil, Ph.D., Assistant Teaching Professor, Plastics Engineering, Umass Lowell
Abstract:
The machine type, screw or rotor design, and processing parameters (e.g., screw or rotor speed, processing temperatures) play a crucial role in determining the level of degradation and the resulting changes in properties when melt compounding polymers. Therefore, it is important to understand how processing systems and variables affect polymer molecular weight to minimize degradation with good end-product quality. Most commercial melt processing is performed with co-rotating twin screw extruders. This research, however, focused on evaluating the performance of other compounding systems which can provide better mixing and greater throughput than twin screw extruders. The first part of this work investigated the impact of reprocessing with a quad screw extruder (QSE) and a comparable twin screw extruder (TSE) on the degradation of polypropylene material. In this work, polypropylene was reprocessed multiple times at different screw speeds; the reprocessed materials were characterized for their rheological, chemical, mechanical, thermal and morphological properties.
The second part of this work investigated the impact of reprocessing on the structure of impact copolymer PP to clarify the effects of processing equipment and conditions. The reprocessed materials from the first part were fractionated to separate the dispersed ethylene-propylene rubber phase and the polypropylene matrix. The reprocessed resins were fractionated and characterized for their rheological, thermal and chemical properties. Third, a full factorial experimental design was performed to evaluate the effects of processing variables on the residence time and melt temperature of high-density polyethylene (HDPE) in a laboratory continuous mixer (CPeX®). The processing variables were the feed rate, rotor design, rotor speed, orifice position and single-screw design. The final part of this work studied the effect of processing parameters of a laboratory continuous mixer (CPeX®) on the degradation of PLA. The processing variables were rotor design, rotor speed, orifice position and screw speed. The critical factor affecting degradation was found to be the rotor design.