The Effect of Mechanical Recycling on the Properties of HDPE for Commercial Applications
Category
Sciences and Technology
Department
Polymer Chemistry
Student Status
Graduate
Research Advisor
Dr. Jeanne Norton
Document Type
Event
Location
Student Center Ballroom
Start Date
10-4-2025 2:00 PM
End Date
10-4-2025 4:00 PM
Description
Modern plastics manufacturing methods create significant waste including sprues, runners, flash, trim, and out-of-spec parts. To reduce the carbon footprint of the plastic industry, post-industrial waste materials are often reprocessed into new parts. This investigation centered on reprocessing HDPE materials and the effects of mechanical recycling on material properties. Specifically, we focused on the degree of mechanical recycling that HDPE can undergo before a degradation in key material properties is observed. Virgin HDPE material was injection molded into test bars and subsequently reduced with a mechanical grinder. Injection molding was then repeated until the HDPE had been molded and ground ten times. Analysis was performed on virgin-, first cycle-, fifth cycle-, and tenth cycle-regrind, to determine if any degradation had occurred as a result of grinding and remolding. Reprocessed samples were analyzed for changes in thermal and mechanical properties. Degradation temperature was determined by TGA, and Crystallization temperature and melting temperature were analyzed by DSC. Melt rheology was analyzed by melt flow indexing. The tensile properties and impact strength were analyzed by tensile and Izod impact testing, respectively. Slight increases in tensile elongation were observed with an increased number of cycles. Notched impact strength and modulus decreased slightly as the number of cycles increased. Thermal stability, melt flow index, melting temperature, and temperature of crystallization were not significantly affected. Crystallinity calculated from Tm and Tc peak area determined by DSC showed no clear trend between percent crystallinity and the number of processing cycles. We demonstrated the recyclability of HDPE without significant loss of properties.
The Effect of Mechanical Recycling on the Properties of HDPE for Commercial Applications
Student Center Ballroom
Modern plastics manufacturing methods create significant waste including sprues, runners, flash, trim, and out-of-spec parts. To reduce the carbon footprint of the plastic industry, post-industrial waste materials are often reprocessed into new parts. This investigation centered on reprocessing HDPE materials and the effects of mechanical recycling on material properties. Specifically, we focused on the degree of mechanical recycling that HDPE can undergo before a degradation in key material properties is observed. Virgin HDPE material was injection molded into test bars and subsequently reduced with a mechanical grinder. Injection molding was then repeated until the HDPE had been molded and ground ten times. Analysis was performed on virgin-, first cycle-, fifth cycle-, and tenth cycle-regrind, to determine if any degradation had occurred as a result of grinding and remolding. Reprocessed samples were analyzed for changes in thermal and mechanical properties. Degradation temperature was determined by TGA, and Crystallization temperature and melting temperature were analyzed by DSC. Melt rheology was analyzed by melt flow indexing. The tensile properties and impact strength were analyzed by tensile and Izod impact testing, respectively. Slight increases in tensile elongation were observed with an increased number of cycles. Notched impact strength and modulus decreased slightly as the number of cycles increased. Thermal stability, melt flow index, melting temperature, and temperature of crystallization were not significantly affected. Crystallinity calculated from Tm and Tc peak area determined by DSC showed no clear trend between percent crystallinity and the number of processing cycles. We demonstrated the recyclability of HDPE without significant loss of properties.
