07/23/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Master's Thesis defense by Akubueze Emmanuel Uzoma on "High Performance Composites of Recycled Polypropylene and Polyethylene Reinforced with Waste Cellulosic Fibers and Fines."

Candidate Name: Akubueze Emmanuel Uzoma
Degree: Master’s
Defense Date: Tuesday, July 30, 2024
Time: 10 a.m. to noon
Location: Perry Hall 115

Committee:

  • Advisor: Amir Ameli , Assistant Professor, Plastics Engineering , University Of Massachusetts Lowell
  • Margaret J Sobkowicz Kline, Professor, Plastics Engineering , University Of Massachusetts Lowell
  • Davide Masato, Assistant Professor, Plastics Engineering , University Of Massachusetts Lowell

Brief Abstract:
This study investigated the feasibility of transforming recycled plastics and waste cellulosic fibers and fines (WCFF) to high performance composites. Recycled polypropylene (PP) and polyethylene (PE) together with WCFF from the pulp and paper industry were used. Recycled plastics and WCFF were first mixed and compounded using a twin screw extruder. Compression molding was then used to prepare composite samples for characterization. Several key factors were investigated to understand their impact on the morphological, mechanical, and thermal behavior of the recycled composites. In particular, the use of compatibilizers, WCFF size distribution, compounding speed, and WCFF loading (0 t 40 wt.%). The results showed that the optimal mechanical performance of PP/20%WCFF was achieved with the addition of 3 wt.% of maleic anhydride grafted PP (MA-g-PP), as a compatibilizer, which improved the fiber dispersion and interaction with PP. This resulted in a 40.06% increase in the tensile strength, compared to that of pure PP. It was found that the strength and modulus of PP/20%WCFF decreased significantly with an increase in the compounding screw speed, which could be due to excessive shear deformation and heating at higher speeds. Interestingly, non-sieved WCFF exhibited the greatest improvement in the mechanical properties, and sieved WCFF batches caused a drop even when the largest fiber length range was used. This was attributed to the preservation of very long fibers as well as the synergistic reinforcement effect from fiber and fines.

Overall, the modulus and strength increased significantly with an increase in WCFF loading in both recycled PP (rPP) and recycled PE (rPE), while strain at break decreased. The maximum enhancement in modulus and strength were 184% and 81.8% % for rPE. These values for rPP were 152.65% and 65.9%, respectively. Moreover, the crystallinity was improved with WCFF loadings up to an intermediate loading level (~ 30 wt.%), beyond which started to decrease. This trend was related to a competition between crystal nucleation and chain mobility hindrance effects of WCFF. This work offers a promising route for developing sustainable materials with enhanced performance from recycled plastic and fiber waste, potentially reducing reliance on virgin plastics and promoting waste valorization.