Gu, Fu
(2015)
Investigation on the use of recycled plastics in the production of automobile parts.
PhD thesis, University of Nottingham.
Abstract
It has been reported that the use of recycled plastics is economical and environmentally-friendly. However, despite studies suggesting that properties of recycled plastics can be improved upon, there is very limited research which focuses on the application of recycled plastics in demanding industrial applications. Disappointingly recycled plastics have been almost totally neglected in the automobile production industry.
This research investigates the use of recycled plastics in the production of automobile parts, starting by identifying of gap in knowledge between academic research and industrial practice. The only existing research into using recycled plastics in automobile production was focussed on closed-loop recycling. In this study, a review of current recycling practice was made with typical products analyzed in detail. It was found the mechanical, thermal and flammability properties of recycled plastics suffered noticeable deteriorations, while rheological properties were altered. Contaminants in recycled plastics were identified as elemental analysis was performed.
At first, three representative fillers, i.e., talcum powder (talc), glass fibre (GF) and organically montmorillonite (OMMT), were selected to mix with recycled plastics to promote the desired properties. Their effects were compared. Experiments showed that GF was the most effective filler in improving most of the mechanical properties, and OMMT was the most effective in promoting flexural properties with the least loading. Talc and OMMT improved both the rheological and flammability performance of recycled plastics. For the first time, the recycled PP/talc composites were found to maintain better mechanical properties in ageing and reprocessing tests compared with virgin composites. At this initial stage, the effects of different coupling agents in compatilising recycled plastics and fillers were identified.
For the study, four data analysis techniques were selected and used to predict, optimise and evaluate the formulae and procedures of recycled plastics: grey model (GM), Taguchi method (TM), principal component analysis (PCA) and cluster analysis (CA). Among these techniques, GM was successfully applied in predicting the effect of adding recycled plastic to virgin plastic based limited trials. TM was successfully applied in optimising injection moudling conditions when using recycled plastics. PCA and CA were successfully applied in analysis and evaluation of the performance of recycled plastics.
This research found that with the addition of certain additives and the application of mathematical methods, recycled plastics and their corresponding composites showed potential in industrial apllications, since some properties of these composites were more favorable than those of industrial composites currently being used in automobile industry. The novel methodology developed in this research was successfully applied in the enhancement of mechanical properties of recycled plastics, an outcome which represented a crucial step towards large-scale utilization of recycled plastics in the production of automobile parts.
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