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Recycled polymers reinforced with paper plastic laminates

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Title: Recycled polymers reinforced with paper plastic laminates
Authors: Mitchell, Jonathan
Item Type: Thesis or dissertation
Abstract: The aim of this research project was to develop new structural materials from the paper plastic laminate (PPL) waste stream. PPLs containing both paper fibre and plastic coatings are problematic for non-thermal recycling options. The current end of life disposal for PPL is primarily landfill. This work focuses on combining PPL wastes with recycled plastics to produce paper plastic composites (PPCs) that can be used as raw materials for a variety of applications. Plastic from a material recycling facility (MRF) consisting of polyolefins, together with polypropylene (PP) from Waste Electrical and Electronic Equipment (WEEE) wastes have been the main source of material for the composite matrix. The PPL wastes investigated include paper polyethylene coated disposable beverage cups and multi-layer Tetra Pak cartons. The majority of disposable cups are made from PPLs which consist of high quality cellulose fibre with a thin internal polyethylene coating. There are limited recycling options for PPLs and this has contributed to disposable cups becoming a high profile, problematic waste. In this work PPL wastes have been shredded to form PPL flakes and these have been used to reinforce polyolefins to form novel paper plastic composites (PPCs) based on the waste streams used. The PPL flakes and polyolefins were mixed, extruded, pelletised and injection moulded at temperatures to prevent degradation of the cellulose fibres. The PPLs were prepared by removing waste contaminants and granulated to the correct size to prevent bridging during extrusion. Processing temperatures were kept as low as possible to prevent fibre degradation. Extruded PPC blends were pelletised and injection moulded to form samples for testing. The effects of PPLs in PPCs on processing and properties have been investigated. This included studying the rheology of the extrusion mixes and the strength and stiffness of the PPCs. The effects of coupling agents such as maleated polyolefins and silane based compatibilisers to enhance adhesion between the PPL and the plastic have also been investigated. The level of PPL flake addition and the use of a maleated polyolefin coupling agent to enhance interfacial adhesion have been investigated. PPCs have been characterised and mechanically tested by a range of techniques including tensile testing, thermogravimetric analysis (TGA) and rheological experiments. Use of a coupling agent allows composites containing 40 wt.% of PPL flakes to increase the tensile strength of the recycled PP in this research by 50% to 30 MPa. The Young's modulus also increases from 1 to 2.5 GPa and the work to fracture increases by a factor of 5. The work presented here demonstrates that PPLs have potential to be beneficially reused as reinforcement in novel PPCs.
Content Version: Open Access
Issue Date: Mar-2014
Date Awarded: Mar-2015
URI: http://hdl.handle.net/10044/1/58274
DOI: https://doi.org/10.25560/58274
Supervisor: Cheeseman, Christopher
Vandeperre, Luc
Sponsor/Funder: Engineering and Physical Sciences Research Council
Nextek (Firm)
Department: Civil and Environmental Engineering
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Civil and Environmental Engineering PhD theses

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