Diverted from Landfill: Manufacture and characterisation of sustainable composites using waste plastics and waste glass fibre
Topic(s) : Life cycle performance
Co-authors :
Kit O'ROURKE (UNITED KINGDOM), Christopher GRIFFIN , Mark HARTMANN , Keith DOYLE , Adrian DOYLE , Conchúr M Ó BRÁDAIGH (UNITED KINGDOM), Dipa RAYAbstract :
The EU's target of recycling 50% of plastic packaging waste by 2025 currently remains unmet, with the recycling rate of plastic packaging in 2020 standing at only 38%. A significant factor in the low recycling rate is the difficulty of recycling low-density polyethylene packaging films, which are flexible and lack strength. Plastic packaging films play a crucial role in safeguarding goods and minimising food waste; however, their recycling system is not adequately developed. Another major challenge is the high cost of separating and sorting different types of plastic waste, which serves as a significant barrier to increasing recycling rates. One solution to reduce this cost is to use waste mixed plastics as a raw material.
Additionally, 150000 tons of glass fibres (GF) end up in landfill in the EU each year, and approximately 67% of GF is sent to landfill sites in the UK each year. Adding GF to waste plastics can convert these disposable materials into value-added composites suitable for a range of applications, such as construction.
This study proposes a technology redirecting two waste streams from landfill to marketable product forms and focuses on manufacturing composites with waste mixed plastics (wMP) reinforced with waste GF (wGF). The wMP used undergoes only one stage of separation (float-sink method) resulting in plastics with densities lighter than water, mostly LDPEs. This novel approach creates a consistent quality starting material (thermoplastic prepreg) for composite manufacturing by extrusion coating. The wGF/wMP prepregs are then converted into laminates via compression moulding. Manufacturing as laminates rather than using extrusion/injection moulding (3D dispersion) ensures a uniform 2D dispersion of wGF in composites and minimises variability arising from different batches of wMP. Composite fire resistance, enhanced with various types and forms of fire retardants, is investigated using cone calorimetry.
The study involves optimising the wGF content, analysing the interface and assessing performance through mechanical and fire resistance testing. The reinforcing wGF were nonwoven mats from production waste with short fibres differing directionally in the longitudinal and transverse directions. A modified Halpin-Tsai equation was used to determine the theoretical tensile modulus of the wMP/wGF laminates, factoring in the void content and the directionality of the short wGF. The research provides valuable scientific insights into the application of mixed waste materials in composites, aiding the creation of a more circular economy for plastic waste and leading to new composite products. The results indicate that 40 wt% wGF in wMP leads to significant improvements in tensile strength (over 300%), tensile modulus (600%), flexural modulus (~800%), compressive strength (350%), and compressive modulus (~700%) compared to unreinforced wMP.
This project involves Johns Manville and PALTECH. A patent application was filed in July 2023.
Additionally, 150000 tons of glass fibres (GF) end up in landfill in the EU each year, and approximately 67% of GF is sent to landfill sites in the UK each year. Adding GF to waste plastics can convert these disposable materials into value-added composites suitable for a range of applications, such as construction.
This study proposes a technology redirecting two waste streams from landfill to marketable product forms and focuses on manufacturing composites with waste mixed plastics (wMP) reinforced with waste GF (wGF). The wMP used undergoes only one stage of separation (float-sink method) resulting in plastics with densities lighter than water, mostly LDPEs. This novel approach creates a consistent quality starting material (thermoplastic prepreg) for composite manufacturing by extrusion coating. The wGF/wMP prepregs are then converted into laminates via compression moulding. Manufacturing as laminates rather than using extrusion/injection moulding (3D dispersion) ensures a uniform 2D dispersion of wGF in composites and minimises variability arising from different batches of wMP. Composite fire resistance, enhanced with various types and forms of fire retardants, is investigated using cone calorimetry.
The study involves optimising the wGF content, analysing the interface and assessing performance through mechanical and fire resistance testing. The reinforcing wGF were nonwoven mats from production waste with short fibres differing directionally in the longitudinal and transverse directions. A modified Halpin-Tsai equation was used to determine the theoretical tensile modulus of the wMP/wGF laminates, factoring in the void content and the directionality of the short wGF. The research provides valuable scientific insights into the application of mixed waste materials in composites, aiding the creation of a more circular economy for plastic waste and leading to new composite products. The results indicate that 40 wt% wGF in wMP leads to significant improvements in tensile strength (over 300%), tensile modulus (600%), flexural modulus (~800%), compressive strength (350%), and compressive modulus (~700%) compared to unreinforced wMP.
This project involves Johns Manville and PALTECH. A patent application was filed in July 2023.