Development of a recycling solution for waste thermoset material: waste source study, comminution scheme and filler characterization

Abstract

End of life electrical equipment is a continuously increasing source of waste in our modern society, and constitute an environmental problem. Understanding this type of waste flow is important to devise proper dismantlement and sorting strategies, and to maximize the material recovery rate and valorization. In this work, a waste pool constituted of electrical meter was studied. The specificities of this equipment in term of design were enlightened, and the overall material composition was determined. An emphasis was put on the characterization of the plastic fraction, both in term of plastic type and presence of regulated substances. It revealed that this fraction is mostly composed of phenolic molding compound (PMC), a thermoset material, which is troublesome in term of recycling. A material valorization solution through mechanical recycling is proposed , consisting in using PMC as functional filler in a thermoplastic matrix. A comminution scheme to obtain such filler is presented in this work, and the comminuted products are characterized. Through 2 or 3 steps of comminution, particle size below 50 µm can be obtained, which is expected to be a sufficient size for incorporation in a thermoplastic matrix.

A Review on the Potential and Limitations of Recyclable Thermosets for Structural Applications

“…The small-sized (<50 mm diameter) powder obtained after mechanical grinding can generally only be used as a filler in new thermoset and thermoplastic materials. 27 Unfortunately, these powders cannot compete economically with conventional filler material such as calcium carbonates and silicates. 28 To have any added value as filler, the ground products should therefore give an additional form of reinforcement as was intended in the original application.…”

Plastic Pollution: A Material Problem?

“…28 The same applies to the other cross-linked polymer class, the thermosets, which can be mechanically ground into small particles (<50 μm) and used as fillers for making composites. 29,30 Thermosets are important polymer matrix materials for making fiberreinforced composites for demanding applications with approximate global production of 65 million tons per year.…”

“…Parallel efforts are being made for waste management and new end-of-life options for rubbers. , For example, ground rubber is used as an additive to asphalt for civil engineering applications to reduce after-use waste . The same applies to the other cross-linked polymer class, the thermosets, which can be mechanically ground into small particles (<50 μm) and used as fillers for making composites. , Thermosets are important polymer matrix materials for making fiber-reinforced composites for demanding applications with approximate global production of 65 million tons per year. Impressive efforts are being made to introduce new concepts of mechanically recyclable thermosets, such as vitrimers, which are recyclable and moldable upon heating in the same way as thermoplastics.…”

Evaluation of the presence of potential hazardous substances from plastic and textile fibre recycling

“…A disadvantage of this approach is that the thermoset matrix and the carbon fibres are not treated separately and as such any orientational advantage of the filler material is lost. The powder obtained after mechanical grinding is generally only used as a filler in new, for example thermoplastic, materials (Bernardeau et al, 2018).…”