Abstract
Composite materials comprising plastic and metal parts generate a large amount of waste containing valuable components that are difficult to separate and recycle. We therefore developed an economical solvent-based process for the recovery of costly manufactured composite materials comprising several copper panels over-moulded with a polymeric matrix of polybutylene terephthalate (PBT). We applied the CreaSolv® Process, which uses proprietary formulations with a low risk to user and environment, in order to dissolve the polymer and retain the inert copper. After separating the metal from the solution, solvent recovery was achieved by means of vacuum distillation and melt degassing extrusion. The recovered solvent was collected and recycled while maintaining its original properties. We tested two candidate solvents with PBT, measuring their impact on the molecular weight (Mw) and polydispersity of the polymer at different residence times and dissolution temperatures. We found that increasing the temperature-time-load had a negative effect on the Mw. Both solvents we tested were able to dissolve the polymeric matrix within 30 min and with moderate energy consumption. Furthermore, we found that the exclusion of oxygen during dissolution significantly increases the quality of the recovered polymer and metal. We transferred the process from the laboratory scale to the small-technical scale and produced material for large analytical and mechanical quality evaluation, revealing no decline in the polymer quality by blending with new plastic. The recovered copper met virgin material properties. Therefore, both components of the original composite material have been recovered in a form suitable for reuse.
Highlights
In certain areas of application, tailor-made plastics have properties which render them superior to natural materials and irreplaceable for modern technical applications
Composite materials containing plastic and metal parts are often used as electrical conductors, for example, in the automotive industry [1]
The influence of the dissolution and drying processes on the molecular weight and polydispersity (PD) of the polymer were analysed by gel permeation chromatography (GPC) to measure qualitative changes in the polybutylene terephthalate (PBT) [28,29,30]
Summary
In certain areas of application, tailor-made plastics have properties which render them superior to natural materials and irreplaceable for modern technical applications. Composite materials containing plastic and metal parts are often used as electrical conductors, for example, in the automotive industry [1]. These plastic-metal hybrid components require complex manufacturing processes to shape the metal parts and introduce the polymer by over-moulding the metal with plastic melt [2]. Such processes often generate large amounts of production waste due to the narrow tolerances during quality control, and the resulting waste streams usually have a high material value due to the presence of both expensive metals and high-performance plastics characterized by high. A non-destructive process for the recovery of both components would be highly beneficial
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