Abstract
Waste electrical and electronic equipment (WEEE) is growing rapidly, and the plastics within WEEE have an important role in fulfilling the recovery and recycling targets defined in the European WEEE Directive. This study considers recycling of WEEE plastics by making a blend of the different plastics instead of separating them. The mechanical and thermal properties can be enhanced by adding a compatibilizer. It was found that one compatibilizer, a styrene-b(ethylene-co-butylene)-b-styrene (SEBS) copolymer named Kraton® G1652 E, had a large impact on the ductility of the recycled WEEE plastics blend. By adding 2.5 weight % (wt%) of this copolymer, the elongation at break increased by more than five times compared with the non-compatibilized samples, with only a small decrease in stiffness and strength. The storage modulus (G’) decreased slightly with increasing compatibilizer amounts while the impact strength increased with increasing amounts of compatibilizer, from 2.1 kJ/m2 (reference material) to 3.6 kJ/m2 (5 weight % (wt%) compatibilizer). It was found that Kraton® FG1901 E (styrene-b(ethylene-co-butylene)-b-styrene (SEBS) grafted with maleic anhydride (MAH)), Royaltuf® 372P20 (styrene acrylonitrile (SAN) modified with ethylene-propylene-diene elastomers (EPDM)) and Fusabond® P353 (polypropylene (PP) with a high degree of grafted MAH) were ineffective as compatibilizers to the blend. Gamma irradiation (50 kGy) did not improve the mechanical properties however: the impact strength of the gamma-irradiated samples was lower than that of the non-irradiated samples.
Highlights
Electronic waste is one of the fastest growing waste streams today, making it important to find new recycling strategies for the different materials included, for environmental, legal and economic reasons
Previous tests performed on WEEE plastics blend of recycled material (WEEEBR) have shown low elongations at break and low impact strengths [13], indicating poor compatibility between the phases, suggesting it is a very brittle material
The MFR decreased with increasing amounts of compatibilizer for the WEEEBR; see Table 5
Summary
Electronic waste is one of the fastest growing waste streams today, making it important to find new recycling strategies for the different materials included, for environmental, legal and economic reasons. The conventional way of recycling plastics is by means of different sorting and separation steps followed by melt-blending of the different types [9] Such a recycling method may leave large rest fractions that are excluded from recycling. We have investigated the use of a compatibilizer to enhance the mechanical properties of a blend material of all of the different thermoplastics within WEEE, with the exclusion of thermosets and other contaminants that could impact the processing equipment or recycled blend negatively [13]. This process would simplify recycling by reducing many of the sorting, separation and washing steps. The influence of gamma irradiation on the plastic properties was investigated since it is known that it can, firstly, cause free radicals and with that either create crosslinks or chain breakage of the polymer chains [14], and, secondly, it can be used to graft one polymer onto another [15]
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