Flame Retardants and their Recyclability, Reason for Environmental Concern

As of today it is estimated that 15 billion devices are digitally connected with one another and experts predict an increase to 50 billion devices in the IoT (Internet of Things) sphere by the year 2020. These things include not only computers, tablets and smartphones, but also wearables, consumer electronics and the vehicles we use. However, although this trend offers consumers far greater convenience, it can present recycling companies with a range of difficulties. Experts are looking at future design as well as recycling technologies to ensure that products remain highly recyclable.

But there are other materials that are causing headaches for recyclers. Apart from the increasingly complex materials, composites of mixed materials, the known legacy heavy metals and halogenated flame retardants, new additives are also beginning to emerge, such as nanoparticles, presenting recycling enterprises with new challenges.

Little research has been done into some of these newest materials with respect to how they behave in traditional recycling processes, he said. It is possible that some of these new materials and additives may also present new dangers with respect to environmental protection and industrial health and safety if not handled with care, particularly during shredding or other size reduction processing. Furthermore, it’s often not easy or even possible for the recycler to know which products have additives that might need special handling as these additives are sometimes kept secret as proprietary.

Annually 2.7 million tons of plastics containing Flame Retardants (FRs) are globally discarded in Waste Electrical and Electronic Equipment (WEEE). Little is known on the feasibility of closing material loops for FR plastics. Therefore, series of experiments were set up to analyze the feasibility of separating plastics containing FRs from one specific product category, namely End-of-Life (EoL) Liquid Crystal Display (LCD) TVs. The characterization of the housings of this waste stream indicated a concentration of 18 wt% Bromine based (Br) FRs and 31 wt% Phosphor based (P) FRs, the remainder not containing FRs. With practical tests it was demonstrated that, after disassembly and plastic identification, the co-polymer poly-carbonate (PC)/acrylonitrile-butadiene-styrene (ABS) containing PFR can be recycled in a closed loop system.

Based on the determined plastic density distributions and separation efficiencies of optical sorters, a purity of 82% was calculated for PFR PC/ABS separated from EoL LCD TVs after size-reduction (shredding). Performed miscibility tests indicated that for this fraction at least a factor 10 dilution with virgin material is required. In addition, higher waste volumes are required for a size-reduction based treatment to become economically viable and technical challenges still need to be faced, whereas closed loop recycling of PFR PC/ABS from the current waste stream of EoL LCD TVs of different brands in a disassembly based treatment is found to be technically feasible and economically viable under at least European boundary conditions.