Several presentations and posters at FRPM addressed recycling:
Jiuke Chen, Empa, presented tests recycling of PET fibres (two re-extrusion cycles, without ageing) containing phosphorus PIN FRs (DOPO derivate, phosphinate) – see Poster Awards above.
Valeria Berner, Fraunhofer ICT, presented recycling of epoxy vitrimers (with an amine hardener containing disulfide bonds) with different commercially available phosphorus PIN FR Vitrimers are innovative polymers which act like thermally-reversible thermosets, see pinfa Newsletter 139. After one reprocessing cycle at 220°C results showed deterioration of fire performance after reprocessing in some cases, but maintained performance in others. Poster online here: https://publica.fraunhofer.de/handle/publica/445003
Marcos Batistella, José‐Marie Lopez‐Cuesta, IMT Mines Alès, Constantinos Xenopoulosc, Holcim, presented tests using specific grades of fly ash from a thermal power plant as an engineering filler in PIN FR systems (ammonium polyphosphate and melamine polyphosphate) for several different polymer systems.
Marcos Batistella, Dylan Seigler, José-Marie Lopez‐Cuesta, IMT Mines Alès summarised tests of reuse of non-sintered polyamide-12 3D-printing powder in LSL printing (Laser Sintered Layer), with and without added PIN FRs. In SLS, layers of powder are deposited, then in each layer the shape is created by laser melt-bonding the polymer, then removing the remaining non-sintered powder. Non-sintered powder was reused in the SLS process for four cycles (total five builds). Addition of ammonium polyphosphate in PLA resulted in changes in the sintering temperature window. Addition of zinc borate showed agglomeration of the FR in reprocessing, probably because it reacts with the laser frequency.
Hai-Bo Zhao, Sichuan University, China, presented laboratory development of chemically recyclable PIN FRs. An experimental phosphorus-siloxane polymer fabric FR coating (wash resistant) could be reversibly redissolved using ethanol. An experimental tannin plus DOPO PIN FR in polyurethane foam could be redissolved out for recycling.
Richard Clay, Stephen Blair, PCL, showed successful mechanical recycling (one reprocessing cycle) of PC/ABC with polyphosphonate PIN FRs (see above)
Dániel Gere and Katalin Bocz, Budapest University of Technology and Economics, presented tests of APP (ammonium polyphosphate) and MMT (montmorillonite) as a PIN FR and synergist in recycled polyethylene (HDPE) reprocessed from post-consumer bottle caps. The objective was to produce a material for outdoor building decorative panelling, so a UV stabiliser was also included (8 hydroxy-benzophenone). Hot pressed samples achieved UL 94 V-0 with 25% APP and 1.5% MMT (the recycled HDPE was UL 94 non-rated without PIN FR addition).
Lein Tange, ICL, summarised the challenges to recycling E&E and technical plastics. Only 6-7 % of post-consumer collected plastics are technical polymers, so sorting and recycling are very uneconomic. A further challenge is the sorting of black plastics, for which Near Infra Red (NIR) laser sorting cannot be used to efficiently separate individual polymers. Consequently, heavier weight polymer plastics are currently in Europe mainly going to incineration or co-combustion in smelters (recovery of precious metals from circuit boards and from other components): HIPS, ABS, PC, PVC, polyamide. Where technical plastics are collected, up to three quarters can often not be recycled because of contamination with other materials or mixing of polymers. Technical polymers have long service lives (several years for E&E, seventeen years on average for automotive, up to half a century for construction materials) so that collected materials are contaminated by “legacy” additives. An increasing proportion today contains chemicals designated as POPs, such as legacy brominated FRs or PFAS, for which the new limit for recycling of 75 ppm for HBCD / 500 ppm for POP PBDEs will be a major obstacle for mechanical recycling but is possible with solvent based purification recycling. The key economic driver for recycling of E&E remains the metal content (copper, silver, gold, rare earths).
Frederico Ulisse, Padova University, presented testing in compression moulded polypropylene of flue gas desulfurization gypsum (main constituent: calcium sulphate dihydrate) with PIN FRs (melamine cyanurate, phosphate ester – the latter also providing plastification. UL94‐V2 (3.2 mm) was achieved. The gypsum inhibits fire by releasing water with heat and contributes to char glassification.
Sophie Duquesne, Lille University, tested whether post-consumer recycled polymers could achieve fire performance standards (PEPSIr project, funded by EcoSystem). HIPS from large household appliances, as being the most available post-consumer EEE polymer (25% of arisings), was considered. Commercially recycled HIPS (rHIPS), with addition of brominated flame retardants (at supplier recommended loadings), was not able to achieve the same levels of fire performance under the glow wire GWFI test as virgin HIPS. Full characterisation of the rHIPS was carried out to identify additives and contaminants resulting from various stages of the first life of the material including inherited substances as well as sorting errors. Deterioration of the HIPS polymer itself was found to be limited. Further studies with model materials are in progress to link the ability of recycled materials to be flame retarded with these additive and contamination aspects.