PIN flame retardants can be compatible with polymer recycling
MECHANICAL RECYCLING = re-using the plastics as such after separation of different kinds, grinding, melting etc. and turning into new products
FEEDSTOCK RECUCLING = breakdown of the plastics into their chemical constituents which can then be used to produce new plastics or other materials
ENERGY RECOVERY = capturing the energy content of plastics, usually by combustion with proper energy generation (electricity, heat, steam)
PIN flame retardants due to their chemical composition do not contribute to possible risk of emissions of dioxins and furans in case of burning of polymers in non-controlled conditions without adequate offgas cleaning. On the other hand, the nitrogen present in PIN flame retardants may increase marginally potential greenhouse gas emissions from incineration of polymers, again if offgas cleaning is not installed.
Also, PIN flame retardants are a first-choice, for sustainability reasons, for companies developing polymers from recycled waste feedstock and wishing to ensure fire safety performance.
SONY 90% recycled feedstock SORPLAS polycarbonate uses a sulphur-based PIN flame retardant.
The material is also multiple recycling compatible. Link
PIN flame retardants can be produced using recycled (secondary) raw materials
Full-scale pilot industry tests have demonstrated that phosphorus can be recovered from sewage sludge or other ashes, and used as a raw material for industry, including PIN flame retardants production (see)
Magnesium industry by-products can be used as input to mineral PIN flame retardant production (see e.g. “Recovery of Magnesium from Waste Effluent in Nickel Laterite Hydrometallurgy Process”, Sun et al., 2012 )
Some PIN flame retardants can be recovered as such during polymer recycling, e.g. “Recovery of triphenyl phosphate from waste printed circuit boards by solvothermal process, Zhang et el., 2013 (see)
Basic chemicals used in PIN flame retardants can be recovered
it is possible to recover some of the basic chemicals used in PIN flame retardants (phosphorus, minerals) in processes where waste polymers are treated (e.g. metal smelters used to recover copper and rare earths from electronic wastes, incinerators producing energy from waste plastics), although this is not to date operational.
A presentation published on ‘Flame Retardancy of Polymers’ website addresses end-of-life recycling issues relating to use of PIN (Phosphorus, Inorganic, Nitrogen) flame retardants in electronics and electrical equipment. Results of materials recycling tests with phosphorus based (organic phosphinic salt) flame retardants show that mechanical and fire safety properties are maintained after several recycles (mixture 50% recycled, 50% new materials). “Flame Retardants: Design for Environment and End-of-Life: is there a life after WEEE, RoHS and REACH?”, A. Beard (Clariant & pinfa) PDF Link
Research into recycling of PIN flame retarded products is developing as these are increasingly used in consumer and industrial products to replace halogenated substances. At the same time, major manufacturers are already implementing recyclable PIN polymer solutions. For example: recyling non-halogenated flame retardant polypropylene : “LeanDfd: A Design for Disassembly Approach to Evaluate the Feasibility of Different End-of-Life Scenarios for Industrial Products”, C. Favi et al., 2012 (see)
Pinfa is developing its own work investigating PIN flame retardant compatibility with polymer recycling, in order to have more publicly-available references. A project has been designed with the Fraunhofer Institute for Structural Durability and System Reliability (LBF). Fraunhofer LBF press release 16/2/2016