Less than 10% PIN FR loading, plus a chain extender, enabled production of quality PET foam from post-consumer bottles. Aluminium-tris-(diethylphosphinate) 8% with montmorillonite (MMT) nanoclay 1% were used as PIN flame retardant and a multi-functional epoxy-based styrene-acrylic oligomer as chain extender (1%). Both foam and injection moulded plates were produced from the recycled PET. PIN FR addition decreased foam cell size, probably due to decreased melt strength, deteriorating foam strength and elasticity. This was resolved when the chain extender was added. Both plates (2 mm) and foam samples achieved UL 94 V-0. Limiting Oxygen Index (LOI) was improved to c. 28 and 31 for FR recycled PET plates and foam, compared to c. 23 without FRs and peak heat release rate (PHRR) was around 50% lower. The authors conclude that these PIN FRs at <10% loading, used with a chain extender, enable recycling of post-consumer PET to quality, fire performance material.
“Flame retardancy of PET foams manufactured from bottle waste”, K. Bocz et al. Journal of Thermal Analysis and Calorimetry 2022 https://doi.org/10.1007/s10973-022-11423-3