Recent Development of Phosphorus Flame Retardants in Thermoplastic Blends and Nanocomposites

Abstract

With the increasing use of thermoplastics and thermosetting polymers on a large scale for applications in buildings, transportation, electrical engineering and electronics, as well as the high fires safety standards which polymer resins should meet, a large variety of flame retardant products have been developed over the past 40 years. Restrictions on the use of polybrominated diphenyl ethers (PBDE) have resulted in the increased use of alternate flame retardant chemicals, such as phosphorus flame retardants (PFR). PFR contains a wide group of different organic and inorganic compounds, with a great variation in their physico-chemical properties. They are non-flammable, non-explosive and odorless substances listed as High Production Volume Chemicals (HPV). Non-halogen, phosphorus-containing flame retardants such as ammonium polyphosphate and red phosphorus are shown to be very effective in thermoset resins. Phosphate esters significantly lower the heat distortion temperature and impact properties of PC/ABS blends while increasing melt flow in so called antiplasticization process. Resorcinol diphosphate (RDP) was the first material developed for PC/ABS and it is a liquid additive with 9 % P content and good efficacy as a flame retardant. Bisphenol A bisphosphate (BADP) is another liquid with properties similar to RDP. Polymer–clay nanocomposites have attracted a great deal of interest due to their improved mechanical, thermal and biodegradability properties. Nano “sponge” structures produced from cyclodextrins have been tested with flame retardants ammonium polyphosphate (APP) and triethylphopshate. The PFRs can be enclosed in the nano sugar sponge structure, improving mixing with plastic polymers and enabling high flame retardant loadings without deteriorating polymer mechanical performance. Fire performance tests using the nano sugar sponge—PFR combination (heat release, heat of combustion, mass loss, smoke) showed that the combination was effective for environmentally friendly structures polypropylene, linear low density polyethylene and polyamide 6.