Liquid Flame Retardant For Prepregs and PU Foams

The project is to produce a novel liquid flame retardant for applications where powder flame
retardants are unsuitable or unsatisfactory. Such applications include epoxy composite
prepregs, resin infusion systems, resin transfer moulding, filament winding , transparent roof
profiles and polyurethane and polyisocyanurate foams.
PD is manufacturing a series of flame retardants including a powder product, Phyrolex
HMED that is proving to be a remarkably efficient flame retardant for most thermosets.
However while it exceeds the performance of other powder flame retardants in loadings and
lightweighting ability it still creates the same problems in terms of formulation and process
complexity and lack of transparency. Powder flame retardants cause a loss of physical
properties, filtration of the powder within the reinforcement, decreased environmental
stability and in the case of halogens, a significant increase in smoke toxicity. Phyrolex HMED
can resolve some of these issues but not filtration and physical property reduction.
The Phyrolex powder chemistry relies on the neutralisation and precipitation of a complex
oligomeric partial phosphate ester. A new nitrogen containing neutralising agent yields very
viscous glass-like liquids with the existing flame retardant partial phosphate esters. The
project proposes to develop novel partial phosphate esters that when, neutralised, will yield a
lower viscosity liquid flame retardant that can be dispersed in polyester and epoxy resins and
polyols for PU and PIR foams. The new product will give the same excellent fire performance
as the Phyrolex powder but as a liquid it will not affect the process sequences listed above. It
will be easy to formulate and assist the drive by all market sectors to lightweight composite
structures, vital for energy saving .
The project will guide the modification of existing Phyrolex reactors and processes such that
commercial production can be started at the moment of first demand.