Kathrin Lehmann, Evonik, summarised the advantages of organomodified siloxanes (OMS) as functional PIN synergists. Inclusion of specific functional groups onto the ends or sides or siloxane molecular chains enables either full polymer compatibility, or to ensure that part of the OMS molecule embeds in the polymer whilst part remains outside giving interface properties.
OMS can thus improve melt flow behaviour, surface appearance or electrical performance of PIN FR polymer compounds and reduce “die drool” in cable extrusion. For example, 1% of specific OMS with inorganic FRs can enable to combine UL94-V0 with melt flow and CTI specifications in polyamides / glass fibre polyamides, TPO/polyethylene or polypropylene. This addresses applications such as thin wall electronics parts or performance cables.
Swaraj Paul, Paxymer, presented the company’s development of PIN FR synergists based on carboxylic functional polymers and acrylate copolymers, which can be used with phosphorus, inorganic or nitrogen flame retardant systems. This enables PIN FR systems in polymers such as polyolefins which do not drip and release no toxic gases in fire [toxicity as tested by pyrolysis (pyr)/ gas chromatography (GC)/ mass spectroscopy (MS]. These systems function for example generation of a fire-protecting carbonaceous char, the stability of which is increased by generation of phosphorus oxynitride, and by release of phosphoramidic acid, a gas phase radical scavenger.
Bansi Kaul, MCA Technologies, presented his company’s PPMT (poly(piperazinyl,morpholinyl)triazines) PIN FR synergists (see previous AMI conferences in pinfa Newsletter n°s 80, 76, 61). In addition to combining PPMT with calcium carbonate and ultracarb (a natural magnesium mineral), previously presented, he showed tests of PPMT in EVA (ethylene vinyl acetate) or HDPE (polyethylene) polymers with PIN FRs and synergists including: kaolin (a natural aluminium silicate clay), piperazine pyrophosphate, APP (aluminium polyphosphate) and siloxane-coated APP, zinc borate, ATH (aluminium trihydrate), MDH (magnesium hydroxide), montmorillonite clay and stearic acid (for intumescence and dispersion). The mechanism of PPMT is presented as the rapid production of resistant intumescent char (reduced shrinking and cracking) due to formation of oxynitrides, which ceramify char structure and increase heat dispersion
De-Yi Wang, IMDEA Materials Institute, Madrid, Spain presented research into new functionalized nano-materials as PIN flame retardants (layered double hydroxides, nano-clays, nano-carbons, nano silicates, etc.) as well as composites combining e.g. minerals (such as iron or aluminium) into nano-materials, or use of nano-materials as interfacial catalysts for ammonium polyphosphate (nano silicates on the surface of APP). These combinations showed better fire performance in epoxies, EVA, PS, PLA etc. than non-functionalised nano-materials or flame retardants without nano synergists. In addition, a new flame retardant mechanism has been proposed.