Yiming Zhang, Case Western Reserve University, discussed possible alternatives to PTFE to prevent melt-drip. PTFE (PTFE (polytetrafluoroethylene, a PFAS chemical) is widely used at low doses to prevent melt-drip of polymers in fire, in particular for PIN-FR thermoplastics. Polymer dripping in fire results from melting (above polymer glass temperature Tg) and polymer decomposition. Burning drips in fire can spread the fire. Melt-drip therefore causes failure of V-0 in UL 94 fire performance testing. In fire, PTFE causes shear-induced fibrillation, effectively entangling the polymer molecules, preventing melt-dripping, and is effective at doses of only 0.5% wt. Many PIN FRs somewhat reduce melt-dripping, e.g. by physical structure (mineral fillers) or by generating char, but these effects require high loadings or are insufficient to achieve UL 94 V-0. Some PIN FRs or PIN synergists do however show potential to be more effective through specific effects on the polymer during fire melt and decomposition: by ceramification (e.g. Tolsa, pinfa member, nano mineral silicates, by causing cross-linking of polymers; Paxymer carboxylic and acrylate polymers, silicones, …) or by generating porous particles which help maintain polymer structure (e.g. zinc borate). These specific PIN FRs have proved able to achieve UL 94 V-0 in certain polymers at 1 – 2 % wt.
Looking for non-halogenated anti-drip
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