Screening new emerging flame retardant technology in various polymer matrices

Abstract

The scope of this work is the investigation of oxyimides as flame retardants for polymeric materials. Still under development, those new additives are currently not used in commercial applications. Early evaluation showed that they have good synergistic effects with common flame retardants. Conducted for PolyOne Corporation, the goal of this project is to identify the potential business opportunities this chemistry could offer to the company. The focus has been put mainly on injection molding polypropylene for Electrical and Electronic applications. In practice, the polymer formulations must pass some regulatory fire tests (UL 94 and Glow Wire) while having a total cost in line with the market price and presenting additional advantages. The work is thus part of an applied development program, though evaluation of a new chemistry inherently considers fundamental aspects. Fire safety engineering being mostly an empirical science, the core of the report lies mainly in the critical interpretation of obtained results. Oxyimides have been tested in combination with metal hydroxides (ATH, MDH and boehmite) and intumescent systems (APP and MPP-based). It has been found that oxyimides do not improve fire performances when employed with intumescent system, MDH and boehmite. On the other hand, they show good synergy with ATH when added in the 0.5-2 wt% range. Improved performances during tests and significant reduction of total loading has been achieved. For the obtained results, formulated compounds are cost-efficient compared to industry standards. Deeper study enabled to better understand modes of action of oxyimides in this specific system. It has been highlighted that the generated radicals responsible for their flame retardants properties act in a large part through a polymer degradation mechanism and associated dripping. If the test configuration or the action of other additives/fillers does not allow this “fuel run-away”, synergism is hindered. In combination with ATH, oxyimides have a neutral effect on the ease of ignition of the material.