Development of a Tough and Flexible Halogen Free Dual Layer Wire insulation System for Electronics Applications

摘要

Due to strict environmental regulations, insulating materials for electrical wires are required to be not only flame retardant but also generate very low smoke upon flaming. Insulation systems containing halogens evolve harmful hydrogen halide gases upon burning. These gases are acidic and toxic in nature. Due to this reason, there have been increased requirements to use insulation systems that contain halogen free flame retardants. However, in order to impart a similar level of flame retardency as halogen containing compounds, these materials must have a very high level of fillers such as metal hydroxides and other inorganic materials. Unfortunately, such high loadings of halogen free, flame-retarding agents adversely impact the physical and mechanical properties (e.g., toughness, flexibility) and processability of the resulting insulating material. The present paper describes the development of a low-smoke, halogen free flexible dual layer insulation system (Flexrad HF Dual Wall), which demonstrates excellent mechanical, thermal and flame characteristics. A key characteristic of this dual wall system is the ratio of the inner to the outer layer thickness. The results of an experiment to determine an optimum ratio of the inside XLPO layer to the outside jacket layer are discussed. We conclude that the thickness of the jacket layer relative to the thickness of the inside insulating layer will influence the ability of the wire to meet the stringent requirements of the UL VW-1 Vertical Flame Test. Further, this thickness ratio influences the ability of the wire to demonstrate very high cut-through resistance.