Flammability testing electrical applications

DeMaio and Baushke [6] used flammability tests to select elastomeric materials, which meet industry flammability standards, with the emphasis on elastomeric materials for mass transit applications and electrical applications. The intricacies of the UL 94 VO listings are briefly considered, flammability ratings for cellular silicones are tabulated and regional fire testing services and UL laboratories in the USA and Canada are listed. 

To reduce the likelihood that a system will experience fire, many Companies write UL VO listings into contract requirements when purchasing electrical enclosures. The UL VO listing is a stringent flammability test for elastomers. But just because a material can serve in high temperature applications, does not automatically guarantee that it has adequate flammability resistance to qualify for the UL 94 VO rating. A case in point is the various brands of silicone. 

Underwriters Laboratories (UL) provide Standards UL 94 Tests for Flammability of Plastic Materials for Parts in Devices and Appliances. The standard is important for classifying polymeric materials (including polymer blends and alloys) for the use in electrical applications. It is widely used and the results are reported in the literature and in company catalogues. However, the requirements are not applicable to polymeric materials used in building construction or finishing. The tests conducted under this standard are summarized below. 

Plastic coating materials have been exposed to all lands of performances and environments to meet the many different requirements that exist in the many different applications. Included are corrosion and chemical resistant, fire retardant or non-flammable, strippable, heat resistant, electrical insulation, and others reviewed above (Chapter 2). What follows is information that highlight some of the properties and tests that influence the performance of coatings. 

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