UL 94 Safety Standards – Why the fuss?

What is UL 94 Standard?

UL 94 is the standard for safety of flammability of plastic materials for parts in electrical equipment and accessories.

Performed by the Underwriters Laboratories, UL 94 classifies plastics based on how they burn, with orientation and thickness level determining a plastic’s tendency to extinguish or spread the flame once ignited, and how well the material resists ignition.

 

 

How is UL 94 Standard Achieved?

Plastic material testing is undertaken with either a Horizontal Burn (HB) test or Vertical Burn (VB) test, determined by the materials application requirements. During all tests the materials are subject to a flame source for a set duration of time.

The UL 94  standard  encompasses multiple ratings for solid plastic materials including:

V-0 (Vertical Burn): Burning stops within 10 seconds after two applications of ten seconds each of a flame to a test bar. No flaming drips are allowed.

V-1 (Vertical Burn): Burning stops within 60 seconds after two applications of ten second each of a flame to a test bar. No flaming drips are allowed.

V-2 (Vertical Burn): Burning stops within 60 seconds after two applications of ten seconds each of a flame to a test bar. Flaming drips are allowed.

5VA (Surface Burn): This is the highest (most flame retardant) UL94 rating. Burning stops within 60 seconds after five applications of five seconds each of a flame (larger than that used in Vertical Burn testing) to a test bar. Test specimens may not have a burn-through (no hole).

5VB (Surface Burn): Burning stops within 60 seconds after five applications of five seconds each of a flame (larger than that used in Vertical Burn testing) to a test bar. Test specimens may have a burn through (a hole).

H-B (Horizontal Burn): Slow horizontal burning on a 3mm thick specimen with a burning rate less than 3”/min or stops burning before the 5” mark. H-B rated materials are considered “self-extinguishing”. This is the lowest (least flame retardant) UL94 rating.

 

 

Why is the UL 94 Standard useful?

By awarding certification for electrical parts and appliances manufacturers, UL 94 offers many advantages including:

 

 

Reduced Safety Hazards

Increased Equipment Performance

Consumer Confidence Boost

Minimised Replacement Costs

 

UL 94 Certified Products Available from Ellsworth Adhesives:

Robnor ResinLab HX439N A thermally conductive flame retardant potting and encapsulating compound offering high adhesion, low shrinkage and good chemical and water resistance.	DOWSIL HC 1100 A one part RTV solventless silicone conformal coating. Grey in colour, HC 1100 offers a fast tack-free, controlled volatility and low viscosity cure.	Dymax 903-E A UV/moisture-cure conformal coating engineered for a quick cure, high chemical resistance, and is tack free immediately after cooling.
Robnor ResinLab PX700K-1 A general-purpose flame retardant potting and encapsulating compound with good thermal conductivity and high electrical insulating characteristics.	Lord SC-309 A two part thermally conductive silicone system with low stress characteristics and superior high temperature electrical properties as associated with silicone resins.	Henkel Loctite Stycast 2850 FT A two component, room temperature curing, epoxy encapsulant offering a low coefficient of thermal expansion, electrical insulative and thermally conductive properties.