Fire Properties

Plastic flammability and secondary effects of burning plastics has become an important factor for the choice of plastic material in a specific construction.  Plastics can ignite both from contact with an open flame and through an electrical overcharge. The thickness of the material is of vital importance, the thinner component, the easier it ignites and the faster it burns. It is of general interest to find ways to classify materials to regarding its fire properties.

Some plastics emit corroding gases, i.e. PVC that emits hydrochloric acid gas at about 200°C. Fire retardant additives are also often based on chlorine or bromide compounds that when heated give off halogen or halogen-hydrogen which are acid and corrosive.

Fire properties are normally certified in the following grades: UL V-0, UL V-1, UL V-2 and UL HB.

MonoBlock™ Heat Exchangers

The MonoBlock™ heat exchanger is available in two different options, normal grade and flameproof. Heat exchangers of the normal grade are manufactured of virgin Polypropylene Co-Polymer. The flameproof option fulfilling UL V-0, is the same base polymer material as the normal grade with approximately 10% flame retardant additives. The Flameproof MonoBlock option is a recognised component by Underwriters Laboratories Inc.

UL Test Procedures

Vertical mounted test specimen: A vertically mounted standard testing specimen is ignited at its lower end with a Bunsen burner during specified conditions. The time of fire is then measured from the moment when the burner is removed. If the test specimen doesn’t let of any burning droplets and the fire goes out within 5 seconds (average of 10 measurements), the material is classified according to UL V-0. If the test specimen burns for more than 5 seconds and the fire goes out within 25 seconds and the specimen doesn’t let of any burning droplets, the material is classified according to UL V-1. The material is classified according to UL V-2 if the fire of the specimen goes out within 25 seconds and burning droplets falls from the tested specimen.

Horizontal mounted test specimen: If the material doesn’t fulfill the requirements from the vertical tests (UL V-0, V-1 and V-2), the fire properties is tested with horizontal mounted specimens. During these test the specimen is ignited at one of its ends and the velocity of which the specimen burns is measured. If the velocity is less than 62,5 mm/min for a 3 mm thick specimen, the material is classified according to UL HB.