Teste de inflamabilidade de materiais plásticos para peças em dispositivos e aparelhos

UL-94 - Test for Flammability of Plastic Materials for Parts in Devices and Appliances

By Caroline Gold

Overview

Plastics have become one of the most useful types of

material known to mankind. Plastic is a high molecular

weight material composed of repeating organic molecules

(monomers). Due to their chemical composition, plastics

can often easily ignite when exposed to sufficient heat in

the presence of oxygen. Due the tendency for plastics to

burn, considerable efforts have been directed to study and

minimize the flammability issues of these materials.

Examples of such efforts are the use of design of experiments

to classify and measure burning characteristics of

plastics and the addition of flame retardant chemicals to

prevent or minimize the combustion of these materials.

There are a variety of industrial flammability tests that are

widely used in industry. Each one is designed to measure

different fire response characteristics. Unfortunately, most

of them fail to predict the behavior of plastics under the

massive effect of heat present in a large-scale fire.

Different sectors of the industry adopt different flame test

specifications. The specification that best meets the I/S

needs (and is mostly used by the electronic industry) is the

flammability specification known as UL-94.

Flammability Testing: UL-94

The test for flammability of plastic material used in parts for

electronic devices and appliances is commonly known as

UL-94. It is a flammability specification issued by the

Underwriters Laboratories Inc. Underwriters Laboratories

is a non-profit organization that operates laboratories

around the world for examination and testing of devices,

systems and materials. Underwriters Laboratories identifies

material properties and their hazards. They also

define and publish specifications that provide procedures

for testing each material.

The flammability specification UL-94, contains several

small-scale flame tests procedures that define parameters

for flame testing of plastic polymers. In this specification,

the behavior of plastic when exposed to fire is expressed

quantitatively. These numbers are obtained from measurements

of the "afterflame" time or from the amount of

material burned in a specific length of time. Afterflame time

refers to the length of time, in seconds, a material continues

to burn after removal of the heat source. The amount

of material burned refers to the length of sample that burns

in