Materials Science : Chemical Properties of Plastics Quiz

*Theme/Title: Chemical Properties of Plastics
* Description/Instructions
Many applications require that plastics retain critical properties, such as strength, toughness, or appearance, during and after exposure to natural environmental conditions. Plastics have a variety of chemical properties.

The absorption of UV light, mainly from sunlight, degrades polymers in two ways. UV light degrades polymers and it can make polymers brittle. Oxidation is a degradation phenomenon when the electrons in a polymeric bond are so strongly attracted to oxygen atoms outside the bond that the polymer bond breaks. Environmental stress cracking occurs when the plastic is exposed to hostile environment conditions and mechanical stresses at the same time.

Crazing. In some cases, an environmental chemical embrittles the plastic material even when there is no mechanical stress applied. Cracks may also appear when the plastic part is stresses (usually in tensile) with no apparent environmental solvent present. Permeation is molecular migration between polymer molecules.

Permeability is a measure of how easily gases or liquids can pass through a material. All materials are somewhat permeable to chemical molecules, but plastic materials tend to be an order of magnitude greater in their permeability than metals.

Flame spread classification ratings are defined as follows:

Flame spread rating Classification
0-25 Noncombustible
25-50 Fire retardant
50-75 Slow-burning
75-200 Combustible
Above 200 Highly combustible

Most untreated plastic materials will burn. Combustion properties of polymers can be improved by the use of additives.

Resistivity of a material is the resistance that a material presents to the flow of electrical charge. Dielectric strength is the voltage that an insulating material can withstand before breakdown occurs. It usually depends on the thickness of the material and on the method and conditions of the test.

For the following quiz, review the above summary to assist you in answering the question. Select the best choice from the given answers.

Group: Science Science Quizzes
Topic: Materials Science

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