Plastics Technology Practice - The Hong Kong Polytechnic University

Plastics Technology Practice
calculated. Smaller density means lighter in weight if the volume of the
materials is the same. ISO 1183
• Water Resistant describes how well an plastic part resists to water
passage. Especially in some outdoor electrical device waterproof should be
considered.
• Dimensional Stability is the property of a polymeric part to retain its form
when subjected to varying degrees of thermal, moisture, pressure, or other
stress.
• Softening and Melting Temperature is the temperature when the
material will soften and melt. Different environment and purpose may
require different temperature range. ISO 75
• Flammability of plastics is tested accordingly Underwriters Laboratories
UL 94 to measure the resistance of plastics to a fame source. UL approval
is given for a particular product at a measured thickness with ratings
ranging from least flame retardant to most flame retardant as HB, V2, V1,
V0, 5VB and 5VA.
• Electrical properties are the resistance, insulation, dielectric strength,
dissipation factor of the plastics. ISO 1325, ISO3915, ISO1325, ISO1325.
• Optical properties are the gloss, transparency, haze, colour and refractive
index of plastics. Plastics can be product with a wide of range of colours to
meet the lifestyle demand of people. ISO 489
2.5.2 Mechanical properties considerations
Mechanical properties describe how a material responds to the application of a
force or load. The followings are some common mechanical properties.
• Tensile Strength is the ability of a material to withstand forces pulling it
apart. ISO527-1
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