Understanding Plastics Properties Part 1: Temperature and Conductivity Considerations

With so many different plastics and plastics properties, it can be overwhelming to know which type to use. In part 1 of our Understanding Plastics Properties guide we’ll look at all plastic properties that pertain to temperature and conductivity:

  • Flammability: A measure of how a material burns under specific conditions (UL94 is the standard for flame ratings). Ratings are listed by thickness and time and are usually supplied by resin suppliers.
  • Dielectric Constant: The rate in which stored energy is released from the plastic. This allows you to compare the rate an electric current passes through different plastics.
  • Dissipation Factor: Measures the dielectric loss in an AC current. This is measured as heat since heat is usually not wanted. For use in electrical applications, look for plastics with a low dissipation factor.
  • Dielectric Strength: The voltage where a 1mm sample fails as an electrical insulator. This property is used to compare materials, not as design criteria.
  • Volume Resistivity: Another way to measure electrical insulation properties. In this case, it estimates how many amps go through the material with a given application of volts.
  • Melt Point: The temperature when crystalline or semi-crystalline material turns from solid to liquid.
  • Glass Transition Temperature: The temperature when amorphous material softens. This is particularly important in thermoforming as this is the min temperature needed to form the material.
  • Continuous Use Temperature (CUT): The maximum temperature a plastic can withstand air for 100,000 hours (11 years) with no load and still retain min 50% of its physical properties. This property is especially important for lightly loaded parts that must withstand long-term elevated temperatures.
  • Heat Deflection Temperature: The temperature when a 0.5 inch thick test bar deflects 0.010 inches. This is essentially a working stress number, an indicator of the maximum operating temperature of a material under load. Usually reported with a load of 264 PSI.
  • Thermal Conductivity: The rate in which heat is conducted through the plastic and determines the materials’ suitability to act as thermal insulator. Lower values of this property mean better thermal insulation.

These are just a few of the properties used to compare plastics. For help choosing the right plastic material for your project, contact the Plastifab team today.

(Next month, we’ll look at other properties of plastics including friction, weight, and strength.)

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