Understanding Plastics Properties Part 2: Friction, Weight, and Strength

At Plastifab it’s our goal to teach you as much about thermoplastics as we can so you have the information to make an informed decision for your next plastic project. We’re always here to lend our expertise, but the more you know about plastics can help speed up the process.

Last month we looked at plastics properties that related to temperature and conductivity. This month we look at properties that pertain to friction, weight, and strength:

  • Specific Gravity: This is the ratio of weight of the plastic vs. the weight of the same volume of water. The higher the gravity, the heavier the part (specific gravity less than 1.00 is lighter than water and thus will float).
  • Density: This is the theoretical weight of the plastic.
  • Tensile Strength: This is a measure of the force required to break the plastic.
  • Tensile Modulus: Similarly, tensile modulus is the ratio of the stress being pulled to strain within the elastic limit.
  • Coefficient of Friction: This is a measure of how well a plastic slides against another material. It refers to the force needed to start a slide (static) and to keep it moving (dynamic).
  • Moisture (Water) Absorption: The percentage increase in weight of a plastic based on how much water it absorbs, or saturates over a 24-hour period. The more water it absorbs usually means the material will enlarge, soften, and become less wear resistant.
  • Elongation: This measures the stiffness of a plastic. It’s the percentage increase in a material length when it breaks.
  • Flexural Strength: Simply, this is how much force the plastic can withstand before it breaks. It is used to determine the maximum weight a part can withstand before deforming.
  • Compressive Strength: This is another strength property that measures how much weight the plastic can withstand in compression. (measured by the stress required to deform the plastic by 10%)
  • Compressive Modulus: Measured in PSI, this calculates how stiff the plastic is when being compressed.
  • Shear Strength: This measures how much force the plastic can take before breaking when subjected to shearing in opposite directions.
  • Rockwell Hardness: This is a measure of how much resistance the plastic has to indentation.
  • IZOD Impact Resistance: This measures the impact resistance of the plastic (aka the toughness of the material). An IZOD impact test consists of striking a clamped, notched, sample with a pendulum dropped from a specific height.

If you are ever overwhelmed with your material choices and plastics properties for your next project, the Plastifab team has been helping people like you with their quality extruded thermoplastic projects since 1975. Send us a message today and let’s talk about how we can bring your idea to reality!

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