Compare
Plastics

All plastics are affected by temperature, so it’s essential to consider the temperature required for your parts. Heat causes the material to soften while freezing temperatures cause many materials to become brittle. Both scenarios will impact the resistance of your part.

Most materials also expand in heat and shrink in cold environments. Changes from winter to summer can affect the functionality of your part if it is an outside application. To prevent this from happening, there needs to be some expansion/contraction tolerance for the material.

There are many different materials available to meet the needs of your design but chemical-resistant materials will prolong your part’s longevity.

Most plastics absorb moisture to some extent, which is an important consideration for your part’s tolerance and application. The more moisture a material absorbs, the more it expands, so you will want to analyze its saturation data to verify how much it can tolerate.

Plastic materials develop internal stress during the production process. This stress level can be reduced through annealing at an appropriate temperature and for an appropriate duration. Time and temperature differ from one material to another.

Annealing is important when you plan to machine parts. Machining causes more stress as well as “movement” in the material. In-Between-Cycle Annealing is recommended if parts are heavily machined or very complex.

Besides the internal stress, there is external stress (chemicals, electricity, mechanical, and thermal) which has an effect on the material. Mechanical stress can deform materials permanently.

The Yield Point is the point at which material won’t return to its original shape and size. The time needed to reach this point is called “creep” or “cold flow” which becomes shorter as temperature increases.

Materials can change properties and compliances once they are filled with other components. Make sure that you refer to the exact requirements for your finished part. For example, glass filler increases the stiffness, heat transfer, and wear properties. Some fillers like glass, carbon, or even color may affect a requested food compliance.

Many factors are reported at maximum levels to make materials look better. To arrive at a safe working value, you should generally divide data by 4.