Tips from RTP Company’s Product Development Engineers

Applications with overmolded “soft-touch” grips commonly use elastomers with low compression set properties. These materials offer high rebound and good resiliency, recovering their original shape quickly after a force is removed. Elastomers with high compression set characteristics are better suited for applications that require sound or vibration damping. Because of their slower recovery rate, these materials function better as an energy absorber, transforming sound waves into mechanical energy.

RTP Company has multiple technologies that increase the energy absorbing properties of various thermoplastic compounds for sound and/or vibration damping. For applications that have a narrow operating temperature range, an elastomeric material with a glass transition temperature (Tg) matched to the application temperature can absorb large amounts of impact, sound, or vibration energy. A more common method, accommodating a wider range of applications, is to add high gravity filler to a low gravity resin. This combination works to capture and weaken energy waves as they transfer back and forth between the light and dense elements in these compounds.

Semi-crystalline, high temperature plastics are ideal for applications where parts are exposed to elevated temperatures. In order to maximize properties in materials such as PPS, PPA, and PEEK, the mold temperature must be greater than 212 degrees F (100 degrees C). To achieve such mold temperatures, electric or oil heaters are required.

Using a colder mold temperature with a semi-crystalline resin results in parts that are more amorphous in nature, with reduced chemical and wear resistance properties. Additionally, these parts will experience a physical property reduction when exposed to higher temperatures because of re-crystallization and are more likely to experience failure.

Annealing a part after molding can promote increased crystallization. This is not a perfect solution because crystals formed during annealing are smaller and less perfect than those obtained during cooling from melt. If an annealing process is chosen, it is important that a temperature above the actual use temperature for the application is selected.

Looking for a “plastic that paints well?” Consider an electrostatic paintable (ESP) compound.

ESP compounds are ideal for applications where plastic and metal components are intermixed and a seamless color and/or surface finish quality are required between the various parts. ESP compounds allow for faster production by eliminating the need for conductive primers usually necessary to accommodate the electrostatic painting of plastics. Without the use of a primer and its accompanying VOC (volatile organic compound) emissions, ESP compounds are a cost effective and environmentally friendly alternative.