Engineering Plastics: Understanding Dimensional Stability in Material Selection
Engineering plastics are ideal for numerous fabrication applications in the commercial and industrial sector. The popularity of this category of materials over the traditional metals can be attributed to the intrinsic properties which enhance performance. In simple terms, the engineering plastics are lighter than most metals. Therefore, manufactured components will not increase product weight, particularly in equipment. In addition, most of the plastics display exceptional resistance to chemical degradation as opposed to metals which are prone to corrosion.
On the other hand, the dimensional stability of different plastics can vary widely, and it is not equal to that of metals. Moreover, this property will affect the long-term performance of the manufactured product. Basically, dimensional stability can be defined as the material's ability to maintain the original or required dimensions after manufacture and installation for the intended application. If the pertinent plastic loses its stability, it will no longer perform as expected. Here are the most critical considerations for selecting a plastic with high dimensional stability.
Thermal Stability
You should evaluate the temperature performance of your preferred engineering plastic before making a selection for your fabrication project. For ideal dimensional stability, the material should display heat resistance, particularly if you are going to utilise it in high temperature environments. You should consider the continuous service temperature that the material can withstand in the air. Additionally, evaluate the potential deflection temperature of the plastic when the component is under load. Suitable materials which have great dimensional stability under high temperature situations include PEEK, Teflon and PPS.
Moisture Absorption
When a material absorbs moisture, the dimensions are likely to change. This will affect the performance of machined components, especially if they are intended for use in applications that demand tight tolerances. Highly stable plastics should have low water absorption; this will ensure consistent function of the manufactured product. Good engineering material choices with regard to structural stability and good moisture performance include PPS, PEEK and polyetherimide. You should note that some manufactured products are exposed to both moisture and high temperature during their applications. If this is the case for your project, consider choosing autoclave-safe plastics like polyetherimide, Teflon or PEEK.
Load Strength
Finally, you should note that the load applied on an engineered plastic component can change the original dimension. Therefore, the loading strength of a material is an important consideration for structural applications. Ideally, you should evaluate both the tensile and compression strength of your preferred material for optimal performance. Engineering plastics which are stable under high loads include PPS and PEEK.
