In our last post on the topic of thermoplastic pumps and valves we looked at how corrosion occurs with thermoplastics. In this article we are looking at the specific materials of choice that are most often used when designing valves and seals with thermoplastics.
As with traditional materials like metal or even wood thermoplastics all have advantages and disadvantages. In my work here at AIN Plastics my job is often to help customers look at all the pros and cons and help determine the best engineering plastic for a particular application.
The task of selecting the right thermoplastic for a machined valve or seal can be detailed and sometimes daunting when you see all the thousands of options available in the market today. Throw in trade names for engineering plastic materials and it can become even more confusing. Many plastic materials exist in their basic form but there are also versions that have certain properties boosted by the addition of fillers like ceramic, graphite and more. Still others, like Dupont™ Vespel®, are made through a proprietary isostatic molding process making it the only one of it’s kind in the plastics industry.
Below is a table I’ve put together as a good starting point for detrmining what type of thermoplastic may be best suited to a job. This table explains the basic advantages and disadvantages of the most popular engineering plastics for pump and valve as well as many other machined part applications. Once the basic crietria are determined, the next step is often making the initial part and testing. From there designers may find a need to move to a material with a filler to, for example, enhance the heat resistance properties.
On the surface some of these engineering plastics appear costly. But, when material selection is done carefully it is often the case that customers are pleasantly surprised to find plastics end up costing less overall. This is due to reduced maintenance time because parts last longer, or they don’t need lubrication. It may also be because you don’t need the most expensive material. While a PAI might have all the properties you need and then some, we might find a less expensive material with a filler can do the job just as well because it fits all the criteria needed.
Industry Segment Manager
thyssenkrupp Materials NA
AIN Plastics Division
Kendall Montague is a veteran of the plastics industry with 16+ years experience working with OEM and MRO engineers assisting in developing thermoplastics material selection as well as custom design and fabrication using CNC equipment.