Rod, Plate and Tube Stock Shapes made of Ryton® PPS
Machining parts from rods, sheets or hollow forms provides an alternative to injection molding for producing heavy walled parts (not possible by injection molding), or to avoid mold construction costs for smaller production quantities or prototyping.
Ryton® PPS Compression Molded Stock Shapes
Large stock shapes made from our Ryton® PPS injection molding compounds are not available because the injection molding compounds are not suitable for producing thick forms. Specialty compression molders are able to supply compression molded PPS rod, plate and tube stock, but it is important to understand that parts machined from compression molded stock shapes will likely not perform the same as parts injection molded from Ryton® PPS injection molding compounds. There are several reasons for this:
- Ryton® PPS injection molding compounds are generally not suitable for compression molding, therefore for compression molding, processors typically purchase raw PPS polymers and blend them with their own combinations of fillers and other additives, formulating compounds that are different from our injection molding compounds.
- In the compression molding process the PPS compound is subjected to an entirely different heat and stress history than is encountered in the molding of articles from injection molding compounds, and the frictional heat of machining operations can also cause development of localized stresses.
- Being a semi-crystalline thermoplastic, PPS is notch sensitive, so surface defects from machining operations may act as crack propagators and compromise the mechanical strength of a part.
- The machined surface, with fillers and reinforcements exposed, is more prone to abrasion and more susceptible to fluid penetration than a "resin rich" molded surface.
Unlike injection molded parts, the mechanical properties of compression molded PPS stock materials are generally more isotropic due to a more random filler distribution and/or glass fiber alignment. The mechanical strength of compression molded PPS stock materials will typically be no more than 50% to 80% of the strength of Ryton® PPS injection molding compounds with similar filler systems, and the effects of machining can dramatically reduce part strength even further.
Compressive properties, dimensional stability, thermal stability and chemical resistance of compression molded PPS stock materials should generally be similar to Ryton® PPS injection molding compounds with similar filler systems. The exposed fillers and reinforcements on a machined surface, however, make the part more prone to fluid penetration, so chemical exposure may tend to cause more swelling and more rapid strength deterioration.
The electrical properties of compression molded PPS stock materials should typically be about the same as Ryton® PPS injection molding compounds with similar filler systems.
Bear in mind, however, that some Ryton® PPS injection molding compounds are specially formulated to enhance certain performance characteristics such as impact resistance, electrical properties and hydrolytic stability.
For recommendations of specialty compression molders, contact our technical specialists.