Processors of Super Engineering resins will understand and unanimously agree there is an inherent difficulty with removing these resins from the processing machinery's screw and barrel. Super Engineering resins, such as PEEK, PPS, PEI, LCP, and the like, process at relatively high temperatures. As their polymer family name implies, they offer exceptional mechanical properties--“super"--or beyond those of regular engineering or commodity resins. These innovative materials make products to advance emerging technologies, and in many cases actually replace metal components.
The nature of the end-use typically will require a heightened level of quality assurance. The goal is to maintain these exceptional mechanical properties, uncompromised. This all begins with a clean, contaminant-free processing system. This usually requires a screw and barrel overhaul between runs and/or prior to shutting down.
Much like when working with metal, if these Super Engineering resins go below their softening temperature, they tend to set up on surfaces with the same level of strength. They can be just as difficult as removing metal by chipping away by hand or using conventional tools. Not fun. This results in the processor having to remove the screw at the elevated temperature which can present its own set of challenges and an additional safety concern.
Once removed, the rapid onset of the material cooling will inevitably require controlled burn-off in a fluidized bed or similar cooker. This is a seriously disruptive and time-consuming process in itself. Furthermore, leaving any residue in the barrel for clean-up by some other mechanical means requires a lot of manual labor and hard work.
If you are a Super Engineering processor and you routinely face these issues, there is an alternative that can greatly minimize these issues. High-temperature commercial purging compounds make a huge difference. These specialized purging compounds have a maximum operating temperature of 790F (420C). Asaclean PX2 is one such grade that is heat-stabilized and incredibly effective at evacuating the Super Engineering resin from the screw and barrel. Additionally, this grade offers aggressive removal of any carbon or contaminants. While keeping an eye on melt pressure and temperature during the process, maximize extruder RPMS for the quickest results! Depending on the length of the production run, this initial step typically requires around 1 to 3 barrel capacities.
After the material removal, move on to screw removal in this two-step process. Introduce and temperature transition down into Asaclean EX grade. With an operating temperature range overlap, EX will displace the PX2 at temperatures above 535F (280C), again with an increased level of RPM. Make certain of the high-temperature purge removal, before dropping the temperature below 535F (280C). Once confirmed the PX2 is out of the screw and barrel, with a lower RPM, reduce the temperature set points to reach 430-460F (220-240C). This is the ideal temperature range to remove the screw. Again, it should take around 1 to 3 barrel capacities of EX to fully displace the PX2. Overall, this practice has seen some amazing results when working with Super Engineering resins. For a free consultation
Learn how to reduce machine downtime with five quick purging compound tips for your injection molding application.