Purge Compounds Improve Efficiency, Reduce Waste and Lower Overall Costs for Thermoplastic Processing
Purge compounds (watch a video to see how they work) are extremely important for modern thermoplastic processors. Carbon build-up in screw and barrel assemblies, as well as on die sets and tooling has a significant impact on processing efficiency, scrap rates, tool & die life and the length of change-over time and equipment maintenance. Purging compounds are usually a compound of polymers and additives. The polymer or polymer combination used within the compound is specific for addressing the particular raw material required to be purged. Lusin® purging compounds use a polymer as a carrier to transport the additives into the machine. The cleaning effect is a combined approach of diluting the polymer and releasing cleaning agents that eliminatethe contaminants. In general, all polymers we address can be placed into three main categories:
- Polyolefins (e.g. PP, PE, TPO)
- High temperature resins (e.g. PEEK, PSU, etc.)
- Engineered resins (e.g. ABS, HIPS, PS, PA, etc.)
Lusin® purging compounds, which are chemical action based, can work for all three categories due to their unique working principle and are completely different from abrasive formulations which are mechanical action based and are usually polymers with high levels of fillers. Mechanical action formulations (scrubbing/scraping) can damage the screw and barrel over time and will damage the mold surface if they come in contact with it. Although our Lusin® purge compounds are chemical, and not mechanical based, they still differ significantly from competitive chemical purge compounds. This is due to Chem-Trend’s 50 years of history in developing some of the world’s most advanced release agents. We have taken the principles of releasing molded products from metal surfaces and applied them to the releasing of colorants and carbon contaminants from extrusion equipment. We have also done it safely, so that our purge compounds can not only be run through the screw and barrel assembly, but they can also be run through the downstream equipment (eg. Hot Runner Systems), where most contamination settles: to remove contamination throughout the process.
Lusin® purging compounds (watch a video to see them in action) are used for color / material changes when:
- transitioning from a dark color to a lighter color
- start-up production has flow marks or swirls from the previous material / color
- changing material with high temperature differences and / or melt flow
In these instances the purging compound is having its effect most notably in the Feeding Zone and Melting Zone as illustrated below.
Lusin® purging compounds are also used for shut-down or upon start-up to help remove black spots and burnt materials caused by:
- processing a heat sensitive material at the wrong setting
- processing of different temperature polymers
- a damaged / worn screw having a dead zone area where material does not move through
In these instances the purging compound is having its effect most notably in the Metering Zone of the screw system illustrated above, and is addressing the heavy areas of carbon and color build-up, as illustrated below.
Penetrating the layer of contaminants and releasing them is a key element of Lusin® purge technology.
Our Lusin® purging compound technology is different than any other found in the market. Our products not only provide the appearance of a cleaned system, but they actually deep clean your system, and we can prove it. Below on the left you see a run of parts that were made with a competitor’s purging compound. On the right, is a picture of parts from the same machine using our purge compound run immediately after the competitor’s product. Notice that although it looked like the competitor’s product cleaned the machine; our purge compound still removed a significant amount of contamination. This is the difference between the appearance of being clean and the machine actually being clean.
Chem-Trend purging compounds are different:
- Our focus is on working at the molecular level, to release contaminants from their bond with metal parts, not on conventional chemistry, and not on mechanical scrubbing.
- Our purge compounds are safe to use throughout the entire machine, not just the barrel and screw.
- You don’t have to change your process, or your machine settings to run our purging compounds, they run within your established parameters of production.
- Our purging compounds work effectively on a consistent basis, you don’t need to keep utilizing an increasing amount of purge compound as time goes on because our product cleans the machine thoroughly each time. Conventional products become increasingly ineffective over time because they leave carbon contaminants behind.
In some applications, such as processing PMMA or Polycarbonate materials for transparent applications, where the quality requirements are not only very high, but the formation of burned material can also be considered as a typical problem, we suggest not only utilizing purging compound at the time of color or material change-over, but also as part of your preventive maintenance process.
Starting from a clean screw, barrel and hot runner†, Lusin® purging compounds are used before the regular production starts, ensuring that the quality of produced parts are within QC requirements. By using Lusin® purge compounds regularly the build-up of carbon will be limited. This keeps production running more smoothly, reduces scrap and extends the life of your equipment. It helps get you from the last good part produced to the first good part produced between change-overs in the shortest amount of time with the least amount of scrap.
There are a large number of different polymers and processes used in the thermoplastic industry today, so we have developed a wide range of purging compounds to address the needs of the market. To learn more, read our Product Selector Guide for Lusin® Purging Compounds.
The majority of our Lusin® purging compounds are also NSF registered.
To take advantage of our expertise in improving operational efficiency, reducing scrap and reducing costs for thermoplastic processing operations, contact us.