Though compounding is extrusion, it’s a unique enough subcategory of extrusion to worth its own debate. Compounding encompasses the inclusion of resins, stabilizers, fillers, reinforcements, and other colorants to a base resin.
What distinguishes film extrusion from compounding is the number of additives introduced to the base resin – this is where compounders add their value. A standard compounding line will have more than one port where additives are introduced to the melt. These ports are areas of low melt pressure and are usually tough for purging compounds to clean.
Due to these differences & challenges, compounding is a subject that’s presently inadequately served by commercial purging compounds. Below we would like to share a few tips with compounding customers to maximize their purging:
- Knowing the capacity of your barrel before purging will let you cautiously regulate the quantity of purge being employed – usually 1 to three barrels full of products are adequate. This will let you regulate inventory, and lessen outlays.
- Slowly rotate the crew to fill the flights. As soon as the purge begins to kick out, amplify screw speed to maximize the performance of the purging compound. Mechanical purges are most efficient at the highest safe screw speeds, where agitation & turbulence are exploited.
- Disco Purge – After the barrel & flights of the screw are full of purge, stop screw rotation, and allow the melted purge to sit & settle into any dead spots for 4-5 minutes. Then start screw rotation once more, repeat multiple times. The dramatic changes in pressure & agitation let purges best perform their task.
- Vents are low-pressure areas that decrease the efficacy of purging instantly after the vent location. Plug the vents manually at the time of purging to amplify local pressure. If plugging the vents isn’t feasible, feed the purge into the vents at the same time it’s being fed into the hopper.
- Mixing areas are usually quite tough to clean. In this scenario, a chemical purge might be an excellent option. Alternately, make use of the “disco purge” method with mechanical purges to make the most of cleaning in this area of the screw.
- Ensure that the purge compound you buy is rated to use with the least clearance in your die. The majority of purging compound manufacturers will have the right grade for your clearance needs.
If you are looking for a Purging Compounds Free Sample before making any costly investment, UNICLEANPLUS™ can help. Whether you are looking for a Purging Compound for Extrusion, Purging Compound for Blow Molding, or Purging Material for Injection Moulding, you can Request UNICLEANPLUS™ for a free trial!