Plastics Technology

FEB 2018

Plastics Technology - Dedicated to improving Plastics Processing.

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A properly executed purging process can save processors thousands a year in lost production while helping them increase output and avoid scrap. Here's how to optimize your results. Follow These Tips to Power Up Your Purging Process This article is an adaptation of a technical presentation given by Jeremy Cooley at Plastics Technology's Extrusion 2017 Conference, held Oct. 18-20 in Charlotte, N.C. Cooley is a technical sales representa- tive at Asaclean-Sun Plastech Inc. and has spent the past 15 years focusing on helping processors develop robust purging programs. These eight tips are aimed at helping processors increase output, lower production costs, reduce machine downtime, and decrease scrap rate. PROPER GRADE SELECTION All purging compounds are not created equal. Some grades may work extremely well for certain applications and resins but are completely ineffective in other situations. Understand what you are working with before you put something in your machine. When selecting a commercial purging compound (CPC), a good strategy to start with is determining compatibility with the resins you are running. Before beginning, ask yourself the following questions: 1) What are my expectations of this CPC? 2) What challenges do I face? 3) Do I struggle with contamination (black specks, color, etc.)? If you can set quantifiable goals, you can check the results against them at the end of the trial. Depending on the machine, the applica- tion, and the answers to the questions above, a chemical purging compound might provide a distinct advantage over a mechanical purging compound, or vice-versa. Mechanical CPCs use the machine's power to create pressure and agitation in the barrel. These types of purge rely on higher viscosity, additives, and inorganic minerals to By Jarred Packard Sun Plastech Inc. WHAT YOU WILL LEARN 1. CPCs ARE NOT ALL THE SAME. What works in some situations may be ineffective in others. Grade selection is critical. 2. COST SAVINGS. Look beyond the per-pound price of CPCs to the cost savings they can offer. Analyze the cost factors. 3. PREVENTIVE PURGES. These might make sense to remove deposits before they have a chance to settle in. 4. READ THE LABEL. Follow the supplier's instructions to set up a baseline, but don't be afraid to experiment thereafter. 5. DISCO PURGING. This procedure creates turbulence in the machine to remove set-in layers of contaminant. CPC grades like Asaclean's EX will not adhere to the barrel/screw and actually peel off the screw similar to peeling a banana. Grades like this can save you hours on screw pulls. 62 FEBRUARY 2018 Plastics Technology PTonline.com Tips and Techniques

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