Part 2 of a series on extrusion for sustainable materials.
Recently, customers have become more focused on extruding recycled plastics and their enthusiasm for bioplastics remains steady, according to Michael Duff, VP for sales and service at Graham Engineering. Graham sells single-screw extruders under the American Kuhne and Welex brands, as well as a co-rotating conical twin-screw extruder known as the Welex Converge CTS.
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Companies are introducing recycled content into their products due to raw material cost pressures and a continued focus on sustainability, he said. In addition, China’s trade policies also influence the recycling market, he said.
One recent trend is that compounding customers that previously used their extruders on a part-time basis to process bioplastics such as PLA, now are dedicating some equipment on a full-time basis to bioplastic production, Duff said.
“The challenges of running PLA or the opportunities to run PLA may be different when you’re running it full-time vs. cycling in and out with other polymers,” Duff said.
Bioplastics like PLA have unique properties that require changes in how extrusion lines are manufactured to ensure the longevity of the equipment. PLA, as compared to traditional polymers, can be more corrosive, especially when a line is down and the material is sitting inside.
“We want to make sure that the metallurgies that we use are compatible with that and don’t lead to any destructive or corrosive situations that then turn into machinery damage and safety hazards,” he said. “That’s probably the biggest overarching concern, and we know how to do that and do it well.”
Several special metals can be used inside an extruder for parts that come in contact with PLA melt, Duff said. The company works with the bioplastic producer to select appropriate metals, he said.
For drying bioplastics and recycled PET that will be processed on Welex sheet extruders, the company works with customers to determine their drying needs.
“Some resins need to be dried and some need to be vented,” Duff said. “Careful consideration needs to be made upfront to truly understand the products that are going to be extruded.”
Graham Engineering Corp., York, Pa., 717-848-3755, www.grahamengineering.com/
