US-based Nordson Corporation has developed a plasticizing system optimized for processing polylactic acid (PLA) bioplastics that provides greater productivity and better product quality than standard screw and barrel systems – while resisting the corrosive and abrasive effects of PLA compounds.
Based on technology developed in cooperation with producers of PLA resins, Nordson’s new Xaloy PLA screw and barrel package incorporates three key elements:
- screw geometries designed specifically for PLA that increase throughput while minimizing shear and controlling melt temperature;
- mixing segments that deliver a homogenized melt; and
- screw and barrel materials that resist the mildly corrosive effects of PLA and the abrasion caused by compound ingredients.
For all PLA applications, barrels in the new package system are lined with Xaloy X-800 inlay, a nickel-based alloy with tungsten carbide that is more wear-resistant than iron, iron-chromium, and nickel-cobalt alloys, providing enhanced abrasion and corrosion resistance. Screws consist of 17-4 ph stainless steel with Xaloy X-183 hardfacing.
Screw designs are provided in accordance with the process:
Extrusion. The Xaloy Efficient barrier screw with patented Xaloy Stratablend II mixer provides chaotic and distributive mixing and homogenized melt temperatures for enhanced quality and productivity.
Injection molding. The Xaloy EasyMelt screw can be tailored to a specific PLA resin grade to provide optimum temperature control and rapid recovery. When mixing is required, the Xaloy Z-Mixer can be added, and it is particularly valuable for applications requiring high clarity.
“The Xaloy PLA package enhances productivity and product quality while providing a longer working life than standard plasticizing components,” said Mark Colella, global product manager.
“Because our technology is optimized for PLA, we can deliver a working system to our customers that minimizes start-up nuisances and is ready to meet production targets out-of-the-box, with no guesswork involved.”