SCREWS/BARRELS: Package For Extruding, Molding PLA

Developed together with PLA material suppliers.

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Nordson Corp., New Castle, Pa., has developed a new screw-and-barrel package optimized specifically for processing polylactic acid (PLA) biopolymer. Compared with standard designs, the new package is said to offer higher throughputs and improved quality while resisting the corrosive and abrasive effects of PLA compounds.

Developed in collaboration with PLA suppliers, Nordson’s new Xaloy PLA screw/barrel package incorporates three key elements: 1) screw geometries designed specifically for PLA that increase throughput while minimizing shear and controlling melt temperature; 2) mixing segments that deliver a homogenized melt; and 3) screw and barrel materials that resist the mildly corrosive effects of PLA and the abrasion caused by compound ingredients.

Screws consist of 17-4 ph stainless steel with Xaloy X-183 hardfacing. For extrusion (first image), the Xaloy Efficient barrier screw features a patented Xaloy Stratablend II mixer that provides homogenized melt temperatures for enhanced quality and productivity.

For injection molding, the Xaloy EasyMelt screw (second image) can be tailored to a specific PLA grade to provide optimum temperature control and rapid recovery. When mixing is required, the Xaloy Z-Mixer can be added, which is particularly valuable for applications requiring high clarity.

Barrels in the new package are lined with Xaloy X-800 inlay, a nickel-based alloy with tungsten carbide that provides enhanced abrasion and corrosion resistance.