Machine Design

Recycled plastics gets bigger role in molding

Engineers at AGS Technology Inc., Schaumburg, Ill., have figured out a way to formulate recycled plastic to make it more suitable for injection molding. The proprietary materials let the company build automotive and durable-goods parts that cost less than those made from virgin plastic.

Traditional plastic compounders grind recycled plastic and extrude it into pellets to create raw material for injection molding. In contrast, AGS Technology skips pelletizing and molds its Injectoblend regrind directly. The so-called "salt-and-pepper"-like blend goes in the injection molding machine and is shot directly into the part mold.

AGS Technology molds most components from engineered materials such as glass-filled nylon, polyethylene terephthalate (PET), and polycarbonate (PC). Materials come from worn-out MacDonald's golden arches, beverage container caps, compact disks, and five-gallon water jugs.

“Our methods for cleaning, segregating, homogenizing, testing, and formulating these polymers eliminate the variability that has stymied injection molders using recycled materials in the past,” says Virgis Gudeika, director of technology at the company. "We also add modifiers to obtain certain properties. For example, modifiers in polycarbonates keep parts from shattering at lower temperatures." “In addition, we verify the properties of our blends by molding ASTM or ISO specimen bars from recycled material, testing them in our lab, and benchmarking test results to internal part specifications, "he says.

Strategic to AGS Technology’s manufacturing operation is that its injection molding machines, drying units, and material-handling equipment are specifically designed to use recycled plastic as the raw material." It is necessary to dry many materials before they are molded,” says Gudeika. “That's because plastic, which is made from carbon polymer chains, has a tendency to absorb moisture. Water causes hydrolysis, which breaks the chains. Typically, hydrolysis makes impact-resistant plastics brittle," he says.

On one PC/acrylonitrile butadiene styrene (ABS) job, the company uses about 250,000 lb of material a year, says Gudeika. "The cost difference between Injectoblend and a virgin resin in this case is $0.80 per lb. This saves our customer $200,000 annually without sacrificing quality," he says.

AGS Technology Inc.,

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