The High-Clarity Styrene Option
High-impact polystyrenes (HIPS) with high-clarity properties have emerged as an attractive alternative to PETG for rigid trays, says Dave Rosten, sales manager, Brentwood Industries Inc. (Reading, PA).
Brentwood has recently tested the HIPS materials and run production parts. Clear HIPS materials are offered by Klöckner Pentaplast (Gordonsville, VA), Spartech (St. Louis, MO), and Impact, he says. “These are not as crystal clear as Eastar, but the clarity is sufficient to see the product.”
Rosten says that Brentwood customers have been attracted by cost and yield advantages when comparing the materials to PETG. “There are some real cost advantages in the clarified HIPS products. We use a modifier of rubber to promote high impact resistance in the styrene.”
“In the past year, we have seen quite a bit of interest in the clarified styrene, and we have run several projects in this material,” he says.
“The white HIPS has always withstood gamma radiation and, true to form, we have not seen any yellowing in the clarified HIPS,” he adds.
Rosten says that HIPS has a wider forming window than does PETG and supports faster thermoforming. “I see HIPS as more form friendly than PETG, but it comes down to design and the characteristics the customer is looking for in a tray. The styrenes can handle EtO, but they have tended to exhibit browning under gamma. If a customer is EtO sterilizing and looking for a lower-cost clear material, they might chose the clear styrene,” says Mike Spolidoro, vice president, engineering, AlgaPlastics (Cranston, RI). “The compatibility of the packaging with the product also has to be considered. The styrenes react with certain component materials. We haven’t seen many products that react with PETG,” he says.
Spolidoro says that “the high-clarity HIPS hasn’t had the impact that some were expecting. It is less expensive than PETG, but more expensive than opaque styrene. If the cost came down to the cost of the opaque, it probably would be more accepted.”
“Clarified polystyrenes have been available for some years,” says Richard Ryder, business manager, medical device films, Klöckner Pentaplast. “While the product has a lower specific gravity than PETG, so far, we have seen a higher haze, less clarity, and higher gel count than PETG, and lower stiffness, which may force upgauging.”
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Spartech reports on its Web site that it has introduced Valiant Ultra, a “crystal clear” clarified HIPS sheet product for uses including medical market thermoformed containers and blisters.