CHICAGO — Clarified-polypropylene uses are expanding as the new generation of clarifiers offer multiple benefits, according to Milliken Chemical (Booth S4018) of Spartanburg, S.C.
Millad 3988, an alkylated sorbitol, overcomes disadvantages of the first two generations of clarifying agents and is prompting new packaging applications. Thermoformed sheet and extrusion and injection blow molding are key processes that capitalize on Millad 3988's benefits, according to Alicia Stack, Milliken's marketing manager for North America.
Milliken is exhibiting new packaging designs based on PP clarified with Millad 3988. Pechiney Plastic Packaging Inc. has developed a multilayer coextruded PP container, Polyplus, that offers high barrier properties, the hot-fill capability of PP and light weight of plastics such as PET, at a lower cost than PET. Its high surface gloss looks like glass, Stack said in an interview at her firm's booth. Polyplus also offers better drop-impact resistance than traditional PP containers. Milliken's booth features a variety of condiments and sauces in Pechiney's new Polyplus-brand container.
Clarified PP is being used in paint cans made by RPL Containers Ltd. The 21/2-liter containers have wraparound labels that allow a window for consumers to see the actual color of the paint in the PP can.
European cosmetics and household chemical firms are converting from clear PVC and opaque high density polyethylene to clarified PP. This provides shelf appeal because most household chemicals, such as cleaners, are brightly colored, and clarified PP allows the colors to catch a consumer's eye.
In South America, S.C. Johnson & Son Inc. has begun using injection molded, clarified PP in its Ziploc containers to provide exceptional clarity. So far the firm's North American Ziploc containers are thermoformed from clarified PP sheet.
"Clarified PP is a cost-effective alternative to other resins," Stack explained. "It has the lowest density of clear plastics and is microwaveable and hot-fillable."
Milliken is expanding capacity for Millad 3988 by constructing a plant in Blacksburg, S.C., its third. The firm also is building a new applications laboratory in Spartanburg and expects to open it by late summer. The lab will include an Illig RDM 54 K in-line thermoforming machine. Illig (Booth N8242) is running the machine at NPE making drinking cups and will deliver the system to Milliken after the show.
Stack said regular PP resin contains crystalline and amorphous regions. Clarifiers increase the rate of recrystallization as the polymer sets after processing, providing for a large number of smaller crystals that provide better clarity. In Millad 3988-treated PP, the clarifier forms microscopic fibrils as melted PP cools. The fibrils provide numerous sites for PP to recrystallize. The fibrils also provide some reinforcing action within the PP, thus improving strength. This allows better part dimensional stability from the edge of thermoformed sheet through the middle to the other edge.
Earlier generation sorbitol-based clarifiers were not as heat stable or as fast acting as Millad 3988, according to Stack. Some also had odor problems with residual aldehydes that interfere with food applications.
Milliken recently opened customer support and technical laboratories in Sao Paulo, Brazil.