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In Packaging, Less May Mean More

By: Terry Glass
Posted: November 10, 2008, from the November 2008 issue of GCI Magazine.

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For example, in applications where the product can be in intimate contact with the body, i.e., eye makeup or lipstick, converters must consider the fact that mold release additives used in the production can actually leech from the container and contaminate the product. This has led to advances in bimodal polyethylene resins that have been designed for such applications and to eliminate the need for mold-release agents, thus reducing concerns about product contamination.

Performance Remains an Issue

While consumers often want the packaging of their personal care products to be eco-friendly and free from things such as additives, they don’t want them to fail. Brand owners are held to a standard of providing products that perform as expected and stand up to consumer daily use, such as tossing the container into toiletry bags or purses without leaking, swelling or bursting. In addition, consumers expect squeeze bottles to expand to their original shape, thus requiring resins with good flexibility that might require plasticizers, which can be another cause for contamination concerns. To strike a balance between these performance and aesthetic characteristics, converters must utilize the most innovative processes.

Again, using bimodal polyethylene resins allows converters to fabricate plastic containers with desired characteristics that are essential for personal care items. The bimodal resins offer attributes such as better toughness and stiffness for “squeezable” bottles while maintaining excellent environmental stress crack resistance (ESCR) without the use of slip/mold-release additives.

Converters must also consider the process equipment. Mold release agents frequently cause plate-out or mold fouling issues that require equipment shutdowns for die cleaning, sometimes as much as once a day. Other options, such as chrome-plated injection blow molds, may be designed to allow for the use of resins without mold-release additives, but this usually requires an investment in expensive tooling to accommodate the change. Such investments and maintenance issues can be eliminated by a simple switch to a bimodal resin.

The advantages of using a bimodal resin versus the alternative with an additive are many, and their performance is especially apparent in terms of sustainability. When extrusion blow molding is used, the resin offers optimum impact strength that allows converters to design containers that maintain durability even with thinner walls. By down-gauging the weight of these containers, converters eliminate costs associated with unnecessary material use which may lead to less energy consumption.

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