Case study: High-clarity, high-stiffness PP cups for milkshakes
Leading Turkish sheet extrusion and thermoforming company, SEM Plastik (www.semplastik.com.tr/), is using a newly formulated polypropylene to fullfil an important contract for high-clarity, high-stiffness polypropylene cups for milkshakes at a global fast-food company in the country. The improved properties of the material are largely due to the incorporation of Hyperform nucleating agent HPN-600ei into the material. HPN-600ei is a high performance nucleating agent manufactured by additives specialist Milliken & Co. (www.milliken.com)
SEM Plastik’s customer had been using imported milkshake cups in 16- and 32-ounce sizes, but was unhappy with the overall quality, especially clarity. Yavuz Eroglu, owner and general manager of SEM Plastik, says the customer was also looking for a lighter cup that would provide environmental as well as economic benefits: “We already had contacts with Milliken, so we worked together on the project with them together with an important Turkish polymer supplier to satisfy all its requirements.”
The project began around the middle of 2010, with the new grade now almost ready for full commercialization. SEM Plastik has been using trial product quantities for several weeks, and is targeting annual production of around 6.5 million cups. It is also making the domed lids for the cups.
Weight, cycle time reductions
Eroglu says that by using the new grade, SEM Plastik has been able to cut the weight of the cups by close to ten percent with no loss of mechanical properties. Thermoforming cycle times are also believed to be between 8 and 12% lower.
“All our major customers have a strong focus on environmental issues as well as costs,” Eroglu says. “So the weight reduction is very important to them because it brings benefits all along the production chain, from less use of non-renewable resources to reduced emissions of vehicles supplying the cups to outlets.” He also notes that people actually using the cups appreciate the new product too: “When the customer grips the cup, they have a more solid touch,” he says.
Polypropylene nucleated with HPN-600ei presents a cost effective alternative to PET and polystyrene (PS). Cups are highly transparent and have an excellent visual appearance, rather than the yellowish appearance that results from the use of sodium benzoate, the conventional nucleating agent in PP. The Hyperform HPN-600ei nucleating agent increases the crystallisation temperature of PP, and thus allows converters to operate at higher line speeds. They may, in fact, achieve output rates on thermoforming equipment to levels normally only achievable with other plastics. The PP parts can be made with the same wall thickness as other materials. So because the material is less dense, processors use less material, gaining further cost savings.