ORLANDO, FLA. — Structural polypropylene applications are now candidates for the use of Mucell microcellular foaming technology.
Nylon has been the main resin benefiting from Mucell to lower weight and costs, but Trexel Inc. and Asahi Kasei say their collaboration should extend Mucell to injection molded PP parts such as housings and auto parts. Trexel first announced the development at NPE 2015 in Orlando.
“A new flow-enhanced polypropylene can use Mucell to make parts with visual appearance about as good as conventionally molded parts,” said Trexel President and CEO Steve Braig.
Over the past year Trexel and Asahi worked on making a polyolefin suitable for Mucell. The joint effort led to success with a family of Asahi Kasei's Thermylene PP specialty compound grades. Not only did the work result in “excellent surface aesthetics,” but it also showed part weight could be cut by 10 percent along with warpage reduction. As well, cycle time was lowered.
“Several customers have shown interest in testing, and it's commercially available,” Braig noted.
Asahi Kasei will supply the special PP grades from its Fowlervillle, Mich., plant for world markets. The company is building a new compounding plant in Athens, Ala., that also could supply the compounds.
Attractive potential uses of the PP/Mucell system include molded-in color auto interior trim, pool and spa components, heavy truck parts and appliances and electrical items.
Also new from Trexel at NPE is a variation of Mucell that can be used to make small parts in the 0.3 to 5 ounce range. The T-100 Super Critical Fluid (SCF) dosing and delivery system solves technical challenges that have made using SCF difficult for small parts.
Braig said it has been difficult to get repeatable dosing of SCF nitrogen for small parts. As little as 20 milligrams of nitrogen would be injected into the polymer melt and such a small amount is difficult to control and disperse. That has been the main problem for SCF in small parts.
Economic arguments for using Mucell in small parts have been weak to date since relative material savings would be small. But many small parts require tight tolerances, a strong point of Mucell, Braig explained. Electrical connectors and complex components are examples of small parts that need tight tolerances.
SCFs are fluids that simultaneously exhibit properties of both gases and liquids.
Braig said current Mucell technology users can easily adopt the SCF system and it also can be installed on presses not using Mucell. The plasticizing screw in the injection press should by 18 to 45 millimeters for the T-100 series but larger screws are suited to the T-200 and T-300 series.
Carbon dioxide SCF is an option for the new technology. Another option is inline detection of nitrogen purity in the gas supply line, an important consideration in developing countries where nitrogen supply might by suspect. Braig said nitrogen purity of 99.9 percent is the target. Oxygen, the most common and problematic impurity in nitrogen supply, can cause polymer to yellow or even degrade.
Trexel also made a personnel announcement at NPE. Fabricio Soprano of Plastic Solutions was named exclusive sales representative in Brazil.
And Trexel announced that Braig has been reappointed to the U.S. Manufacturing Council by Secretary of Commerce Penny Pritzker for 2015 and 2016. The council was established in 2004 to serve as the principal private sector advisory body to the Secretary of Commerce on matters relating to the U.S. manufacturing industry.