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REPRINTED FROM ASIAN PLASTICS NEWS - July/August 2000
MuCell makes its mark in range of processesTrexel has made huge advances with its MuCell microcellular foam technology since it made it's NPE debut three years ago. At this year's exhibition, it announced new developments in the use of MuCell in injection moulding, extrusion and blow moulding processes. Based in Woburn, Massachusetts, Trexel is commercialising the microcellular technology which uses supercritical fluids of CO2 and N2 to create tiny air bubbles with diameters of around 5-50 microns in a plastic product. These reduce resin usage by 10-50% and give processing and mechanical property improvements, including reduced stress levels, improved tolerances and reduced warpage. Because the cells of air are so small, they allow the foaming of thin-wall parts. At NPE, Trexel announced that Krauss Maffei and Van Dorn are the latest injection moulding machine manufacturers have signed licenses to use MuCell in their injection moulding operations. They include: Johnson Controls Interior of Germany; the European operations of Magna EYBL; MIG Plastics of the U.S.; plus Inoac and Takagi Seiko of Japan. According to the company's president and CEO, David Bernstein, the total number of processors with MuCell licenses worldwide stands at 50 and most of these are for injection moulding applications. He predicts that by June 2001 the number of injection moulding licensees will reach 200. The MuCell process is being used on a wide range of injection moulding machines. The smallest so far is a 60-tonne Arburg used for fine wire encapsulation, while at the other end of the scale MIG Plastics is purchasing a 2,000-tonne Husky machine for micrcocellular moulding. 'Our customers are using MuCell for far more than material savings,' says Bernstein, 'they are using it as a problem solving tool'. The specific advantages which MuCell brings to injection moulding include reductions in cycle times, clamp forces, injection pressures, melt viscosities and melt temperatures. Its major drawback is the patchy surface finish created by entrapped air. This restricts its use to components where visual appearance is less important, such as under-the-bonnet components and mechanical parts for business machines. The process is also being exploited in back-injection processes with in-mould decorative layer during back injection. While injection moulding is emerging as the area of highest activity for MuCell licensing, extrusion is also proving to be a growth area. This year it was announced that Alusuisse Composites is using the technology to produce laminated foam boards for graphic arts, mounting and three dimensional modelling applications. In addition, Eclipse of the US is using the MuCell process to produce vertical blind slats that are thicker and stiffer than conventional versions but are also 35% lighter. In addition, the foamed PVC extrusions have improved opacity and reduced warpage. In a separate development, Trexel is currently investigating the use of extruded microcellular PP sheets in thermoforming applications. On the blow moulding front, the company has been working with one of the world's leading users of HDPE bottles to demonstrate how MuCell can be used to successfully reduce the weight of such packaging by 20%. It is now planning trials on high-volume wheel-type blow moulding machines. In a separate development with Uniloy Milacron, Trexel has produced a prototype milk bottle using a reciprocating screw blow moulding machine. This application is also achieving 20% reductions in weight without a loss in top load, stiffness or impact properties. The MuCell process can only be used to produce opaque bottles, but the surface finish is not adversely affected. In fact, a HDPE shampoo bottle produced with MuCell exhibited a good semi-pearlescent type finish, while the opacifying effect of the process could eliminate the need for Ti02 pigments in white milk bottles. Return to Top | Return to Magazine Articles 00-01 |
