Engel will show a potentially cost saving process for medical and other parts at PLASTEC West, which is held concurrently with MD&M West Feb. 12-14 in Anaheim, CA.
A new ultraviolet vulcanization process will be shown that fits into an Engel strategy to develop multi-component molding systems that respond to growing pressure to reduce system costs while also improving quality. "This technology is not limited to medical applications; it would be suited for any low-temperature vulcanization processes," Steve Broadbent, LSR/ELAST Project Engineer, Engel Machinery Inc. (York, PA) told PlasticsToday.
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| Bottle stopper from LSR project. (Engel) |
In Engel's booth (3715) at PLASTEC West 2013, an e-motion all-electric machine will demonstrate the new process, molding a two-component bottle stopper.
"In the application we are showing we are using a low-temperature thermoplastic that could not be overmolded using a standard silicone that cures at high temperatures," Broadbent said. "The other application would be a very thick cross section silicone part which would require a longer curing time since the temperature needs to penetrate the entire cross section properly vulcanize the part."
UV vulcanization requires cavity inserts in the mold that are permeable to light. For an application demonstrated by Engel earlier this year, Elmet (Oftering, Austria) employs translucent plastic inserts for UV light and integrates UV lamps into the mold for irradiation.
"Enhancements to silicone rubbers in the past two years have opened the door to new applications in multi-component technology for this material class", says Professor Georg Steinbichler, head of research and development technologies at Engel Austria.
"Whereas conventional silicone rubbers require high temperatures for cross-linking, the new types vulcanize with exposure to light in the ultraviolet wavelength range at room temperature. This enables silicones to be combined with a wide range of thermoplastics via two-component and multi-component injection molding. Even temperature-sensitive materials such as polypropylene can now be processed with silicone in a single step."
In an earlier demonstration, polypropylene was overmolded with liquid silicone from Momentive Performance Materials. Irradiation time for the vulcanization of the silicone components was around 20 seconds. "In the conventional high-temperature process, silicone parts with a similar wall thickness need more than a minute for cross-linking", said Steinbichler. "UV vulcanization not only facilitates new applications, therefore, but also reduces the cycle times and energy consumption associated with silicone processing."
The technology, material and mold design are still in the developmental stage and there are no commercial applications to date.
