A new family of materials reportedly makes it possible to produce dimensionally stable parts, without air entrapment, at higher extrusion speeds.
ALBANY, N.Y.—A new platform of elastomer products recently launched by Momentive Performance Materials, Inc., can be cured by simple exposure to ultraviolet (UV) light, the company announced recently. Typically, silicone elastomers (HCR) are vulcanized with peroxide catalyst and cured by heat exposure; however, the new UV-sensitive, platinum catalyzed curing system also allows curing at room temperature. According to Momentive, cure times for part geometries commonly produced by extrusion processing can be significantly less than those required for conventional silicone elastomers.
Momentive says that the demand for silicone elastomers has grown steadily over the past decade. Addition cure materials, in particular, are increasingly being used in medical or food contact and water applications, due to a lack of peroxide residues, as well as FDA and BfR conformity.
Ultraviolet cure technology can help provide energy savings and higher extrusion speed while maintaining the physical properties of silicone elastomers, the company says. The UV exposure time for the cure, reportedly, can be as short as 0.5 seconds, depending on the speed of the line and UV intensity. As the cure is initiated through UV radiation, the speed of cure is independent of the diameter and cross-section of the extruded tube or profile. This allows high-speed extrusion without the risk of under-curing. Also, because the new UV silicone elastomers cure at room temperature, the technology is said to “open the potential” for co-extrusion of silicones with temperature-sensitive materials, such as polyolefins and thermoplastic elastomers—something that isn’t possible with traditional thermal-cure silicone elastomers.
“UV curing systems have been used in several industries for a number of years,” said Holger Albrecht, global marketing manager for Momentive, in a statement from the company. “Now, for silicone extrusion, we have developed a unique product and patented process technology. Together with our industry partners, we have introduced a new approach that does not require long heating tunnels. A small UV unit is sufficient for a high output in a small space. Based on this technology, the development of complex profiles and co-extrusion parts is now possible.”
Benchmark-supported test runs have reportedly shown that the new materials typically cure at a much higher speed for equivalent mechanical properties, resistance to heat, and other characteristics normally achieved with the traditional thermal systems. According to Momentive, the UV system offers the processing advantages of extrusion without heat, as well as minimal shrinkage in the final part. The shapes of the extruded parts are said to have shown excellent dimensional stability in applications such as thick round tubes and complicated profiles.
Momentive says that customers have been impressed with the achievable line speed, which has reached the limit of extrusion machines. Because heating or radiation tunnels are unnecessary for this technology, the required space to manufacture complex profiles is reduced. Moreover, the company says, the investment required for proper UV light sources is typically affordable in comparison to conventional curing tunnels.
Momentive Performance Materials (www.momentive.com) is a specialty materials company that provides high-technology materials to the silicones, quartz, and ceramics markets.
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