The new family of fiber-reinforced LSRs, which process like standard liquid silicone rubbers in terms of cure speed and flowability, has been developed jointly by Momentive Performance Materials of Albany, NY, and the Woco Group of Bad Soden, Salmünster, Germany.
"Fiber-reinforced elastomers have been used in the industry for decades," says Oliver Franssen, global marketing manager for automotive elastomers at Momentive. "However, outside of the tire industry little has been done in the area of automotive mass-production applications... Based on the heterogeneous fiber distribution in the low viscosity LSR, the development of complex reinforced parts with homogeneous material properties is now possible."
Target markets for this new class of materials include applications where the silicone elastomer alone cannot withstand pressure, or where reinforcement is contributing to the safety of the part. This includes products such as membranes, pressure hoses and exhaust hangers. In addition to a significant potential cost reduction through high yield and less wasted material in the LSR process, considerable weight savings can also be achieved in certain applications.
"Our main targets for development are automotive and industrial applications", says Ralf Möller, leader of the CAE department of the Woco Group. "The development process took quite some time, to ensure that we can predict parts performance with this new material by means of non-linear finite element analysis, to minimize the risk of failure."
The Woco Group is a privately owned automotive supplier with more than 3,000 employees in Germany, the United States, China and 17 other countries. Its specialties include molded parts in rubber and plastics for antivibration systems and seals. Injection molding of liquid silicone rubber (LSR) is a process to produce pliable, durable parts in high volume.
Liquid silicone rubber is a cured silicone with low compression set and great stability, which can resist extreme temperature. Silicone rubbers make up about 30 percent of the silicone family. Seals are typical applications for liquid silicone rubber as are electric connectors, multi-pin connectors, infant products requiring smooth surfaces are desired, medical applications as well as kitchen products. Silicone rubber is often overmolded onto rigid thermoplastics, such as nylon 6,6.
Another new sealing material from Momentive is fully fluorinated silicone liquid elastomers (FFSLs), which combine physical and chemical properties of previous fluorosilicone elatomers with the unique processing and productivity advantages of an addition-cured, platinum-catalyzed LSR. The materials were demonstrated last fall on one of the smallest LSR injection molding machines available--the BabyPlast machine.