Liquid silicone rubber is an increasingly important competitive weapon for American injection molders. Molding technologies are advancing, creating new opportunities for the thermoset elastomer, which boasts an impressive set of properties: chemical resistance, UV stability, low compression set, and stable mechanical properties at a wide temperature range. High-value medical applications, in particular, are attractive.
More than 20 exhibitors will show developments in LSR at NPE2015, which focuses on plastics not rubber. The reason is the opportunity to use LSR in highly automated, modified plastic molding equipment. Often elastomeric LSR is mated in-mold with rigid thermoplastics.
Following are a few examples of the action at NPE2015, which will be held March 23-27 in Orlando, Florida.
Silcotech (W2753) has developed with Dow Corning what is described as a “step change” in LSR processing. A new multi-shot processing system is said to be capable of simultaneously molding nine discrete substrates or shapes that exhibit a broad range of durometers, textures and colors utilizing the Dow Corning QP1 Silicone Elastomer product family. Costs remain comparable to a single shot system, according to Silcotech.
“Radically new processing technologies don’t come along every day, but our new process changes the paradigm by allowing medical device manufacturers to design with an entirely new template that adds a whole new dimension of options,” says Michael Maloney, president of Silcotech. “Our customers can now cost-effectively produce finished, highly differentiated components in a single process that integrates materials with different durometers, chemical functional groups, surface textures, colors and other properties. The potential combinations for designers are virtually endless, and introduce a bold new chapter for competitive differentiation and success in today’s fast-growing global healthcare sector.”
Momentive Performance Materials (S15079), which recently completed a financial restructuring, has developed a fiber-reinforced LSR that is said to combine the flexibility of a silicone elastomer with the high strength of polymeric fibers for applications that need increased stiffness, like wrist bands for wearable electronic devices. Momentive says it can shave costs by eliminating the need for an additional fabric layer.
Arburg (W3729) will demonstrate the production of vacuum suction pads made from
thermoplastic and LSR on an electric Allrounder 570 A equipped with two injection units in L-position and a 4+4-cavity mold from Rico. Pre-molded PBT parts are robotically placed in the LSR cavities. Four vacuum suction pads (used for moving bulky or heavy loads in handling equipment), are produced in a cycle time of around 40 seconds.
Engel (W1303) will also demonstrate LSR overmolding in an automated process. Double-ended wrenches will be molded on a system using two e-mac 170/55 US machines with four-cavity molds from Roembke (Ossian, Indiana). The wrenches are made of carbon-fiber-reinforced polyamide overmolded with silicone between the two ends for better grip. The part is injection molded on the first machine in the cell, removed by a linear robot and immediately placed in the mold of the second injection molding machine.
Wittmann Battenfeld (W2743) will mold two-component LSR tear duct plugs in a MicroPower micromolding machine.