EXTON, Pa.—Liquid silicone rubber, used in automotive, medical and other markets, is growing so quickly that molders are experiencing resin shortages, according to Rick Ziebell, vice president of technology for R.D. Abbott Co. Inc.
Ziebell, the first speaker at an April 9-11 open house at Boy Machine Inc. in Exton, called the shortages "the elephant in the room."
The last major shortage happened back in 1992, he said, when a lot of new applications in the automotive industry—the biggest LSR market—drove up demand for materials. New uses for LSR included coatings for airbags and parts where anti-flammability is critical.
Add in ever-growing electronic connectors, where durable silicone seals are superior to rubber ones, engine seals, and new optical silicone applications, and "the need for silicones has expanded greatly," Ziebell said.
Glues and adhesives also use the same raw materials. It adds up to a tripling of sales of silicones in the last five years, he said.
Ziebell delivered some good news: Major manufacturers are planning a total investment of about $1.4 billion over the next few years.
LSR is a thermoset elastomer that gets pumped into a mold through a water-cooled nozzle and gets cured quickly inside a heated mold. The very fast curing is why LSR systems keep Part A and Part B separated, until just before they come together and go into the mold.
Medical offers big growth rates because LSR has good biocompatibility, Ziebell said.
"We're starting to see more LSR implantable medical devices," he said, especially diagnostic products.
"In about two years, you're going to see all kinds of things coming out. If you think the FitBit and the iPhone Watch is super, wait till you're taking a pill and it's measuring digestive systems. There'll be a little chip inside the pill that'll be communicating to your watch. Not only that, but on the therapeutic side, you'll get pulses back from various other devices implanted in your body to control and regulate metabolism throughout the body. It's amazing where we're headed," he said.
Ziebell, who outlined the chemistry behind liquid silicone rubber, spelled out one fundamental challenge with molding LSR: The huge change in viscosity that goes on throughout the pumping and molding cycle.
"The varying degree of shear mixing changes the silicone's viscosity attributes," he said. As shear increases, viscosity goes down.
When the two components come together, they start to set up and cure right away. Silicone goes from paste to water inside the injection press machine, he said, which means molding machines have to do "phenomenal things" to compensate when running LSRs. Precise cycle times and the flow speed are very important, he added.