Novel Class of Super-High-Elongation Silicones for Molding

A new class of silicone elastomers with unprecedented elongation and shape-recovery abilities has been developed by Gelest, Inc., Morrisville, Pa. The initial solid, two-component products are industrial-grade Gelest ExSil 100 for applications such as diaphragms, microfluidics, vibration damping, high-performance seals, and optical or electrical interconnects; and a more highly refined, biocompatible medical grade for implantable medical devices. Gelest is working to apply the technology to a liquid silicone rubber and expects to introduce LSR versions in the next three to four months.

 

According to Gelest president and CTO Barry Arkles, these silica-nanoparticle-reinforced materials approach 5000% elongation at break, which he describes as revolutionary. “A 2-yard piece stretches the length of a football field. By contrast, a highly-stretchable elastomer such as a household rubber band, with 200% to 400% elongation at break, would break at about 6 to 8 yards; while a high-performance stretchable elastomer with 1000% elongation at break would extend to about 20 meters.” On a smaller scale, according to Arkles, a cylindrical sample with a 1-cm diam. will narrow to approximately 1-mm at full extension and then return to its original shape when tension is released.

 

According to Gelest senior R&D manager Jonathan Goff, “The elastomer has no apparent crosslinking, which is a typical requirement for elastomeric behavior in silicones. We believe this is the key feature that differentiates this material from conventional silicone elastomers and is what accounts for the unprecedented elongation.”

 

The ExSil 100 elastomer enables design engineers to create microfluidic devices that can withstand movement, elongation and distortion, yet still retain functionality. Due to its shape recovery, the medical grade is applicable for implantable devices that can be stretched, rolled, and inserted into a syringe, injected through a small opening into the body, and then, once in place, can return to its original shape. Other potential applications are formable micro-electrode arrays, synthetic skin and other compliant materials (i.e., intelligent skin, e-skin, and Micro-ID). Company officials say these new elastomers will be priced in line with other specialty silicone elastomers—on the order of $150-200/kg ($68-90/lb).