ENGEL develops new silicone vulcanisation process

ENGEL AUSTRIA has opened the door to new opportunities in multi-component technology with a new process for silicone vulcanisation at low temperatures. In mid-June, UV vulcanisation was unveiled to the world at the ENGEL Symposium 2012 in St. Valentin.

ENGEL demonstrated its new UV vulcanisation process at the Symposium by producing wine bottle stoppers.

“Enhancements to silicone rubbers in the past two years have opened the door to new applications in multi-component technology for this material class”, reveals Professor Georg Steinbichler, head of research and development technologies at ENGEL AUSTRIA. Whereas conventional silicone rubbers require high temperatures for cross-linking, the new types vulcanise with exposure to light in the ultraviolet wavelength range at room temperature. This enables silicones to be combined with a wide range of thermoplastics via two-component and multi-component injection moulding. Even temperature-sensitive materials such as polypropylene can now be processed with silicone in a single step.

Cavity inserts in the injection mould that are permeable to light are the prerequisite for UV vulcanisation. For this application, ENGEL partner firm Elmet from Oftering in Austria utilises translucent plastic inserts for UV light and integrates UV lamps into the mould for irradiation.

Reducing cycle times and energy consumption
At the Symposium, ENGEL was demonstrating the UV vulcanisation process by producing wine bottle stoppers on an ENGEL victory 200/80 LIM injection moulding machine using an Elmet mould. In the process, polypropylenes are overmoulded with liquid silicone from Momentive Performance Materials. The irradiation time for the vulcanisation of the silicone components is around 20 seconds. “In the conventional high-temperature process, silicone parts with a similar wall thickness need more than a minute for cross-linking”, said Steinbichler. “UV vulcanisation not only facilitates new applications, therefore, but also reduces the cycle times and energy consumption associated with silicone processing.”