Platinum Cured HCR Silicone Sheet
SSP4749 High Purity Series
SSP4749-XX high performance silicone rubber is a unique high consistency rubber (HCR) that is platinum catalyzed. This platinum cured silicone is an excellent choice for medical device (non-implant) applicationsmeeting USP Class VI, food contact applications that need to meet FDA CFR 21 177.2600 and other applications that may have sensitivities to outgassing or leaching. Stockwell Elastomerics provides SSP4749-XX to customers that need this high performance silicone rubber for such applications.
Platinum Cured vs. Peroxide Cured High Consistency Rubber (HCR)
SSP4749-XX is a unique high consistency rubber (HCR) that is platinum catalyzed. Platinum catalyzed silicones are often used in medical and food contact applications as a result of the “cleaner” curing process. Free radical curing, which typically uses peroxide as a catalyst, generates organic acids as a by-product that can leach or be extracted. For medical devices, food contact and other sensitive applications, peroxide cured silicones may not be allowed or may require post curing to drive off the volatiles. In general, platinum cured silicones like SSP4749-XX are the best choice for sensitive applications. In these industries, the terms “platinum cured”, “platinum cure”, “addition cure”, and “addition cure” are used interchangeably.
SSP4749-XX vs. Liquid Silicone Rubber (LSR)
Most liquid silicone rubber (LSR) materials are addition cured so they don’t generate the organic acids that peroxides do. Stockwell Elastomerics injection molds LSR for 3D geometries. For applications that need to be die cut, require a wider temperature range or greater elongation and tear properties – SSP4749-XX is the better option. SSP4749-XX is made in continuous rolls vs. Stockwell Elastomerics’ LSR 12”x12” sheets. These continuous silicone rubber rolls offer better efficiency for die cut, waterjet cutting, and tool-less flashcutting.
Processing High Consistency Rubber (HCR) vs. Liquid Silicone Rubber (LSR)
High Consistency Rubber (HCR) silicone is sometimes called gum based silicone in contrast to liquid silicone rubber. Traditionally HCRs are peroxide cured and in raw form look like potters clay. LSRs are generally platinum cured and in raw form are Part A and Part B liquids. These liquids are mixed and either injection molded or cast and heat cured. SSP4749-XX is a cleaner platinum cured HCR or gum based silicone that can be compression molded or roto-cured into continuous sheets.
SSP4749-XX Benefits and Properties
SSP4749-XX combines the benefits of the “cleaner” platinum cure system, commonly associated with liquid silicone but with better physical properties associated with HCRs. These include a wide temperature range of -67°F (-55°C) to 392°F (200°C), high tear strength, and greater elongation. SSP4749-XX can also be post cured to further improve its excellent outgassing properties. Many silicone rubber products are not able to meet the total mass loss (TML) and/or Collected Volatile Condensable Materials (CVCM) limits for low outgassing. NASA defines the low outgassing thresholds of 1.0% TML and 0.10% CVCM.
Improved Compression Set Properties After Post-Cure
When post-cured for 2 hours at 200°C (392°F), SSP4749-XX has improved compression set properties. For example, this post-cure improves the compression set values of SSP4749-50 from 19% to 11% at 70°C and from 33% to 12% at 100°C. The improved compression set, along with the purity of the platinum cure silicone have found favor with the Fuel Cell industry. The LV suffix, such as SSP4749-XXLV, is used to indicate post-cure.
Platinum Cured High Consistency Rubber (HCR), Silicone
Stockwell Elastomerics offers SSP4749-XX material in 7 different hardnesses, from 10 durometer to 70 durometer.
- SSP4749-10 – 10 durometer High Consistency Rubber (HCR)
- SSP4749-20 – 20 durometer High Consistency Rubber (HCR)
- SSP4749-30 – 30 durometer Platinum Cured High Consistency Rubber (HCR)
- SSP4749-30LV – 30 durometer Platinum Cured High Consistency Rubber (HCR) with Post-Cure
- SSP4749-40 – 40 durometer Platinum Cured High Consistency Rubber (HCR)
- SSP4749-50 – 50 durometer Platinum Cured High Consistency Rubber (HCR)
- SSP4749-50LV – 50 durometer Platinum Cured High Consistency Rubber (HCR) with Post-Cure
- SSP4749-60 – 60 durometer Platinum Cured High Consistency Rubber (HCR)
- SSP4749-60LV – 60 durometer Platinum Cured High Consistency Rubber (HCR) with Post-Cure
- SSP4749-70 – 70 durometer Platinum Cured High Consistency Rubber (HCR)
- SSP4749-70LV – 70 durometer Platinum Cured High Consistency Rubber (HCR) with Post-Cure