Uncured Silicone Handling Best Practices
Mosites Rubber Company supplies uncured silicone sheet for fabrication into various configurations. When dealing with uncured silicone sheet, shelf life becomes very important. Mosites policy has been to recommend that the sheet be kept under refrigerated storage at a temperature below 40°F. We also recommend that fabrication occur within 8 weeks after our customer receives the shipment. This time frame guarantees that the material will strip properly from its liner, seams and splices can be properly skived or feathered, and that the sheet will cure properly.
Sheet Fabrication Suitability Tests
Sometimes a customer will have material which has been stored longer than recommended. The following procedure is a quick inspection to determine if the sheet is still suitable for fabrication.
- Remove a portion of the polyethylene film liner and check to see if the silicone adheres to the film. Aged stock often is difficult to strip from the liner.
- Take a spatula or “skive” and try smearing the uncured sheet edge. If the silicone makes a smooth “feathered” edge, it is still usable. If it tends to shred or roll up it is probably aged to the point of causing lay-up problems.
- Take two small pieces of the uncured sheet and lay them together applying light pressure. Observe the degree of adhesion between the pieces. Usable stock should adhere tightly.
The above tests are only guidelines to help determine if aged silicone sheet is still usable. Many customers routinely manufacture lay-ups from sheet that is 6 months old if it has been stored properly. As long as the sheet can be removed without distortion from its polyethylene liners, vulcanization and subsequent physical properties are not affected.