Silicone rubber selection: molding, coating and sealing

• For injection molding, evaluate cavity filling, venting, demolding and the mechanical properties of the actual molded geometry.
• For fabric coating, prioritize substrate wetting, coating consistency and anchorage after flexing and relevant conditioning.
• For adhesive gel, use penetration, peel behavior and residue criteria rather than assuming Shore hardness is the main measure.
• For fluorosilicone seals, measure swelling and retained mechanical properties in the actual oil or solvent and at the required exposure conditions.
• Control mixing ratio, component identity, specimen preparation and cure inhibition checks before interpreting a property difference.

VN-SI-1279 is directed at liquid injection molding. Its documented mechanical specimen condition is a 2 mm sample cured at 105°C for 15 minutes, while the use guide gives 120–150°C as a cure-development range with time adjusted to the process. These statements describe different contexts; do not use the property-test preparation as an automatic production setting.

VN-SI-1280 targets textile, glass-fiber and related coating applications and lists A:B options of 10:1 or 1:1, requiring confirmation of the supplied pair. VN-SI-1281 is also coating-oriented; wording about flow or fast curing does not quantify a speed advantage. VN-SI-1278 is an adhesive gel with A:B=1:1 and penetration data, making it a different selection route from a load-bearing molded rubber.

VN-SI-1139 provides a general fluorosilicone compound reference. VN-SI-1140 emphasizes tear strength, VN-SI-1141 low compression set and VN-SI-1142 resilience. These are distinct selection objectives, not a universal quality ladder. Compare at the required hardness and a consistent cure history, then reproduce the actual seal deformation and fluid exposure where relevant.

When cure is incomplete or adhesion inconsistent, examine ratio accuracy, mixing, substrate cleanliness and contacting materials before changing grade. For addition-curing systems, include a cure-inhibition screen for pigments, tools and substrates. If a seal swells or loses recovery, compare the actual fluid exposure and retained properties, not only unaged tensile strength. Application descriptions do not establish food-contact, medical or other finished-article approval.