LOCTITE SI 596 RED, also known as LOCTITE Superflex Red RTV Silicone or LOCTITE 596, is a silicone-based acetoxy silicone sealant supplied as a red homogeneous paste that functions as a one component system requiring no mixing before application. This thixotropic material is engineered to reduce migration of liquid product after application to the substrate, ensuring controlled placement during gasketing or sealing operations. The curing mechanism is room temperature vulcanizing (RTV), where the material reacts with atmospheric moisture and develops tack free condition in approximately 1 hour, achieving full cure within 24 hours, depending on temperature, humidity, and joint gap. The product emits an acetic acid odor during cure and is suitable for applications typically up to 315 °C. The formulation enhances flexibility and improves load bearing and shock absorbing characteristics of the bonded area, making it ideal for gasket dressing and formed-in-place gasket systems. It is specially developed to meet low silicone volatiles requirements of the automotive industry for 315°C flange sealants and delivers consistent sealing performance in valve covers, rocker covers, oil pans, water pumps, end seals, intake manifolds, and rear axle housings. In addition, it serves as a sealant and adhesive for assembly and repair of industrial furnaces, ovens, boilers, exhaust stacks, high temperature ducting systems, and heating elements in electrical appliances. In the uncured state, the material has a specific gravity of 1.05 at 25 °C. Under test conditions of 0.62 MPa pressure, 15 seconds extrusion time, and 25 °C temperature, the extrusion rate from a Semco cartridge is ≥250 g/min. Flash point details are available in the Safety Data Sheet (SDS). After curing for 7 days at 25 °C and 50% relative humidity, the silicone demonstrates Shore Hardness ≥18 (ISO 868, Durometer A), elongation ≥300% (ISO 37), and tensile strength ≥1.5 N/mm² (≥217 psi) according to ISO 37. When cured for 14 days at 25°C, the 180° peel strength is ≥1.73 N/mm (≥9.88 lb/in) on both aluminum and steel substrates. Environmental resistance performance was evaluated on a 3.2 mm thick film cured for 7 days at 25 °C and 50±5% RH, then tested at 25 °C. During heat aging at 204 °C for 1, 2, 4, and 8 weeks, Shore Hardness values recorded were 29, 28, 25, and 22 respectively, tensile strength (ISO 527-3) ranged from 2.0 to 2.3 N/mm² before reducing to 1.9 N/mm² at 8 weeks, and elongation (ISO 527-2) progressed from 370% to 500%. At 260 °C for 1, 2, 4, and 7 weeks, Shore Hardness values were 23, 16, 15, and 17, tensile strength decreased from 1.3 to 0.3 N/mm², and elongation reduced from 520% to 210%. At 316 °C for 1, 2, and 3 weeks, Shore Hardness increased from 48 to 82, tensile strength ranged between 1.4 and 1.6 N/mm², and elongation declined from 175% to 25%. Softening observed at 260°C is attributed to reversion and occurs irrespective of cure method, which can be advantageous in flange sealing. Hardening at 315°C results from thermal rearrangement of the polymer combined with oxidation, although oxidation is reduced when used as a flange sealant. For optimal application, bonding surfaces must be clean and free from grease. Moisture curing begins immediately upon exposure to atmosphere, so components should be assembled within minutes after dispensing. Parts should be pressed or firmly clamped together without sliding. Excess uncured material may be removed using non-polar solvents, while cured residue can be trimmed with a knife or single edge razor blade. The product should not be used for gasketing carburetors or fuel control devices where continuous contact with hydrocarbon fuels may cause excessive swelling and loss of mechanical properties. Storage should be in unopened containers kept in a dry location, ideally between 8 °C and 21 °C. Exposure below 8 °C or above 28 °C may adversely affect product properties. Material removed during use should not be returned to the original container to prevent contamination. Standard engineering conversions include (°C × 1.8) + 32 = °F, N/mm² × 145 = psi, MPa × 145 = psi, N/mm × 5.71 = lb/in, N × 0.225 = lb, mm ÷ 25.4 = inches, µm ÷ 25.4 = mil, kV/mm × 25.4 = V/mil, N·m × 8.851 = lb·in, N·m × 0.738 = lb·ft, N·mm × 0.142 = oz·in, and mPa·s = cP.
