Detailed explanation of low temperature resistance of polyurethane sealant
1、 Conventional operating temperature (long-term work after curing)
Universal building/automotive PU sealant: -40 ℃~+90 ℃, maintaining elasticity, no cracking, no debonding at -40 ℃, and can follow the thermal expansion and contraction deformation of the substrate at low temperatures.
Cold resistant special polyether PU: -50 ℃~+85 ℃, brittle temperature * * -50~-70 ℃ * *, flexible even after freezing at -50 ℃, preferred for high cold, cold chain, and northern outdoor environments.
Polar/Military Ultra Cold Resistant Formula: It can serve at a minimum of -70 ℃ and is commonly used for sealing engineering machinery, refrigerated carriages, and polar equipment.
Comparison: Acrylic adhesive hardens and becomes brittle at 20 ℃, while epoxy is prone to fracture at 30 ℃. PU has a significant advantage in low-temperature elasticity.
2、 Low temperature performance
Hardness change: The hardness increases by 5% to 10% for every 10 ℃ decrease in temperature. It becomes harder at low temperatures but still maintains high elongation (>100%) without brittle fracture;
Elastic recovery: -40 ℃ elastic recovery rate>75%, can adapt to joint expansion and contraction, vehicle bumps and vibrations;
Adhesive stability: Low temperature shrinkage without edge detachment or warping, waterproof sealing without failure.
3、 Key points for low-temperature construction (uncured)
Conventional construction environment: * *+5 ℃~+35 ℃ * * is optimal; Moisture curing significantly slows down below 5 ℃, resulting in thickening of the adhesive and difficulty in extrusion;
Winter low-temperature construction plan: The adhesive material should be warmed up to room temperature in advance, and low-temperature curing PU (which can be used for construction at 0 ℃) should be selected to avoid outdoor sub zero gluing.
4、 Differentiation of low-temperature resistant formulas
Polyester PU: Conventional -40 ℃, strong adhesion, good oil resistance, ordinary doors and windows, automotive sheet metal;
Polyether PU: a cold resistant ace, starting at -50 ℃, with low water absorption rate, suitable for cold storage, high-altitude infrastructure, and cold chain carriages.
