Conventional polyurethane sealant has a long-term high temperature resistance of about 80-90 ℃ and a short-term peak temperature of 100 ℃; The dedicated heat-resistant type can withstand 100-120 ℃ for a long time, and the maximum formula can reach 130 ℃.
1、 Temperature range (core data)
Standard type (universal for construction/automotive)
Long term use: -40 ℃~80 ℃ (stable elasticity, no flow)
Short term peak: 90 ℃ (no significant aging within a few hours)
Representative: 3M 540, ordinary single/two-component building adhesive
Heat resistant modified type (industrial/near heat source)
Long term use: -40 ℃~100 ℃ (engine compartment, equipment joints)
Short term peak: 120 ℃ (intermittent high temperature, such as near the exhaust pipe)
Formula: Add heat-resistant fillers and special isocyanates
Extreme heat resistance type (specially customized)
Long term use: 120 ℃
Short term peak temperature: 130 ℃ (requires specialized formula, high cost)
2、 Performance under high temperature
≤ 80 ℃: Stable performance, high retention rate of elasticity/adhesive strength.
80-100 ℃: gradually softens, slightly decreases modulus, and retains about 70% strength after long-term (>1000h) thermal aging.
100 ℃: prone to softening, flowing, foaming, and adhesive failure; >Accelerated degradation and cracking at 130 ℃.
3、 Compared with silicone adhesive (high temperature resistance)
Polyurethane (PU): long-term 80-90 ℃, short-term 100-120 ℃; High mechanical strength, good elasticity, and oil resistance, but its long-term heat resistance is not as good as silicone.
Silicone (SR): long-term 180-200 ℃, short-term 250 ℃; Better heat resistance/aging resistance, but lower strength, poor oil resistance, and average adhesion.
4、 Selection suggestions
Ordinary environment (buildings/doors and windows/car interiors): Choose the standard type (≤ 90 ℃) for high cost-effectiveness.
High temperature environment (engine/equipment/roof exposure): Choose heat-resistant modified type (100-120 ℃).
Continuous high temperature of 120 ℃: Priority is given to silicone sealant, or customized extreme heat-resistant PU.
5、 Key points to note
Construction temperature: 5-40 ℃. High temperature (>40 ℃) construction is prone to foaming and uneven curing.
Thermal aging effect: After 90 ℃ × 1000h, the strength/elongation retention is about 70%, which is acceptable.
Avoid long-term temperatures above 100 ℃: it will significantly shorten the lifespan and reduce reliability.