The overall aging resistance of high-strength PU sealant is above average: it can be used outdoors for 5-10 years, but it is not resistant to strong UV, high temperature, and long-term hot water. The formula and selection directly determine the lifespan.
1、 Core aging performance and data (high-strength version)
- Photooxidative aging (primary failure)
UV+thermal oxidation: The surface is prone to powdering, cracking, loss of gloss, yellowing, and a decrease in mechanical properties.
Typical test: Xenon lamp/UVB 300-2000h
Ordinary PU: strength retention rate of 60-75%, with obvious surface powdering.
Weather resistant modified PU (with UV absorber/antioxidant/rare earth filler): retains ≥ 80% after 300 hours, ≥ 70% after 2000 hours, without obvious powdering.
Outdoor practice: significant aging after 3-5 years of unprotected direct exposure; Sunshade/coating can be extended for 8-10 years. - Thermal aging
Short term heat resistance: 120 ℃ × 3h, strength loss<2%. Long term thermal oxidation: 70 ℃ x 28 days, strength retention ≈ 70-85%, hardening and brittleness. Temperature resistance range: * * -40 ℃~+90 ℃ stable; >100 ℃ * * Rapid degradation. - Water/Damp Heat Aging
Room temperature immersion: 7-day strength retention ≈ 85-95%, slight water absorption expansion.
Hot/alkaline water: 70 ℃ × 168h, strength decreases by 15-30%, ester bond hydrolysis and adhesion decrease.
Damp heat cycle (-40 ℃~80 ℃ × 50 times): No cracking or delamination, strength retention ≥ 80%. - Chemical/Media Aging
Good oil resistance, solvent resistance, and salt spray resistance: no softening of salt spray after 3000 hours.
Not resistant to strong acids and alkalis, long-term hot water, and ozone (prone to cracking).
2、 Key factors affecting aging resistance
Molecular structure: Polyether PU (ether bond)>Polyester PU (ester bond), significantly better water resistance/hydrolysis.
Cross link density: The higher the density, the more heat-resistant/solvent resistant it is, but the more brittle and the displacement ability decreases.
Formula additives: UV absorbers, antioxidants, light stabilizers, and rare earth fillers can increase the weather resistance life by 20-40%.
Substrate and construction: Bottom coating, cleaning, full and bubble free, can reduce interface aging and failure.
3、 Selection and usage suggestions (extending lifespan)
Priority should be given to weather resistant modified versions: labeled as “UV resistant” and “outdoor specific”, with a tensile strength of ≥ 6MPa and an elongation rate of ≥ 400%.
Outdoor protection must be taken: shading, painting coverage, and avoiding long-term direct sunlight.
Environment matching
Long term hot water/humidity: choose polyether type+water-resistant formula, avoid polyester type.
High temperature>80 ℃: Choose high-temperature resistant special PU or switch to silicone.
Strong UV: Choose UV resistant modification+surface protection.
Life expectancy
Indoor/cool: 10-15 years.
Outdoor sunshade/coated: 8-10 years.
Outdoor direct exposure: 3-5 years (ordinary PU)/5-8 years (weather resistant PU).