The aging resistance of polyurethane sealant belongs to the upper middle level, and it is durable in conventional outdoor environment, but long-term strong ultraviolet, high temperature and humidity or chemical corrosion will significantly shorten its life.
1、 Main aging factors and manifestations
Ultraviolet (photoaging)
Weakness: UV in sunlight is the biggest killer, which can break molecular chains, causing yellowing, powdering, cracking, and decreased elasticity.
Performance: Yellowing begins after 3-6 months of outdoor exposure, and the surface becomes brittle after 1-2 years.
Difference: Aromatic compounds are prone to yellowing; Fatty compounds have good UV resistance and are not easily discolored.
thermal oxygen aging
High temperature (>50 ℃) accelerates oxidation, causing colloids to harden, become brittle, and decrease in strength.
The aging rate often doubles for every 10 ℃ increase in temperature.
Hydrolytic aging (moisture/water)
The ester type has average water resistance and is prone to foaming, whitening, and adhesive failure when soaked in water or high humidity for a long time.
Ether type has better water resistance and is more suitable for humid environments.
Chemical media
Good resistance to oil, weak acid, and weak alkali.
Not resistant to strong acids, strong bases, and strong solvents (ketones, esters, etc.), it will swell and degrade.
2、 Service life (reference)
Indoor/sheltered, no direct light: 25-30 years
Ordinary outdoor (sunlight, rain, temperature difference)
High quality fatty acids: 15-20 years
Ordinary aromatic: 10-15 years
Adverse environment (strong UV, coastal salt spray, acid-base, high temperature): 5-10 years
Dynamic seam/frequent vibration (automotive, movable seam): 5-8 years
3、 How to improve anti-aging life
Choose the right type
Long term outdoor exposure: prioritize aliphatic polyurethane (UV resistant, non yellowing).
Damp/soaked in water: Choose polyether type (better water resistance than ester type).
Formula and additives
Adding UV absorbers, antioxidants, and carbon black can significantly delay aging.
Construction and Protection
The grassroots is clean, dry, and fully cured.
Outdoor exposure can be coated with matching paint/stickers to block ultraviolet rays.
4、 Simple comparison with silicone adhesive (weather resistant adhesive)
Polyurethane (PU)
Advantages: high strength, wear resistance, oil resistance, good toughness, wide adhesion
Disadvantages: average UV resistance, prone to yellowing, average alkali resistance
Lifespan: 10-20 years outdoors
Silicone
Advantages: extremely UV resistant, strong weather resistance, high and low temperature resistance, long-term non brittleness
Disadvantages: Low strength, oil resistance, weak adhesion of some materials
Lifespan: 20-30 years outdoors+
