Flexible packaging polyurethane laminating adhesive is the core material of food, daily chemical and outdoor packaging lamination molding, and its weatherability directly determines the service life and stability of lamination film, which is the key index to measure the comprehensive quality of adhesive. When packaging is stored, transported and used outdoors, it is often affected by ultraviolet radiation, alternating temperature and humidity, damp-heat aging and other environmental factors, and it is prone to problems such as yellowing of adhesive layer, decrease of peeling strength, delamination and degumming, etc., and excellent weather resistance can effectively avoid such quality defects.
The difference of weather resistance of polyurethane laminating adhesive comes from molecular structure design. The conventional aromatic
Polyurethane Adhesive has high bonding strength and excellent cost performance, but the molecular structure has aging groups, which are prone to oxidative degradation and yellowing after long-term illumination. It is only suitable for indoor ordinary packaging scenes. However, the aliphatic polyurethane laminating adhesive does not contain unsaturated aging bonds, and has outstanding anti-ultraviolet and anti-humid aging capabilities. After curing, the adhesive layer is transparent and stable, and it is not easy to yellow and crack, which is suitable for outdoor packaging, long-term fresh-keeping packaging and other weather-resistant demand scenarios.
The industry often verifies its weatherability through QUV accelerated aging test and moist heat cycle test. After long-term aging test, high-quality modified products can still maintain stable adhesive strength and flexibility. At present, by optimizing the ratio of polyols, improving the catalyst system and adding weather-resistant additives, the environmental adaptability of adhesives can be further improved, taking into account the bonding performance and durability stability, and meeting the long-term use requirements of high-end flexible packaging.
