Polyurethane laminating adhesives belong to a high-activity two-component chemical system and are extremely sensitive to storage environment, sealing conditions, and stacking temperature. Many factories have experienced batch problems such as glue not drying, bubbling, strength plummeting, and abnormal mixing ratios, which are not caused by production process errors but are instead due to improper storage of raw materials leading to premature deterioration and loss of activity, resulting in continuous poor composite quality after being put into production, which is an easily overlooked pre-quality hazard.
Moisture absorption and deterioration of curing agents is the most common storage failure. Polyurethane curing agents contain a large number of isocyanate groups, which are prone to chemical reactions when exposed to water, generating carbon dioxide and ineffective urea bonds. Inadequate sealing of the glue bucket, damp warehouse, and failure to seal immediately after opening the lid, continuous infiltration of water vapor from the air, can cause the curing agent to become cloudy, clump, and bulge with gas inside, resulting in insufficient cross-linking and continuous gas production after being put into production, causing composite bubbling, non-drying, and re-adhesion defects.
Abnormal temperature storage will accelerate the aging and failure of the glue. High-temperature storage environments will accelerate the sedimentation of the main agent resin, the precipitation of additives, and the aging of the system, leading to poor rheological properties of the glue liquid, poor coating flowability; long-term low-temperature storage will cause local crystallization of the resin, stratification, and thickening, and a decrease in dilution stability. At the same time, excessive storage of the glue beyond the expiration date, accumulation of free monomers, and consumption of active groups will directly lead to significant degradation of bonding performance, water boiling resistance, and aging resistance.
Standardized warehouse management can prevent glue deterioration at the source. Raw materials need to be stored in a sealed and dark environment, maintaining a dry, ventilated, and moderately temperature-controlled warehouse, and avoiding extreme high or low temperature environments. Immediately seal the opening after taking out the bucket and prevent long-term exposure to moisture; strictly follow the first-in-first-out principle and prohibit mixing of expired glue. Store the main agent and curing agent separately to avoid mixed storage and reactions. Through standardized warehouse management, ensure the stability of the
Polyurethane Glue's activity and the qualified state of the glue put into production.
