The reasons and control measures for the shortened application period of polyurethane laminating adhesive and the early thickening and gelation of the glue solution during production
2026,09,24
After the two-component polyurethane laminating adhesive is mixed, it should normally have sufficient usable time. However, during production, problems such as the glue thickening prematurely, sudden increase in viscosity, and bottom blockage and gelation often occur, resulting in the inability to apply normally in the middle, the roughening of the glue surface, and the need to discard the entire barrel. This problem is mostly not due to the quality of the glue itself, but rather caused by factors such as working conditions, ratio, and environmental factors that accelerate the reaction, significantly shortening the application period of the glue, leading to waste of raw materials and production downtime.
The core causes are the imbalance in the ratio and the introduction of impurities. Excessive addition of curing agent during manual mixing and large measurement deviations will directly accelerate the cross-linking reaction rate, causing the glue solution to thicken rapidly in a short time. The acetate ethyl ester used for dilution contains water, alcohol, acid and alkali impurities, which will prematurely consume the active groups of the curing agent and trigger abnormal polymerization reactions, resulting in premature gelation and blockage.
Environmental temperature and working methods accelerate the failure rate. In summer, when the workshop is exposed to high temperatures and the glue barrel is exposed to direct sunlight storage, and the mixed glue is placed in a high-temperature area for a long time, the activity of polyurethane molecules will increase, accelerating the cross-linking and aging of the glue solution. Excessive one-time glue mixing volume, prolonged open placement, and repeated exposure to air will cause the glue solution to continuously absorb moisture and accumulate heat, which will also rapidly shorten the application period and result in unstable viscosity during operation and local gelation particles.
On-site control requires standardizing the mixing and application procedures of the glue. Strictly follow the standard ratio for weighing and prevent excessive addition of curing agent; uniformly use high-purity anhydrous solvents to avoid interference from impurities in the reaction. During the high-temperature period in the workshop, mix the glue in small quantities as needed, use it immediately after mixing, and store the glue solution in a sealed container throughout the process. Regularly test the viscosity of the in-use glue solution and replace the near-expiration glue solution in time to stabilize the application state and reduce glue waste and process fluctuations.
