In the winter and autumn seasons, polyurethane laminating adhesive is prone to experiencing seasonal problems such as abnormal viscosity increase, poor leveling, slow curing, and low bonding strength. Many factories have stable production in summer and autumn, but after the onset of winter, they frequently encounter hidden defects such as uneven coating, slight whitening, incomplete drying, and local delamination. Most of these are not due to batch issues of the adhesive, but rather due to the significant decline in the rheological properties and reaction activity of the adhesive caused by low temperatures, which is a typical seasonal process failure.
The most direct impact of low temperatures is abnormal increase in adhesive viscosity. The
Polyurethane Adhesive resin system is sensitive to temperature. When the environmental temperature is low, the molecular movement slows down and the resistance increases, causing the viscosity of the adhesive to rise sharply. If the normal temperature dilution ratio is still used, it will result in excessively high working viscosity, difficulty in coating spread, incomplete closure of the mesh roller dots, causing orange peel, vertical lines, local thin coating, and a significant decline in the appearance and uniformity of the composite film.
Low temperatures will significantly reduce the crosslinking reaction activity. In winter workshops and curing rooms, the room temperature is low, and the curing reaction rate slows down. Under the same curing time, crosslinking is incomplete, and it is prone to softening during curing, surface re-adhesion, insufficient peel strength. At the same time, the low-temperature air humidity is high, and the curing agent is prone to absorbing moisture and hydrolyzing, causing imbalance in the ratio, gas production, whitening, and poor durability of bonding, and subsequent easy occurrence of delamination and water resistance decline.
Winter construction requires targeted adjustment of process standards. Preheat the adhesive at a constant temperature to reduce the initial viscosity, adapt to the winter dilution parameters, and ensure stable coating leveling. Strictly control the temperature and humidity in the workshop, supplement the curing temperature and duration, avoid semi-curing before the adhesive is fully cured. Store the adhesive in a sealed manner to prevent moisture absorption and deterioration. Dynamically adjust the coating parameters to completely solve the various seasonal malfunctions of polyurethane adhesive during winter construction, and stabilize the quality of mass products.
