During the storage of polyurethane masterbatch, phenomena such as bottom sedimentation, upper layer thin liquid, and overall stratification often occur. Many workshops mistakenly believe that the glue has deteriorated and directly scrap it, resulting in unnecessary losses. In fact, most of the stratification and sedimentation are normal resin settling and not complete failure. However, if the glue is not treated and directly mixed and used for production, it will cause uneven solid content, color difference in coating, fluctuation in strength, and unstable dry weight, and lead to a series of composite quality problems.
Long-term static storage is the main reason for the stratification of glue. The
Polyurethane Adhesive resin system contains high molecular particles and fillers. When stored in a static state without turning over, the high-density resin slowly sinks, while the low-density solvent remains suspended in the upper layer, resulting in a clear solid-liquid separation. Especially in a low-temperature storage environment, the solubility of the resin decreases, and the sedimentation speed accelerates. The phenomenon of sedimentation and stratification will be more severe in winter.
Long storage time and unstable storage temperature will aggravate the sedimentation. The stability of the glue system will deteriorate after prolonged storage, with resin agglomerating and forming hard sediment that is difficult to disperse. Changes in temperature in the warehouse, large temperature fluctuations, will cause the resin to repeatedly dissolve and precipitate, destroying the uniformity of the system. In addition, some manufacturers' high-solid-content glues have high viscosity and a heavy system, making them more prone to natural sedimentation.
Correct usage guidelines can effectively avoid quality risks. After opening the bucket, it is necessary to first turn the bucket completely, fully mix, and completely disperse the bottom sediment to ensure uniform solid content and viscosity of the entire bucket of glue. It is prohibited to directly extract the upper thin glue for use, to avoid insufficient dry weight and low strength. Daily storage should maintain a constant temperature, regularly turn the materials, follow the first-in-first-out principle, and this can effectively solve the process fluctuations caused by stratification sedimentation, and stabilize the composite quality.
