37. What are the main factors affecting the quality of coated products?
Answer PU coating finishing is a comprehensive finishing. The main factors affecting the quality of PU coating products are PU coating agent, base fabric and finishing process. PU coating agent is the key to affecting the quality of PU coating products. In addition to the general particle size, viscosity, pH value, ionic type, and solid content, the technical indicators of PU coating agent are also very important for PU coating used for work clothing fabrics. For layering agents, the film is required to be soft but not sticky. A high content of methyl methacrylate or methyl acrylate will make the hand feel harder. A low content will affect the strength of the film. If there is too much butyl acrylate, it will feel soft, but it will be sticky. Therefore, the PU coating agent should have a viscosity suitable for finishing. Adding a thickener can adjust the viscosity, but it must have good rheology to facilitate finishing operations. Another example is that water-blocking PU coating products require the PU coating agent to meet the water pressure resistance of water-repellent products, so the content must be high. The content of foreign PU coating agents can reach 60%, while the content of domestic products is only 40%, generally around 30%. Because certain additives are added to the PU coating agent, bubbles are often generated during cleaning, which will also affect the water pressure resistance. The PU coating agent also requires good compatibility with other chemical raw materials, otherwise it will easily become thinner or thicker, affecting the coating finish. The base fabric used for PU coating needs to be pre-treated. The fabric cannot contain surfactants such as acids, alkalis and other cleaning agents. The fluff on the surface of the fabric needs to be singed clean to avoid affecting the bonding fastness of the PU coating and the generation of scraping coating. Defects such as hair drag, slivers, etc. The surface of the fabric also needs to be clean and flat, with the yarns arranged neatly and without “thin paths” or “tightening”, so that it can be evenly coated and not easily penetrated into the back of the fabric when scraping, thereby improving the hand feel.
The quality of water-blocking PU coated fabrics depends on the warp and weft density of the fabric. High density means good water-blocking properties; conversely, the water-blocking properties are poor. When using the same PU coating finishing method, the water blocking performance is 47.24 threads/cm×27.56 threads/cm (120 threads/inch × 70 threads/inch), which is greater than 39.37 threads/cm×20.87 threads/cm cm (100 strands/inch × 53 strands/inch) is greater than 16.93 strands/cm × 24.8 strands/cm (43 strands/inch × 63 strands/inch). The finishing process of PU coating depends on the use of the final product and the base fabric. For example, pure cotton canvas fire-fighting protective clothing is required to have water-blocking properties such as water resistance and water repellency. Because the base fabric has a low warp and weft density and the fabric surface is not smooth, it is difficult to meet the requirements. For this reason, it is necessary to increase the coating amount and add functional additives to the PU coating agent in terms of technology.
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