Everyone must be familiar with the word "PU coating." So what is PU? What kind of material is it? How is the coating processed? Now I will briefly introduce some common sense in this area to discuss with you, hoping to help everyone have some emotional perception of the concept of PU coating, there is less than that please correct me and add.
PU is actually polyurethane, its performance is mainly characterized by wear resistance, solvent resistance and low temperature resistance (below 30°C), good waterproof and moisture permeability, windproof, soft and other characteristics. Under normal circumstances, it is a milky white emulsion that can be used with knitted fabrics and plain weaves. Fabrics such as cloth and non-woven fabrics are compounded into various fabrics or linings. Films with various properties can be processed in two or more layers. We usually contact with PU coating products that are mainly used for outdoor clothing and wrapping fabrics, and for example PU leather products such as imitation leather (leatherettes) and suede suede. Polyurethane PU coating can form a lot of multi-functional / \\ (?! & # | \? #) / high value-added textile products, widely used in clothing, decoration, military and other industries.
The PU coating step is divided into its coating form. In simple terms, it can be divided into water-based and solvent-based polyurethane. Solvent-type film-forming properties are good, strong adhesion to fabrics, high water pressure resistance, and are more suitable for waterproof and moisture-permeable coatings. However, the solvent type has certain toxicity and flammability. It is not environmentally friendly. The water-based type is safe and non-toxic. It is environmentally friendly. However, it has poor adhesion to fabrics and its water pressure resistance is weaker than that of the solvent type.
PU coating agent is a block polymer consisting of repeated alternating of soft and hard segments. The soft section makes the PU soft and elastic, and is composed of a polyether or a polyester diol. The molecular weight of the soft part can also affect the soft hardness of the PU. The hard section makes the PU have strength and elastic modulus and is composed of various diisocyanates. Constituted with chain extenders. The ratio of the two and the structure of the raw materials can determine and influence the performance of the product.
The synthesis method is generally made of a diisocyanate, a polyester diol or a polyether diol plus a chain extender and a catalyst by solution polymerization or bulk polymerization. Substantially granular or powdery can be made by bulk polymerization. Aqueous emulsions can be made using emulsifiers or hydrophilic groups introduced from milk. The solvent type is made of different organic solvents as required.
The coating processing methods include dry method, wet method, hot-melt method, transfer method, and bonding method. Among them, the dry method is the most widely used method. The dry method is to uniformly coat the coater slurry on the base cloth. After heating, the solvent or water volatilizes, and the coating forms a film on the fabric surface. The PU thin coating is a high-grade product in the dry direct coating, and is mainly used for apparel fabrics.
There are many characteristics and types of polyurethane PU coating materials, and other products and applications are not described here.
In addition, when I recently researched a large PU coating material company, I used a rough understanding of PTFE film. According to the relevant personnel, some (PTFE) films were also coated with a layer of polyurethane ( (PU) membrane made waterproof breathable composite membrane.
Polyurethane and PTFE film composite dry film production. Using a mixed solvent, the PU can be well adhered to the surface of the PTFE material. The polyurethane adhesive is applied to the PTFE film using a doctor blade process.
The moisture permeability of this composite membrane is attenuated as the thickness of the membrane increases, and vice versa. The polyurethane used for the composite film is a thermoplastic adhesive. After the composite film and the fabric are heat-press bonded, a waterproof fabric with good water repellency can be obtained.
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