Waterproof and moisture permeable fabrics are called "breathable fabrics". Fabrics woven from these fabrics should have two functions: one is waterproof, that is, water and raindrops from outside can not reach the fabric interior through the surface of the fabric under certain pressure; the other is sweat, moisture and air permeability, that is, human sweat can be permeated in the form of water vapor. The fabric diffuses to the outside world, thus avoiding sweat and other accumulation between the human skin surface and clothing, in order to maintain clothing.
Comfort. In recent years, more and more people use waterproof and moisture permeable film. There are two kinds of products, one is microporous PTFE film represented by Gore-Tex, the other is porous molecular film represented by thermoplastic polyurethane (TPU).
一、Chemical Constituents of TPU
TPU, also known as thermoplastic polyurethane rubber or thermoplastic polyurethane elastomer, is a linear block copolymer composed of soft segments of oligomer polyols and hard segments of isocyanate, as shown in Figure 1:
Macromolecular diols and isocyanates are linked to form long chain structure, which is flexible due to their long chain. Small molecule polyols and isocyanates are linked to form short chain structure because of their short chain, thus showing rigidity and forming hard segment structure in macromolecular chain structure. Soft segments usually alternate with rigid hard segments in the TPU molecular chain and are connected by covalent "tail-tail" bonds, as shown in the figure.2 show.
Due to the interaction between hard segments of polyurethane, it has good properties.Mechanical properties. The good resilience of TPU is due to the phase of molecular chain.For motion, this is particularly evident in terms of low temperature flexibility. Transport of Molecular Chains The dynamic properties depend to a great extent on the chemical properties of the soft segment and the length of the chain.The more indeterminate the soft segment is, the better its flexibility will be.
Comparison of common waterproof and moisture permeable films
In the textile industry, we generally require that thin films not only prevent liquid from passing through, but also allow water vapor to escape. In order to achieve the perfect combination of these two functions, it is necessary to make the coating or film permeable both water vapor and liquid. Dense film and microporous film can be used. At present, the most popular waterproof and moisture permeable films are PU film, TPU film and PTFE film.
TPU film is a kind of compact film, which is made of TPU raw material by plasticizing and blowing. Because of its high cost performance, complete product line and high, medium and low moisture permeability series, PTFE film is widely used in textile industry; PTFE film is a kind of microporous film, which is produced by directional stretching of PTFE, because it is not washable, easy to absorb dust, environmental protection and other factors, it is limited to use in military and other special fields; It is a kind of compact film, which is coated by PU paste on specific materials. It is a transitional body between PTFE and TPU. It is adopted by some personalized customers. The performance of common waterproof and moisture permeable film is compared with that of table 1.
From Table 1, it can be seen that TPU film has high tensile strength, elongation, tear strength, environmental and chemical corrosion resistance, wide hardness range, large load-bearing capacity, excellent wear resistance, oil resistance, and wide application range.Widely spread. This function cooperates with the textile industry's conformity processing technology and greatly improves the added value of textiles. In addition, TPU waterproof and moisture permeable membrane has become one of the mainstream materials in the 21st century due to its good weather resistance, recyclability and decomposition.
Detailed product information can be found on our company's website