The Implementation Method of Waterproof and Breathable Fabric

The first is to use the difference between the minimum diameter of water droplets and the diameter of water vapor or air to achieve waterproofing. That is, the pores between the warp and weft interweaving of the fabric or the pore diameter of the fabric composite are between the minimum diameter and the diameter of water vapor or air to achieve waterproofing. For the purpose of breathability, waterproof and breathable fabrics designed based on this principle include ultra-fine high-density fabrics,

Extra high-density cotton fabrics, etc. The moisture permeability type of this type of fabric is due to the natural diffusion of pores between yarns. High-density fabrics are widely used in sports and outdoor activity clothing due to their lightness, durability, good moisture permeability, softness, good drape, and wind resistance. The main disadvantage is poor waterproofness. Due to the high density of the fabric, the tearing performance of the fabric is poor. The spinning must be specially treated, which results in high production costs and difficult processing.

The second is to use a microporous film so that the pore diameter of the film's micropores (micropore diameter is about 1nm) is between water droplets and moisture, and the film and fabric are combined to give the fabric waterproof and breathable functions. The microporous polymer film can be combined with the fabric through lamination or coating processes to give the composite waterproof and breathable functions.

There are many ways to produce micropores: micropores can be produced by biaxial stretching of the film, fillers (such as ceramics) can be added to the polymer to form pores between the polymer and the filler, or through phase Separation (wet method of polyurethane) produces micropores, and drilling technology (such as laser) can also be used mechanically to create gaps in the non-porous film to achieve breathability.

The third is to use the hydrophilic component of the polymer film to provide enough chemical groups as stepping stones for water vapor molecules. Due to hydrogen bonds and other intermolecular forces, water molecules adsorb water molecules on the high-humidity side and pass through the polymer chain. The upper hydrophilic group is transferred to the low humidity side for desorption, forming an "adsorption-diffusion-desorption" process to achieve the purpose of breathability.

The hydrophilic component can be the hydrophilic group in the molecular chain or the hydrophilic component of the block copolymer. Its waterproofness comes from the continuity of the film itself and the larger surface tension of the film. Lamination/coating of film and fabric makes the fabric waterproof and breathable.

The fourth is to utilize the characteristics of shape memory polymers. In the glass transition temperature region, the breathability of shape memory polymers undergoes a qualitative mutation due to the micro-Brownian motion of the molecular chains, and its breathability changes with changes in external temperature. That is, intelligent functions, just like human skin, can adjust with changes in external temperature and humidity.

Using this shape memory polyurethane to produce waterproof and breathable fabrics can use non-porous lamination/coating methods, which reduces shortcomings such as micropore blockage due to micropores during use. More importantly, the moisture vapor permeability of the fabric can be improved over time. It changes with changes in human body temperature to achieve an "intelligent" effect, making it suitable for wearing under various conditions.