Protective clothing must not only ensure that medical staff can effectively isolate the virus, but also ensure that medical staff have a certain degree of comfort during long-term wearing. The comfort of protective clothing must be considered from the fabric design of the protective clothing. At present, the mainstream protective clothing fabric is composed of SFS (spunbond|microporous film|spunbond) three-layer breathable and waterproof fabric. Protective clothing with poor air permeability (wet) will be very stuffy when medical staff wear protective clothing. After working for a long time, they will be hot and humid. The function of spunbond non-woven fabric is mainly to enhance tension and hydrostatic pressure and protect the middle layer (breathable Membrane), the real breathable structure lies in the polymer breathable membrane.
According to the type of breathability, it can be divided into two types: microporous hydrophobic and nonporous hydrophilic; different raw materials, breathable membranes can be divided into PE breathable membrane, TPU breathable membrane, PTFE breathable membrane, PTFE breathable membrane, etc.
The microporous breathable membrane is used as a water-proof membrane, mainly through countless channels, and the size of the pore size is designed by using the difference between the size of gas and liquid. Generally, the pore size is 0.01~10μm. The pore size cannot penetrate liquid and has a barrier effect on liquid. There are many passages in the membrane, and the water resistance of the membrane depends on the pore size and passage length of the breathable membrane. The main materials commonly used at present are polyethylene microporous membrane, PTFE, PU microporous membrane (the earlier breathable microporous membrane), of which the cost of PE membrane is lower, and the cost of PTFE is higher.
PE/PP breathable film
PE/PP polyolefin breathable film is blended by adding about 50% of special calcium carbonate in a resin carrier, and then extruded into a film, and stretched under certain conditions. During stretching, polyethylene and calcium carbonate Interfacial peeling occurs between the particles, forming interconnected pores or channels around the calcium carbonate, so that it has a certain degree of air permeability (moisture).
PTFE breathable membrane
PTFE breathable membrane is a new type of waterproof and breathable material at present. PTFE microporous membrane is formed by mixing high molecular weight PTFE dispersion resin with lubricants, extruding rods and belts, and after stretching and heat setting at a temperature below the melting point. Flexible and smooth microporous film. During the extrusion process, due to the shearing force, the adjacent spherical polytetrafluoroethylene particles are forced to extrude the short fibers to cross-link and form a network structure, but the PTFE resin particles are not damaged. The pore size of the PTFE film can reach between 100 and 500 nanometers under the control of the stretching ratio, and the porosity can reach over 85%.
TPU and TPEE non-porous breathable (wet) membranes use the principle of hydrophilic moisture absorption of the hydrophilic base to conduct water vapor from the one with high concentration and pressure to the other, and evaporate and dry. The transportation, conduction, and volatilization of the polymer carrier is roughly similar to the principle of water molecules entering the cell, and the prerequisite is a difference in concentration or pressure.
TPEE breathable membrane
TPEE thermoplastic polyester elastomer is an ester-based block polymer. After melting, blow molding or casting can prepare TPEE non-porous breathable film. TPEE is a linear molecular chain prepared by polycondensation technology using linear polyester materials and polyether materials. It is a crystalline network structure that can be restored to a linear molecular structure when melted. Because polyester and polyether materials have A certain degree of hydrophilicity and affinity for carbon dioxide, oxygen, etc., so TPEE has excellent breathability and moisture permeability.
TPU breathable film
TPU is a linear block copolymer composed of oligomer polyol soft segment and diisocyanate-chain extender hard segment. Polyether TPU and SiO2 additives are melt-blended and plasticized, extruded from the machine head through a slit die, and melted through special processes such as calendering, stretching, film blowing, coating, etc., to prepare a non-porous and uniform thickness The non-porous breathable TPU film. For TPU film, blown film method and casting method are more common, and blow molding processing is rare.
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