Is there a contradiction between clothing heat preservation and air permeability?Seemingly contradictory questions are not.

First of all, air permeability is not moisture permeability. The standard test method for air permeability is ASTM D737, which measures the air passage rate.The standard test method for moisture permeability is ASTM DE96, which measures the water vapor pass-through rate.The two are totally different!Warmth is determined by how much air the clothes can hold between the skin and the outside world, so there is a concept of how fluffy the down jacket is.Put this problem aside, clothing table cloth is of course the worse the air permeability, the more locked air, air mobility becomes the lowest, the clothes will be more warm.

Fabric permeability the ability of a molecule of gas to pass through a fabric.Air permeability affects the comfort of the fabric, such as heat insulation, warmth, ventilation and coolness.Affect the fabric performance, such as parachute, airbag, sail, hot air balloon, boat and so on airtight and breathable effectiveness.

The air permeability of fabric is essentially related to the size and connectivity of pores, length, arrangement and surface characteristics of channels, volume fraction and thickness of fabric, etc.It is also related to the temperature, humidity and air pressure difference of the environment.More importantly, it is related to the distribution characteristics of pore size in the fabric.The air permeability depends more on the large holes in the fabric than on the small holes.

When the number of warp and weft yarns is constant and the arrangement density increases, the permeability decreases.If the tightness of the fabric remains unchanged, the permeability of the fabric decreases with the increase of density or the increase of yarn fineness.The porosity of the fabric varies with its structure.When the pore distribution of the fabric varies greatly, the breathability of the fabric depends more on the number of large pore diameter rather than the number of small pore diameter.Only when the pores of the fabric are evenly distributed does the breathability depend on the average pore size, that is, on the interyarn porosity.

Fiber properties and moisture regain of yarn structure fibers have obvious influence on air permeability.This is the result of the radial expansion of the fiber.Most profiled fabrics have better air permeability than round fabrics.The compact structure of the yarn results in a smaller permeability within the yarn and a larger permeability between the yarns.Smooth yarn is conducive to transparency.

When the temperature is constant, the air permeability of the fabric decreases with the increase of relative humidity (RH).When relative humidity is constant, air permeability increases with temperature.

The degree to which an insulating fabric maintains the temperature of the coated hot body.The heat preservation of fabric is mainly related to the heat preservation of bedding and clothing, thermal insulation lining and cushion materials used in cold season or low temperature environment.

Heat preservation mechanism: the heat preservation of the fabric is essentially a process of preventing heat transfer from the higher temperature side to the lower temperature side under the condition of temperature difference between the two sides of the fabric.The human body is covered by fabric. When it comes into contact with air and there is a temperature difference, it will generate heat conduction, convection and radiation. The human body will feel cold or hot.In solids, heat conduction is significant.Human body must maintain certain temperature, undertake producing quantity of heat and the balance that give off quantity of heat thereby, this kind of heat is balanced besides the function of human body oneself, fabric becomes the medium that the heat between human body and outside air transfers, adiabatic sex is better, heat preservation sex is better also.

Fiber properties there is a layer of air on the surface of the fiber, which is fixed on the fiber due to the adsorption of friction.The smaller the fiber diameter is, the larger the specific surface area is, and the more "trapped" still air is, the better the insulation performance is.The insulation of hollow fiber is also very good.Fiber moisture regain, not conducive to insulation.Fabric made of fibers with high elastic recovery rate for good heat retention.

The geometric structure of the fabric there is an approximately linear relationship between the thermal insulation of various fabrics and their thickness.(so wear thick clothes in winter.)

Waterproof finish and air permeability by coating the surface of the fabric with an impermeable and water-insoluble continuous film layer, the water permeability of the fabric can be reduced, which often makes the fabric impermeable and hard to handle, generally not suitable for clothing, but can be used for canopy or rain cloth.If water repellent and multi-porous coating film is used, the coating fabric with excellent waterproof performance, breathable and moisture permeable can be formed.

Summer clothing thin and loose to reduce heat resistance, the surface of the fabric is smooth, high reflectivity, absorption of radiation heat less with good water absorption, heat dissipation, moisture, permeability and other properties.Accordingly, summer should choose light, thin, hairiness is little, twist is big, fine fine and special gauze fabric with good flexibility, and the fabric such as silk, man-made silk, cotton, polyester/cotton.

Winter clothing is mainly cold and windproof, especially outer clothing, the thermal conductivity of the fabric is required to be small that is, the thermal resistance, the amount of static air contained in the fabric to be large and ventilation to be small, that is, should choose the permeability of small, thick, tight fabric, or even coating.Underwear is general bulk, thicker.To wool knitting pullover is given priority to.Close-fitting winter underwear, to make water vapor evaporate and do not condense dew, should choose the pure cotton fabric with hygroscopicity and good permeability, soft bulk.

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