Waterproof and breathable, waterproof and breathable, windproof and breathable… Dear you, are you confused by these words? Why does the jacket obviously have excellent moisture permeability, but in actual wearing process, it often feels stuffy, and moisture permeability is equal to Vapor permeability, doesn’t it mean breathability? If the air can’t get through it, how can it be breathable?
Moisture permeability
The moisture permeability of a fabric refers to the ability of moisture to pass through the fabric, also known as water vapor permeability. It is the ability to maintain the heat balance of the human body’s heat production and heat dissipation when the human body dissipates heat and sweats. The simple understanding is that the rainwater from outside cannot come in, and the sweat emitted by the human body is discharged through the pores of the coating and membrane.
Water-vapor transmission rate (Water-vapor transmission rate, abbreviated as WVT, expressed in g/m2/24h) refers to the formation of a specific humidity difference on both sides of the sample under certain standard laboratory conditions, allowing water vapor to pass through The sample enters the dry side, and parameters such as the water vapor transmittance of the sample can be obtained by measuring the change in weight of the moisture-permeable cup over time.
There are two testing methods for moisture permeability: straight cup and inverted cup.
Positive cup method: GB/T 12704.1-2009 “Textiles – Test methods for moisture permeability of fabrics – Part 1: Moisture absorption method”; GB/T 12704.2-2009 “Textiles – Test methods for moisture permeability of fabrics – Part 2: Evaporation method – Method A”.
Pour cup method: GB/T 12704.2-2009 “Textiles – Test methods for moisture permeability of fabrics – Part 2: Evaporation method – Method B”.
Breathability
The breathability of a fabric refers to the ability of gas molecules to pass through the fabric, resulting in air convection. To put it bluntly, it refers to the penetration of air that can be directly felt when blown over. It mainly affects the wearing comfort of the fabric, such as heat insulation, warmth retention, transparency, In outdoor products, they are usually combined with the windproof function, that is, windproof and breathable, in order to ensure that the fabric is windproof and warm and achieve a certain breathability to improve wearing comfort. In outdoor textile products, it is feasible to achieve a certain degree of breathability while blocking winds of level 4-5.
Air permeability R (Method Air Permeability): It means the performance of air permeability through fabric; under specified pressure difference conditions, measure the air flow rate vertically passing through a given area of the sample within a certain period of time, and calculate the air permeability. The air flow rate can be measured directly or converted by measuring the pressure difference on both sides of the flow aperture. This is called true breathability!
Test standard: GB/T 5453-1997 “Textiles – Determination of fabric air permeability”, the air permeability unit is expressed in mm/s or m/s.
Identification and application of moisture permeability and breathability functions
The functional description of waterproof and breathable is mostly used in the category of jackets, which means that more sweat and water vapor can pass through the fabric to maintain comfort during exercise.
Windproof and breathable function descriptions are mostly used in soft-shell products, which means reducing the air permeability of the fabric to achieve the purpose of windproofing and keeping warm, and at the same time confirming the range of air permeability to achieve a balance between windproof and comfortable.
Source: Outdoor Technology
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