Experimental Study On Thermal And Moisture Comfort Properties Of Jade Fibers

jade fibre By using extraction and nano technology, jade and other mineral materials can be submicron sized and then melt into polyester melt melt, and then processed by spinning. The addition of jade and other mineral particles endows jade fibers with many unique functions, such as health care, cooling, antibacterial and so on. Each of the jade fibers is honeycomb like structure inside and outside. This unique microporous structure makes the surface area of the fiber increase and the capillary core aspiration effect is good, thus improving the surface properties of the fiber, so that it has the characteristics of moisture absorption, sweating and quick drying. Fig. 1 is the morphologic structure of jade fiber. Because jade can improve the blood microcirculation, promote metabolism, and take away heat, so as to achieve the cooling effect. The fabric made of jade fiber has a better cool feeling and is especially suitable for wearing in hot summer or sports. The test proves that when the temperature is above 32 c, the jade fabric can cool 1.2 ~ 2 C, which is the best material for T-shirt, underwear, sportswear and other fabrics. In this paper, the two important indexes of thermal and moisture comfort of jade fiber were studied, and the factors affecting their warmth retention and moisture permeability were analyzed.

1 Experiment

1.1 the experimental environment experiment was conducted in the constant temperature and humidity room, the temperature was 23 + 1 degrees, the humidity was 65% + 2%, and the wind speed was less than 0.1m/s.

1.2 experimental materials choose polyester, modal 4 kinds of fabrics made of polyester cotton, cotton + superfine polypropylene and fabric specifications are similar to those of jade fabric. The ingredients and specifications of the 5 fabrics are shown in Table 1.

1.3 testing instruments and methods

1.3.1 warmth retention test

(1) testing of fabric thermal insulation under dry condition. PBW-25 intelligent flat fabric insulation tester was used.

(2) fabric moisture retention test under sweat condition. A moisture absorbent knitted fabric was selected to moisten the skin and simulate the sweating state of the human skin on the surface of the experimental board. The thermal insulation property of the sweaty fabric was measured by the PBW-25 smart plate fabric insulation instrument.

(3) the influence of air layer on fabric warmth retention. The air layer support with different thickness is installed on the experimental board of the heat preservation instrument. The jade fabric is sequentially arranged under different thickness air layers, and the thermal insulation property of the fabric is determined by PBW-25 intelligent plate type fabric insulation apparatus.

1.3.2 moisture permeability test using PBW-25 smart plate fabric insulation instrument, simulated evaporation hot plate method to determine fabric moisture permeability. A thin moisture absorbent knitted fabric was selected to moisten and cover the surface of the test board to simulate the evaporation of water on the porous electrothermal test board. Textile Moisture permeability.

2 experimental results and analysis

2.1 there are many indicators of fabric warmth retention in terms of warmth retention analysis. The Crowe value is used here. The Crowe value of fabric is related not only to fiber material but also to fabric thickness. In order to eliminate the effect of different fabric thickness on fabric thermal resistance, the fabric thermal resistance is divided by the thickness of the fabric, and the heat resistance of fabric thickness (clo. Mm-1) is obtained.

Analysis of fabric thermal insulation under 2.1.1 dry and wet condition. The thermal resistance of 5 fabrics in dry and sweaty conditions is shown in Table 2.

(1) when the fabric is dry and there is a temperature difference between the inside and outside surface, the heat dissipation is mainly conduction heat dissipation.

In the 5 fabrics, the dry thermal resistance values of polyester and polyester cotton fabrics are close to each other, which are quite large, indicating that the thermal conductivity of polyester fiber is poor. Because cotton blended with super fine polypropylene fiber is blended into super fine polypropylene fiber, its thermal conductivity is slightly better than that of polyester cotton. Modal is cellulose regenerated fiber with high wet modulus, and its thermal conductivity is better. The dry state thermal resistance of jade fibers is the smallest in 5 fabrics, because jade fibers are honeycomb like hollow structures inside and outside. The micro porous structure makes the specific surface area of fibers increase. The large specific surface area increases the conduction heat dissipation area of fibers, and the honeycomb pore structure penetrated inside and outside helps air convection, thereby accelerating the exchange of heat with the outside. Therefore, it has good heat dissipation performance.

(1) under the wetting condition, the thermal resistance of the 5 fabrics decreased significantly, indicating that the wettability of the fabrics had a great influence on the warmth retention. The most of the moisture in the fabric pores was replaced by water vapor. The thermal conductivity of the water was much higher than that of the fibers, and the thermal conductivity of the fabrics was larger than that of the air. So the overall thermal conductivity is significantly increased, that is, the fabric's thermal insulation is greatly reduced.

Among them, cotton + superfine polypropylene fiber has the lowest thermal resistance and the best heat dissipation performance. This is because cotton fiber has good hygroscopic performance, and super fine polypropylene fiber has good water conductivity, which can quickly absorb moisture from cotton fiber to the outer part of the fabric to evaporate and improve the heat dissipation speed of the fabric. The wet thermal resistance of jade fibers is also small. When the fabric is wetted, most of the moisture exists in the form of intermediate water. It is filled with water droplets in the gap between fabric yarns, and capillary water is formed along the yarn fibers to form capillary moisture. Because of its unique microporous hollow structure, jade fiber has good capillary suction effect and can rapidly discharge capillary water in the fabric and evaporate on the outer surface of the fabric, so the heat dissipation performance is good. Because of the poor hygroscopicity, polyester fiber has poor moisture absorption but poor moisture absorption, so its heat dissipation in wet condition is not ideal. {page_break}

Influence of 2.1.2 air layer on thermal insulation of jade fabric

When wearing a garment, because the body surface is an irregular curved surface, clothing can not be completely attached to the human skin, there is a gap between the human body and clothing, that is, the air layer. Air is a poor conductor of heat and has a significant effect on the thermal resistance of clothing. The influence of air layer thickness on the thermal resistance of jade fabric under dry and wet conditions is studied experimentally. Fig. 2 shows the relationship between the thickness of the air layer and the thermal resistance of the fabric.

It can be seen from Fig. 2 that the change trend of thermal resistance is similar under dry and wet conditions. When the fabric is close to the hot plate, the measured thermal resistance is the smallest. When the air layer between the fabric and the hot plate has a certain air layer, the thermal resistance of the fabric increases with the thickness of the air layer. Below the air layer thickness of 10mm, the trend of thermal resistance increases obviously. As the air layer continues thickening, the trend of thermal resistance increases slowly. This is because the air convection increases when the thickness of air layer increases to a certain extent. When the air layer thickness is 15mm, the thermal resistance reaches the highest value. In fact, thermal convection always exists, but when the air layer thickness is below 15mm, the performance is not obvious. When the air layer thickness increases to more than 15mm, the air molecules are active and the convection effect is obvious, which is reflected in the decrease of the thermal resistance value. Therefore, the thermal resistance increases first and then decreases with the increase of the thickness of the interlayer air.

2.2 moisture permeability analysis

Because of the change of heat in the process of moisture permeability, the ratio of moisture permeability index to thermal resistance is usually used to evaluate the moisture permeability of fabrics. The ratio of moisture permeability index to thermal resistance is called evaporative cooling efficiency. The efficiency of evaporative cooling is the moisture permeability index proposed by Dr. Goldman of the US Army's Institute of environmental medicine. The formula is as follows: evaporative cooling efficiency =im/Rt.

Formula Rt - clothing And the total thermal resistance of the boundary layer air; im - the moisture permeability index of clothing. The greater the thermal resistance, the lower the evaporative heat dissipation efficiency; conversely, the higher the evaporative heat dissipation efficiency. Table 3 is the evaporative heat dissipation efficiency of 5 fabrics.

It can be seen from table 3 that the evaporation and heat dissipation efficiency of jade fiber is the highest, which indicates that the moisture permeability is better than other kinds of fibers. The micro porous structure of jade fiber makes the specific surface area of the fiber increase, the surface energy increases, the number of water molecules adsorbed on the surface is large, and the hygroscopicity is strong. The pores of the fiber surface pass through the hollow part, and the moisture can quickly invade the hollow part from the fiber surface. Due to the capillary effect, it can move to the outside part of the hollow part and diffuse into the outer space, and quickly evaporate into the surrounding atmosphere, so that the fabric can be dried quickly and achieve a good sweating, moisture absorption and quick drying effect. It is especially suitable for the clothing or sportswear fabrics worn by a large number of sweating or hot climates.

3 conclusion

Experiments show that the thermal resistance of jade fiber is the smallest, and its heat dissipation performance is obviously better than the other 4 fibers. It has better cool feeling, good moisture permeability, good sweat, moisture absorption and quick drying effect. It is suitable for making underwear, sportswear and Xia Jizhi material with high heat dissipation performance.