| Compared with the shortage of cotton resources and its rising price, polyester capacity is relative surplus and its price is much lower than that of cotton. So developing the technology of cotton-like polyester can not only use the excess production capacity of polyester, but also alleviate the shortage of cotton fibers. The modification principle of cotton-like polyester is to improve its shortcomings like poor hygroscopicity, bad antistatic property, easy fuzzing and pilling and poor dyeing property, while keeping the advantages of polyester including good elasticity, stiffness and smooth, quick-drying etc in the same time. With the development of cotton-like polyester fibers and their products, the establishment of related evaluation system has become a key problem in the research.Five different kinds of cotton-like polyester fibers, ordinary polyester, full dull polyester with cross-shape and cotton fiber were chose as samples. Firstly, their longitudinal morphology, cross section shape, macromolecular structure and state of aggregation structure werestudied. Secondly, their mechanical properties, thermal performance and absorption and wetting properties were analyzed. In order to study the thermal-wet comfortable properties of cotton-like polyester fabric further, the representative cotton-like polyester fiber was chose to blend with cotton, and six different blending ratio yarns were designed to knit fabrics. Then simple hot or wet transmission method and microclimate evaluation method were used to evaluate the thermal-wet comfort of those fabrics. The conclusions are as follow.(1)Cotton-like polyester was modified by both physical and chemicalmodification. Physical modification was mainly heteromorphosis of fiber’s cross section shape such as cross-shape and trilobal shape. Adding the third monomer sodium dimethyl isophthalate-5-sulfonate (SIMP) and fourth monomer polyethylene glycol (PEG) to change chemical modification of polyester’s macromolecular structure. More over, Adding them would bring in polar group (sulfonic acid group) and flexible chain, which damages the ordered structure of polyester’s macromolecular structure. The fiber crystallinity and crystal speed were reduced, so did glass-transition temperature (Tg), melt temperature (Tm) and cooling crystallization temperature (Tcc). Compared with ordinary polyester, the breaking tenacity, extension at break, initial modulus and specific work of rupture of cotton-like polyester were reduced, but all higher than that of cotton fiber. The decrease of these indexs helped to make the fabric soft and reduce pilling, which was good to imitate cotton for polyester.(2)The addition of SIMP and PEG affected the polyester fiber’s hygroscopicity and moisture releasability, and different amount showed different influence. B1, B2and B3fibers consisting of more PEG had higher moisture regain than that of B4and B5but much lower than that of cotton, which was about three times of ordinary polyester. The increase of the moisture regain would increase the balance time of moisture absorption and release. But the heteromorphosis of cross section shape (cross-shape, trefoil) could speed up the moisture absorption and release, which helped to keep the good moisture releasability of polyester and improved its poor hygroscopicity.(3)There are two problems existing in today’s microclimate instrument. One is the controlling inaccuracy of the water bath temperature. The second is the inconvenience of supplying evaporated water. Previous textile moisture permeability tester was developed by reforming its temperature control process, and a new fabric microclimate instrument based on LabVIEW was designed. The microclimate instrument used PID to control the water bath temperature, and the visualization software LabVIEW was used to monitor temperature variation, thus control the water bath temperature immediately and stably with high precision. Through the continuous debugging control parameters including Kp (proportional gain), Ti (integral time)and Td (derivative time), ideal PID curve was got when Kp=6, Ti=9,Td=0.01, and the temperature was controlled to stay stable in three hours. The instrument could be used to simulate the heat and moisture transferring process as that when human wear fabrics, using passive sweating mode and "one-step" principle to test fabric water-vapor permeability, water-vapor resistance and thermal resistance. The water-vapor permeability tested by the microclimate instrument was highly related to that getted by moisture absorption method. The related coefficient was0.92, which proved that the instrument was feasibile.(4)A series of indexs such as heat preservation ratio, heat transfer coefficient, CLO value, permeating rate, water-vapor permeability and moisture regain were tested by the pure heat or moisture transmission test method. The result showed that heat transfer coefficient and water-vapor permeability of pure cotton-like polyester fabric was higher than that of pure cotton fabric. Others were lower than that of pure cotton fabric. But they did not varied as the change in amount of the cotton-like polyester fiber. When the blending ratio of polyester and cotton is35/65, water-vapor permeability of the fabric is highest. When the blending ratio of polyester and cotton is20/80, permeating of the fabric is best.(5)Water-vapor resistance and thermal resistance of the knitted fabric with different blending ratios were measured by microclimate instrument. The result showed that water-vapor resistance and thermal resistance of pure cotton-like polyester fabric was higher than that of pure cotton fabric. But they did not varied as the change in amount of the cotton imitation polyester fiber. When the blending ratio of polyester and cotton is35/65, the thermal-wet comfort of the fabric is best, followed by20/80. |
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