Study On The Preparation,Structure And Properties Of Hydrophilic Copolyester Fibers

By means of the advantage of good processing performance and low cost, polyethylene terephthalate （PET） fiber has been widely used in the fields of garment, household and industry. However, because of high degree of molecular chain arrangement and the lack of effective adsorption group, the moisture absorption of PET fiber is poor. The moisture regain is 0.4% and vlume specific resistance of PET fiber is 1014Ω·cm in the standard temperature and humidity atmospheric environment, leading it poor wear-comfort in the application of sportswear, under garment, furniture, bedding and so on. An important function of textiles is supplying a maximum of wearing comfort to human bodies. Clothing materials should thus have a high water retention capacity and high water transportation properties to maintain a constant temperature and humidity between skin and fabric when the human body is in a state of movement or hot environment. The aim of this paper is to improve the hydrophilic behavior of PET fiber. Based on the moisture absorption and desorption characteristics of natural high moisture absorption cotton fiber and PET fiber, a new modified PET fiber was prepared in this paper. The prepared route, structure, property, moisture absorption and desorption mechanism and engineering experiment were studied, the main research as below:First of all, poly （ethylene terephthalate）/polyethylene glycol copolymers （PETG） with various molecule weight of polyethylene glycol ranging from 200 to 8000 g/mol were synthesized by melt polycondensation. Nuclear magnetic resonance spectra （NMR） of copolymers confirmed the prepared copolymers were the target product. The samples of PETG800, PETG2000 and PETG6000 were choosen to study the influence of molecular weight of PEG on sequence structure of PETG copolymers. Under the same feed mass ratio, the block numbers of PETG800, PETG2000, and PETG6000 are 9,11 and 17 respectively. With the increase of molecular weight of PEG, the sequence structure of PETG copolymers shows the characteristic from ordered structure to random structure. The average sequence length of PET increased and the PET segment was restricted weakly, and then rigid segment and soft segment formed their own crystalline structure. Laser Scanning Confocal Microscope （LSCM） comfirmed the micro structure of PETG copolymers.Secondly, the influence of molecular weight of PEG on the melting behavior of PETG copolymers was discussed by DSC （Differential Scanning Calorimetry） method. Flory equilibrium crystallization theory was usded to analyze the melt decay of PETG copolyester. With the increase of molecular weight of PEG, the melting point increases due to the sequence structure of PETG copolymers from random structure （with PEG from 100 to 2000 g/mol） to ordered one （with PEG from 2000 to 8000 g/mol）. Futher more, the influence of molecular weight of PEG on the nonisothermal crystallization kinetics of the PETG copolymers was investigated. Crystallization curves and the value of AHm at different cooling rates were observed. The experimental date was analyzed using Avrami, Ozawa and Mo methods. The relationship between relative crystallinity （Xt） and temperature （7）, time （t） were discussed. The relationship curves between half crystallization time （tm） and molecular weight of PEG was established. The results suggested that only the Mo method was satisfactory in describing the nonisothermal crystallization kinetics of all PETG copolymers at all temperatures and different cooling rates selected. With the increase of molecular weight of PEG, the values of tm decrease. PEG chains with high molecular weight was functioned as the nucleating agent of nonisothermal crystallization process and improved the chain mobility of PET segment. To improve the thermal behavior of PETG copolymers, Zinc oxide nanoparticles have been used in situ polymerization. To solve with the inhomogeneous dispersion of ZnO, ZnO nanoparticles were modified with SA to make dispersed homogeneously in PETG copolymers. The thermal stability and decomposition of composites were determined. The results shows that ZnO nanoparticles modified with SA （stearic acid） was as the function of physical crosslinking. Thermal motion of PEG chains with poor thermal stability can be restricted at high temperature and the temperature at the most rapid thermal decomposition ratio can be improved about 40℃.And then, the interaction mechanism between water and polymer was further investigated. The hydrophilic properties of PETG copolymers were measured by surface contact angle and moisture adsorption capaicty, revealing the molecular weight of PEG has a positive effect on the hydrophilic behavior of PETG copolymers. With the increase of molecular weight of PEG, the surface wettability of PETG copolymers increases. The surface contact angle of PETG copolymers are less than 60° compared with that of PET. Water adsorption behavior in PETG block copolymers was investigated using time-resolved FTIR-ATR （Fourier Transform Infrared Attenuated Total Reflection） spectra. The analysis of relaxation time component with different states show that with the increase of molecular weight of PEG, the water adsorption capacity increases due to the microphase separation behavior of PETG copolymers. The data was analyzed by two-dimensional correlation spectra （2D-COS）, which provided relevant and complementary information on the adsorption mechanism and the molecular interactions formed （H-bonding）. The problem of low resolution of one dimensional infrared spectrum overlapping was definitely settled by 2D-COS method. It is found that there are two kinds of absorbed water molecules, named bound water and free water in adsorption process. Furthermore, two-dimensional correlation analyses revealed that in the adsorption process, water molecule was tightly bound with PEG flexible chains at first stage, and then water molecules could swell the PETG copolymers, additional water permeating into the swelling copolymers.Based on the theory of hydrogen proton relaxation, the water state and distribution in PET and cotton fibers were studied to simulate the human body in the state of motion. There are three different states of adsorbed water in the fiber materials. The adsorbed water can be assigned to the bulk water （T22）, microporous structure confined water （T21） and water trapped by hydrogen bond (T_2b) respectively. During desorption process, three types of water in the fibre materials work together to present the time-domain spectra. Relative adsorption ratio parameter （P2） was introduced into this study and the relationship between surface wettability, moisture absorption capacity and P_2b （The proportion of rexlation signal of water trapped by hydrogen bond in total rexlation signal of water） was estabilished. The results show that with the value of P_2b increasing, surface wettability, moisture absorption capacity of fiber increase. The relationship between water absorption capacity and P21 （The proportion of rexlation signal of microporous structure confined water in total rexlation signal of water） was estabilished. The results show that with the value of P21 increasing, water absorption capacity of fiber increase. Based on the interaction relationship between muti-structure of fibre materials and adsorbed water, PET fiber materials were chosen to investigate water adsorption and desorption behavior. PETG hollow fibers were prepared by copolymerization with PEG2000 at 10% mass fraction and morphology design method. The experiments of surface contact angle of fiber and fabric, moisture adsorption, water adsorption, wicking distance and water vapor permeability were carried out. The moisture regain, surface contact angle are higher than 1.2%, less than 60° respectively. The instant moisture absorption rate of PETG hollow fiber increases by 2 times. Besides that, PETG hollow fiber has quick drying characteristics. The antistatic property and dying behavior were also discussed. The results showed that the prepared PETG fibers had better antistatic and dyeing properties compared with the unmodified ones.At last, based on the investigation of polymerization spinning in lab experiment, engineering technologies on large capacities polymerization, online addition and spinning test have been carried out. The target of industrial production for hydrophilic PETG fibers has been achieved.