Research On The Processing And Properties Of Spunlaced Nonwovens With Hydrophilic PET Fibers

As we know, the properties of nonwovens depend on the performance of raw materials and processing methods. PET fibers are increasingly used as spunlaced nonwovens raw material. With the development of spunlaced industry, it is used in more and more application area and the requirement for properties of PET fibers is becoming more and more sophisticated. Improvement of processing performance of PET fibers and properties of PET spunlaced nonwovens, and the control of manufacturing cost all call for the constantly improvement of the PET fibers.In recent years, with the research and development of hydrophilic PET staple fibers, particularly the general hydrophilic PET staple fiber and high hydrophilic PET staple fiber, it brings new properties to the spunlaced nonwovens and the high hydrophilic PET staple fiber is becoming a promising fiber of the spunlaced manufacturers. However, the development of high hydrophilic PET staple fiber is still in the trial phase in the domestic chemical fiber manufacturers, and the research of the processing and properties of spunlaced nonwovens with high hydrophilic PET staple fiber is in a blank area in China.In order to understand the properties of hydrophilic PET fiber in depth, especially the impact of the high hydrophilic PET staple fiber on the processing and properties of spunlaced nonwovens, based on the literature review and experimental research, this paper focus on the following aspects: Firstly, the method of hydrophilic treatment of hydrophilic PET staple fiber was analyzed; secondly, the structures and properties of the common PET staple fiber, general hydrophilic PET staple fiber and high hydrophilic PET staple fiber were studied; thirdly, the processing technology, structures and properties of three kinds of different hydrophilic PET spunlaced nonwovens were investigated; finally, the entanglement mechanism and its affected factors in the spunlaced processing were analyzed, and the reasons of the improvement of the mechanical properties of hydrophilic PET spunlaced nonwovens were discussed in view of the entanglement mechanism of fibers and the mechanical characteristics of entanglement points in the spunlace nonwovens.Through the research above, this subject mainly came to the following conclusions:(1) Hydrophilic PET staple fibers are mainly obtained by changing the performance of second spinning finish in the spinning process. The hydrophilic groups of second spinning finish agents can graft and polymerize on the surface of fibers, and a layer of hydrophilic film is formed in the finish impregnation processing.(2) During the carding process, it is found that there are more fibers dropping off the carding cylinder for common PET fibers, while there are less fibers dropping off for the high hydrophilic PET staple fibers. This is due to the improvement of the moisture absorption of high hydrophilic PET staple fibers.(3) Through the research on the structures and properties of three kinds of fibers, we discovered that there is little difference in the crystallinity, length, fineness and crimp among them; the surface of high hydrophilic PET staple fiber has more particles, which may be due to the effect of special spinning finish. In addition, three kinds of fibers have the similar mechanical performance, but high hydrophilic PET staple fiber has the highest elongation and the lowest initial modulus. The high hydrophilic PET staple fiber also has the highest friction, electrical properties and moisture absorption.(4) Through the area density and thickness test analysis, we discovered that high hydrophilic PET spunlaced nonwoven has the best product uniformity. On the other hand, hydrophilic PET spunlaced nonwoven has the smallest thickness, which is due to the decrease of electric resistivity and increase of cohesion between the fibers. In addition, the thickness of three kinds of PET spunlaced nonwovens decreases with the increase of spunlaced pressure.(5) Through analysis on the stiffness and softness, permeability performance and moisture absorption, we discovered that high hydrophilic PET spunlaced nonwoven exhibited excellent moisture absorption, bending performance, feel and softness. This is mainly due to the improvement of moisture absorption and entanglement of high hydrophilic PET staple fibers. At the same time, wicking effect of high hydrophilic PET spunlaced nonwoven has also been improved, and wicking effect of MD direction is better than CD direction.(6) The subject analyzes the mechanism of differences in the mechanical properties of three kinds of PET spunlaced nonwovens, from the entanglement mechanism of fibers and the mechanical characteristics of entanglement points in the spunlace nonwovens. Through the research on the entanglement morphology, thickness and permeability performance of three kinds of PET spunlaced nonwovens, we discovered that entanglement effect of high hydrophilic PET spunlaced nonwoven is the best, which is due to the improvement of bending modulus, moisture absorption and network performance of high hydrophilic PET staple fiber. Through the set-up of the model of entanglement point, a formula between the strength of entanglement points and the friction coefficient of fiber was found. It is found that the strength of entanglement points increases exponentially with the increase of the friction coefficient of fiber. To a certain extent, this model explains the reason of higher tensile-strength of high hydrophilic PET spunlaced nonwovens.