The Characterization And Modelling Of The Adhesion Property Of Wet Fabrics

Fabrics have been performing their duty of providing comfortable life and beautiful appearance since the beginning. They have also been playing important roles in various walks of life. During processing and application, fabrics are not always in their dry state. They tend to perform different properties under wet condition. There are many situations that would wet fabrics. The fabrics usually tend to adhere tightly to another object and hard to be separated. This is the primary reason of various discomfort and other defects in their applications of apparel, medical, etc. But for fabrics of some other industrial applications, strong wet adhesion is needed. As a result, studying adhesion property of fabrics under wet condition is a matter of critical importance.The worldwide researches on fabrics have been focused mainly on the properties under dry condition. Researches on fabrics under wet condition are much less reported and most of them are on comfort of heat or moisture transfer and properties of sweat uptake or transportation. The adhesion property of wet fabrics needs much concern and more research work. For the adhesion of fabrics under dry state, adhesion strength of laminated fabrics and cohesion strength between textile fibers and matrix in the composites are mostly reported. The wet adhesion of fabrics caused by liquid of low viscosity such as water, sweat, urine, etc. are seldom reported.In this research project, we are fully aware of the serious and universal problems caused by wet fabrics. To solve these problems, a systematic research has been conducted on the adhesion property of fabrics under wet condition, from the principle, testing device and measurement, theoretical model, objective test, sensory evaluation, solutions, to the case of product development.(1) The principle of the wet adhesion phenomenon was specified. This phenomenon is mainly caused by the pressure difference between air and liquid in contact with the fabric and by the surface tension of the liquid. The adhesion between wet fabrics and other objects could be simplified and described by a model of fabric – liquid bridge system. The process of the fabric being separated from the liquid could be divided into three stages, namely pulling up, separating and detached.(2) A new testing device and a corresponding method were developed, enabling an objective and accurate measurement of the evaluation and comparison of wet adhesion property of fabrics. The property was comprehensively evaluated by three indices of maximum adhesion force, maximum adhesion distance, adhesion work and a curve of adhesion force – adhesion distance. The testing result of typical woven fabrics, knitted fabrics, non-woven fabrics and films showed reliable differentiation and repeatability. The testing conditions would affect the results. Among them, the separating speed affected different fabrics to different extents. A larger separating speed usually led to larger test results. A larger pretension would lead to a larger adhesion force and a steeper slope of the curve. The wetting duration affected significantly the testing results of fabrics that got wet slowly, but not quite significantly of those fabrics that quickly achieved the balance of wetting. The lower the water temperature, the larger the adhesion force. But the quick wetting effect of hot water to some fabrics would lead to a larger adhesion force. Different types of liquid would affect the force that applied to the fabrics, and hence affect the adhesion force and adhesion distance. The testing conditions of separating speed, pretension, wetting duration, water temperature and liquid type should be properly controlled to assure the comparability of the results.(3) Two theoretical models and expressions of adhesion force of wet fabrics were proposed. The predicted values from theoretical calculation could both meet the results obtained by adhesion property testing device of wet fabrics. The models and expressions provided theoretical foundation for the evaluation and prediction of adhesion property of wet fabrics. The first model was based on liquid surface tension, the cause of adhesion. It could predict the second stage(separating stage) of the adhesion force between fabrics and the liquid. The second model based on the volume of the liquid bridge could predict the adhesion force in both the first stage(pulling up stage) and the second stage(separating stage). According to the theoretical analysis and experimental results, when selecting the materials, designing the surface morphology or designing material structure, measures that could enlarge receding contact angle, narrow the area of fabric – liquid interface, diminish the volume of the liquid bridge would decrease the adhesion between fabrics and the liquid.(4) Practical solutions for regulating and controlling the adhesion between fabrics and the liquid were proposed, including altering the hydrophilicity of the materials and controlling a series of fabric structures such as distance between the surface protrusions, spacing between yarns, size of the annular structure, scale of the opening, etc. The solutions gave specific directions to the developing of fabrics with controlled adhesion property under wet condition. A theoretical expression on the relation between the surface hydrophilicity and the adhesion property of wet fabrics was given. Different types of typical fabrics were treated by atmospheric pressure plasma jet(APPJ) to improve the surface hydrophilicity. The adhesion property test under wet condition showed that the improvement of hydrophilicity significantly increased the maximum adhesion force and the adhesion duration, leading to more severe discomfort of the fabric when got wet. The experiment could meet the theoretical prediction quite well. In order to diminish the adhesion and discomfort of wet fabrics, the hydrophilicity of the fabric surface should be reduced. When controlling the adhesion of the wet fabric through special structures, the spacing in the structures should be larger than the critical value to avoid the liquid bridge from climbing and dwelling inside the narrow gaps of the fabric. In this way, severe adhesion of wet fabrics could be avoided by preventing the growing of the liquid-solid contact area and the volume of the liquid bridge.(5) Comparing experiment of sense evaluation and objective test was conducted. The results of a series of wet adhesion related sense evaluation of different types of typical fabrics were reasonably consistent with the experimental results obtained by adhesion property testing device. Research with objective measurement and together with subjective sense could improve the scientific characterization of the adhesion property of wet fabrics. The sense evaluation of fabrics under dry and wet conditions was carried out on human skin. The intensity of subjective senses of stickiness, restrictiveness, wetness, dripping, coldness, stiffness and roughness were divided into 7 degrees. Typical fabrics with different structures, different components and with the function of liquid absorbing and quick drying were graded according to the intensity of different senses mentioned above. The comfort under wet condition was important. Turning wet from dry state would greatly damage the comfort of fabrics. There was no inevitable connections between the senses under wet condition and those under dry condition. Some of the commercial fabrics with the function of liquid absorbing and quick drying were not able to eliminate the discomfort of wet fabrics when large amount of liquid took place. The sense of stickiness under wet condition was positively correlated with general discomfort, restrictiveness, wetness, dripping and coldness under wet condition, but was negatively correlated with stiffness and roughness. The sense of stickiness under wet condition was an important factor that influence the comfort of wet fabrics. Flat and smooth surfaces were unfavorable for the comfort of wet fabrics while hydrophobic surfaces and special structures with meshes or openings were favorable. By altering the fabric structures, both sense of beauty and sense of comfort under wet condition could be enhanced. Fabrics with stronger sense of stickiness usually had larger maximum adhesion force under wet condition. The adhesion property under wet condition could reflect the true feelings of human skin in a certain extent.(6) A short sleeve shirt with special jacquard patterns was designed and developed according to the distribution of easily sweating body parts. Human body wearing experiment showed that the shirt had largely improved the sense of comfort under wet condition. It provided a feasible way of developing fabrics and apparel with better comfort under wet condition. During the human body wearing experiment, the subjective senses were graded for two different shirts(the ordinary shirt and the shirt with jacquard patterns according to body parts) under both dry and wet conditions. Under dry condition, the experiment results showed no obvious harm to the comfort of the jacquard shirt compared to the ordinary one. When worn under wet condition, the scores of comfort for both shirts degraded compared to those under dry condition. However, the jacquard shirt was much more comfortable than the ordinary one on the parts of back and oxter and for the overall feelings. The design of jacquard pattern according to body parts could significantly improve the comfort of easily sweating body parts under wet condition. The seamless design between jacquard parts and other parts on the same garment piece was also favorable for improving the comfort. As a result, the design method of constructing jacquard pattern according to the distribution of easily sweating body parts to form special fabric structures could effectively improve both the comfort and the beauty of the clothing. It was an effective way of reducing adhesiveness of wet fabrics.This research project provided theoretical foundation, objective testing device and measurement, subjective experiment method for the research of adhesion property of wet fabrics. It also brought forward a series of valid solutions and development directions. The research project could lay a solid foundation for further work of this research field, guide the design and production of fabrics with reasonable adhesion property under wet condition, help promote wearing comfort and life quality for every human being.