Evaluation And Research On Water Impermeablity Of Fabric Under Constant Pressure

With the improvement of living standards, people’s requirements on wet comfort of cloth are also increasing. The indexes of influence on wet clothing comfort include water water-permeability, hygroscopic ity and ventilation etc. Among them, the water impermeability of fabric is a very important aspect of wet comfort research.Water impermeability (that is, hydrostatic pressure) is an important index of waterproof fabric. At present, Hydrostatic pressure testing is that the three drops of water permeated the other side of the fabric which needed the hydrostatic pressure as the evaluation standard, but in the constant low water pressure, the fabric can not seepage in a very long time, while the fabric inside might be wet, At this moment, the assessment standards of three drops of the water will lose the effect. Therefore, this subject puts forward a new evaluation method of fabric of impermeable performance and index system.This research is according to the principle that after the fabric being moistened, the electrical resistance on it declines rapidly. By setting up the fabric resistance sensor, the variation of resistance value of fabric in the process of seepage water permeated the fabric at each time point can be determined. And through calibrating resistance value and moisture regain, it can indirectly reflect the moisture regain variation in liquid water permeable process, from this the transmission rule of the liquid water transferring in the porous media fabric that under constant water pressure can be obtained. And based on the three major theories of fluid mechanics, capillary core sucking and classical mechanics, the theoretical equations of the transmission theory of the liquid water transfer in the porous media fabric is obtained. Using the postal cloth, waterproof cloth as the experiment fabric, combined with the influence factors of the fabric materials, thickness, compact structure, surface contact angle size, fabric surface treatment and coating, the permeating time of fabric in the constant water pressure conditions was measured, every factors effect on the liquid water transmission was analyzed, and then put the experimental results into the theory equation to prove, it indicated that the theory equation basically satisfied the experimental result.At the same time, on the basis of numerous testing, we had put forward a set of new experimental equipment and method to appraise the impermeability performance of fabric, and has established the corresponding criterion system in order to achieve a more complete approach to appraise the impermeability performance of the fabric, using the time of seepage water permeated the fabric under the function of constant water pressure resistance, resistance’s change rate, seepage rate and surface moisture regain as indexes to replace the original index hydrostatic pressure as the time of three drops of seepage water permeated the fabric. Research results played the theoretical and experimental role in fabric permeable performance evaluation that under the constant water pressure in daily life.