THE EVALUATION OF MOISTURE PERMEABILITY FOR WATERPROOF BREATHABLE OVERCOAT ON WEARING CONDITON

Transcription

1 THE EVALUATION OF MOISTURE PERMEABILITY FOR WATERPROOF BREATHABLE OVERCOAT ON WEARING CONDITON C. H. Huang, Y. W. Lin, R. H. Gao, G. T. Jou Department of Testing and Evaluation, China Textile Institute, Taiwan, R.O.C INTRODUCTION The evaluation of moisture permeability can be carried out by some standard s such as ASTM E96, JIS L 1099, ISO and BS79 for waterproof and moisture-permeability fabric. However, in our experience, the results of these standard usually did not have the consistence among one another, and the response of it to wearing condition in practice was still unclear. For further understanding of these relationships, we designed three condition i.e. rest, exercise, and rainfall condition for wearing test. The correlations between wearing test and some standards of water vapor transmission were considered to clarify the performance of moisture permeability. METHODS 1. Material There were six different waterproof overcoats selected for the subject of this study. Their fundamental specification of fabric for these overcoats was described in Table 1. Table 1 The specifications of fabrics for the overcoats to be tested Code Material Lining Thickness (mm) Weight (g/m 2 ) micro porous Null PU micro porous 100% Nylon PU micro porous 100% Nylon PU micro porous 100% Nylon Hydrophilic PU non-porous 100% Nylon film raincoat Null The evaluation for physiological response in wearing condition The evaluation proceeded in the climate chamber controlled in the temperature ±0.2 and the relative humidity (R.H.) 35% ±3%. A sensor that measured the R.H. of the microclimate between skin and clothing was put on the back of the human body. SHINYEI TRH-DM3 recorder was utilized to continuously record the variance of measured value. 3. Experimental procedure There were three different conditions for wearing test, e.g. rest condition, exercise condition, and rainfall condition. Two persons individually dressed in a clothing system, which included cotton 1

2 long-sleeve sportswear, slacks and the overcoats to be tested, entered into the chamber. The meaning of rest condition was that the person took a seat in the chamber for minutes. Exercise condition included 3 sessions that began with a 10-minute rest, followed by a 10-minute jogging at the speed of 5.6 Km/hr, and the last a -minute of recovery (1). Rainfall condition began a 10-minute rest, followed by a -minute exposure in a simulated rainfall of 1mm/hr, and after that, a -minute rest to recover his body to original state. The information about the two persons participating the test was listed on the Table2. Table 2 The information about the physiology of the two persons Sex Height (cm) Weight (kg) Age Person 1 Male Person 2 Male Testing moisture transmission with different standard s We measured all the water vapor transmission of the six samples with different standard s in order to understand the correlation between those standards and practical wearing condition. The result of the measured value was shown on the Table 3. Table 3 The result of moisture transmission with different standards (2,3,4) Moisture (g/m 3.24hr) ISO11092 JIS L1099 A-1 desiccant JIS L1099 A-2 water ASTM E96 B water ASTM E96 BW inverted water Water cup of temperature control RESULTS 1. Rest condition Figure 1 illustrated that the overcoats with moisture permeability, except material, could adjust the microclimate humidity into a lower relative humidity at the rest condition. R.H REST Time Figure 1 The variance of R.H. in microclimate as a function of time in rest condition 2

3 2. Exercise condition Figure 2 showed that the higher the moisture transmission was, the less the moisture dissipated from the body was retained in microclimate. R.H. (%) REST JOGGING RECOVE Time (minute) Figure 2 The variance of R.H. in microclimate as a function of time in exercise condition 3. Rainfall condition R.H. (%) REST RAINFALL RECOVER Y Time (minute) Figure 3 The variance of R.H. in microclimate as a function of time in rainfall condition Figure 3 showed that, after -minute exposed in the rainfall, the test result showed that the higher the water vapor transmission of the fabric was, the more the R.H. in microclimate was. This tendency was exactly opposite to the result derived from the rest and exercise condition. This was caused by the reason that the mass of water vapor ( g/m 3.) in microclimate near to skin was lower than that (17.3 g/m 3 ) of the chamber in rainfall condition. Therefore, when the moisture permeability of the fabric was higher, the R.H. of microclimate became higher due to water vapor easier to pass through from ambient environment. Though, in the rain, the water vapor easily crossed through the permeable fabric. The R.H. of the microclimate close to the skin still maintain below 65% after mnutes. 3

4 4. The correlation between the humidity of the microclimate and moisture transmission Table 4 The correlation between different wearing state and the testing standards Moisture (g/m 3.24hr) th minute of rest condition th minute. of exercise condition th minute of exercise condition th minute of rainfall condition th minute of rainfall condition ISO11092 JIS L1099 A-1 desiccant JIS L1099 A-2 water ASTM E96 B water ASTM E96 BW inverted water Water cup of temperature control According to the result of the correlation on Table 4, JIS desiccant appeared to be the highest correlation with the wearing test, ASTM E96 BW being the least one. In terms of after exercise, the result measured by most of the standards is assumed to be perfectly response to the microclimate of the human body. With reference to the rainfall condition, the result of the microclimate humidity at th minute, which was the simulated rain stopped, was only some positive correlation with the results of these standard tests. However, if the measured value of microclimate humidity was considered at th minute, the correlation between wearing test and these standard become significantly low because the wetness on the fabric surface took place. This situation affected the capability of the moisture permeability for these six subjects. DISCUSSION According to the result of evaluating the performance of waterproof and moisture permeability by human body wearing test, the following suggestions can be provided as our conclusion: 1. In the rest condition, if wearing the waterproof overcoat without moisture permeability function, after a period of time, the person may feel muggy because of moisture and heat gathering inside the clothes. 2. In the exercise condition, the human body sweats in the exercise procedure. After this procedure, those who wear the waterproof overcoat with higher moisture permeability feel comfortable because the moisture inside the clothes can immediately decrease to the acceptable level. 3. In the rainfall condition, if the human body do not work or take any activity, the mass of water vapor in ambient environment is higher than that inside the clothes. Therefore, the moisture would dissipate from ambient into the clothes. This status causes higher humidity in the microclimate near skin, but the humidity almost not reach above 65%. 4. At present, the testing standards of moisture transmission are all considered in the circumstance without rainfall. However, the performance of moisture permeability for some of waterproof fabric varies with its wetness level. If the performances of waterproof and moisture transmission are considered simultaneously, the simulation of rainfall included in the test of moisture transmission 4

5 is required. ACKNOWLEDGEMENTS We acknowledge the support from the Department of Industrial Technology of Minister of Economic. REFERENCE 1. Gohlke, D. J., Gore-Tex Fabric for Chemical Protective Clothing, J. Coated Fabrics, 19: Gretton, J. C., Brook, D. B., Dyson, H. M., Harlock, S.C A Correlation between Test Methods Used to Measure Moisture Vapor Transmission through Fabrics, J. Coated. Fabrics, 25: Japanese Standard Association 1994, JIS L 1099, JIS Handbook, American Society for Testing and Materials 1992, ASTM E96, Annual Book of ASTM Standards,