INVESTIGATION OF HYGIENIC PROPERTIES OF MATERIALS FOR HOSPITAL UNDERWEAR

The infl uence of peculiarities of raw material composition and structure of traditional and innovative linen textile materials on their hygienic properties was investigated. Using the standardized and the developed methods, adapted to the peculiarities of the conditions of use of the hospital underwear, the characteristics of water absorption of the materials were experimentally determined.


INTRODUCTION
The use of hospital linen is necessary to prevent the spreading of infections in medical facilities [1]. Hospital linen is a product of multiple applications, which have to provide a comfortable and hygienic stay of patient during therapy. Nowadays the creation of comfortable and aesthetic hospital clothing with functional and structural elements that simplifi es carrying out of medical procedures for the personal and patients has been actively engaged by both scientists and specialists in the fi eld of clothing design. Such clothes are traditionally considered as adaptive. Its use by patients take it easier dressing and undressing, for medical staff -provides easy access to diff erent parts of the body during medical or hygienic procedures.
Compared to household clothing, hospital clothing has to meet a number of specifi c requirements, which are determined by the particular course of the Choice of materials for adaptive clothing is a complex process that includes medical, hygienic, technical and social requirements. The analysis of conditions of use of hospital underwear in clinics allowed defi ning its following main functions:  providing a comfortable microclimate of underwear;  protection against adverse environmental conditions (change of microclimate, biological factors, harmful chemicals, etc.);  protection against mechanical damage (injuries, irritation, pressure ulcers);  providing convenience to patients and medical staff in carrying out various medical procedures;  creation of psychological comfort of the patient.
The materials of hospital underwear, above all, must ensure the proper functioning of the body -to absorb and remove liquid and vapor moisture freely from the surface of the body, to protect the body from cooling, overheating and contamination, to clean the skin from sweat and fat. In addition, they must be resistant to multiple washing, to abrasion, mechanical deformation, be light, soft to the touch, and free of toxic and allergic substances. An important factor is the price of the product, which determines the availability of adaptive clothing for a wide range of consumers.
Hospital linen for a long time traditionally has been made of cotton, linen and mixed (cotton + PES) fabrics. The advantages of these materials are their good hygienic properties -high hygroscopicity, cap-illarity, water absorption capacity. Also, they are quite durable, stable to numerous cycles of sterilization. The disadvantages include their ability to produce a large amount of dust as a result of friction, which is a source of pollution and causes allergic reactions in patients, as well as a leaky structure that does not limit the exchange of human life products between the patient and the environment. The occurrence of textiles from new types of fi bers can signifi cantly expand the range of fabrics for the manufacture of hospital linen. Particular attention is paid to fabrics made of bamboo and Tencel fi bers, taking into consideration valuable properties of these materials. Studies have shown that bamboo materials due to the porous fi ber structure and the presence of the natural component "bamboo kun", which prevents the propagation of pathogenic microorganisms [2,3], have a number of advantages over traditional cotton -higher hygroscopicity, antimicrobial properties, softness, drapery and other valuable consumer qualities. Fabrics from Tencel® fi ber, which is made from eucalyptus wood, are highly hygroscopic, durable, soft, pleasure in touch, bacteriostatic [4].
The purpose of this work is to study the infl uence of the peculiarities of raw material composition and structure of traditional and innovative linen fabrics on their hygienic properties.

Materials
As objects of study were selected fi ve samples of fabrics for hospital underwear, which are diff erent in the raw material composition and characteristics of structure ( Fig.1 and Table 1).

RESULTS AND DISCUSSION
Air permeability is an important characteristic of the hygienic properties of textile materials, which largely determines the parameters of the clothing microclimate (temperature, humidity, concentration of CO 2 ), possess heat exchange and human well-being. Air permeability for the studied samples of fabrics A key factor of thermophysiological comfort when using hospital linen is the evacuation of moisture from clothing microclimate. The processes of absorption, transfer and desorption of moisture are determined by the peculiarities of the raw material composition and structure of used textile material. Assessment of moisture conductivity is a very actual task in the development of a model of moisture transfer, prediction of properties and the choice of materials for clothes.
The ability of a textile material to absorb water in direct contact with a liquid is characterized by capillarity and water absorption values. The capillarity, which was measured by the height h of the fl uid lifting in a sample immersed at one end into the liquid during one hour, characterizes the processes of moisture absorption by the longitudinal capillaries of the material. The obtained values of h (Fig. 2) showed that in all tested samples capillarity is higher on the warp than on the weft, the highest value of capillarity has cotton fabric (sample No. 4), the lowest -both on the warp and on the weft -fabric from 50% cotton and 50% polyester fi bers (sample No. 5). More rapidly, especially in the fi rst 20 minutes, the liquid rises (Fig.2), in cotton and Tencel fi bers, and this process passes very slowly in the mixed fabric (Sample No. 5).
High sweating, which is characteristic for ill patients, needs the rapid absorption of moisture as the most eff ective way of maintaining a sense of comfort. When used materials with high moisture absorption properties, sweat from the surface of the skin spreads rapidly throughout the fabric, providing dry feeling. Moisture capacity, determined by the standardized method, for the studied materials are quite diff erent ( Table 2). The lowest moisture content has the fabric sample No. 5. The ability of bamboo fabric (sample No. 1) to retain water in its structure twice or bigger in comparison with other samples. This is due the unique loose structure of bamboo fi bers with a large volume of voids [4].
While wetting, the bamboo fi bers absorb a considerable amount of water, noticeably increasing in transverse dimensions, which is contributes to the presence of a suffi ciently large amount of through pores between threads. For comparison, we determined the values of air permeability and moisture content of another 100% bamboo fabric with a much denser structure, by satin weave. These values are much smaller than all other fabrics studied ( Table 2). For all samples, the intensive process of water absorption occurs mainly in the fi rst minutes (Fig. 3a). Then the fl uid in the structure accumulates more slowly and after half an hour, almost all samples reach the level of maximum moisture saturation, which is almost unchanged. To ensure the comfort of hospital underwear, except the ability of materials to absorb liquid moisture, an important indicator of their quality is the intensity of the moisture loss process, which is determined by the rate of drying. The faster the moistened linen dries, the less the body of a sick person needs to expend energy on this process. To characterize the moisture output the drying time τ d [min] was determined from the curves of the drying kinetics of the samples of materials after the study of moisture absorption. Overage of water from the sample surface was removed by squeezing the samples, which was placed between three layers of fi lter paper on both sides, by roller. Then the samples were dried at room temperature to reach constant mass, and every 10 minutes they were weighed using analytical weights. The curves of the drying kinetics (Fig. 3b) indicates that the fastest drying time (in half an hour) has sample No.5 from blended cotton/polyester fi bers, for all other investigated fabrics the drying process is one and a half times longer.
Despite the peculiarities of the operating conditions, it should note that the materials of the hospital underwear are moistened, preferably under body pressure at horizontal contact with the source of moisturizing (sweaty skin of the lying patients). In order to determine the water absorption under conditions simulating this process, the following experiments has been done. A microfi ber substrate uniformly moistened to the full saturation of the structure was placed in the Petri dish, covered by a sample of the fabric, the dimensions of which corresponded to the diameter of the dish. From above, through a thin layer of glass gasket, a load was imposed (Fig. 4a). The value of the load was calculated based on the data obtained [5] in measuring the pressure with which the body of the lying person acts on the bed -this value was 5000 Pa. The amount of water absorbed by the sample of the material was fi xed over time by analytical weights every 5 minutes. The diff erence in the mass of dry and wetted material for each step of the measurements allowed to evaluate the dynamic characteristic of the moisture absorption of the studied materials. Measurement deviations never exceeded ±3 units in the second signifi cant digit after the decimal point, which determines the level of accuracy of the data obtained.
The moisture absorption kinetics curves obtained in these experimental conditions (Fig. 4b) indicate that the speed of reaching the maximum moisture saturation in the tested fabric samples, compared to the experiment conditions, when they are immersed in water, increased to half an hour. The values of W in this method of moistening for all samples, except No. 1, practically coincide with those determined by the standardized method (Table 2), only for bamboo fabric the moisture capacity decreased by 1.2 times. Obviously, this may be due to the fact that the pore volume in the loose bamboo fi bers decreases significantly under pressure.