209 CHAPTER 7 DESIGN AND DEVELOPMENT OF MULTILAYERED HOSPITAL TEXTILES 7.1 INTRODUCTION This part of the research work deals with design and development of multi layered knitted and woven fabrics for hospital textiles and analysis of their comfort characteristics. Tri-layered knitted and woven fabrics were developed using the fibres like lyocell, bamboo charcoal, bamboo and micro polyester in different combinations. The tri-layer fabric comprise of two fabric layers joined together by a connecting yarn. The tri-layer weft knitted fabric is soft, with good thermal conductivity and wickability, which appeals to the comfort properties of the user. This fabric possesses certain exceptionally good functional characteristics, such as moisture absorbency, where the moisture from the body is absorbed by the base layer, passed through the connecting layer and gets evapourated from the top layer. 7.2 Production of Multi layered structure Four types of tri-layer fabrics were constructed from lyocell, bamboo charcoal, bamboo and micro polyester yarns in two different combinations. The fibre composition of the different types of multi layered fabrics produced are given in the Table 7.1.
210 Table 7.1 Composition of Multi layered structures S.No Multi layered Top layer Connecting Bottom fabric Layer Layer 1 Knitted fabric 1 Bamboo Micro polyester Lyocell BC:L/MP/L charcoal /Lyocell 2 Knitted fabric 2 Bamboo Micro polyester Lyocell B/MP/L 3 Woven fabric 1 Bamboo Micro polyester Lyocell BC:L/MP/L charcoal/ Lyocell 4 Woven fabric 2 Bamboo Micro polyester Lyocell B/MP/L 7.2.1 Production of Weft Knitted Tri-layer Fabrics Weft knitting machine with two sets of needles has the ability to create two individual layers of fabric that are held together by tucks. Such a fabric was referred as a double-faced fabric, also called as tri-layer fabric. Doubleface fabrics can be produced on dial and cylinder machines. It requires the use of at least three different yarns for each course of visual fabric. 1) Yarn for the cylinder needles, 2) Yarn for the dial needle, 3) A binding yarn, connecting the two layers. The distance between the two fabrics can be manipulated by dial height adjustment, ultimately determining the amount of yarn being put between the two fabrics. The degree of space or height between the two fabric faces is determined in the circular knitting machine by the setting of the dial height relative to the machine cylinder. Figure 7.1. Sequence of operation in knitting tri-layer fabric is given in the
211 Figure 7.1 Knitting sequence of Tri-layer fabric a) Tucking on dial and cylinder needles at the same feeder b) Tucking on the dial and cylinder needles on feeders 1 and 4 on low and high butt needles alternately (this connects the two layers together) c) Knitting dial needles with dial yarn at feeders 2 and 5 on low and high butt needles alternately d) Knitting cylinder needles with cylinder yarn at feeders 3 and 6 on low and high butt needles alternately The details of knitting machine used for knitting tri-layer fabric is given in the Table 7.2. Table 7.2 Parameters of knitting machine Feeders 72 Number of needles 32*18 Diameter 32 Gauge 18 Machine speed 20-25 rpm Machine Make Germany Company Fomaco
212 The cam diagram used for the production of multi layered knitted fabric is shown in the Figure 7.2 below. Front layer back layer middle layer Figure 7.2 Cam arrangements to knit Tri-layer structure The tri-layer knitted fabrics were produced in two fibre combinations such as bamboo charcoal / micropolyester / lyocell and bamboo / micropolyester / lyocell. In bamboo charcoal / micropolyester / lyocell combination, the top layer contains bamboo charcoal and lyocell yarns and the bottom layer contains lyocell yarn, and the micro polyester acts as the connecting layer. Similarly in the bamboo / micropolyester / lyocell combinations, the top layer contains bamboo yarn and the bottom layer contains lyocell yarn, and the micro polyester acts as the connecting layer. 7.2.2 Production of Woven Tri-layer Fabrics The tri-layer woven fabric was produced in a sample loom using three warp sheets and two types of weft yarns. In bamboo charcoal / micro polyester / lyocell combination fabric, the top layer contains bamboo charcoal yarn in warp direction and lyocell yarn in the weft direction. Lyocell is introduced in the weft direction to ensure maximum moisture spreading along the width of the fabric, so that the wetness is transferred away from the body
213 of the patient. The bottom layer is made of lyocell to ensure rapid absorption of water from the inner layer and faster drying. The connecting layer is made of micro polyester warp which interweaves with the face and back weft alternatively, assisting in moisture transfer from the inner layer to the outer layer. Micro polyester with high wicking ability acts as an efficient medium to transfer moisture from the inner layer to the outer layer. The weave structure is given in the Figure 7.3. Figure 7.3 Weave structure of Tri-layer woven fabric In the bamboo / micro polyester / lyocell combination fabric, bamboo yarn is used in the top layer and lyocell yarn in the bottom layer. The connecting layer is made of micro polyester warp. The four tri-layer fabrics produced were tested for fabric parameters and comfort properties and are given in the Table 7.3 and Table 7.4.
214 Table 7.3 Parameters of Tri-layer Fabrics Sample.No Ends(or)wales/inch Picks(or) course/inch Fabric weight (g/m 2 ) Fabric thickness (mm) Warp Strength (kgf) Warp Elongation (%) Weft Strength (kgf) (%) BC/MP/L (Knit) 15.74 9.5 306.73 Bursting strength 63kgf B/MP/L (Knit) 15.74 9.5 248.75 Bursting strength 55kgf BC/MP/L (Woven) 27.6 20 162.60 130 24.75 80 28.75 B/MP/L (Woven) 27.6 20 174.53 193 23.91 100 33.83
Table 7.4 Comfort properties of Tri-layer Fabrics Sample No BC/L/MP (KNIT) Air permeability Thermal conductivity W/M/K Water vapour permeability (g/m2/day) Face Absorption(sec) Back Spreading area Face (cm 2 ) Spreading area Back (cm 2 ) Vertical wicking (Warp) ) (cm) Vertical wicking (Weft) ) (cm) Inplane wicking (g/cm 2 ) (5s) Inplane wicking (g/cm 2 ) (10s) 77.84 0.0361 2556.56 1.548 3.944 3.52 3.94 15.0 11.0 2.07 3.45 B/L/MP (KNIT) BC/L/MP (WOVEN) B/L/MP (WOVEN) 65.55 0.0316 2543.88 3.924 4.100 3.14 4.90 10.0 11.5 1.97 2.08 31.13 0.0314 2228.67 1.998 2.136 7.50 9.50 12.0 10.0 1.06 1.56 20.75 0.0418 2193.82 4.220 4.120 9.00 11.00 8.5 9.0 2.02 2.78 215
216 7.3 RESULTS AND DISCUSSION The comfort properties of the multilayered fabrics were analyzed and are discussed below. 7.3.1 Air Permeability of multi layered fabrics Air permeability is a measure of the amount of air passing through a fabric and the air permeability of the tri-layer fabrics are shown in the Figure 7.4. Figure 7.4 Air permeability of multilayered fabrics Better air permeability is noticed in the case of bamboo charcoal/ lyocell / micro polyester tri-layer fabrics in both woven and knitted structures. The bamboo lyocell combination has comparatively lower air permeability. The higher air permeability of bamboo charcoal combination may be attributed to the highly porous structure of bamboo charcoal. Compared to woven tri-layer fabrics, knitted fabrics have higher air permeability due to the loop structure. Obviously, the multi layered structures have lower air permeability than the single layered structures.
217 7.3.2 Thermal conductivity of multilayered fabrics in the Figure 7.5. The thermal conducting behaviour of multi layered fabrics is shown Figure 7.5 Thermal conductivity of multilayered fabrics The bamboo charcoal fabrics exhibit higher thermal conductivity when compared to bamboo/lyocell combinations. Bamboo charcoal as well as bamboo fibers have very good thermal conductivity required for human comfort. The woven tri-layer fabric made of bamboo charcoal / lyocell combination has higher thermal conductivity values than the remaining three fabrics. The thermal conductivity of tri-layer fabric remains similar to that of single layered fabrics. 7.3.3 Water vapour permeability of multilayered fabrics The amount of water vapour passing through the multi layered fabrics is shown in the Figure 7.6. The tri-layer fabrics maintain the same trend as the single layered fabrics in the water vapour management. The highest water vapour permeability is observed in case of bamboo charcoal trilayer fabrics, which may be due to the presence of carbon particles in the fiber
218 and also the highly porous nature of bamboo charcoal leading to higher water vapour permeability and higher water absorption. Figure 7.6 Water vapour permeability of multilayered fabrics than knitted fabrics. The woven tri-layer fabric has lower water vapour permeability 7.3.4 Water absorbency of multi layered fabrics The rate of water absrption, measured in face and back of the four tri-layered fabrics are shown in the Figure 7.7. Figure 7.7 Water absorption of multilayered fabrics
219 The bamboo charcoal fabrics were noticed to have higher water absorbing tendency owing to the combination of three fibers having excellent moisture absorbing and transporting property. Presence of bamboo charcoal, micro polyester and lyocell leads to rapid absorption of moisture. Bamboo / lyocell combination also has good moisture absorbing property. The tri-layer fabrics exhibit very good water absorbency compared to single layered structures, resulting in immediate transfer of moisture to inner layers and hence gives a dry feel. This property is essential to keep the patient dry and hence avoids problem created by wet skin. 7.3.5 Spreading area of multi layered fabrics The extent to which a drop of water, spreads in warp and weft direction or in course and wales direction of the fabric is shown in the Figure 7.8. Figure 7.8 Spreading area of multilayered fabrics In the Bamboo charcoal multi layer fabrics, the bamboo char coal surface has lower spreading area when compared to the lyocell side of the fabric. This trend has already been noticed in single layered structures. Similar trend is seen in bamboo/lyocell union fabrics, lyocell side of the fabric spreads more than the bamboo side of the fabric. Tri layer woven
220 fabric spreads water to a greater extent and it exhibits more distribution of water in the warp and weft direction. 7.3.6 Vertical wicking of multi layered fabrics The height to which water is wicked in ten minutes, in both warp and weft directions is shown in the Figure 7.9. Figure 7.9 Vertical wicking of multilayered fabrics The bamboo charcoal tri-layer fabric exhibits higher wicking tendency due to the presence of bamboo charcoal and micro polyeater combinations. Compared to single layered fabrics, multi layered structure has almost 3 to 4 times increase in wicking height. The bamboo / lyocell combination tri-layer structure shows lower wickability but still 3 to 4 times higher than that of single layered structure. 7.3.7 Inplane wicking of multi layered fabrics The amount of water absorbed along the plane of the multi layered fabrics in five and ten seconds respectively are shown in the figure 7.10. The bamboo charcoal/lyocell combination fabric absorbs more moisture when compared to the bamboo/ lyocell fiber combination. This is again due to the micro porous structure of bamboo charcoal and micro fiber combinations.
221 Figure 7.10 Inplane wicking of multilayered fabrics When compared to single layered fabrics, the bamboo charcoal combination tri-layer fabric absorbs around 250 times more water which is exclusively due to the multi layer structure and combination of moisture absorbent fibers. The bamboo fiber based multi layered structure shows 29 times more water absorption when compared to the corresponding single layered structure. This higher absorbing tendency of the multi layered structure results in absorption of more amount of sweat from the skin and hence keeps the patient in comfort zone. 7.3.8 Drying rate of multi layered fabrics The time taken to dry a fabric which is wetted with water of 30% on the weight of the fabrics are shown in the Figure 7.11. Quick drying capability of a fabric could be evaluated by its drying rate.
222 Drying Rate 70 60 RWR% 50 40 30 20 BC/L/MP (KNIT) B/L/MP (KNIT) BC/L/MP (WOVEN) B/L/MP (WOVEN) 10 0 10 min 20 min 30 min 40 min Figure 7.11 Drying rate of multilayered fabrics From the figure, it is observed that bamboo charcoal fabrics have faster drying rate and addition of lyocell delays the drying time of the fabrics as the moisture content of lyocell fiber is more than the polyester based bamboo charcoal yarns. But still the bamboo charcoal/ lyocell combination dries faster than the bamboo/lyocell combinations. 7.4 DEVELOPMENT OF MULTILAYER COMBINATION FABRICS Three multi layered combination fabrics were developed by combining three single layered fabrics together by arranging the fabrics one over the other. Different combinations of fabric layers were prepared based on their ability to complement and maximize the essential comfort properties of a bed linen. Considering the moisture management property as the key factor, various fabric combinations were analyzed and the following combination of fabric layers were selected and tests were carried out to analyze the comfort characteristics.
223 Lyocell terry pile with Lyocell twill fabric (LP/LT) Lyocell terry pile with micro polyester twill fabric(lp/mpt) Lyocell terry pile with cool finished single jersey knitted fabric (LP/K) Two layers of lyocell terry pile structures were used as base layer over which three different fabrics were tried as top layers. Terry pile structure is selected as the base layer because of its higher absorbing tendency and resilience. For the top layer, the fabrics having smooth surface such as lyocell twill, micro polyester twill woven fabrics and a single jersey cotton fabric treated with cool finish were used. The fabric parameters of the multi layer combination fabrics are shown in the Table7.5. Table 7.5 Parameters of Tri-layer combination Fabrics S.No Fabric type Yarn count (Ne) Fabric structure Ends /cm Picks /cm Fabric weight g/m 2 Fabric thickness (mm) 1 Lyocell 30 Terry Pile 10 7 240 0.310 2 Lyocell 30 Twill 11 9 150 0.135 4 Cotton(cool 30 Single 7.87 9.8 150 0.150 finish) jersey wpcm cpcm 5 Micropolyester 32 Twill 11.8 9 70 0.140 The above listed multilayered combination fabrics were tested and analyzed for their comfort properties and the reslts are given in the Table 7.6. From the table it is clear that the multilayered combination fabrics having lyocell terry pile with lyocell twill combination, has higher air permeability followed by the fabric with lyocell pile with micropolyester twill combination fabrics.
224 Table 7.6 Properties of Tri-layer combination Fabrics S.No Air permeability (cm 3 /cm 2 /s) Thermal conductivity (w/m/k) Water vapour permeability (g/m2/day) Water Absorption(sec) Spreadingarea (cm 2 ) Vertical wicking (Warp) ) (cm) Vertical wicking (Weft) ) (cm) Inplane wicking (g/cm 2 ) (5s) Inplane wicking (g/cm 2 ) (10s) Frictional Factor (static) Frictional Factor (dynamic) Lyocell pile with knitted cotton Lyocell pile with Lyocell Twill 51.89 0.0361 2838.5 3 1.60 3.0 3.4 0.013 0.015 9.64 8.74 73.26 0.0373 3015.91 5 0.58 3.2 3.8 0.014 0.22 8.04 7.11 Lyocell pile with 88.96 0.0382 5410.9 5.5 0.59 micropolyester 3.4 4.0 0.017 0.025 8.24 7.42 twill Thermal conductivity is found to be higher for lyocell pile and cool finished knitted fabric combination, followed by lyocell pile and lyocell twill combination. This shows that these two combinations can conduct away heat from the body easily and keeps the patient cool. All the three combinations exhibited very good water absorbency resulting in immediate transfer of moisture to inner layers and ensures dry feel. Regarding the water spreading area, lyocell pile and cool finish combination immediately spreads the drop of water to maximum extent and proves its water management ability. Lyocell pile, micro polyester twill combination shows higher wicking tendency due to more inter fibrillar capillary space. An analysis of all the overall performance of these fabrics ensures that the lyocell pile and lyocell terry combination proves to be a suitable
225 combination for hospital textiles in all aspects likes air permeability, thermal conductivity and moisture management property. 7.5 CONCLUSIONS Based on the analysis of the multi layered knitted and woven fabrics made of bamboo charcoal / lyocell / micro polyester combinations and bamboo / lyocell / micro polyester combinations, the following conclusions are arrived: Higher air permeability, water vapour permeability, water absorbing tendency, wicking tendency and faster drying rate are noticed in the case of bamboo charcoal /micro polyester / lyocell tri-layer fabrics for both woven and knitted structures. The woven tri-layer fabric made of bamboo/lyocell combination has higher thermal conductivity value. Generally, multi layered structures have better moisture management properties when compared to single layered fabrics. The knitted multilayered fabric is a more suitable choice for hospital textile application because of its comfort and elongation characteristics. Similarly, multilayered bed sheets made of lyocell twill: lyocell pile combination proves to be a suitable combination for hospital textiles. Hence use of multi layered fabrics can improve the comfort properties of hospital textiles.