1. Evaluation of the thermal comfort performance of different knitted fabrics and fibre blends suitable for skin layer of firefighters’ protective clothing Nazia Nawaz, OlgaTroynikov Royal Melbourne Institute of Technology, Australia 1Corresponding author: nazia.nawaz@student.rmit.edu.au

2. RMIT University©2008 Information Technology Services 2 Introduction Protective clothing is required to shield the wearers from a variety of hazardous environments or extreme conditions encountered by humans in some industries, military or firefighting. Firefighters’ protective clothing Firefighters’ protective clothing plays a vital role for their protection against heat, hot liquids, chemicals and mechanical impacts. The protective clothing facilitates the firefighter to approach the fire to rescue people from fire and to fight the fire. Modern firefighters’ clothing is a multi-layered garment assembly which is usually worn over an undergarment (skin layer).

3. RMIT University©2008 Information Technology Services 3 Firefighting and thermal comfort Firefighting is an exhaustive physical task which generates body heat, also in addition extremely hot working environment results in substantial elevation of body core temperature. To reduce that temperature to normal, the body perspires in liquid and vapour form. For better control of body temperature in keeping it a normal level the evaporation of perspiration is necessary. Thermal comfort of human body is maintained by perspiring both in vapour and liquid form and moisture transmission through clothing has a great influence on its thermal comfort

4. RMIT University©2008 Information Technology Services 4 Firefighting and thermal comfort To provide thermal comfort to the human body the garment next to skin must have three important attributes: to absorb Heat Vapour Liquid perspiration from skin and then transfer these to the outside of the garment Thermal comfort and fabric properties Thermal comfort properties of textile fabrics are actually influenced by the type of fibre spinning method of yarns yarn count yarn twist yarn hairiness fabric thickness, fabric cover factor fabric porosity and finish

5. RMIT University©2008 Information Technology Services 5 Background Milenkovic et al. (2009) demonstrated that fabric thickness, enclosed still air and external air movement are the major factors that affect the heat transfer through fabric. Ozdil (2007) experimentally verified that yarn properties such as yarn count, yarn twist and spinning process influence thermal comfort properties of 1×1 rib knitted fabrics. He verified that, The 1 × 1 rib fabrics produced from finer yarns showed lower thermal conductivity and higher water vapour permeability values than coarser yarns counts. Combed yarn showed the higher water vapour permeability By increasing yarn twist used for 1 × 1 rib fabrics, thermal and water vapour permeability of the fabrics was also increased. Thermal resistance values decreased as the twist coefficient of yarn increased. Thermal resistance values of fabrics knitted with combed cotton yarns were lower than the fabrics knitted with carded cotton yarns. Milenkovic, L., Skundric, P., Sokolovic, R., Nikolic, T., (1999). "comfort Properties of Defence Protective clothing." The scientific Journal Facta Universities 1(4): 101-106. Özdil, N., A. MarmaralI, et al. (2007). "Effect of yarn properties on thermal comfort of knitted fabrics." International Journal of Thermal Sciences 46(12): 1318-1322.

6. RMIT University©2008 Information Technology Services 6 Background Arzu Marmarali (2009) studied thermal comfort properties of blended yarns and knitted fabrics of Cotton /Soybean fibres and Cotton/Seacell fibres in different blend ratios and found that, The thermal resistance value of 100% cotton fabric was significantly higher than whole blended materials. 50/50% blend ratio of both fabrics (Co/Seacell, Co/Soybean) had the lowest thermal resistance values than the other blend ratios and that was due to lower fabric thickness value of 50/50% Co/SeaCell and Co/Soybean fabrics. Therefore with the decreasing of fabric thickness, thermal resistance decreases. Troynikov et.al (2011) studied moisture management properties of wool/ polyester and wool/bamboo knitted in single jersey fabrics for the sportswear base layers and concluded that, Blending wool fibre with polyester fibre and, in particular, wool fibre with regenerated bamboo fibre, improved moisture management properties than fabrics in wool fibre or regenerated bamboo fibre without blending. Troynikov, O., et all, Wiah, W., (2011). "Moisture management properties of wool/polyester and wool/bamboo knitted fabrics for sportswear base layer." Textile Research Journal 0: 1-11. Arzu Marmarali, M. B., Tuba Bedez Ute, Gozde Damci (2009). Thermal comfort Properties of Blended Yarns Knitted Fabrics. ITMC. Casablanca, Morocco.

7. RMIT University©2008 Information Technology Services 7 Objective of the study The Objective of present study is: To evaluate thermal and moisture management properties of six commercially available knitted fabrics of different fibre blends and knitted structures for skin layer garments of firefighter’s protective clothing The assessment and ranking of their thermal and moisture management performance.

8. RMIT University©2008 Information Technology Services 8 Materials and methods Following are six commercially available knitted fabrics having different fibre content and knit structure that were evaluated 100% Merino wool 60% Merino Wool/ 40% Bamboo 100%Cotton 94% Merino wool/ 6% spandex 100%Polyester 52% Merino wool / 48% Biophyl

9. RMIT University©2008 Information Technology Services 9 Fabric physical properties Fabric mass per unit area (gram / meter square) Fabric thickness (mm) Fabric density (No. of wales/cm and No. of courses/cm) Fabric Moisture management properties For evaluation of fabrics’ moisture management properties Moisture Management Tester (MMT) was used according to American Association of Textile Chemists and Colourists (AATCC) Test Method 195–2009. Figure 1. Moisture management testerFigure 2. Schematic view of tester sensors

10. RMIT University©2008 Information Technology Services 10 Moisture management tester indices A series of indexes are defined and calculated to characterize liquid moisture management performance of the test sample by using moisture management tester, which are as follow; Top wetting time WTt and bottom wetting time WTb Top absorption rate (ARt) and bottom absorption rate (ARb) Top max wetted radius (MWRt) and bottom max wetted radius (MWRb) Top spreading speed (SSt) and bottom spreading speed (SSb) Accumulative one-way transport index (AOTI) and overall moisture management capacity (OMMC)

11. RMIT University©2008 Information Technology Services 11 The OMMC is an index indicating the overall capacity of the fabric to manage the transport of liquid moisture, which includes three aspects 1. Average moisture absorption rate at the bottom surface 2. One-way liquid transport capacity 3. Maximum moisture spreading speed on the bottom surface The larger the OMMC is the higher the overall moisture management ability of the fabric is. According to AATCC Test Method 195–2009, the indices are graded and converted from value to grade based on a five grade scale (1–5). The five grades of indices represent: 1 – Poor 2 – Fair 3 – Good 4 – Very good 5 – Excellent Moisture management tester indices

12. RMIT University©2008 Information Technology Services 12 Table 1. Grading of MMT indices

13. RMIT University©2008 Information Technology Services 13 Fabric thermal properties (Thermal and water vapour resistance) Thermal resistance and water vapour resistance of fabrics were evaluated using sweating guarded hot plate according to ISO 11092. Sweating guarded hot plate is able to simulate both heat and moisture transfer from the body surface through the clothing layers to the environment. It measures both the thermal resistance (insulation value) and water vapour resistance of fabrics. Figure 3. Sweating Guarded Hot Plate Figure 4. Schematic diagram of sweating guarded hot plate

14. RMIT University©2008 Information Technology Services 14 Fabrics’ thermal resistance For the determination of thermal resistance of the sample, the air temperature is set to 20  C and the relative humidity is controlled at 65%. Air speed generated by the air flow hood is 1 m/s. After the system reaches steady state, total thermal resistance of the fabric is governed by: (1) Where, Rct is the total thermal resistance plus the boundary air layer measured in m² K/W, A, the area of the test section in m ² Ts, the surface temperature of the plate in K Ta, the temperature of ambient air in K H, the electrical power in Watts

15. RMIT University©2008 Information Technology Services 15 Fabrics’ water vapour resistance To measure the water vapour resistance of the fabric air temperature is set at 35  C and relative humidity is controlled at 40%.After a steady state is reached, the total evaporative resistance of the fabric is calculated by: Where, Ret, is total vapour resistance provided by liquid barrier, fabric and boundary air layer measured in m 2 KPa/W) A, the area of test section in m 2 Ps, the water vapour pressure at plate surface in Pa Pa, the water vapour pressure of the air on Pa H, the electrical power in Watts (2 )

16. RMIT University©2008 Information Technology Services 16 Fabric code Fibre composition ConstructionFabric weight (g/m 2 ) Fabric thickness (mm) No. of wales/c m No. of courses /cm SJ1100% Merino wool Single Jersey1390.3518 SJ260% Merino Wool/ 40% Bamboo Single Jersey1560.3416 SJ3100%CottonSingle Jersey1490.471915 SJ494% Merino wool/ 6% spandex Single Jersey1850.5520 IM1100%Polyest er Interlock based mock mesh1680.6116 IM252% Merino wool / 48% Biophyl Interlock based mock mesh2160.971612 Results and discussion Table 2. Physical and structural properties of sample fabrics

17. RMIT University©2008 Information Technology Services 17 Moisture Management Properties of sample fabrics Table 3. MMT results in value Fabric codeWTt (sec) WTb (sec) ARt (%/sec) ARb (%/sec) MWRt (mm) MWRb (mm) SSt (mm/sec) SSb (mm/sec) AOTI (%) OMMC SJ1 CV 63.312 1.265 50.515 1.343 3.671 1.414 5.117 0.290 2.5 1.414 5 1.414 0.365 1.414 0.959 1.414 319.182 0.011 0.448 0.112 SJ2 CV 7.883 0.071 5.000 0.137 8.152 0.236 5.925 0.114 12.5 0.282 12.5 0.282 1.286 0.097 3.102 0.098 133.396 0.251 0.379 0.030 SJ3 CV 41.255 0.249 5.416 0.979 8.061 0.194 14.286 0.276 13.33 3 0.216 13.333 0.216 0.349 0.419 1.600 0.614 102.118 0.394 0.244 0.383 SJ4 CV 3.281 1.084 29.274 1.064 7.153 0.046 6.853 0.181 5050 10 0 3.131 1.035 1.154 0.043 500.714 0.033 0.521 0.057 IM1 CV 30.617 1.165 47.063 1.242 39.894 0.953 5.200 0.548 7.5 0.471 7.5 0.471 0.947 1.280 0.941 1.329 102.399 0.283 0.203 0.397 IM2 CV 119.953 0 3.835 0.250 0000 5.069 0.561 0000 7.5 0.471 0000 0.898 0.091 434.105 0.184 0.487 0.036 Results and discussion

18. RMIT University©2008 Information Technology Services 18 Figure 5. WTt and WTb grades of sample fabrics Figure 6. ARt and ARb (%/sec) grades of sample fabrics Results and discussion

19. RMIT University©2008 Information Technology Services 19 Figure 7. MWRt and MWRb (mm) grades of sample fabrics Figure 8. SSt and SSb (mm/sec) grades of sample fabrics Results and discussion

20. RMIT University©2008 Information Technology Services 20 Figure 9. AOTI % and OMMC grades for sample fabrics These results show that SJ1, SJ4 and IM2 have better moisture management properties as compared to the other sample fabrics of the study. These three fabrics are composed of 100% wool, wool/spandex and wool/biophyl and having single jersey structures Results and discussion

21. RMIT University©2008 Information Technology Services 21 Thermal properties (Thermal and vapour resistance) Results and discussion Figure 10. Thermal resistance (Rct) of sample fabrics

22. RMIT University©2008 Information Technology Services 22 Results and discussion Figure 11. Water vapour resistance (Ret) of sample fabrics

23. RMIT University©2008 Information Technology Services 23 Conclusion The results and discussions demonstrate that wool and wool blends are the most suitable fabric to be used next to skin to achieve thermal comfort The fibre content, fabric construction and fabric thickness influence thermal comfort significantly. Therefore it can be concluded that 100% wool and wool blends with spandex and bamboo (SJ1, SJ2 and SJ4) in single jersey structure are more suitable to use next to skin than SJ4, IM1 and IM2. 100% cotton in single jersey structure can also be a good choice because it has lower thermal and water vapour resistance like SJ1, SJ2, and SJ3 but not in extremely hot environments like firefighting where body perspires heavily in liquid form and cotton is unable to provide better liquid moisture transfer properties like wool and wool blends to keep skin dry.

24. RMIT University©2008 Information Technology Services 24