8.2.1 Survey outcomes
This is the first survey about understanding the abaya for its comfort. It presents the opinion of a small population of women in Saudi Arabia regarding the comfort of the abayas they were using. The survey provided an insight into the problems and causes of discomfort by wearing an abaya in hot environments. It revealed that the degree of comfort depends on the type of abaya fabric and the design as well as the clothing worn underneath.
The survey identified that most abayas were made from woven synthetic (polyester) fabrics. The areas of the body that experienced maximum heat stress were the neck, front of the body and back of the body (which represent the torso area). The torso area typically has multilayers of clothing including bra, shirt, abaya and some part of a headscarf. Wearing jeans or slacks with short sleeves or sleeveless dresses underneath the abaya increased the comfort and the freedom of movement as compared to a skirt or
jalabiah (a traditional dress falling straight from the shoulder to the ankle with a loose
fitting shape). The fabrics investigated in this research were selected for further investigation based on the survey results.
8.2.2 Fabric properties
Traditionally, woven fabrics were used for abayas because their stiffness in comparison to knits made them conducive to hide the body contours of women. The increasing use of knitted fabrics globally is making them a fashion choice as well. Therefore, this study selected some woven and knitted fabrics that are used commercially for abayas. Studies on the woven and knitted fabrics confirmed that fabric structure, fibre composition and other fabric properties significantly affected the comfort performance of abaya fabric. Among the woven fabrics, 100% polyester (3/1×1/3 mixed twill weave), 65/35 polyester/cotton (plain weave), 80/20 viscose/polyester (crepe weave) and 100%
162
polyester (satin weave) fabrics, the last fabric, polyester produced using a fine yarn count, had the best air permeability, drapeability and moisture management properties. It also had the lowest thermal resistance and lowest water vapour resistance. However, the fine yarn count in this fabric was observed to make it slightly translucent.
Knitted fabrics selected for abayas were mainly evaluated for thermal comfort properties. The polyester/elastane (96/4) single jersey knit fabric showed better air permeability, stretch and recovery properties, lower thermal and water vapour resistance compared with the nylon filament fabric, polyester/cotton (65/35) single jersey fabric, wool single jersey fabric, and 50/50 wool/nylon fabric. The polyester/elastane fabric did not appear to be able to effectively evaporate water into the environment and would keep the sweat between the skin and the next surface of the fabric. Since knitted fabrics are normally not dimensionally stable, knitted abayas could take on body contours. This may be avoided by using thicker fabrics with a greater mass per unit area or a modified abaya design.
8.2.3 Thermal manikin testing
Three designs of abaya (worn from the shoulder with either tight sleeves or loose sleeves and worn from top of the head with tight sleeves), in combination with daily-wear clothing ensembles (underwear, long-sleeved shirts as well as skirt/slacks) and shoes were investigated. Each design of abaya was made from a knitted and a woven fabric. This research is the first to utilise a sweating thermal manikin (female form) to assess the thermal comfort of the abaya in combination with common daily-wear clothing ensembles. Both stationary and walking modes were evaluated. Analysis of data was carried out on the basis of key locations of the body such as head, torso, lower torso and the abaya.
Temperature logging and an infra-red (IR) camera measured the surface temperature between daily wear clothing and an abaya. Infra-red thermography results were consistent with established findings that surface temperatures decrease when the layers
163
of clothing increase. Air gaps between the body (manikin) and multiple layers of clothing and an abaya affect the heat loss as still air serves as an excellent insulator.
The skirt ensemble had higher thermal and evaporative resistance than the slacks ensemble in the stationary standing mode. However, this trend was reversed in the walking mode, because the air movement increased, which helped to release the warm and wet air close to the body. Irrespective of type of clothing, the thermal resistance and evaporative resistance in the abaya combinations were higher than for the clothing ensemble by itself.
Among the types of abaya design evaluated, those worn on the head offered slightly higher thermal and evaporative resistance than those worn from the shoulder with tight or loose sleeves. In addition, abaya combinations in the studied woven fabric could be slightly more comfortable than chosen knitted abaya combinations, although the abaya itself contributes heavily to thermal stress in hot weather. These results highlight the importance of the air trapped in the microclimate between the body and garments on thermal comfort properties.
8.2.4 Improvement of comfort performance for abaya
fabrics
The use of an energy-reflecting chemical to improve the thermal comfort of the traditional black abaya was investigated. The experimental results showed that such treatment slightly improved the thermal comfort properties without significantly affecting air permeability and water vapour resistance at a 95% confidence interval. However, among the fabrics evaluated the blended fabrics (50/50 polyester/wool fabric and 63/37 polyester/wool fabric) showed improved water vapour resistance and moisture management performance. Thermal imaging results showed that the treatment with an energy-reflecting chemical of a black abaya type fabric reduced the radiant heat by around 1.8−0.7° C when the fabrics were tested in a natural outdoor environment at 40 °C and
164
40% RH. When the same fabrics were tested under controlled indoor conditions of 35 °C and 40% R.H, it was found the radiant heat reduced by around 0.9−0.1° C. The results also lead to the conclusion that the black 100% polyester and polyester/wool blend fabrics studied appeared to be thermally more comfortable than the 100% wool fabric, especially after the energy-reflecting chemical treatment.