Climate chamber measurement

The absorption and desorption of samples are also tested in the climate chamber where temperature is set as 20^oC and the RH is changed from 7% to 95%. The absorption and desorption of the specimen are calculated by following formula

Moisture amount change % = (𝑁𝑒𝑤 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒− 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 𝑤𝑒𝑖𝑔ℎ𝑡)

𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 𝑤𝑒𝑖𝑔ℎ𝑡 *100 (2)

Each samples weighed inside the chamber after every 1 hour. This experiment gives valuable information regarding the time and efficiency of absorption and desorption of specimens. The experiment is repeated 3 times.

Standard Upright cup method

Standard Upright cup method or Gore cup method (ASTM E 96-66) is used to analyze the overall loss of water from the reservoir. The car seat cover material with classic layer structure of X,Y, Z and P is firstly analyzed and then the SAF layer is inserted between layer X and Y to determine the effect of SAF layer on moisture resistance of the complete sandwich material.

Layer P is a thick PU-foam and is well-known for being impermeable and act as moisture barrier from back side of the sandwich material. The PU-foam protect the SAF not to absorb moisture from the chamber environment so results of Cup method would be precise as flow of moisture will be only from the top Layer “X”. The visual illustration of the samples is shown in figure 37.

Figure 37 Visual Illustration of specimen layers during Ret testing.

6.2.5 Results and Discussion

The specimen is put in the sealed container having different amount of different saturated salt solutions until weight equilibrium could be assumed. 4 samples are placed in each container with 5 different salts solution and tested after 4, 8 and 12 days, therefore a total of 15 containers are used for this experiment. Different salts as shown in table 22 are used to obtain required humidity level in sealed containers. The Figure 38 shows the percentage gain of moisture with respect to time.

Figure 38 Moisture absorption with respect to time

It is observed that the SAF absorbed nearly 70% moisture in with respect to their weight at 100%RH. Specimen “A” showed the highest rate of moisture gain measured after 12 days.

There was no difference between the measurement taken at 8 days and 12 days of testing and results observed after 12 days can be considered as the maximum moisture absorbed by the sample. The process of testing the samples at different salts providing different humidity levels is quite slow but provides accurate results.

The PU- foam sample gained less than 2% of moisture after 12 days.

The absorption and desorption of samples are also tested in the climate chamber where temperature is set as 20^oC and the RH is changed from 7% to 95%. The experiment is repeated 3 times. Figure 39 shows the rate of absorption and desorption of samples.

Figure 39 Rate of absorption and desorption

Specimen A is inserted in between the car seat sandwich layers as shown in Figure 16 to test the water vapor permeability cup method (ASTM E 96-66). The car seat is covered by PU-foam which is impermeable to moisture. The presence of superabsorbent will help in absorption of moisture though the top layer of the fabric and causes decrease of the water level in the cup.

The superabsorbent layer is pre-dried at 35% RH that is the average ambient humidity inside the car. Later on layer is inserted in between the car seat layer as shown in figure 16 (experimental part).

Figure 40 Effect of superabsorbent on moisture permeability

As shown in figure 40 the experiment is repeated 3 times and show a significant difference of moisture transport when superabsorbent is used.

6.3 Summary

The breathability of car seat is a serious issue and in this research a unique concept of perforated molded PU-foams is used instead of classical foams, the results shows that the perforation plays a significant role in the moisture transfer. An average human perspire 20-30g per hour during driving and classical foams are impermeable and causes a discomfort for the driver, on the other hand perforated foam and the top layer together works efficiently to transfer nearly 40g/hour of moisture. The car seat cover with 3d spacer fabric provides better transportation of moisture in compare to PU foam. The perforated foams can be future replacement for the classical foams.

Different design of grooves and shapes of holes can also be introduced to increase the porosity

of the foams. This is novel and initial work and further research will be done regarding the life time of the perforated foams.

The use of super absorbent polymers (SAP) for moisture absorption and comfort is still unexplored. In this research the efficiency of different SAP fibrous webs are determined under different moisture percentage to examine the sorption and desorption efficiency. The SAP fibrous web with low thickness and high moisture absorption are tested with multilayer sandwich structure of car seat cover to determine the moisture absorption through cover material. Standard Cup method is used to determine the moisture permeability of different car seat cover with superabsorbent layer closed with impermeable polyurethane foam. It is observed that the SAP fibrous layers are very effective in absorbing and desorbing water vapor under extreme high and low moisture percentages. In extreme humid condition (95%RH) the 20g of SAP layer absorbs nearly 3g of water vapor per hour and reaches the maximum absorption capacity in 6 hours.

The following is concluded from this research

 The superabsorbent material are efficient to absorb and desorb water vapor and 50% and higher rate of absorption can be easily achieved under extreme humidity level.

 The fast sorption and desorption process can be repeated multiple times and make it potential use in the comfort of car seat.

The research is initial work to see the utilization of superabsorbent in car seat. This is novel and initial work and further research will be done regarding the life time of the SAF in car seats.