*3.4.2 SEM analysis procedure*

SEM settings: Backscatter detector, 20 kV accelerating voltage, working distance of 10 mm. Magnification between 1000 and 4000x.


### **3.5 Raman microscopy and spectroscopy**

#### *3.5.1 Raman sample preparation*

Raman analysis needs no sample preparation. Images of the fibres were taken with the SEM after which the sample was moved from under the SEM pole piece to the Raman objective in the SEM chamber and a Raman map was acquired of the same area.

#### *3.5.2 Raman analysis procedure*

Raman Settings: Laser wavelength 532 nm, the laser power was 2 mW, map areas were 50μmx50μm with data points every 0.5 μm, integration time (time spent on each point) 0.2 seconds.

*The Effect of Laundering on the Physical and Thermal Properties of Phase Change Textile… DOI: http://dx.doi.org/10.5772/intechopen.105064*


## **4. Analysis**

Comparative analysis was applied to the DSC, TGA, SEM and Raman analytical results.

### **5. Results and discussions**

The main objective of this study is to determine the effect of repeated laundering at different wash temperatures, on the thermal and physical related properties of the PCM as measured by TGA, DSC, SEM and Raman.

#### **5.1 Thermal gravimetric analysis (TGA)**

#### *5.1.1 TGA results of multiple washed samples at different temperatures*

Thermal gravimetric analysis (TGA) is generally used to investigate chemical reactions in which weight changes occur. Most TGA curves illustrate mass losses, for example in **Figures 1**-**3** the TGA thermograms show 3 different degradation regions that indicate a combination of paraffin wax that forms the core of the microcapsule, an acrylic resin as the polymeric shell of the microcapsule and polymeric fibres which can be identified as Polyester (PES), Polyamide (PA) and Polyethylene Terephthalate (PET) present in the PCM sample.

### *5.1.2 Mass loss percentage (%) comparison of different wash temperatures after 10 washes*

In **Figure 4** the thermogram of the first segment was identified as the paraffin wax, where it is observed for the sample washed at 30°C there is a mass loss of 15.8% at a heating temperature of around 208°C, for the sample washed at 40°C there is a mass loss of 18.8% at a heating temperature of approximately 205°C and for the sample washed at 60°C a mass loss of 19.1% was observed at a heating temperature of nearly 200°C. The thermogram indicate that the mass loss at wash temperature 60°C is slightly higher with a lower heating temperature compared to the wash temperature of 30°C and 40°C where the mass loss is lower at a higher heating temperature.

The thermogram of the second degradation segment, was identified as the acrylic resin of the microcapsule, which exhibit a mass loss of 24.5% of the sample at wash temperature 30°C, a mass loss of 31.8% of the sample at wash temperature 40°C and

#### **Figure 1.**

*TGA thermograms showing the effect of repeated laundering on mass loss (number of washes at 30°C).*

#### **Figure 2.**

*TGA thermograms showing the effect of repeated laundering on mass loss (number of washes at 40°C).*

a mass loss of 35.1% of the sample at wash temperature 60°C with heating temperatures ranging from 300 to 400°C. This proves that a higher mass loss occurred for the sample at wash temperature 60°C compared to the samples of the lower wash temperatures, this is due to the PCM microcapsules breaking during the laundering process.

The last segment which indicates the thermal degradation of the polymeric fibres (PES, PA, and PET) show a mass loss of around 87.5% ±2% for the samples washed at temperatures 30°C, 40°C and 60°C at a heating temperature up to 500°C.

The difference in onset degradation is caused by the different wash temperatures where loss of mPCM content occurred during the laundering process. The thermogram clearly indicate that there is a higher mass loss at wash temperature 60°C, than at wash temperature 30°C and 40°C, respectively. The difference in average mass loss percentage between the sample at wash temperature 60°C compared to the sample at wash temperature 30°C is about 4.6%.

*The Effect of Laundering on the Physical and Thermal Properties of Phase Change Textile… DOI: http://dx.doi.org/10.5772/intechopen.105064*

#### **Figure 3.**

*TGA thermograms showing the effect of repeated laundering on mass loss (number of washes at 60°C).*

#### **Figure 4.**

*TGA thermograms illustrating the effect of wash temperatures on mass loss after 10 washes.*

#### *5.1.3 Mass loss percentage (%) of unwashed sample vs. multiple washed sample at 60°C*

**Figure 5** shows a transition at around heating temperature of 150°C for the sample at wash temperature 60°C, which is not present for the unwashed sample. The onset degradation for the sample washed at 60°C, differs with a mass loss percentage of 26.12% compared to the unwashed sample. The difference in mass loss is substantial and is due to the PCM capsules being broken at the wash temperature of 60°C and the associated loss of thermoregulating content, whereas with the unwashed sample, the thermoregulating content was unchanged.

#### **Figure 5.**

*TGA thermogram demonstrating mass loss for the unwashed sample and a multiple washed sample at 60°C.*

The mass loss for each degradation phase, indicate that the mass loss is higher for the sample washed at 60°C. The difference in average mass loss between the sample washed at 60°C compared to the unwashed sample is about 9.4%. It is evident that both samples burn out around the same heating temperature of around 500°C, where the ash content can be calculated as a repeatability average of approximately 12.5%.

## **5.2 Differential scanning calorimeter (DSC)**

The DSC analysis is used to assess the melting point, crystallisation, and heat of fusion to determine the change in thermal properties of the PCM due to the different wash temperatures. The DSC analysis results are presented in the form of thermograms as illustrated in **Figures 6**-**8**. The primary focus is to evaluate the effect of

**Figure 6.** *DSC analysis of washed samples (wash temperature 30°C).*

*The Effect of Laundering on the Physical and Thermal Properties of Phase Change Textile… DOI: http://dx.doi.org/10.5772/intechopen.105064*

#### **Figure 7.**

*DSC analysis of washed samples (wash temperature 40°C).*

the different wash temperatures in terms of the heating and cooling peaks of wash temperature (30°C, 40°C and 60°C), also of the samples at 10 washes to observe the worst-case scenario.

**Figure 9** shows 3 distinct melting peaks for each of the samples at wash temperatures (30°C, 40°C and 60°C), these melting peaks are probably related to the molecular structure of the hydrocarbons in the paraffin wax PCM (tetradecane, hexadecane, and octadecane). The main interest is the enthalpy values of the third melting peaks where the enthalpy of the octadecane content changed, indicating phase transition of the PCM from solid to liquid state at a heat temperature of 28°C ± 2°C for all three of the samples at different wash temperatures.

**Figure 8.** *DSC analysis of washed samples (wash temperature 60°C).*

**Figure 9.** *Endothermic results showing the effect of different wash temperatures on the heat flow for samples washed 10 times.*

It is apparent that the heat capacity of 1.8 W/g for the sample washed at 60°C is lower than the sample washed at 30°C, with a heat flow of 2.62 W/g, and for the sample washed at 40°C, with a heat flow of 2.16 W/g. It can be established that the heat loss is greater at wash temperature 60°C, this is due to the loss of thermoregulating content, broken microcapsules, and loss of fibres.

#### *5.2.1 Exothermic results of multiple washed samples at different temperatures*

The crystallisation temperature is defined as the lowest point of the cooling peak. The enthalpy of crystallisation is being determined by the area under the curve. **Figure 10** shows details of crystallisation occurring where the cooling peaks of samples washed at different wash temperatures coincide at heating temperatures of 9°C ± 2°C at wash temperature 30°C, 14°C ± 2°C at wash temperature 40°C and 23°C ± 2°C at wash temperature 60°C.

The primary focus is on the third cooling peaks where the heat flow was at its peak. It can be observed that the sample at wash temperature 60°C has significantly less degree of crystallinity with a heat flow of −0.99 W/g compared to the samples at wash temperature 30°C, where the heat flow is −1.48 W/g, and at wash temperature 40°C, where the heat flow is −1.26 W/g. These results could be explained by leakage or evaporation of paraffin after the rupture of the PCM microcapsules during the laundering process at wash temperature 60°C.

#### *5.2.2 Effect of 10 washes on thermal properties*

The effect of multiple laundering (10 washes at 60°C) on the thermal properties are shown in **Figure 11**. The multiple washing exhibits lower treatment heat capacity and cooling capacity than the unwashed sample. There is a difference of *The Effect of Laundering on the Physical and Thermal Properties of Phase Change Textile… DOI: http://dx.doi.org/10.5772/intechopen.105064*

#### **Figure 10.**

*Exothermic results showing the effect of different wash temperatures on the heat flow for samples washed 10 times.*

**Figure 11.** *Effect of 10 washes at wash temperature 60°C compared to the unwashed sample.*

approximately 50% latent heat capacity between the unwashed sample and the sample washed at 60°C, this is due to the loss of PCM content after 10 wash cycles at a higher wash temperature.

#### **5.3 SEM analysis**

The SEM analysis will discuss the effect of multiple washes at different temperatures on the morphology (shape and size of PCM microcapsule) that was examined by the means of SEM images at different magnifications.
