**7. Textile application**

Since these materials may be in a liquid state, they cannot be easily incorporated into a textile carrier without being contained in capsules, which must be as small as possible to facilitate thermoregulation. Microencapsulation techniques may vary depending on the constitution of the membrane. Nevertheless, they all start with an oil-in-water or water-in-oil emulsion step depending on the solubility of the principle to be encapsulated in one or the other of these phases. In our case, the dispersion of paraffin in water is done by means of a rotor-stator. Microcapsule synthesis is continued by adding a melamine-formaldehyde-based prepolymer and reducing the pH for polycondensation of resin chains around PCM droplets. The formation of the aminoplast shell allows the active principle to be correctly isolated from the external environment and prevents any diffusion, and provides an interesting mechanical and thermal resistance for application on textiles. This in situ polymerization allows the production of microcapsules with a relatively narrow and controlled granulometry, by controlling the different physico-chemical parameters governing the emulsion stages (shear, pH, temperature, surfactants, interfacial tension…) and membrane growth [5, 6, 44].

Regardless of the physical state of the material inside these microcapsules (solid, liquid, or both), it remains trapped inside. This allows it to be integrated into a textile coating or incorporated into different artificial fibre compounds and can be effective as long as the coating or fibres themselves remain intact. For the application of these materials on textiles by bath impregnation, we used a thermodynamic approach to wetting to characterize the textile/binders/microcapsules interfaces. Thus, the comparison of the components of the surface energy of the polyurethane binders with those of the resins forming the membrane of the microcapsules, allowed us to optimize our formulation, before validating it by the ISO 6330 standard.

A 100% cotton fabric (566 dtex warp and 564 dtex weft yarns at densities of 26 ends/cm × 16 picks/cm, weighing 270 g m<sup>−</sup><sup>2</sup> , thickness of 0.50 mm), labelled COT, a 100% polyester fabric (345 dtex warp and 290 dtex weft yarns at densities of 18 ends/cm × ~7 picks cm<sup>−</sup><sup>1</sup> , weighing 178 g m<sup>−</sup><sup>2</sup> , thickness of 0.22 mm) (PES), and a PES nonwoven (155 g m<sup>−</sup><sup>2</sup> ) were chosen as the textile specimens (**Table 2**).

The thermal resistance to exchanges is expressed in m2 °C W<sup>−</sup><sup>1</sup> . The clothing isolation unit used is the clo, defined as the isolation of clothing necessary to maintain the thermal balance of a resting subject exposed to calm air and a temperature of 21°C. In practice, 1 clo corresponds to the isolation provided by classic streetwear and common underwear.

The heat transfer resistance for a sample, including the thin layer of air between the textile and the module, is calculated according to the Eq. (7).

$$R\_t = \frac{(T\_{sk} - T\_a)A}{H} \tag{7}$$

**87**

*Phase Change Materials for Textile Application DOI: http://dx.doi.org/10.5772/intechopen.85028*

**Rt (m2**

 **°C W<sup>−</sup><sup>1</sup>**

*Thermal resistance of the obtained textile samples determined at 21 and 32°C.*

than that of the reference.

**Table 2.**

exploit the results.

containing PCMs than without.

not allow a uniform film to be obtained. Thus, there is a competitive phenomenon between the modification of factors influencing convection, such as the volume, porosity, and geometry of the textile, decreasing the amount of air within the material, and the action of microcapsules containing phase change materials. When the structure is uniformly covered, which is the case for PES1/2-(50) and PES1/2- (101), and that the film is sufficiently impermeable to air, thus to the renewal of the microclimate through the textile, the thermal resistance of the samples is higher

**Sample label Ta = 21°C Tb = 32°C Weight deposited (g m<sup>−</sup><sup>2</sup>**

**Rt (m2**

 **°C W<sup>−</sup><sup>1</sup> )**

**) Rt (clo)**

Pristine cotton 0.070 0.451 0.094 0 COT1/2-(17) 0.068 0.438 0.085 17 COT1/2-(39) 0.069 0.445 0.090 39 Pristine PET 0.071 0.460 0.098 0 PES1/2-(35) 0.068 0.443 0.096 35 PES1/2-(50) 0.074 0.480 0.099 50 PES1/2-(101) 0.068 0.437 0.105 101 Pristine nonwoven 0.093 0.604 0.093 0 NT1/2-(65) 0.094 0.608 0.146 65 NT1/2-(95) 0.089 0.577 0.113 95

**)**

The choice of a process for implementing microcapsules of PCMs on textile support remains a crucial step in the implementation of thermoregulatory structures. The functionalization of nonwoven is an excellent example since it is the structure with the highest % of free volume, its construction is random, and it is the thickest, that is, as much of factors that make the inherent insulating power of air predominate. Thus, whatever the mass deposited, its thermal resistance remains lower than that of the original textile at 21°C. The full bath coating with squeezing not only modifies the porosity of the material but also its compactness, making it difficult to

Therefore, the most suitable process for nonwovens is the lick roller coating. However, the thermal properties of the samples are worse than the reference but higher than those of NT1/2-(95). When analyzing their samples of foam-coated nonwovens and PCM microcapsules, Shim et al. [45] also, reveal that the thermal resistance of their materials reduced to one unit thickness is lower for structures

The evaluation of the thermal behavior of textile structures has shown that it is linked to the deposition process used, the mass deposited, the nature and the context of the textile support used. The modification of the textile fabric structure during impregnations has a significant influence on the thermal behavior of textile composites. Indeed, small deposited masses generate a lower thermal resistance than the reference sample due to the decrease in air permeability. Also, the temperature gradient within the structure influences the loading of MPCMs. Thus, surface impregnation allows a higher rate of active ingredient to be activated over a wider thermal window. Because of the results, it is necessary to deposit a certain amount of MPCMs to compensate for the thermal insulation lost when the context

where Rt is the thermal resistance in m<sup>2</sup> °C W<sup>−</sup><sup>1</sup> , A the surface area in m<sup>2</sup> , Tsk the temperature (35°C), Ta the ambient temperature (°C) and H the heat flow in W.

The coating generates a modification of the surface and the context of the support, thus modifying the transfer of heat flows. Nevertheless, the evolution of Rt as a function of the mass deposited shows, and in particular in the case of cotton, that a low coating makes the textile less insulating and that a minimum quantity is required to reach the level of the reference sample. This characteristic is closely linked to the presence of an uniform or uneven deposition on the surface that modifies the contribution of air, by substituting free volumes with polymer volumes. Indeed, a low rate, as is the case for the COT1/2-(17) and PES1/2-(35) samples, does *Phase Change Materials for Textile Application DOI: http://dx.doi.org/10.5772/intechopen.85028*


#### **Table 2.**

*Textile Industry and Environment*

Since these materials may be in a liquid state, they cannot be easily incorporated into a textile carrier without being contained in capsules, which must be as small as possible to facilitate thermoregulation. Microencapsulation techniques may vary depending on the constitution of the membrane. Nevertheless, they all start with an oil-in-water or water-in-oil emulsion step depending on the solubility of the principle to be encapsulated in one or the other of these phases. In our case, the dispersion of paraffin in water is done by means of a rotor-stator. Microcapsule synthesis is continued by adding a melamine-formaldehyde-based prepolymer and reducing the pH for polycondensation of resin chains around PCM droplets. The formation of the aminoplast shell allows the active principle to be correctly isolated from the external environment and prevents any diffusion, and provides an interesting mechanical and thermal resistance for application on textiles. This in situ polymerization allows the production of microcapsules with a relatively narrow and controlled granulometry, by controlling the different physico-chemical parameters governing the emulsion stages (shear, pH, temperature, surfactants, interfacial tension…) and membrane

Regardless of the physical state of the material inside these microcapsules (solid,

A 100% cotton fabric (566 dtex warp and 564 dtex weft yarns at densities of 26

) were chosen as the textile specimens (**Table 2**).

a 100% polyester fabric (345 dtex warp and 290 dtex weft yarns at densities of 18

lation unit used is the clo, defined as the isolation of clothing necessary to maintain the thermal balance of a resting subject exposed to calm air and a temperature of 21°C. In practice, 1 clo corresponds to the isolation provided by classic streetwear

The heat transfer resistance for a sample, including the thin layer of air between

(*Tsk* − *Ta*)*A*

temperature (35°C), Ta the ambient temperature (°C) and H the heat flow in W. The coating generates a modification of the surface and the context of the support, thus modifying the transfer of heat flows. Nevertheless, the evolution of Rt as a function of the mass deposited shows, and in particular in the case of cotton, that a low coating makes the textile less insulating and that a minimum quantity is required to reach the level of the reference sample. This characteristic is closely linked to the presence of an uniform or uneven deposition on the surface that modifies the contribution of air, by substituting free volumes with polymer volumes. Indeed, a low rate, as is the case for the COT1/2-(17) and PES1/2-(35) samples, does

°C W<sup>−</sup><sup>1</sup>

, weighing 178 g m<sup>−</sup><sup>2</sup>

The thermal resistance to exchanges is expressed in m2

the textile and the module, is calculated according to the Eq. (7).

*Rt* = \_\_\_\_\_\_\_\_\_

where Rt is the thermal resistance in m<sup>2</sup>

, thickness of 0.50 mm), labelled COT,

, thickness of 0.22 mm) (PES), and a

. The clothing iso-

, Tsk the

°C W<sup>−</sup><sup>1</sup>

*<sup>H</sup>* (7)

, A the surface area in m<sup>2</sup>

liquid, or both), it remains trapped inside. This allows it to be integrated into a textile coating or incorporated into different artificial fibre compounds and can be effective as long as the coating or fibres themselves remain intact. For the application of these materials on textiles by bath impregnation, we used a thermodynamic approach to wetting to characterize the textile/binders/microcapsules interfaces. Thus, the comparison of the components of the surface energy of the polyurethane binders with those of the resins forming the membrane of the microcapsules, allowed us to optimize our formulation, before validating it by the ISO 6330

**7. Textile application**

growth [5, 6, 44].

standard.

ends/cm × ~7 picks cm<sup>−</sup><sup>1</sup>

PES nonwoven (155 g m<sup>−</sup><sup>2</sup>

and common underwear.

ends/cm × 16 picks/cm, weighing 270 g m<sup>−</sup><sup>2</sup>

**86**

*Thermal resistance of the obtained textile samples determined at 21 and 32°C.*

not allow a uniform film to be obtained. Thus, there is a competitive phenomenon between the modification of factors influencing convection, such as the volume, porosity, and geometry of the textile, decreasing the amount of air within the material, and the action of microcapsules containing phase change materials. When the structure is uniformly covered, which is the case for PES1/2-(50) and PES1/2- (101), and that the film is sufficiently impermeable to air, thus to the renewal of the microclimate through the textile, the thermal resistance of the samples is higher than that of the reference.

The choice of a process for implementing microcapsules of PCMs on textile support remains a crucial step in the implementation of thermoregulatory structures. The functionalization of nonwoven is an excellent example since it is the structure with the highest % of free volume, its construction is random, and it is the thickest, that is, as much of factors that make the inherent insulating power of air predominate. Thus, whatever the mass deposited, its thermal resistance remains lower than that of the original textile at 21°C. The full bath coating with squeezing not only modifies the porosity of the material but also its compactness, making it difficult to exploit the results.

Therefore, the most suitable process for nonwovens is the lick roller coating. However, the thermal properties of the samples are worse than the reference but higher than those of NT1/2-(95). When analyzing their samples of foam-coated nonwovens and PCM microcapsules, Shim et al. [45] also, reveal that the thermal resistance of their materials reduced to one unit thickness is lower for structures containing PCMs than without.

The evaluation of the thermal behavior of textile structures has shown that it is linked to the deposition process used, the mass deposited, the nature and the context of the textile support used. The modification of the textile fabric structure during impregnations has a significant influence on the thermal behavior of textile composites. Indeed, small deposited masses generate a lower thermal resistance than the reference sample due to the decrease in air permeability. Also, the temperature gradient within the structure influences the loading of MPCMs. Thus, surface impregnation allows a higher rate of active ingredient to be activated over a wider thermal window. Because of the results, it is necessary to deposit a certain amount of MPCMs to compensate for the thermal insulation lost when the context

is modified. Indeed, this modification during the coating with the binder and microcapsules reduces the porosity of the material. Thus, from higher mass deposits, the thermoregulatory effect of MPCMs is perceptible and allows to improve thermoregulation. Nevertheless, the optimization of the binder/microcapsule ratio is essential to more explicitly quantify the role played by these two elements in the perceived effect.
