Technical Field

The present invention relates to a textile product containing phase change material and a method for obtaining thereof which perform dynamic heat management by means of nanofiber webs being capable of heat management in low temperature (T<18°C) and/or normal temperature (18°C<T<43°C) and/or high temperature (43°C<T<70°C) regions.

Background of the Invention

Smart material is defined as a material that can detect environmental stimulants such as temperature change, light, moisture and react to these stimulants, and can change itself according to external ambient conditions. Whereas dynamic heat management is a new concept used in heat exchange of various systems with the environment. Functional materials that store heat and regulate temperature can be used for the purpose of heat management. “Smart” textiles being capable of dynamic heat management and sensitive to temperature changes of the environment are functional textile products that are used in clothing systems; textile products such as tents, blankets, etc. for protection against cold and hot environments; buildings; automotive, space industry; biomedical applications; applications of temperature sensitive packaging, solar energy panels, etc.

In the development of clean energy technologies, the demand for high- performance materials is rapidly increasing for the purpose of thermal energy management. Thermal energy storage (TES) is a method that has a great potential for different thermal applications. Creation of composite systems that can absorb heat from the environment when the ambient temperature rises, store the energy it absorbs and dissipate heat to the environment when the ambient temperature decreases by utilizing high heat absorption and release capacities of materials called as “phase change material (PCM)” in the phase change processes is one of the active or dynamic heat management methods by TES. PCMs are inorganic or organic substances capable of performing repeated conversion between solid- liquid or solid-solid phases. Today, there are more than five hundred PCMs known as synthetic or natural. These materials vary by their phase change temperatures or thermal capacities. Addition of PCMs to the final product is a challenging application issue. Solid-liquid PCMs are introduced into an organic or inorganic carrier material added to the structure directly, in order to perform dynamic heat management in various systems. Thereby, their thermal properties can be utilized. Various methods are tried and applied so as to perform dynamic heat management with solid-liquid organic PCMs in textiles. PCMs are expected to improve heat management of textile materials; repeatability of the heat absorption and release process; to prevent PCMs from evaporating, melt flowing and mixing into textile structure; to improve their thermal stability, thermal conductivity properties; and not to affect mechanical properties and other quality properties of the final product adversely as well. Therefore, there is need for developing PCMs, increasing their applicability and energy conversion efficiency and products to provide these and methods for obtaining thereof.

The Chinese patent document no. CN105237680, an application in the state of the art, discloses a method comprising steps for preparation of solid-solid phase change material with a cross-linked structure which controls heat absorption and release to improve energy use. A higher fatty alcohol and maleic anhydride are used as raw materials in order to synthesize maleic acid bis-fatty fatty alcohol ester via esterification reaction by melting it. Then, maleic acid bis higher fatty alcohol ester is heated, melted and triallyl isocyanurate is added. A molten reaction method is used to obtain a solid-solid phase change material with a cross- linked structure under initiator, nitrogen protection. Preferably, the higher fatty alcohol is tetradecanol, cetyl alcohol or stearyl alcohol. More preferably, the initiator is benzoyl peroxide or azobizobutyronitrile.

The United States patent document no. US7790283, another application in the state of the art, discloses a fabric providing thermal regulation. The said fabric comprises a set of cellulosic fibers. The cellulosic fiber consists of a fiber body comprising a cellulosic material and a set of microcapsules. The microcapsule set has a latent heat of at least 40 J/g and a transition temperature in the range of 0° C to 100° C. The phase change material provides thermal regulation and has the ability to absorb and release thermal energy under different environmental conditions. There is a containment structure that encapsulates, absorbs this phase change material regulating temperature. The containment protects the phase change material and facilitates its handling. These cellulosic fibers are included in various products in order to provide thermal regulation. The protect can be used in textiles, medical products, personal hygiene products, containers and packagings.

Summary of the Invention

An objective of the present invention is to realize a textile product and a method for obtaining thereof which comprise a thermally stable and non-toxic phase change material which does not lose its high heat capacity at different molecular weight and chain length.

Another objective of the present invention is to realize a textile product and a method for obtaining thereof which enable dynamic heat management in low, normal and high temperature regions.

Detailed Description of the Invention “A Textile Product Containing Phase Change Material and a Method for Obtaining thereof’ realized to fulfil the objectives of the present invention is shown in the figures attached, in which:

Figure l is a flow diagramof the inventive method.

Figure 2 is a view of a reaction that takes place when obtaining the inventive fatty alcohol maleic acid.

Figure 3 is a view of a reaction that takes place when obtaining the inventive fatty alcohol-g-PAN (poly acrylo nitrile).

Figure 4 is a SEM view of the inventive hexadecanol-g-PAN and %6 PAN solution and fiber diameter distribution histogram of the SEM image. Figure 5 is a view showing the layers of the inventive textile product.

The components illustrated in the figures are individually numbered, where the numbers refer to the following:

100. Method

A: maleic anhydride (MAH)

B: p-toluene sulfonic acid (PTSA)

C: maleic acid

D: fatty alcohol which is at least one of decanol, dodecanol, tetradecanol, hexadecanol, octadecanol E: fatty alcohol-melaic acid F : acrylonitrile (AN)

G: azobisisobutyronitrile (AIBN)

H: fatty alcohol-g-PAN (poly acrylo nitrile) copolymer

I: textile layer

II: fusible interlining

III: web with fatty alcohol-g-PAN and PAN nanofiber structure The inventive method (100) used for obtaining a textile product containing phase change material comprises steps of: obtaining fatty alcohol maleic acid by esterification reaction from fatty alcohol (101); obtaining fatty alcohol-g-PAN from fatty alcohol maleic acid ester by free radical polymerization (102); obtaining composite nanofiber from fatty alcohol-g-PAN and PAN mixtures by electrospinning (103); and adding webs with fatty alcohol-g-PAN/PAN nanofiber structure to textile products (104).

At the step of obtaining fatty alcohol maleic acid by esterification reaction from fatty alcohol (101) of the inventive method (100); a certain amount of fatty alcohol (D) that is at least one of decanol, dodecanol, tetradecanol, hexadecanol, octadecanol and a stoichiometric amount of maleic anhydride (MAH) (A) are taken into a three-neck reaction flask at first and a condenser assembly is prepared. The temperature is gradually increased to range of 65°C-75°C in the inert environment in the three-necked reaction flask and the reactants are dissolved in acetone p-toluene sulphonic acid (PTSA) (B) catalyst is added to the reaction flask up to 2% by mass of the reactant amount after completion of the dissolution. Maleic anhydride (A) is converted into maleic acid (C) by catalyst (B). The reaction between fatty alcohol (D) and maleic acid (C) is continued at 950-1050 rpm (revolutions per minute) for 22-26 hours at the same temperature and in inert atmosphere (The reaction taking place in the reaction flask is shown in Figure 2). The reaction solution is precipitated in distilled water and filtered at the end of the period. Non-reacting reactants are removed by washing the precipitate with distilled water at least three times. Then, the fatty alcohol-MA complex is poured into petri dish and dried upon being kept at room temperature overnight and fatty alcohol-MA (E) is obtained. Details about the transesterification reaction conditions applied for obtaining fatty alcohol-MA (maleic acid) (E) and the amount of materials used are given in Table 1. Table 1. Transesterification reaction conditions applied for obtaining fatty alcohol-MA and the amounts of the materials used

Fatty PTSA

Alcohol MAH (catalyst) Rxn Mixing Ti amount amount amount T speed me

Ester (mole) (mole) (g) (°C) (rpm) (h)

Decanol-MA 4.0xl0 ² 4.0xl0 ² 0.205 ~ 1000 24

Dodecanol-MA 4.0xl0 ² 4.0xl0 ² 0.227 70 1000 24

Tetradecanol-MA 4.0xl0 ² 4.0xl0 ² 0.250 70 1000 24

Hexadecanol- MA 4.0xl0 ² 4.0xl0 ² 0.272 70 1000 24

Octadecanol-MA 4.0x1 O ² 4.0x1 O ² 0.295 70 1000 24

At the step of obtaining fatty alcohol-g-PAN from fatty alcohol maleic acid ester by free radical polymerization (102); a certain amount of fatty alcohol-MA (E) ester is dissolved in 25 mL DMAc (dimethylacetamide) solvent in the range of 55°C-65°C. Acrylonitrile (AN) (F) is added to the solution such that stoichiometric ratio will be 1:1. Inert gas is passed through the reaction flask for 25-35 minutes and it is continued to mix at the same temperature. Azobisisobutyronitrile (AIBN) (G), which is used as initiator, is added to the reaction flask up to 0,1% by weight of the acrylonitrile (F) amount at the end of the period. The reaction is continued under condenser by increasing the temperature to the range of 65°C-75°C and mixing at 450-550 rpm for 46-50 hours in inert atmosphere (The reaction taking place in the reaction flask is shown in Figure 3). At the end of the period, the solution cooled to room temperature is precipitated in distilled water. Non-reacting reactants are removed by washing the resulting precipitate with distilled water at least three times and fatty alcohol-g- PAN copolymer (H) is obtained by allowing it to dry at room temperature. Details about the reaction conditions applied in fatty alcohol-g-PAN copolymer (H) synthesis by free radical polymerization method and the amounts of starting materials used are given in Table 2. Table 2. The reaction conditions applied in fatty alcohol-g-PAN copolymer synthesis by free radical polymerization method and the amounts of starting materials used

Fatty AN AIBN Mixing

Rxn Time

Alcohol- m (catalyst) speed

Copolymer T(°C) (h) MA g) m (g) (rpm)

Decanol-g-PAN 3.00 3.00 0.003 70 500 48

Dodecanol-g-PAN 3.00 3.00 0.003 70 500 48

Tetradecanol-g-PAN 3.00 3.00 0.003 70 500 48

Hexadecanol-g-PAN 3.00 3.00 0.003 70 500 48

Octadecanol-g-PAN 3.00 3.00 0.003 70 500 48

Phase change temperature ranges and heat capacities of the fatty alcohol-g-PAN copolymers (H) and the fatty alcohols (D) that are their starting raw materials resulting at the end of the step of obtaining fatty alcohol-g-PAN from fatty alcohol maleic acid ester by free radical polymerization (102) of the inventive method (100), are determined by differential scanning calorimetry device (DSC) in the 10 ^th heating-cooling cycle are shown in the Table 3. It is observed that fatty alcohol-g-PAN (H) solid-solid phase change materials -DSC results of which are obtained- have properties suitable for dynamic heat management studies in low (T<18°C) and/or normal (18°C<T<43°C) and/or high temperature

(43°C<T<70°C) regions, fatty alcohols (D) are successfully grafted into the copolymer structure and fatty alcohol-g-PAN copolymers (H) that can change solid-solid phase maintain their thermal properties in heating cooling cycles. In addition, FTIR, 1H-NMR and 13C-NMR measurement results of the fatty alcohol-g-PAN copolymers (H) synthesized prove that fatty alcohol oligomers (D) are grafted to acrylonitrile (F) chemically and show that copolymers can preserve their structure up to 400°C without degradation.

Table 3. Phase change temperature ranges and heat capacities of fatty alcohols and Fatty Alcohol-g-PAN copolymers by DSC in the 10 ^th heating-cooling cycle.

10. Cycle

10. Heating 10. Cooling

DΪΐ DH

(Jg ¹ ) (Jg ¹ ) (> ₀ ) Tbeg-Tena (°C) (<0)

Decanol (Cio) 4—16 203 2 — 8 205

Decanol-g-PAN 3— 28 108 2 — 21 85

Dodecanol (C12) 23—32 188 20—12 187

Dodecanol-g-PAN 22—29 81 -6 — 11 61

TetadecanoiTCw) 36-45 241 32-22 242

Tetradecanol-g-PAN 34—60 109 29—14 117

^H ^^ ⁿ a ciD 48-60 228 47-34 225

Hexadecanol-g-PAN 45—60 165 30—23 114 255 53-35 255

Octadecanol-g-PAN 40-70 83 42-35 85

At the step of obtaining composite nanofiber from fatty alcohol-g-PAN and PAN (poly acrylo nitrile) mixtures by electrospinning (103) of the inventive method (100); 10 g fatty alcohol-g-PAN (Decanol-g-PAN, Dodecanol-g-PAN, Tetradecanol-g-PAN, Hexadecanol-g-PAN and Octadecanol-g-PAN) (H) is added into 10 g of 6% PAN solution in DMAc at first, the mixture is mixed at 450-550 rpm for 8-12 minutes and a single shell solution is formed. The flow rate of the shell solution through the injector is determined by monitoring the Taylor cone formation and nanowebs consisting of hollow nanofibers are produced by pumping air from the inner injector at a rate of a ¹ , while the shell solution is being pumped from the external injector. Biaxial electrospinning parameters and experimental conditions optimized for fatty alcohol-g-PAN nanoweb production are included in Table 4. Phase conversion properties of the samples with Al, A2, A3, A4 and A5 code -which are produced from shell solutions of fatty alcohol-g- PAN and 6PAN mixture- measured by DSC in the 10 ^th heating-cooling cycle are summarized in Table 5.

Table 4. Biaxial electrospinning parameters and experimental conditions optimized for fatty alcohol-g-PAN nanoweb production

Shell Core pump pump speed speed

Shell mixture

(mLmin (mLmin T Time Specimen (1:1 by weight) Core (°C) (min)

A1 Decanol-g-PAN and 6% PAN Air 0.03 0.01 10.0 10.0 25 60 A2 Dodecanol-g-PAN and 6% PAN Air 0.03 0.01 9.0 8.0 25 60 A3 Tetradecanoi-g-PAN and 6% PAN Air 0.03 0.01 9.0 9.0 25 60 A4 Hexadecanol-g-PAN and 6% PAN Air 0.03 0.01 9.0 8.0 25 60 A5 Octadecanol-g-PAN and 6% PAN Air 0.03 0.01 9.0 9.0 25 60

Table 5. Phase conversion properties of Fatty Alcohol-g-PAN and 6PAN mixture nanowebs measured by DSC in the 10 ^th heating-cooling cycle

10. Heating 10. Cooling

DH DH

Sample Tbeg Tend (Ί g ' ) Tbeg Tend (Jg ' )

A2 22 30 42 -7 -15 30

A3 36 63 56 28 12 58

A4 46 63 82 30 21 65

A5 48 72 42 40 33 45 At the step of obtaining composite nanofiber from fatty alcohol-g-PAN and PAN (poly acrylo nitrile) mixtures by electrospinning (103) of the inventive method (100); SEM image of a sample with code A4 prepared from one-to-one mixture of hexadecanol-g-PAN and %6 PAN solution and fiber diameter distribution histogram of SEM image are shown in the Figure 4. These fibers have a cylindrical, smooth-surface, knot-free structure and they are approximately 78 pm in length. Fiber diameter distribution below 500 nm indicates a fiber formation that is inclined to left, very fine and fine fiber formation. Average fiber diameter is calculated as 186 ± 121 nm. Solid-solid phase change temperature range of the specimen with A4 code -that is quite successful in terms of nanofiber formation- in the 10 ^th heating cycle measured by DSC is measured as 46°C-63°C and its heat capacity is measured as 82 Jg-1 and its solid-solid phase change temperature range in the 10 ^th cooling cycle is measured as 30°C-21°C and its heat capacity is measured as 65 Jg ¹ . Leftward shifts observed in the cooling cycle are compatible with the over-cooling tendency of pure copolymers.

In all specimens created at the step of obtaining composite nanofiber from fatty alcohol-g-PAN and PAN (poly acrylo nitrile) mixtures by electrospinning (103) of the inventive method (100); tendency of the solid-solid phase conversion from less regular structure to regular crystalline structure to shift to low temperature range in cooling cycles and the fact that less amount of heat release compared to heating cycles do not change the phase conversion temperature range of nanoweb specimens in heating cycles and the heat capacity. The fact that no change occurs in the phase change temperature ranges and the heat capacity in the 10 ^th heating cooling cycles show that samples are thermally stable and indicate that they are suitable for repeated use.

At the step of obtaining composite nanofiber from fatty alcohol-g-PAN and PAN (poly acrylo nitrile) mixtures by electrospinning (103) of the inventive method (100); thermally stable structures are obtained wherein heat capacities of the nanofiber webs formed are in the order of 42—82 Jg-1, their fiber lengths are 70-100 mih, fiber diameters range from 186-277 nm, the length/width ratios are 300 times and more and which have characteristic of performing smooth, cylindrical, hollow, thermal cycling and also which are thermally stable.

At the step of adding webs with fatty alcohol-g-PAN/PAN nanofiber structure to textile products (104) of the inventive method (100); a multilayer textile product is obtained. While preparing the layered textile product, the web with fatty alcohol-g-PAN and PAN nanofiber structure (III) is inserted between two thin layers of fusible interlining (II) at first. Then this structure (II-III-II) is laid between two textile layers (I). In a preferred embodiment, the textile layer (I) can be a layer prepared from cotton/wool/synthetic polymer/biopolymer based woven fabric or nonwovens or felt layers prepared from these starting materials specified. The sample (I- II-III-II-I) prepared as in Figure 5 is taken between wax paper and removed through the cylinders after being kept for 20-28 seconds under a pressure of 2.5 bars in a rotating cylinder system that is pre-adjusted to a temperature in the range of 125°C-140°C. The fact that textile composite samples consisting of fatty alcohol-g-PAN and PAN nanoweb that is fixed between two textile surfaces by fusible interlining have heat capacities of 30-65 J/g and their heat absorption- release temperature ranges, thermal stabilities, impermeability properties, high thermal insulation and high thermal effusion values, and exhibit viscoelastic and elastic deformation are found favourable for applications to be carried out in low (T<18°C) and/or normal (18°C <T<43°C) and/or high (43°C<T<70°C) temperature ranges with engineering stress values of 150 MPa and above.

With the use of webs with fatty alcohol-g-PAN/PAN nanofiber structure obtained by the inventive method (100) in textile products, it is not necessary anymore to cover phase changing materials with shell material and the phase changing material is prevented from dispersing in the main material, evaporating and reacting with the external environment. Additionally, heat transfer area is extraordinarily increased thanks to the very thin nanofiber structure. In addition, it is easily applied to textile structures without hindering the basic properties of textile products while nanoweb volumes containing phase changing material remain fixed and it does not affect normal conditions of use.

The textile product which is obtained by the inventive method (100), has a fatty alcohol-g-PAN and PAN nanoweb (III) fixed between two textile layers (I) by fusible interlining (II) and a textile layer (I) located on the upper surface of the nanoweb (III) can be used for providing dynamic heat management in low (T<18°C) and/or normal (18°C<T<43°C) and/or high temperature (43°C<T<70°C) ranges.

The textile product containing web with fatty alcohol-g-PAN/PAN nanoweb structure obtained by the inventive method (100) can be used as inner packing material in transport boxes of medical products and biomedical products such as medicine, blood and blood derivatives, serum that should be stored and transported below a certain temperature (2°C<T<18°C); in storage and transport containers (T<0°C) of ready-made foods such as ice cream, cooked fish and meat and cold drinks; cryogenic temperature control devices operating by the thermoelectric principle in electronic and biotechnology industries; cold therapy materials; for reducing the energy consumed with the purpose of cooling in air- conditioning systems; in biomedical materials intended for thermal therapy; in wearable thermal sensors; in cold and hot climate sportswear; for utilizing solar energy; in thermoelectric system designs and in electronic circuit protections.

Within these basic concepts; it is possible to develop various embodiments of the inventive method for obtaining a textile product containing phase change material (1); the invention cannot be limited to examples disclosed herein and it is essentially according to claims.