Patent Application
20230203358
This invention relates to phase change materials (PCMs) and the preparation method thereof. More particularly, the present invention relates to biocompatible complexes of phase change materials and polysaccharides and to a method for preparing complexes comprising PCMs and polysaccharides.
Polysaccharides, as carbohydrates consisting of long chains of simple sugars, are derived from renewable sources, such as plant cell walls and microorganisms, and are utilized for diverse applications in different industries, to name a few food, textile, paper, cosmetics and biomedical. They have been also employed as water superadsorbents and adsorbents for the separation of substances present in aquatic environment, i.e. water treatment. The industrial use of these versatile carbohydrates relies on their functional features e.g. stabilizing, thickening, chelating, emulsifying, encapsulating, swelling and gel forming properties. Intrinsic characteristics of biocompatibility, biodegradability, bioadhesivity, nontoxicity, natural-availability and cost-effectiveness further account for the increasing interest on environmental applications of polysaccharides [1].
Polysaccharides are categorized as storage, e.g. starch and guar gum, structural, e.g. cellulose and chitin, and bacterial, e.g. alginic acid (alginate) and xanthan gum. For example, alginate, derived from different species of seaweed (brown algae), is a polyanionic polysaccharide, formed from linear chains of guluronic acid and mannuronic acid residues. Alginate is vastly utilized for its unique bio-colloidal properties such as solution thickening, suspension/emulsion stabilizing, and gelling in e.g. food, textile, paper, and pharmaceutical industries. Furthermore, it can undergo complexation with di/multivalent cations such as calcium and magnesium, which results in mechanical/structural improvement [2, 3].
Xanthan gum is another bacterial, acidic polysaccharide secreted by Xanthomonas campestris bacteria (industrially produced from glucose through fermentation by the microorganism). It is made of the β-D-(1, 4)-glucose backbone chain with a trisaccharide side-branch that consists of β-D-(1, 2)-mannose, β-D-(1, 4)-glucuronic acid, and β-d-mannose. Xanthan gum shows high stability under harsh conditions such as acidic, high salinity, high shear stress, and thermal hydrolysis, better than many synthetic polymers, possibly due to its ordered helical structure [4].
Starch is an abundant and inexpensive storage polysaccharide. Starch and cellulose consist of glucose units, linked through, respectively, α-(1, 4)- and β-(1, 4)-glycosidic bonds [1, 5]. Starch contains linear amylose units and highly branched non-linear amylopectin. Cellulose and chitin are, respectively, the first and second most abundant structural polysaccharides, serving different functions including reinforcement and strength to the endoskeleton of e.g. plants and crustaceans [6, 7].
Wood-based cellulose pulp is the main resource for paper production. Chitin, which is rich in nitrogen, originates in the exoskeletons of marine crustaceans, shellfish, and insects as well as some fungi and microorganisms. The primary and secondary hydroxyl and amine functional groups in its molecular structure enable various chemical modifications for the desired applications. Deacetylation of chitin by alkaline treatment results in chitosan containing randomly distributed units of β-(1, 4)-linked D-glucosamine and N-acetyl-D-glucosamine. As a polycationic linear polysaccharide, chitosan has wide range of applications in e.g. agriculture, food, water treatment, biomedical, pharmaceutical industries [8-10].
Thus, polysaccharides from renewable agro-resources provide great potential to develop novel bio-based recyclable materials suitable for a variety of environmentally benign applications, hence reducing the dependency on fossil fuels and associated environmental concerns [11].
Likewise, there is a growing interest on phase change materials (PCMs) for their inherent temperature regulative and heat storage characteristics. Phase change phenomenon, for example from a solid to a liquid state and vice versa, involves a relatively significant amount of heat exchange with the surrounding environment resulting in temperature stabilization. PCMs can therefore absorb, store and release large quantities of heat (thermal energy), which make them suitable for temperature regulation (heating and cooling) and heat storage applications. Furthermore, as the temperature of charging and discharging heat to the PCMs remain constant, i.e. a constant temperature of fusion, PCM-based heat storage can benefit specific applications requiring constant working temperature.
For this, PCMs have be employed in a variety of applications including temperature responsive textiles, thermally active packaging, thermal protection in electronics, energy-positive buildings, air-conditioning, cooling, domestic hot water production, and solar heating system etc. [12-15].
However, the most critical limiting factors linked to the real-world use of PCMs are the useful life cycle of PCM-container systems, fluidity/leakage in the melt state, phase separation, poor thermal stability, undesired heat release, and corrosion between the PCM and the container that causes the necessary use of special devices, which in return will increase the associated cost. Thus, the application of PCMs usually requires a method to thermally and structurally stabilize their thermophysical properties, to prevent their fluidity as leakage in their melt phase and to control their volume change during the phase change process.
Shape-stabilization, encapsulation and confinement by support materials such as polymers, minerals, porous carbons and metals have been devised to overcome these issues linked to the applicability of PCMs. PCMs are commonly used, for example, in the form of capsules in the heat storage containers. The encapsulation material and PCMs need to be chemically and structurally compatible within the working temperature range without experiencing deformation and thermal degradation [14, 16-18].
U.S. Pat. No. 6,689,466 to Hartmann [19] introduces stabilized phase change compositions consisting of a PCM and a stabilizing agent such as antioxidants and thermal stabilizers. Hartmann discloses the application of their stabilized PCM composition in temperature regulative synthetic fibres, fabrics and textiles.
U.S. Pat. No. 6,183,855 to Buckley [20] introduces a flexible composite material comprising a PCM within a flexible matrix, with proposed applications in wearables for heating or cooling purposes.
European Pat. No. 1838802 B1 to Rolland and Reisdorf [21] relates to a material composition comprising a PCM (20-80 wt %) and one or more low polarity synthetic polymers (20-80 wt %) selected from for example very low density polyethylene, ethylene propylene rubber, and styrene copolymers. They disclose the PCM compositions for various thermal applications e.g. in constructions, automotive, packaging, and garments.
U.S. Pat. No. 5,916,477A to Kakiuchi et al. [22] discloses a heat storage/heat radiation method comprising a sugar alcohol heat storage material in an apparatus under an oxygen depleted atmosphere. They introduce the method as a preventive approach for oxidation of sugar alcohols duo to low thermal stability during repeated heating and cooling cycles which causes gradual decrease of fusion latent heat.
U.S. Pat. No. 5,785,885A to Kakiuchi et al. [23] discloses a heat storage material composition including one/more sugar alcohol e.g. erythritol, mannitol and galactitol, and a sparingly soluble salt. The role of the salt is explained as a supercooling inhibitor for a reproduceable crystallization.
U.S. Pat. No. 6,108,489A to Frohlich, Koellner and Salyer [24] discloses a heating device for food and other products, which include a unit containing a phase change material, which is capable of being charged with thermal energy.
After charging with heat, the PCM-incorporated device releases heat to keep foods and other objects warm. U.S. Pat. No. 5,370,814A to Salyer [25] discloses a powdered mixture of a PCM and silica particles. They disclose the usage of the mixture in different articles such as medical wraps, tree wraps, garments, blankets, and temperature sensitive articles e.g. aircraft flight recorders. US Pat No. 20020033247A1 to Neuschutz and Glausch [26] discloses usage of PCMs in heat sinks for electronics for thermal shock protection.
The advantages and the drawbacks of PCMs in practice are well-stablished knowledge. In order to be applicable, PCMs require one or more supporting elements to improve and/or to solve the linked issues or simply enhance and create new functionality. Considering the principles of sustainability and green chemistry, important inherent characteristics of materials such as renewable against finite, benign against hazardous, and biodegradable against non-degradable need to be addressed from the design stage with the raw materials to manufacturing and the final products [27].
While synthetic polymers have been vastly utilized as supporting materials for stabilization and encapsulation of PCMs, polysaccharides, natural/bio polymers originating from renewable sources have remained underused for this purpose. Due to the increasing environmental concerns, utilization of greener eco-friendly materials is getting increasingly essential, especially, for industries previously relaying on nondegradable polymers in their products and precursors. Synthetic petrochemical based polymers are less preferred compared to polysaccharides, which are derived from plants and/or microorganisms with intrinsic properties of biocompatibility, biodegradability and non-toxicity, especially in the eyes of environmentally conscious consumers [28].
U.S. Pat. No. 6,765,042 B1 to Thornton et al. [29] discloses a process for producing an acidic polysaccharide-based superabsorbent, comprising one/more polysaccharides with acidic functional groups, e.g. carboxymethyl cellulose and/or 6-carboxy starch, crosslinked by a crosslinking agent, to be used for odor control of malodorous fluids.
US Pat. No. 0023658 A1 to Stroumpoulis and Tezel [30] discloses tunably cross-linked biocompatible polysaccharide compositions, in particular, compositions of hyaluronic acid gels that are cross-linked with a multifunctional crosslinker, and the methods of making such cross-linked hyaluronic acid gels. There are several affecting factors on the functional properties of polysaccharide-based super-adsorbents, e.g. swelling and fluid retention capacity, include hydrophilicity, crosslinking density, and ionic strength [31].
However, covalent cross-linking agents pose the risk of toxicity and reduced swelling fluid retention properties [32]. On the contrary, ionic agent bridges between the polysaccharide macromolecule through reversible ionic bonds, resulting in easy reconfiguration and tunable physical properties and self-healing from physical damage, unlike chemical crosslinking through irreversible covalent bonds. Polysaccharides provide numerous non-covalent secondary interactions, mainly intra and inter-chain hydrogen bonding, defining their solubility in the surrounding environment. Ionic interactions, ion-binding and ion-complexation also play a key role in creating and modifying polysaccharide based materials [33].
For example, water molecules exist in different states of binding in the phase transition region surrounding a polysaccharide macromolecule: (i) strongly attached water that is incapable of phase transition, (ii) moderately attached water undergo phase transition and (iii) bulk and capillary water filling the pores in the fibrous structure [33, 34].
It is an aim of the present invention to provide novel temperature responsive phase change bio-complexes (PCBC) with tunable thermophysical properties.
It is another aim of the present invention to provide a preparation method thereof.
The present phase change bio-complexes comprise a phase change material (PCM) (or mixture of PCMs) and a polysaccharide (or combination of polysaccharides).
The polysaccharide provides mechanical and thermal stabilization and the PCM provides temperature responsive properties to the complexation. In order to undergo complexation with polysaccharides, sugar alcohols and salt hydrates classifications of PCMs are preferred which results in compatibility and homogeneity of the bio-complexes.
In the method, complexes comprising PCMs are prepared in the presence of polysaccharides, thus forming a temperature responsive network or “bionetwork” entrapping the PCM due to their compatible intermolecular interactions, which results in thermal and structural stabilization.
The thermophysical properties of the bio-complexes may be tuned through molecular interactions and complexations such as ionic interaction by addition of mono- and/or multivalent cations and/or salts of an acid. Incorporation of di/multivalent cations, i.e. alkaline earth and transition metal ions, in the complexation may also provide added strength.
More specifically, the present invention is mainly characterized by what is stated in the independent claims.
Unlike previously reported polymers as stabilizing agent of PCMs, which often require petroleum-based hazardous monomers, polymerization reaction, covalent toxic crosslinkers, and hazardous explosive initiators with high-demanding safety precautions, the phase change bio-complexes of present invention are composed of bio-compatible and nontoxic feedstock such as polysaccharides from agro-recourses such as plant and bacteria and food-grade salts.
Compared to previously stabilized PCMs, the phase change bio-complexes provide high-heat storage capacity (latent heat charge and discharge) due to embedding high content of PCM. Solid-to-gel transition provides the bio-complexes with structural-stability and leakage-preventive properties of the PCM in the melt state owing to the stabilizing and gel-forming properties of the polysaccharide.
The phase change bio-complexes may be used repeatedly in the view of thermal and mechanical stability. The phase change complexes may be prepared through simple blending in water and/or water-miscible solvents. The phase change bio-complexes may be processed through different methods such as casting, spinning, additive manufacturing, freeze-drying and moulding, to prepare articles in different forms e.g. films, pellets, sheets, beads, sponges, filaments, papers etc. providing tunable temperature-reversible properties.
The phase change bio-complexes can be used in highly concentrated liquid and/or gel forms as well as fully dehydrated forms. The phase change bio-complexes can be applied for thermal management purposes e.g. heat storage and thermal protection via heat absorbing-releasing, for instance in building, packaging, electronics, temperature sensitive items (black boxes), tree wraps and wearables.
The preparation and processing are entirely aqueous and with environmentally benign feedstock resulting in efficient sustainable production of the bio-complexes. The method is conducted in the presence of an ionic agent, for example, but not limited to, salts of an acid such as citric acid and/or di/multivalent cations such as calcium, magnesium, iron etc. acting as chelating/complexation agent for tuning the thermophysical properties of the compositions including structural-stability and the phase change temperatures and latent heat of fusion.
The presence of alkali metal ions e.g. sodium increases the reactivity and swelling properties of polysaccharides in the bio-complexes so that it can be loaded with high content of PCM. The alkaline earth and/or transition metal ions act as chelating agent bridging between different chains of polysaccharides and ligands for PCM molecules. The bio-complexes provide highly repeatable and tunable thermophysical properties including glass transition, solidification and melting temperatures and fusion enthalpy and structural stabilization.
Addition of multivalent cations, such as alkaline earth metal ions, may also provide additional mechanical strength to the bio-complexes. Due to the miscibility of the incorporated compounds, the complexes show homogeneous structure in both solid and melt states of the phase change compound. The phase change bio-complexes can be easily processed in different structurally stable articles for example, but not limited to, powder, granules, beads, sheets, films etc. and applied for thermal management purposes in thermal energy storage and protection via latent heat of fusion. The design, preparation, processing and final bioproducts disclosed in present invention fulfil both the function and the principles of sustainability and green chemistry such as renewability, nontoxicity, and biodegradability.
The current invention discloses that natural polysaccharides in various available forms, including powder, fibres, and particulates, enable thermal and structural stabilization of PCMs, preferably from sugar alcohols and salt hydrates categories, due to providing high miscibility and molecular-level interactions.
The mechanism of stabilization would seem to rely on complexation of polysaccharides with the smaller molecules of the PCMs which is assisted by the presence of an ionic agent such as salt of an acid, e.g. sodium citrate, sodium tripolyphosphate, and/or di/multivalent cations e.g. calcium, magnesium, and other metal ions.
The thermal properties of the developed bio-complexes can be tuned by adding the ionic agents. The disclosed bio-complexes may be applied for sustainable and stabilized thermal management applications including heat storage and thermal protection.
The novel bio-products of the present invention provide added benefits and open new applications for the complexes of polysaccharides and phase change materials in thermal energy storage and conservation, thermal protection of electronics and temperature sensitive items e.g. black boxes and in a broader view cosmetics, textiles, packaging and other environmentally friendly applications.
As used herein, the term “average molecular weight” refers to a weight average molecular weight (also abbreviated “Mw” or “Mw”).
Unless otherwise indicated, the molecular weight has been measured by gel-permeation chromatography using polystyrene standards.
As used herein, the complexes provided are also referred to as “bio-complexes” to denote that at least some of the components thereof are biocompatible or of non-synthetic origin. Examples of such components are polysaccharides.
As will appear, in embodiments, the present phase-change complexes or “bio-complexes” are typically composed of bio-compatible and nontoxic feedstock, such polysaccharides from agro-recourses such as plant and bacteria and food-grade salts.
Unless otherwise stated herein or clear from the context, any percentages referred to herein are expressed as percent by weight based on a total weight of the respective composition.
The phase change bio-complexes comprise, consist of, or consist essentially of a phase change material (PCM) (or mixture of PCMs) and a polysaccharide (or combination of polysaccharides). The polysaccharide provides mechanical and thermal stabilization and the PCM provides temperature responsive properties to the complexation.
In order to undergo complexation with polysaccharides, sugar alcohols and salt hydrates classifications of PCMs are preferred which results in compatibility and homogeneity of the bio-complexes. Addition of multivalent cations (for example in the form of water soluble salts) and/or salts of an acid tunes the thermophysical properties of the bio-complexes, such as tunable temperature and latent heat of fusion and structural and thermal stability.
In embodiments of the present technology, polysaccharides are introduced as sustainable and biocompatible support matrices for the PCMs, which both improve and stabilize the structural properties as stabilization of form and prevention of leakage and/or phase separation and enhance and tune the thermal properties.
In embodiments, biocompatible complexes of polysaccharides and derivatives with bio-based phase change materials are introduced in order to tune the thermophysical characteristics, in particular, the phase change and structural properties.
As a result, ionically cross-linked or complexed bio-complexes are provided.
The bio-products of the present embodiments have the advantages of tunable thermal properties such as glass transition and phase change temperature and corresponding latent heat. Prepared through a simple water-based fabrication method, disclosed bio-complexes perform more effectively and stably in both thermal and structural properties than the pristine phase change materials.
Analogous to the compositions of polysaccharides previously disclosed as water super-adsorbents, polysaccharides show high potential as superabsorbent of PCMs for thermal and structural stabilization purposes in thermal management applications.
Embodiments generally relate to compositions of and phase change material (PCM) complexed with polysaccharide, methods of preparing and tuning the thermophysical properties with the aid of an ionic agent such as salt of an acid and/or di/multivalent cations, and method of using such compositions.
Elements involved in the bio-complexation include polysaccharide as mechanical and thermal stabilizer, PCM as the thermal energy storage, and ionic agent as the tuner of thermophysical properties.
The phase change bio-complexes can be charged with large amounts of latent thermal energy at a constant temperature of fusion without leaking of the PCM due to fluid retention properties of the polysaccharide and the stored heat can be released by crystallization at tunable temperature through ionic agent.
Various polysaccharides may be utilized as feedstock in embodiment of the present invention including structural polysaccharides, such as cellulose pulp and chitin particulate, as well as storage and bacterial polysaccharides for example, but not limited to, starch, guar gum, xanthan gum, and alginic acid along with other derivatives such as ionic and/or non-ionic derivatives including chitosan and carboxymethyl cellulose.
Numerous secondary non-covalent interactions are related to the miscibility of PCMs within the polysaccharide bionetwork. Along with intra and inter-chain hydrogen bonding, ionic interactions and ion-chelating play a key role in creating the complexation and stabilization of phase change molecules, as illustrated schematically in
The functional groups including carboxyl, hydroxyl and amine on the molecular structure of polysaccharides enable ion exchange, for instance, with multivalent cations e.g. metal ions including alkaline earth and transition metals such as calcium, magnesium, iron or cupper cations. Ion containing polysaccharides provide higher stabilization through providing more ligands for complexation with phase change molecules.
In embodiments, the presence of alkali ions, such as sodium and potassium, increases the reactivity and swelling properties of polysaccharides leading to higher stabilization. As different ions can have different level of influence on the swelling and fluid retention properties of polysaccharides, suitable ionic agents include salts of an acid such as, for example, but not limited to, acetic acid and oxalic acid and/or multivalent cations such as calcium, magnesium, and other alkaline earth and transition metal ions. Both ions involved in the salt may affect the polysaccharide complexation ability with the PCMs.
In order to undergo complexation with polysaccharides, sugar alcohol and salt hydrate classifications of PCMs are preferred.
The existence of phase change substances with suitable functional groups, for example hydroxyl groups on the molecular structure of sugar alcohols, in the system increases the potential of the ionic agents. The involvement of all ionic compounds and hydroxyl groups of phase change molecules undergo complexation with functional groups on the polysaccharide chains resulting in physical stabilization. Furthermore, the smaller molecular size molecules of phase change materials can penetrate the swollen fibrous structure of structural polysaccharides, e.g. cellulose and chitin, so that pore filling and capillary forces also contribute in stabilization process.
More specifically,
In embodiments of the present technology, the phase change polysaccharide-based bio-complexes are classified as a class of soft materials with tunable thermophysical properties.
The structural stabilization results in leakage-preventive properties of ionic complexes of PCMs by polysaccharides (
In embodiments, the polysaccharides undergo swelling in the melted PCM and hold a large amount of PCM while preserving the physical structure. Since the bio-complexes are ionically cross-linked (noncovalent cross-linking), easy dissociation and formation of new secondary bonds can restructure the physical network. Reversibility of these interactions, in return, leads to tunable physical properties, such as resiliency to mechanical damage, which can improve the life cycle of the phase change bio-complexes under repeated heating-cooling cycles.
Analogous to the swelling of polysaccharides during hydration, three different states of stabilization exist for the phase change molecules within the polysaccharide bio-complexation. As presented schematically in
The second state is the phase change molecules yet stabilized due to milder intermolecular interactions with polysaccharides, e.g. hydrogen bonding and Van der Waals forces (B fraction in
In embodiments, the existence of unstable phase change molecules is prevented and controlled by the weight percentage and adsorptive strength of the polysaccharide in the complexation as well as the addition of ionic agent.
Ionic agents significantly affect the stabilized and super-stabilized fractions of the PCM in the complexes. Alkali salts increase the reactivity and swelling of polysaccharides, resulting higher availability of active adsorptive sites on the macromolecule chains for attractive interactions with phase change molecules. The alkaline metal and transition metal ions such as calcium, magnesium, iron, and cupper act as chelating ligands for the complexation between the macromolecule chains as well as phase change molecules. In other words, incorporation of ionic agent result in stronger involvement of PCM and polysaccharides and consequently higher stabilization. In the case of structural polysaccharides such as chitin fibrillous particulates and pulp, the presence of ionic agents for activation of active sites to undergo complexation may be necessary.
The thermal properties, including glass-transition, crystallization and melting, of the disclosed phase change bio-complexes can be tuned by the amount of the polysaccharides and the presence of the ionic agents.
In a first embodiment, the phase-change bio-complexes consist of a phase change material (PCM) (or mixture of PCMs) and a polysaccharide (or combination of polysaccharides).
In a second embodiment, the phase-change bio-complexes consist of a phase change material (PCM) (or mixture of PCMs), a polysaccharide (or combination of polysaccharides), and cations.
In a third embodiment, the phase-change bio-complexes consist of a phase change material (PCM) (or mixture of PCMs), a polysaccharide (or combination of polysaccharides), Table 1 gives a compilation of the phase change properties of some examples of bio-complexes with varying compositions of polysaccharide, PCM and ionic agent, including the temperatures of glass-transition (Tg), crystallization (Tc), and melting (Tm) and the corresponding latent heat of charring and discharging.
As will appear, in embodiments, the phase-change complexes comprise generally about 1 to 50%, for example 5 to 40%, in particular 10 to 35% by weight of the total weight of the complex of a polysaccharide, and up to 25%, for example 1 to 20%, or 1 to 15% by weight of the total weight of the complex of an ionic agent.
The phase change bio-complexes may be prepared from a base polysaccharide (or mixture of polysaccharides). In order to form complexation with polysaccharides, PCMs from sugar-alcohols, for example, but not limited to, erythritol, dulcitol, mannitol, glycerol, sorbitol, xylitol etc. and/or their mixture, and salt hydrates e.g. sodium acetate trihydrate, sodium carbonate decahydrate etc. may be preferred. To tune the thermal properties and improve structural complexation and physical gelation, an ionic agent for example, but not limited to, the salt of an acid, e.g. sodium citrate, sodium tripolyphosphate, and/or di/multivalent cations from alkaline earth and transition metal ions such as calcium, magnesium, iron, zinc etc. may be used in the embodiment of present invention. High loading of the PCM with highly repeatable phase change properties may be achieved due to the compatible nature as well as spontaneous and reversible interactions of incorporated components.
The following non-limiting examples disclose further details of embodiments of the present invention:
One embodiment of a phase change bio-complexes according to this invention may be prepared via a simple aqueous fabrication method by using bacterial polyanionic polysaccharides, e.g. alginic acid and xanthan, as follows:
A known amount of polyanionic polysaccharides, e.g. sodium alginate and xanthan gum, is dissolved in water at elevated temperature e.g. 50° C. until a homogenous hydrogel is obtained. PCM dissolved in water is added to the hydrogel under vigorous mixing. The PCM-polysaccharide system may be ionically cross-linked through in-situ addition of calcium ions, i.e. powdered CaCO3 and glucono-δ-lactone are dispersed in the PCM-alginate solution or by addition of water soluble metal salts and/or salts of an acid, e.g. sodium citrate. The phase change bio-complexes may be processed in the form of beads, films, granules etc. by casting, moulding, additive manufacturing etc. and dried to be used for thermal energy managements. Due to compatible nature of the polysaccharide and the PCM (both water loving) high loading of PCM (up to 95 wt %) is achievable for desired stabilized thermal and structural properties.
Different samples of the phase change bio-complexes of sugar alcohol and alginate and xanthan were prepared and characterized by differential scanning calorimetry (DSC).
Table 1 compiles the related values for thermal properties of erythritol complexed with the polysaccharide in the absence and presence of ionic agent including glass transition temperature, crystallization temperature, melting temperature, and the corresponding latent heat of fusion.
A phase change bio-complexes according to this invention may be prepared by using a polysaccharide derivative, e.g. chitosan and carboxymethyl cellulose, via following method:
A predetermined amount of chitosan is dissolved in dilute aqueous acidic solution, e.g. 0.1 M acetic acid, at e.g. 50° C. until a homogenous gel is obtained. A predetermined amount of PCM dissolved in water is added to the gel under contentious mixing. An ionic agent for example, but not limited to, sodium citrate salt and/or di/multivalent cations e.g. Zn, Fe, Cu or Ni are added to in the PCM-chitosan solution. The final bio-product is produced via dehydration and melted prior to the use.
Several compositions of the phase change bio-complexes, e.g. erythritol and mixture of sugar alcohols, by chitosan were prepared and characterized by differential scanning calorimetry (DSC).
A phase change bio-complexes according to an embodiment is prepared by using non-ionic polysaccharide, for example, but not limited to, starch and guar gum, via the following method:
A predetermined amount of the non-ionic polysaccharide is dissolved in water at elevated temperature, e.g. 50° C., until a homogenous gel is obtained. A predetermined amount of PCM, preferably dissolved in water, is added to the hydrogel while carefully mixing. In the case of non-ionic polysaccharide, addition of an ionic agent is necessary for stabilization. An ionic agent as exemplified by, but not limited to, sodium citrate salt and/or water-soluble metal salts, di/multivalent cations e.g. calcium, are added to the solution in order to tune the thermal properties. The final bio-product is produced via dehydration and melted prior to use.
Several compositions of the phase change bio-complexes sugar alcohols by starch and guar were prepared and characterized by differential scanning calorimetry (DSC).
A phase change bio-complexes of the present invention embodiments may be prepared by using structural polysaccharide, for example, but not limited to, cellulose pulp and chitin particulate, via the following method:
A predetermined amount of the structural polysaccharide (e.g. pulp and chitin) is dispersed in water at elevated temperature e.g. 80° C. while vigorously mixing until a homogenously dispersion is obtained. A predetermined amount of PCM, preferably dissolved in water is added to the dispersion under mixing. An ionic agent, for example, but not limited to, citric acid together with water soluble metal salts, e.g. calcium chloride, is added to the suspension. Complexation can further proceed with the addition of di/multivalent cations such as Fe and Cu for added strength. In the case of structural polysaccharide addition of ionic agent is necessary for stabilization. The final step is dehydration via different processing methods casting, moulding etc.
Several compositions of the phase change bio-complexes sugar alcohols by pulp and chitin were prepared and characterized by differential scanning calorimetry (DSC).
The thermal properties are tuned mainly by the ionic agent. Table 1 above gives a compilation of the corresponding values for the thermal properties of the bio-complexes.
The structural stabilization of the complexed PCM by pulp and chitin in pellet and powdered forms is demonstrated in
An embodiment includes ionically complexed polyethylene glycol PCM with polysaccharides. As both components are highly missile in water, the preparation is simple, and water based. To ensure complexation citric acid together with a di/multivalent cation such as alkane earth metals such as calcium and/or transition metals e.g. Fe, Cu are necessary.
The preparation is preferably conducted at an elevated temperature of, e.g., 80° C. In order to undergo complexation with polysaccharides, lower molecular weight (Mw) polyethylene glycol for example, but not limited to, Mw 600-4000 are preferred.
An embodiment of the present invention includes fatty acids by example, but not limited to myristic acid, lauric acid and decanoic as PCMs to be ionically complexed with polysaccharides. In the case of fatty acids, suitable solvents for preparation includes weakly polar organic solvents, such as ethanol. To avoid precipitation of the PCM during preparation and processing, the ratio of water for dissolving polysaccharide and the solvent for the PCM is typically adjusted to e.g. 1/1 or 2/1 wt %. The preparation is preferably conducted at elevated temperature selected in accordance to the fusion temperature of the PCM for complexation, preferably lower. In order to undergo complexation with polysaccharides, the number of carbons in the fatty chain is preferred to be smaller.
As will be understood from the preceding description of the present invention and the illustrative experimental examples, the present invention can be described by reference to the following embodiments:
It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated.
Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.
The present materials comprising phase change bio-complexes can be applied in different form-stable formats, such as powders, films, pellets, sheets, beads, sponges, for thermal management purposes including thermal energy storage and thermal protection via heat absorbing-releasing, for instance, in building, packaging, electronics, temperature sensitive items (black boxes) and wearables. In particular the phase change bio-complexes can be used in the form of highly concentrated liquids, gels and/or in fully dehydrated form.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20207095 | May 2020 | FI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2021/050394 | 5/31/2021 | WO |
