Methods for producing cellulose-based porous aerogel product and cellulose-based porous aerogel composition, and use

Abstract

The application relates to a method for producing a cellulose-based porous aerogel product, in which cellulose nanofibrils and a phase change material are mixed to form a homogenous suspension mixture, a carbon-based and / or mineral agent is added to the suspension mixture, and the suspension mixture is treated to form the porous aerogel product comprising a three-dimensional shape. Further, the application relates to a method for producing a cellulose-based porous aerogel composition. Further, the application relates to a use of the method.

Description

[0001] METHODS FOR PRODUCING CELLULOSE -BASED POROUS AEROGEL PRODUCT AND CELLULOSE -BASED POROUS AEROGEL COMPOSITION, AND USE

[0002] FIELD

[0003] The application relates to a method defined in claim 1 for producing cellulose-based porous aerogel product and a method def ined in claim 14 for producing cellulose-based porous aerogel composition . Further, the application relates to a use defined in claim 17 .

[0004] BACKGROUND

[0005] Heat transfer and insulation play a vital role in a wide range of applications from thermal management of powerful electronic devices , thermal protection of aerospace apparatuses , safe handling of temperature sensitive products , to indoor thermal comfort and energysaving of buildings . According to the International Energy Association, for instance , energy-related greenhouse gas emissions from buildings have increased recently due to growing energy demand for heating, cool ing, and air-conditioning, as well as extreme weather conditions . These emissions can be potentially reduced by decreasing the use of fossil-fuel-based products and devising more energy-efficient and sustainable buildings . Commercially available insulation materials , however, include mainly fossil fuel-based expanded polystyrene (EPS ) and polyurethane ( PU) foams as well as mineral wools . Renewable-based insulation materials can yet facilitate the technology transition towards more sustainable designs and the climate change mitigation .

[0006] An effective insulation is directly attributed to the large surface area and abundant voids for air trapping within the structure of the insulation materials . Thus , material density, porosity, specific surface area, as well as pore si ze distribution influence the insulation properties of insulation materials . Aerogel materials , i . e . gels with air as the dispersant , are highly attractive for thermal insulation purposes due to their highly porous structure , low density, large surface area and small pore diameters . The ultralow thermal conductivity of aerogels results from effective suppression of thermal radiation as well as minimi zed thermal conduction through high porosity of the nanostructure and a pore si ze distribution smaller than the mean free path of gas phase .

[0007] Aerogel materials can yet play a strategic role for the global insulation market . As such, manufacturing of aerogel products requires focusing on reducing the cost , creating new aerogel types , and targeting large commercial markets where the overall demand for such products is governed by their applications as thermal and acoustic insulation .

[0008] Biopolymer-based aerogels are known . Biopolymer-based aerogels are more attractive as sustainable materials compared to the more common fossil fuel-derived synthetic polymer aerogels . Biopolymers also provide a high level of surface-active groups e . g . , carboxyl groups on cellulose , that creates new functionality for such materials . They are also biocompatible and nontoxic, which make them suitable for eco-friendly applications example for buildings and packaging . Cellulose , lignin, and hemicellulose are extracted from different biomass sources including trees as one of the largest available biomass resources . Cellulose derived from birch trees , for example , is a highly abundant biopolymer in the Boreal region, enabl ing its competitive market value . Lignin accounts for 15% to 30 % total dry mass of wood fiber precursor and has an interestingly complex structure . Its macromolecular structure is amorphous , comprised of aromatic units , e . g . guai- acyl , p-hydroxyphenyl and syringyl , with different degree of functional groups depending on the plant source and its environment .

[0009] Typically, heat is transferred via convection, radiation, and conduction phenomena . Conduction is the heat transfer through matters in solid, liquid, or gaseous states without a bul k movement of the matter . In gaseous and liquid states , conduction happens because of molecular collisions and diffusion by the random movement of molecules , while in sol id state it is caused by a combination of molecular lattice vibrations and free electrons ' energy transport . Heat transfer thus depends on the mechanical , thermal , or geometrical characteristics of the materials . Gas conduction plays an important role for the heat transfer within highly porous materials such as aerogels , whilst convection is negligible since the gas transport does not rely on mobility through the temperature gradient thanks to the significantly small pore si ze distribution of the material . At ambient temperatures and standard pressure , thermal transport by radiation is negligible , yet some research has showed considerable contribution of radiation for specific porous material cases with effectively low thermal conduction and low densities .

[0010] The heat transfer in insulating materials can be minimi zed via manipulation of their porosity content and dimensions . According to the Knudson effect and phonon scattering, the insulation performance can be improved if the mean free path of the pores is smaller than the gas molecules . Therefore , microsi zed fibers have the advantage of forming smaller pore si zes in the material , compared to non-microf ibrillated fibers . Conventional cellulose-based insulation, for example , shows thermal conductivity values ranging within 0 . 040 - 0 . 050 W nr1K-1, whilst aerogels can provide significantly lower thermal conductivity, as low as 0 . 025 W nr1K-1. Addition of endothermic opacifiers , consisting of a metal oxide shell and phase change material core structure , to silica aerogels causes a significant delay in heat transfer and enhancement in short-term thermal insulation performance through radiation heat transfer suppression and solid-liquid phase change enthalpy . Thermal insulation also correlates with the degree of pore alignment . Structural anisotropy can promote perpendicular thermal dissipation and directional heat transport . High anisotropic distribution, for instance , can decrease radial thermal conduction .

[0011] The continuous demand for energy conservation pushes the drive to achieve more sustainable renewablebased alternative insulative materials providing lower thermal conductivity and density as well as higher thermal inertia and structural stability for larger scale applications . Cellulose based aerogels have been studied for thermal insulation purposes . Cellulose-based aerogels facilitate the handling, installation, and transportation of the product and cause less greenhouse gas emissions during the transport because of their low weight . However, lightweight feature typically results in low thermal inertia of the insulation and poor dis sipation of thermal energy during hot seasons , challenging their use for example in building applications .

[0012] From US 8614154 is known a fiber insulation material for the manufacture of a non-woven fiber batt .

[0013] From US 20140186576 is known a nonwoven web of unmodified or cyanoethylated nanocellulose as well as a mixture of nanocellulose and polymetaphenylene isophthalamide as electrical insulating material for transformers .

[0014] From US 5770295 is known an insulation system composed of a sandwiched structure with an inner layer of insulative material , an intermediate layer of phase change material therebetween and an outer layer of insulative material .

[0015] From US 6855410 is known a composite material having a flexible matrix containing a phase change thermal storage material as a method for metabolic cooling and insulation of a user in a cold environment .

[0016] From US 8221910 is known a thermally regulating construction material consisting of a base material and a polymeric phase change material bound to it .

[0017] From US 5804297 is known a coating composed of a base material and microcapsules , containing a thermal energy absorbing material .

[0018] From US 20130134347 is known a composite structure with heat storage capability composed of a PCM, adsorbent material and encapsulant material .

[0019] From US 5669584 is known an apparatus to maintain a space vehicle at a constant temperature .

[0020] From US 5569513 is known thermally insulative aerogel-containing foam compositions and their preparation .

[0021] From US 6887563 is known a composite material containing 5 to 97 %-vol aerogel particles , at least one polymeric or inorganic binder, and at least one fibre material .

[0022] OBJECTIVE

[0023] The obj ective is to solve the above problems . Further, the obj ective is to disclose a new-type method for producing new aerogels comprising cellulose-based material . Further, the obj ective is to achieve ultralight aerogel product easily with good properties . Further, the obj ective is to produce the cellulose-based aerogel material effectively . SUMMARY

[0024] The methods and use are characterized by what are presented in the claims .

[0025] The method for producing a cellulose-based porous aerogel product comprises mixing cellulose nanofibrils and a phase change material to form a suspension mixture , adding a carbon-based and / or mineral agent to the suspension mixture , and treating the suspension mixture to form the porous aerogel product .

[0026] The method for producing a cellulose-based porous aerogel composition comprises mixing cellulose nanof ibrils and a phase change material to form a suspension mixture , and adding a carbon-based and / or mineral agent to the suspension mixture .

[0027] DETAILED DESCRIPTION

[0028] In the method for producing a cellulose-based porous aerogel product , cellulose nanofibrils (CNF) and a phase change material ( PCM) are mixed to form a homogenous suspension mixture , a carbon-based and / or mineral agent is added to the suspension mixture , and the suspension mixture is treated to form the porous aerogel product comprising a three-dimensional shape . In one embodiment , the suspension mixture and / or the porous aerogel product is dehydrated or dried, e . g . by supercritical drying, freeze-drying or other suitable drying .

[0029] In the method for producing a cellulose-based porous aerogel composition, cellulose nanofibrils (CNF) and a phase change material ( PCM) are mixed to form a homogenous suspension mixture , and a carbon-based and / or mineral agent is added to the suspension mixture .

[0030] Preferably, the cellulose-based porous aerogel product and composition, such as a hybrid insulative aerogel product and composition, can be produced, in which the aerogel can undergo a reversible solid-to-gel transformation into highly porous organogel showing low thermal conductivity and high thermal inertia. In the method, a hybridization of functionalized lignocellulosic nanofibrils with the phase change material may be used for providing a product comprising high porosity, ultra-low density, ultralow thermal conductivity and / or high thermal inertia for insulation and leakage-proof thermal uses.

[0031] In this context, the aerogel means any aerogel, organogel, cryogel or any combination thereof, preferably a hybrid aerogel, e.g. hybrid insulative aerogel. Aerogels are porous ultralight solid material which is preferably derived from a suspension, mixture or gel or the like.

[0032] In this context, the cellulose-based porous aerogel means any cellulose-based or lignocellulosic aerogel, which comprises at least cellulose nanofibrils and desired phase change material. Further, the aerogel comprises the carbon-based and / or mineral agent. Preferably, the cellulose-based porous aerogel product is formed from the cellulose-based porous aerogel composition. The cellulose-based porous aerogel composition may comprise one or more additional components, e.g. one or more additives.

[0033] The method for producing cellulose-based porous aerogel may be provided using bio-based materials.

[0034] In one embodiment, the cellulose nanofibrils, CNF, is selected from the group consisting of oxidized CNF, lignin-containing CNF, or acetylated CNF, or any combination thereof. In one embodiment, the oxidized CNF is a TEMPO-oxidized CNF, i.e. TEMPO-CNF.

[0035] In one embodiment, the cellulose nanofibrils are modified. Modification and micro-fibrillation of cellulose nanofibrils enable the creation of high porosity and lightweight features in the aerogels. Further, the coupled phase change material provides temperature regulation and high thermal inertia through enthalpy of phase transition. In one embodiment, the cellulose nanofibrils are functionalized. In one embodiment, the cellulose nanofibrils are treated by a hybridization. In one embodiment, the cellulose nanofibrils are acetylated. In one embodiment, the cellulose nanofibrils are oxidated, e.g. TEMPO-oxidated .

[0036] In one embodiment, the amount of CNF is selected from 8 to 40 wt-% based on total dry mass, preferably from 10 to 25 wt-% based on total dry mass, in the aerogel product.

[0037] In one embodiment, the dry matter content of CNF in the suspension mixture is 0.2 to 2.5 wt%, in one embodiment 0.5 to 2.0 wt%.

[0038] Preferably, the phase change material (PCM) is mixed with the cellulose nanofibrils to form a suspension mixture. In one embodiment, the phase change material, PCM, is selected from the group consisting of polyethylene glycol (PEG) , fatty acid or a mixture of fatty acids, or any combination thereof. Preferably, the phase change material is polyethylene glycol, fatty acid, fatty acid mixture, or any combination thereof. The phase change material, PCM, may comprise one or more components. In one embodiment, the PCM is a medium chain fatty acid, such as decanoic acid, stearic acid, and / or myristic acid. In one embodiment, the PCM is selected from the group consisting of a medium chain fatty acid, such as decanoic acid, stearic acid, and / or myristic acid, or a mixture of fatty acids. In one embodiment, polyethylene glycol (PEG) has a molecular weight in the range of 500 to 10000 grams per mole, in one embodiment 600 to 8000 grams per mole.

[0039] Preferably, the phase-change material is added, and then the suspension contains PCM with CNF. In response to the temperature changes, the PCM content undergoes a leakage-proof solid-to-gel transformation instead of a typical solid-to-liquid phase transition enabling thermal energy storage. The formed nanohybrid may provide a tailorable fusion temperature by selection of PCM's molecular mass.

[0040] In one embodiment, to create highly porous and homogeneous aerogels that can undergo a leakage-proof and reversible solid-to-gel transformation, polyethylene glycols having molecular weight in range 500-10000 g mol-1or medium-chain fatty acids are preferred as the phase change material.

[0041] In one embodiment, the amount of the phase change material, PCM, is selected from 60 to 92 wt-% based on total dry mass, preferably from 75 to 90 wt-% based on total dry mass, in the aerogel product.

[0042] Preferably, the carbon-based agent and / or the mineral agent is added to the suspension mixture. In this context, the carbon-based and / or mineral agent may be any agent, component, material or additive which consists of carbon-based and / or mineral material.

[0043] In one embodiment, the carbon-based agent is added to the suspension mixture. In one embodiment, the mineral agent is added to the suspension mixture. In one embodiment, the carbon-based agent and the mineral agent are added to the suspension mixture.

[0044] In one embodiment, the carbon-based agent is selected from carbon microparticles, carbon nanoparticles, biochar, graphite, or any combination thereof. The the carbon-based agent may comprise one or more components, i.e. one or more carbon-based agents. In one embodiment, the carbon-based agent consists of carbon microparticles and / or nanoparticles. In one embodiment, the carbon-based agent consists of biochar or biochar particles. In one embodiment, the size of the biochar particles is below 25 pm. In one embodiment, the carbonbased agent consists of graphite. In one embodiment, the carbon-based agent consists of biochar and / or graphite. In one embodiment, the carbon-based agent consists of carbon particles, e.g. microparticles and / or nanoparticles, which are added to further enhance the insulation properties .

[0045] In one embodiment, the mineral agent is selected from mineral nanoparticles, sepiolite and montmorillonite, or any combination thereof. In one embodiment, the mineral agent contains sepiolite and / or montmorillonite, or their particles, such as nanoparticles. The mineral agent may comprise one or more components, i.e. mineral agents.

[0046] In one embodiment, the amount of the carbonbased and / or mineral agent is selected from 0.1 to 3 wt- % based on total dry mass, preferably between 0.5 to 3.0 wt-% based on total dry mass, in the aerogel product.

[0047] In one embodiment, an aqueous suspension comprising the cellulose nanofibrils and phase change material is formed. In one embodiment, the cellulose nanofibrils and phase change material are mixed into the aqueous suspension to form the homogeneous suspension mixture. In one embodiment, the phase change material is dissolved in a solvent, e.g. water or ethanol, and the formed solution is added to the aqueous suspension comprising cellulose nanofibrils. In one embodiment, the aqueous suspension comprises water.

[0048] In one embodiment, an aqueous suspension comprising the cellulose nanofibrils (CNF) is formed, and the phase change material (PCM) is added to the aqueous suspension to form the homogenous suspension mixture. In one embodiment, the phase change material (PCM) is dissolved in water or ethanol, and a formed solution is mixed to the suspension comprising the cellulose nanofibrils (CNF) .

[0049] Preferably, the suspension mixture comprises at least the cellulose nanofibrils, phase change material and carbon-based and / or mineral agent. In one embodiment, the suspension mixture comprises three main components, i.e. the cellulose nanofibrils, phase change material and carbon-based and / or mineral agent, in the suspension. In one embodiment, the suspension mixture comprises the aqueous suspension. In one embodiment, the suspension mixture may comprise at least one additional component, e.g. additive.

[0050] In one embodiment, at least one additive is added, e.g. to the suspension mixture. In addition to the carbon-based and / or mineral agent, any other suitable additive may be added for forming the aerogel product. In one embodiment, the cellulose-based aerogel composition may include additives in trace amount for opacification and radiation / heat-absorbance enhancement. In one embodiment, to further enhance the insulation properties, additives such as metal-oxide are incorporated in a trace amount for opacification and radiation / heat- absorbance. In one embodiment, the additives may be selected from opacifying additives, light-absorber additives, inorganics particles, carbonates, metal-oxides , or any combination thereof. In one embodiment, the additive is dispersed, e.g. in water, to form a dispersion. In one embodiment, the additive or additive dispersion is ultrasonicated. In one embodiment, the additive dispersion is added to the suspension mixture. In one embodiment, the suspension mixture is again ultrasonicated .

[0051] Combining the cellulose nanofibrils with other nanosized or nano-porous materials or additives, e.g. metal and graphene oxides or minerals, can enhance porosity and further reduce the heat transfer and provide other functional properties such as opacification or flame retardancy.

[0052] In one embodiment, the aerogel composition is formed from the suspension mixture, such as from the aqueous suspension. In one embodiment, the aerogel product is formed from the suspension mixture, such as the aqueous suspension . In one embodiment , the aqueous suspension contains 0 . 5 - 2 . 0 % dry matter content of cellulose nanofibri ls , preferably for forming 10 - 25 wt% of the aerogel product total mass . In one embodiment, the aqueous suspension contains 10 - 25 wt% cellulose nanofibrils of the aerogel composition total mass , 90 - 75 wt% phase change material of the aerogel composition total mass and 0 . 1 - 3 wt% carbon-based and / or mineral agent of the aerogel composition total mass .

[0053] In one embodiment , the suspension mixture is mixed with a suitable mixer or mixing means . In one embodiment , the suspension mixture is mixed until a homogeneous mixture is achieved .

[0054] New hybrid aerogel compositions can be formed for providing reversible solid-to-gel transformations while maintaining a resilient porous structure . Further, preparation method can be achieved for insulation applications . In one embodiment , the method includes the hybridi zation of functionali zed lignocellulosic nanofibrils with PCM enabling highly porous structure , ultra-lightweight , ultralow thermal conductivity as well as high thermal inertia for insulation and leakage-proof thermal regulation applications . The aerogel composition can additionally include additives in trace amount as opacifiers and radiation / heat-absorbance enhancers .

[0055] The method can be used to produce any cellulose-based porous aerogel product .

[0056] In one embodiment , the cellulose-based porous aerogel product can be produced via different processing methods such as material manufacturing, e . g . additive manufacturing, or f reeze-templating or mold-casting . In one embodiment , the cellulose-based porous aerogel product can be produced via different processing methods such as material manufacturing, f reeze-templating or mold-casting, and a subsequent drying . In one embodiment , the suspension mixture is treated using a treatment selected from the group consisting of material manufacturing, 3D printing, freeze templating, moulding, casting or mold casting, or any combination thereof for forming the aerogel product. In one embodiment, the cellulose-based porous aerogel product is formed using the material manufacturing. In one embodiment, the cellulose-based porous aerogel product is formed using the 3D printing. In one embodiment, the cellulose-based porous aerogel product is formed using the freeze-tem- plating. In one embodiment, a centrifuge may be used in the f reeze-templating . In one embodiment, the cellulose- based porous aerogel product is formed using the casting or mold-casting. In one embodiment, defoaming is used in the mold-casting.

[0057] In one embodiment, the suspension mixture is dried. In one embodiment, the suspension mixture is dehydrated, and the dehydration to produce the porous aerogel product is done by drying. In one embodiment, the drying is carried out by freeze-drying.

[0058] Any suitable device or devices can be used to form the cellulose-based porous aerogel composition and product .

[0059] The aerogel product may comprise a desired shape. In one embodiment, the product has a two-dimensional or three-dimensional structure.

[0060] In one embodiment, the aerogel product has ultralow density which is about 0.015 - 0.030 g cm-3. In one embodiment, the aerogel product has low thermal conductivity which is about 0.030 - 0.040 W nr1Kr1. In one embodiment, the aerogel product has high latent heat of fusion which is within 115-186 J / g. In one embodiment, the aerogel product has ultralow density of about 0.022 g cm-3, low thermal conductivity of about 0.035 W nr1Kr1and high latent heat of fusion within 115-186 J / g.

[0061] In one embodiment, the method can be used to produce materials and structures to be used as loose- fill , sheets , films or any particular types of thermal , radiation, and / or sound insulation or in leakage-proof thermal regulation applications . The aerogel compositions can be used in loose-fill , sheets , films or any particular shapes enabling particular types of insulation for example pipe and wire insulation or for use in buildings , transformers , electronics or aerospace apparatus for thermal , radiation or sound insulation purposes .

[0062] Thanks to the invention, the cellulose-based porous aerogel product can be produced effectively . The aerogel product has good properties , for example insulation, acoustic absorbance and sound absorption properties . The phase change materials ( PCMs ) are incorporated to increase the thermal inertia and protection against thermal shocks of the aerogel compositions . Thus , in the preparation and processing methods , highly porous aerogel s can be achieved that can undergo a leakage-proof reversible solid-to-gel transition with high fusion enthalpy while maintaining the porous structure during the transition . The aerogel compositions provide low density and high porosity for light-weight feature , low thermal conductivity for high insulation performance as well as high fusion enthalpy for high thermal inertia .

[0063] The method offers a possibility to produce the cellulose-based aerogel products easily, and energy- and cost-effectively . The present invention provides an industrially applicable , simple and affordable way to produce the different aerogel products . The method is easy and simple to reali ze in connection with different production processes .

[0064] BRIEF DESCRIPTION OF THE DRAWING

[0065] The accompanying drawings , which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate some embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

[0066] Fig. 1 presents a molecular formula of TEMPO- oxidization and acetylation modifications of CNF on the exposed hydroxyl groups. Cellulose chemistry and functionality influence the intermolecular interactions between the initial materials and the pores arrangement in the final aerogel structure hence the insulation performance .

[0067] Fig. 2 presents hybrid insulative aerogels prepared via additive manufacturing (images of first column from left) , f reeze-templating (images of middle column) and mold-casting (images of third column) . The compositions include 80 wt% PEG as PCM and 20 wt% Lignin-CNF (upper row images) and Acetyl-CNF (middle row images) , TEMPO-CNF (last row images) .

[0068] Fig. 3 presents highly porous and aligned structure of hybrid insulative aerogels under scanning electron microscope; compositions PCM 80 wt% and 20 wt% Lignin-CNF (upper images) and Acetyl-CNF (lower images) prepared via FT.

[0069] Fig. 4 presents SEM images of hybrid insulative aerogel including additive: composition PEG 74 wt%, Lignin-CNF 24 wt%, and 2% TiO2 prepared by mold-casting. The lower right image is on a thawed sample indicating the porosity is maintained during phase transition.

[0070] Fig. 5 presents form-stability and leakageproof phase transition of hybrid phase-change insulative aerogels composed of PEG (74 wt%) , Lignin-CNF (24 wt%) and TiO2 (2 wt%) through adsorptive interactions and hydrogen bonding.

[0071] Fig. 6 presents dynamic mechanical analysis of the hybrid insulative aerogel including additive: composition PEG 74 wt%, Lignin-CNF 24 wt%, and 2% TiO2 prepared by mold-casting. Fig . 7 presents DSC heating graphs of hybrid phase-change insulative aerogel compositions under 5 Kmin-1scan rate , depicting the endothermic melting phase change of the aerogels .

[0072] Fig . 8 presents DSC cooling graphs of hybrid phase-change insulative aerogel compositions under 5 Kmin-1scan rate , depicting the exothermic crystalli zation phase change of the aerogels .

[0073] Fig . 9 presents the DCS graphs and insulation film .

[0074] Fig . 10 presents sound absorbance of hybrid insulative aerogel compositions compared with that of mineral wool and pure cellulose nanofibril aerogel .

[0075] Fig . 11 presents hybrid phase-change insulative aerogel and a schematic illustration of its solar irradiation absorbance and latent heat release to regulate temperature during day and night . The bottom plot shows the temperature variations in the sample exposed to light and latent heat release during consecutive cooling in the dark . The PCI composition absorbs the energy of irradiation and undergo a leakage-proof phase transition when exposed to light / heat , while releases the absorb energy during consecutive cooling in the dark during the reverse phase transition . It is observed that the PCI composition containing TiO2 enables higher temperature increase during heating (higher irradiation absorbance ) and longer heat release during cooling (dark) due to the nucleating agent behavior of TiO2 -

[0076] Fig . 12 presents the indoor temperature variation graphs of a small model wooden house insulated with hybrid phase change insulative ( PCI ) aerogel (middle image ) and commercial mineral wool ( right image ) under irradiation and in the consecutive dark . Due to its passive phase change property, the PCI can absorb the energy and prevent temperature raise during irradiation while release the absorb energy during consecutive cooling in the dark and regulate the indoor temperature around its phase change temperature .

[0077] EXAMPLES

[0078] The cellulose-based porous aerogel product is formed from bio-based materials . Highly porous hybrid insulative aerogel is formed . The aerogel can undergo a leakage-proof phase change through a reversable solid- to-gel transformation to highly porous organogel . The phase change insulative ( PCI ) aerogel composition results from hybridi zation of functionali zed lignocellulosic nanofibrils with a compatible phase change material ( PCM) that enable ultralightweight and low thermal conductivity thanks to their highly porous structure and high thermal inertia owing to their leakage-proof phasetransition .

[0079] A broad range of functional characteristics can be achieved through modification of biopolymer-based materials . Cellulose nanofibrils (CNF) , the most naturally abundant biopolymer, are formed through microfi- brilation process . The nano-si ze increases active surface area, and further modifications can tailor the chemical nature of CNF, such as charge density, interfacial forces , or self-assembly . Surface modification of CNF can be done by substituting the exposed, primary hydroxyl functional groups , with other active sites such as carboxyl and acetyl groups .

[0080] According to the example , three types of functionali zed CNFs , particularly TEMPO-oxidi zed CNF ( TEMPO-CNF) , illustrated in Fig . 1 , containing carboxylate functional groups , acetylated CNF (Acetyl-CNF) , Fig . 1 , containing acetyl functional groups , and TEMPO- oxidi zed CNF coupled with residual lignin (Lignin-CNF) were formed . Never-dried Birch cellulose pulp was used to prepare CNF suspension through TEMPO-mediated oxidation . Acetyl-CNF aqueous suspension was produced by heterogeneous acetylation, on Kraft birch wood to obtain acetylated cellulosic fibers that were also microfluidi zed . Lignin-CNF was made us ing recycled f ibers of unbleached Spruce and Pine softwood . It was observed that these modifications lead to different surface chemistry and pore properties of the final aerogel affecting the insulation performance .

[0081] The hybridi zation of these functionali zed cellulose nanofibrils with a compatible phase change material can result in highly porous structures that can absorb and release thermal energy for simultaneous insulation and temperature regulation purposes . PCMs are used to store and conserve energy through latent heat of fusion . Typically, PCMs absorb energy through melting on heating and release the stored energy through crystalli zation on subsequent cooling . One of the main is sues with PCMs is the leakage of liquid phase above the fusion temperature . In the method, insulative aerogel compositions are formed, and the said aerogels are free of any leakage issue due to compatible intermolecular interactions between the incorporated PCM and entangled CNF scaf fold which replace the typical sol id to liquid transition with a leakage-proof solid-to-gel transformation . The PCI compositions may also include additives for opacification and radiation absorbance to enhance the insulation properties .

[0082] The hybrid phase-change insulative compositions can provide phase change enthalpy, as disclosed in Table 1 , that can be applied for thermal regulation within an environmentally relevant temperature range , e . g . 18 - 65 ° C, depending on PCM' s selection for example PEG with molecular weight in the range 600 - 8000 g mol-1or medium-chain fatty acids . High amount of PCM up to 90 % of total dry mass can be entangled with the CNF matrix via organo-gelation or PEGylation of non-covalent interactions . The PCI compositions show aerogel characteristics below the fusion temperature , whilst under radiation or heat absorbance they turn into highly porous and reversible organogels above the fusion temperature .

[0083] The hybrid insulative aerogels can be formed via simple aqueous preparation routes from colloidal suspensions of the initial materials CNF, PCM and mineral material / carbon-based material / other additive . Another desired additive may be added . Processing method of the initial colloidal suspension can cause different morphological structures in the final PCI aerogels , thus affecting their insulation properties .

[0084] According to the example , three different processing methods , by example not limitation, were used to produce the PCI compositions : material manufacturing, such as additive manufacturing, or freeze templating, or mold casting to form articles of desired forms . Material manufacturing decreases the overall density of the scaffold through 3D patterns enabling large contents of voids / pores . Freeze templating enables higher degree of pore alignment to reduce radial thermal conduction and to enhance thermal protection . Mold casting influences self-assembly that promotes structural elasticity . After processing the suspension goes through drying preferably freeze-drying which helps preserving the porous structure of the final aerogels .

[0085] Material manufacturing, i . e . additive manufacturing, (AM) is an emerging technique that can be exploited for tailoring macro / micro-structures with great precision, that can have a direct influence on the heat transfer and absorption by controlling pore interconnectivity . Achieving lightweight efficiency, while maintaining mechanical strength, can be tailored by adj ustments of the percent infill of a geometrically stable scaffold . According to the example , the structure was printed in two ways an alternating honeycomb pattern and a checkered pattern .

[0086] Freeze templating (FT ) , also known as the unidirectional freeze-drying method, is used to produce uni-directional alignment by steadily immersing the biopolymer suspension in liquid nitrogen . According to the example , the PCM-CNF suspension was forced in the direction of ice formation, where the suspension can move in the unoccupied space from the ice crystals . The final morphology exhibits a good radial insulation due to the phonon scattering phenomenon that lowers gas conduction . The mesoporous structure formed at the walls of the FT- structure can control gas conduction .

[0087] According to the example , in the mold casting (MC) , the PCM-CNF suspension was poured into appropriate holders to gain the desired shape of the casting . The casted PCM-CNF suspension maintains its shape with high level of flexibility . This method can result in product with high elasticity and good pore alignment , due to lack of share force in the processing method .

[0088] The concentration of CNF suspension can influence the porosity of the final aerogels . A 0 . 5-2 % dry fibril content of CNF suspension result in appropriate porosity content and apparent elasticity of the final product . Obtaining high porosity structures from colloidal suspensions is achieved by removing the solvent in various ways , for example , convective drying, solvent exchange and super critical drying . According to the example , freeze-drying was used which is a relatively fast and easy way to produce foams or aerogels preserving the porous structure . For al l processing cases , freeze-drying was implemented at the final step of AM, FT , and MC . This method allows the pre-frozen solvent to sublimate under a vacuum, bypassing the triple point and maintaining a solid network for the fibers . Fig . 2 shows PCI aerogels products in different shapes prepared via AM, FT, and MC methods. Figs. 3 and 4 indicate highly porous and aligned structure of the developed PCI aerogels under scanning electron microscope.

[0089] Additives, such as opacifying or light-absorber additives or other additives, can be incorporated in the PCI structure to further improve insulation and thermal inertia performance. Integration of such additives in trace amount could enhance the insulation by increasing the porosity, heat transfer path and radiation absorbance, as well as the passive thermal energy storage by acting as the nucleation agent for the PCM crystallization during cooling. Opacifying particles interact with radiation in the porous fibrillar matrix further enhancing the insulation performance. Combining CNF with nanosized particles can optimize the porous structure and reduce the thermal transfer. The additives can be selected from inorganics, e.g. Ti02, ZnO, Fe2Os, AI2O, Si02 or mineral particles, as well as carbon particles e.g., biochar (fine particles of carbonized biomass) or graphite. In one embodiment, the additive is Ti02, which is recognized as a photoactive, semiconduc- tive material with low cost, appreciable chemical stability, low toxicity, and biocompatibility. In one embodiment, mineral additives such as sepiolite and montmorillonite minerals can also act as flame retardant and enhance the fire retardancy of the PCI composition. In one embodiment, several additives may be used.

[0090] In one embodiment, the additive is added at a trace amount, for example, within the range 0.5% to 3% of the total aerogel dry mass. Broader light absorption resulting in excess energy conversion can increase latent energy storage and thus improving the PCI's thermal inertia and regulation. The incorporation of multiscale initial materials can further enhance the porous backbone of the aerogel compositions, hence their thermal insulation properties. In one embodiment, another potential advantage of additives, such as TiCt and ZnO, is their antimicrobial advantages that can possibly prevent growth of microbes on the material.

[0091] PCI aerogel compositions show high insulating capabilities, and they could serve for applications that conserve energy in the form of latent heat, for example in building insulation within the walls or ceiling, water heating systems, aerospace apparatus, heat generating electronics, and temperature sensitive products packaging .

[0092] The PCI aerogel compositions including acetyl- CNF for instance showed low thermal conductivity (0.035 W nr1K-1) and ultra-low density (0.028 g cm-3) , attributed to their high porosity content (97.9%) , as disclosed in Tables 1 and 2, for physiothermal properties of different PCI compositions. Solving the PCM leakage issue owing to numerous intermolecular secondary interactions (Fig. 5) can provide multiple opportunities to exploit this material for practical applications.

[0093] The strain behavior of the PCI aerogels under mechanical stress was measured using dynamic mechanical analysis (DMA) strain ramp under compressive force (Fig. 6) . The form-recovery during relaxation time after mechanical stress can be important for insulation in buildings and packaging for transport. The PCI aerogel showed -27% strain under 1 N force and was able to recover 12% of its form after 1 minute relaxation time. A -49% strain was observed at a subsequent 3 N compressive force and 28% height recovery after 1 minute of relaxation. The sample showed -79% compressive strain under high 16 N loading force and 20% recovery after 1 minute relaxation. Therefore although, the aerogel is highly porous, it shows good mechanical stability and elasticity .

[0094] Featuring lightweight benefits applications in buildings, electronics, wearables, and aerospace apparatus by facilitating the handling, installation, and transportation of the product . It further reduces the greenhouse gas emission during transportation . However, lightweight materials typically enable low thermal inertia in buildings and are unable to dissipate thermal energy during hot seasons , which further motivates the incorporation of PCMs to provide higher thermal inertia and protection against thermal shocks . Thus , the disclosed lightweight PCI aerogels can be used for eco- friendly and energy-efficient insulating applications owing to low conductivity and high thermal inertia .

[0095] Table 1 shows phase change and specific heat properties of the insulative aerogel compositions prepared via different processing methods of different aqueous concentrations of lignocellulosic fibril suspension . The values were measured by DSC on dried compositions .

[0096] Table 2 shows thermal conductivity, bulk density, and porosity values of the insulative aerogel compositions . The values are for dried compositions .

[0097] Table 1

[0098] Processing Method PCM CNF Additive Tm AHm AHc Cp,s CP,I

[0099] (wt%) (wt%) (wt%) ( °C) (J g1) (J g1) (J g-'K-1) (J g-'K-1)

[0100] PEG TEMPO- (1.7wt fibril aqueous suspension concentration)

[0101] MC 85% 15% 62.4 140.0 -137.2 1.76 2.25

[0102] MC 80% 20% 62.5 137.3 -131 1.42 2.09

[0103] FT 80% 20% 57.6 132.4 -127.7 0.98 1.35

[0104] MC 80% 20% 57.6 133.5 -128.2 1.05 1.65

[0105] Acetylated- (0.97% fibril aqueous suspension concentration)

[0106] AM 85% 15% 57.4 144.1 -138.1 1.89 1.58

[0107] AM 80% 20% 59.6 135.3 -128.4 0.83 1.35

[0108] FT 80% 20% 60.2 150.7 -141.4 2.24 3.24

[0109] AM 60% 40% 63.4 180.3 -171.4 1.12 1.59

[0110] FT 60% 40% 60.8 186.0 -177.8 1.42 2.08

[0111] Acetylated- (0.5% fibril aqueous suspension concentration)

[0112] MC 75% 25% 56.8 123.6 -118.1 1.4 1.90 MC 74% 24% 2% (TiCh) 58.4 115.1 -109.7 1.16 1.76

[0113] Lignin (1.13% fibril aqueous suspension concentration)

[0114] AM 80% 20% 58.8 138.5 -133.9 1.02 1.42

[0115] FT 80% 20% 58.6 135.5 -131.7 1.04 1.40

[0116] MC 80% 20% 57.0 159.8 -152.5

[0117] Lignm- (1.0% fibril aqueous suspension concentration)

[0118] MC 74% 24% 2% (TiCh) 57.4 142.0 -137.3 1.21 1.94

[0119] Lignin- (0.5% fibril aqueous suspension concentration)

[0120] MC 75% 25% 57.8 152.4 -148.0 1.32 1.78

[0121] MC 74% 24% 2% (TiCh) 58.2 142.6 -137.2 1.27 1.86

[0122] MC 74% 24% 2% (biochar) 59.0 121.7 -118.4 1.15 1.63

[0123] MC 74% 24% 2% (ZnO) 61.8 127.0 -122.0 1.03 1.49

[0124] Table 2

[0125] Composition Thermal conduc- Bulk Density Porosity

[0126] PCM CNF AdditivetivitY (gcm'3) (%)

[0127] (wt%) (wt%) (wt%) (W m1K1)

[0128] PEG Acetylated-

[0129] 74% 24% 2% (TiCh) 0.035 0.028 97.9

[0130] TEMPO-

[0131] 79% 19% 2% (biochar) 0.035 0.035-0.037 95.5-96.9

[0132] 74% 24% 2% (ZnO) 0.030 97.2

[0133] Lignin-

[0134] 75% 25% - 0.039-0.040 0.022 97.9

[0135] 74% 24% 2% (TiCh) 0.036-0.037 0.027 97.8

[0136] 74% 24% 2% (biochar) 0.023 97.9

[0137] 74% 24% 2% (ZnO) 0.021 97.8 Further, following Examples 1 - 8 describe some

[0138] PCI aerogel compositions , their preparation, and their properties .

[0139] Example 1 In this example , the hybrid phase change insulative ( PCI ) aerogel compositions were produced using simple preparation methods by using TEMPO-oxidi zed cellulose nanofibrils ( TEMPO-CNF) aqueous suspension . The predetermined amount of PCM, dissolved in appropriate solvents e . g . , water or ethanol depending on the PCM selection, is added to certain amount of TEMPO-CNF aqueous suspension, preferably 0 . 5-2 % dry fiber content, at elevated temperature and preferably below the fusion temperature of the used PCM. The suspension mixture was mixed until a homogeneous . The initial concentration of nanofibrils in the aqueous suspension can affect the physical properties of the final aerogels . For instance , CNF suspens ion with 0 . 5% dry fiber content provides higher porosity and better resilience whilst 1 % dry fiber content results in better mechanical strength but less plasticity . To provide highly porous and homogeneous hybrid aerogels that can undergo phase change , the PCM is preferably selected from polyethylene glycol classification with a molecular weight within the range 500 - 10000 g mol-1that show a compatible nature with CNF and melting temperature within 18 -70 ° C range . The suspension may be processed by means of casting, molding, additive manufacturing, freeze templating etc . to form hydrogels of desired forms , by example not limitation, sheets , films , pellets etc . The processed hydrogels can be dehydrated via different drying methods , preferably freeze drying, to form aerogels of desired shapes and porosity . Providing the compatible nature between CNF and the selected PCM, high amount of PCM, e . g . 85 wt% , can be coupled with CNF to produced highly porous aerogels that can undergo phase change with desirable thermal and insulation properties and no leakage above the melting point . Fig . 5 depicts a schematic of the interaction mechanisms between coupled materials resulting in the porosity and form-stability of PCI .

[0140] Various samples of the PCI aerogels , made from PEG and functionalized CNF, were prepared using different processing methods , as illustrated in Fig . 2 . Highly porous structure of the developed aerogels were observed under scanning electron microscope depicted in Figs. 4 and 5. A high degree of pore alignment was observed for the PCI aerogels produced via FT method (Fig. 4) , while the aerogels produced via MC showed higher elasticity and resilience. The phase change properties of the developed PCI compositions were characterized using differential scanning calorimetry (DSC) . Figs. 7 and 8 show the DSC graphs of the aerogel compositions demonstrating distinct phase change behavior during heating and cooling cycles. Table 1 compiles related values for the calculated phase change and specific heat of the PCI compositions demonstrating up to 140 J g-1fusion enthalpy and 2.25 J g-1K“1specific heat capacity. Thermal conductivity was measured via modified transient source plane method. The PCI aerogels containing TEMPO-CNF reached 95.5-97.2 % porosity, 0.030-0.037 g cm-3bulk density and 0.035 W nr1Kr1thermal conductivity (Table 2) .

[0141] Example 2

[0142] The PCI compositions were produced using a simple preparation method by using acetylated cellulose nanofibrils (Acetyl-CNF) aqueous suspension, analogous to the procedure explained for Example 1. Briefly, dissolved PCM in appropriate solvent is added to certain amount of Acetyl-CNF aqueous suspension (0.5-1% dry fiber content) at elevated temperature, preferably below the fusion temperature of the used PCM and mixed to obtain a homogeneous solution. The suspension may be processed through described processing methods to form articles of desired shapes and porosity. The processed articles can be dried to be used for thermal management purposes. Fig. 2 shows PCI aerogel compositions incorporating Acetyl-CNF produced via different processing methods and Table 1 includes their phase change properties demonstrating up to 182 J g-1fusion enthalpy and 3.24 J g-1K“1specific heat capacity. The PCI aerogels containing Acetyl-CNF showed 97.9 % porosity, 0.028 g cm-3bulk density and 0.035 W nr1Kr1thermal conductivity (Table 2 ) .

[0143] Example 3

[0144] The PCI compositions were produced using a simple preparation method by using Lignin-CNF aqueous suspension, in accordance with the procedure explained for examples 1 and 2. Briefly, Lignin-CNF aqueous suspension (0.5-1.2% dry fiber content) was mixed with certain amount of dissolved PCM at elevated temperature, preferably below its fusion temperature, until a homogeneous mixture was obtained. The suspension was then processed and dried to form articles of desired shapes and porosity. Fig. 2 shows PCI aerogel compositions incorporating Lignin-CNF produced via different processing methods. Table 1 includes the phase change properties of the compositions produced with Lignin-CNF and PCM, particularly PEG, including enthalpy and temperature of phase change and specific heat capacity, demonstrating up to 160 J g-1fusion enthalpy and 1.94 J g-1K“1specific heat capacity. The PCI aerogels containing Lignin-CNF indicated 97.8-97.9 % porosity, 0.021-0.027 g cm-3bulk density and 0.036-0.040 W m-1K“1thermal conductivity (Table 2) .

[0145] Example 4

[0146] Embodiments of the PCI compositions were prepared using the procedure and formulation of Examples 1-3 except that the samples included also one of these opacifiers: titanium dioxide, iron oxide, or zinc oxide in an amount within 0.5-3% of total aerogel dry mass. Certain amount of the opacifying particles was dispersed and ultrasonicated in distilled water. The dispersion was then added to PCM-CNF suspension. This mixture was again ultrasonicated to ensure full dispersion of the opacifying particles in the PCM-CNF suspension, which was then processed and dehydrated to produce articles of different shapes and porosity. Tables 1 and 2 includes the phase change and insulation properties of samples produced with PCM (74 wt% PEG) , functionalized CNF (24 wt%) , and nanoparticles (2 wt% TiO2 or ZnO) that provided 0.021-0.030 g cm-3density, 140 J g-1fusion enthalpy and 0.035-0.038 W nr1Kr1thermal conductivity.

[0147] Example 5 Embodiments of the PCI aerogel compositions were prepared using the procedure of Examples 4 except that instead of inorganic opacifying particles the samples included carbon-based opacifiers such as biochar particles (carbonized biomass < 25 pm) or graphite and / or mineral additives in the amounts 0.5-3% of total dry mass. The additive is dispersed and ultrasonicated in distilled water. The dispersion is then added to PCM- CNF suspension and is ultrasonicated again to ensure full dispersion of the additive particles in the mixture, which is then processed and dehydrated to produce articles of different shapes. Tables 1 and 2 shows the phase change and insulation properties of samples produced with PCM (74 wt%, particularly PEG as the PCM) , Lignin-CNF (24 wt%) , and biochar additive (2 wt%) that provided 0.023 g cm-3density and 122 J g-1fusion enthalpy .

[0148] Example 6

[0149] The PCI aerogel compositions include mineral additives such as sepiolite or montmorillonite nanoparticles or carbonates that can act as both flame retardant and opacifier, in the amounts 0.5-3% of total dry mass or more until fire resistance is achieved. The additive needs to be dispersed and ultrasonicated in distilled water . The dispersion is then added to PCM- CNF suspension and it is ultrasonicated again, processed and freeze-dried to produce articles of different shapes .

[0150] Example 7

[0151] Embodiments of the PCI compositions include medium chain fatty acids such as decanoic acid, stearic acid, and myri stic acid or a mixture of fatty acids as PCMs . The fatty acid is dissolved in appropriate organic solvents such as ethanol and then added to CNF suspension at elevated temperature , preferably below the fusion temperature of fatty acid while mixing . The amount of PCM solvent needs to be enough to dissolve the fatty acid and to prevent its solidification during processing . The ratios of the solvent used for PCM to the water content of the CNF suspens ion may be selected in a way that it prevents the undes ired solidification of the fatty acid in the final suspension : preferred ratios include 1 / 1 or 1 / 2 if applicable . The suspension may be processed at elevated temperatures to avoid undesired solidification of the fatty acids during processing which can deteriorate the porosity content of the resulted PCI aerogel . Fig . 9 shows the DCS graphs and insulation film made from fatty acid and acetylated CNF, providing 156 J / g fusion enthalpy .

[0152] Example 8

[0153] In this example , the PCI aerogel compositions were tested for acoustic absorbance in the range of 500 - 6000 Hz , the conceivable acoustic frequency range to a human ear, and were compared with that of mineral wool insulator as illustrated in Fig . 10 . The PCI aerogel compositions containing Acetyl-CNF exhibited 100 % absorbance at moderate frequencies ( 1600 Hz ) . The PCI aerogel compositions containing Lignin-CNF reached 90% absorbance ratios at 5000 Hz . Both composition types provide rough surfaces that can possibly contribute to the sound absorption, known as phonon scattering effect . The PCI aerogel composition containing TEMPO-CNF exhibited 70 % sound absorbance near 3500 Hz , which may be due to the reflectance of the sound waves by its smoother surface . The acoustic absorption behavior of PCI aerogels resembled coefficients close to that of the commercial mineral wool , achieving absorbance in a more difficult , low frequency range .

[0154] Example 9

[0155] In this example , the PCI aerogel compositions were tested for light absorbance as well as used to insulate a small model wooden house under light irradiation and were compared with commercial mineral wool insulation as illustrated in Figs 11 and 12 . The disclosed hybrid phase-change insulative aerogels absorbed heat / energy of irradiation and released latent heat during cooling in the dark, enabling temperature regulation around its phase transition (Fig . 11 ) . The PCI composition underwent a leakage proof phase transition when exposed to irradiation, while maintaining the aerogel structure . The PCI compositions containing additives absorbed more heat during irradiation and released more heat during cooling in the dark due to the nucleating agent behavior of additive for recrystalli zation of molten PCM and effective activation of thermal energy storage of the PCM . The indoor temperature variation of a small model wooden house insulated with the PCI aerogel and commercial mineral wool was tested under irradiation and in the consecutive dark ( Fig . 12 ) . Due to its passive phase change property, the PCI can absorb the energy and prevent temperature raise during irradiation while releasing the absorb energy during consecutive cooling in the dark and regulate the indoor temperature ( thermal inertia) around its phase change temperature . The PCI regulated the indoor temperature more effectively compared with that of mineral wool , which can stem from high thermal inertia provided by leakage proof phase change behavior of the PCI .

[0156] The manufacturing devices and techniques of the process used in the examples are known per se in the art , and therefore they are not described in any more detail in this context .

[0157] The method is suitable in different embodiments for producing desired cellulose-based porous aerogel compositions and products from different starting materials .

[0158] The invention is not limited merely to the examples referred to above ; instead many variations are possible within the scope of the inventive idea defined by the claims .

Claims

CLAIMS1. A method for producing a cellulose-based porous aerogel product, wherein the method comprises- mixing cellulose nanofibrils (CNF) and a phase change material (PCM) to form a homogenous suspension mixture,- adding a carbon-based and / or mineral agent to the suspension mixture, and- treating the suspension mixture to form the porous aerogel product comprising a three-dimensional shape .

2. The method according to claim 1, wherein the CNF is selected from the group consisting of oxidized CNF, lignin-containing CNF, or acetylated CNF, or any combination thereof.

3. The method according to claim 1 or 2, wherein the amount of CNF is selected from 8 to 40 wt- % based on total dry mass, preferably from 10 to 25 wt- % based on total dry mass.

4. The method according to any one of claims 1 to 3, wherein the dry matter content of CNF in the suspension mixture is 0.5 to 2.0 wt%.

5. The method according to any one of claims 1 to 4, wherein the PCM is selected from the group consisting of polyethylene glycol (PEG) , fatty acid or a mixture of fatty acids, or any combination thereof.

6. The method according to any one of claims 1 to 5, wherein the PCM is selected from the group consisting of a medium chain fatty acid, such as decanoic acid, stearic acid, and / or myristic acid, or a mixture of fatty acids.

7. The method according to claim 5, wherein PEG has a molecular weight in the range of 600 to 8000 grams per mole.

8. The method according to any one of claims 1 to 7, wherein the amount of PCM is selected from 60 to92 wt-% based on total dry mass, preferably from 75 to 90 wt-% based on total dry mass.

9. The method according to any one of claims 1 to 8, wherein the carbon-based agent is selected from carbon microparticles, carbon nanoparticles, biochar, graphite, or any combination thereof.

10. The method according to any one of claims 1 to 9, wherein the mineral agent is selected from mineral nanoparticles, sepiolite, montmorillonite, or any combination thereof.

11. The method according to any one of claims 1 to 10, wherein the amount of carbon-based and / or mineral agent is selected from 0.1 to 3 wt-% based on total dry mass, preferably between 0.5 to 3.0 wt-% based on total dry mass.

12. The method according to any one of claims 1 to 11, wherein the suspension mixture is treated using a treatment selected from the group consisting of a material manufacturing, 3D printing, freeze templating, moulding, casting or mold casting, or any combination thereof .

13. The method according to any one of claims 1 to 12, wherein the suspension mixture is dehydrated, and the dehydration to produce the porous aerogel product is done by drying.

14. A method for producing a cellulose-based porous aerogel composition, wherein the method comprises: mixing cellulose nanofibrils (CNF) and a phase change material (PCM) to form a homogenous suspension mixture, and adding a carbon-based and / or mineral agent to the suspension mixture.

15. The method according to claim 14, wherein an aqueous suspension comprising the cellulose nanofibrils (CNF) is formed, and the phase change material (PCM) is added to the aqueous suspension to form the homogenous suspension mixture.16 . The method according to claim 14 or 15 , wherein the phase change material ( PCM) is dissolved in water or ethanol , and a formed solution is mixed to the suspension comprising the cellulose nanofibrils (CNF) . 17 . A use of the method according to any one of claims 1 to 13 , wherein the method is used to produce materials and structures to be used as loose-fill , sheets , films or any particular types of thermal , radiation, and / or sound insulation or in leakage-proof ther- mal regulation applications .

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