High Internal Phase Phase Change Composites For Customized Thermal Management And Anti-Counterfeiting

Phase change materials can absorb or release latent from the environment through the change of their own phase states,thus reducing the imbalance of energy supply and demand and improving the effective utilization of energy.Among them,solid-liquid phase modified materials are the most favored by researchers.Biomass materials have abundant reserves and wide sources,and most of them have natural pore structure,which can be used as the carrier of phase change materials.In recent years,the research of chitin nanofibers has attracted more and more attention.Nanofibers are the basic building blocks of chitin.They not only inherit the advantages of biocompatibility,high crystallization(70～85 %),biodegradability,low thermal expansion coefficient(10 ppm/K)and solvent resistance,but also exhibit unique nano effects,such as high specific surface area and good flexibility.In this study,chitin biomass-based and PCMs composites are combined,and the performance of the obtained chitin biomass-based PCMs composites is better than that of traditional PCMs composites.At the same time,the basic properties,phase transformation characteristics and composite methods of several commonly used PCMs composites(polyethylene glycol,paraffin,fatty acid)are also introduced.On this basis,the preparation methods of different biomass based composite phase change materials were summarized,including porous adsorption method,encapsulation method and copolymerization grafting method,and the characteristics of each method were analyzed.Finally,this study introduces the latest research progress of biomass based composite phase change materials,and Outlines the challenges and future research priorities in this field.The main innovations of this work include: In this study,phase change microcapsules are embedded into the chitin biomass base support matrix by encapsulation method.By using the excellent mechanical properties and adhesion properties of chitin nanofibers,high inner phase composite phase change materials with a volume fraction of up to 95% are obtained by unique drying and wetting training method,which solves the problem that the microcapsule type composite phase change materials cannot be formed.It also makes up for the defects of poor stability and weak mechanical properties of porous adsorption composite phase change materials.Specific research contents and conclusions include: First,the chitin nanofibers are modified with glutaric anhydride to give the chitin nanofibers amphiphile properties.Then,octadecane is used as the internal phase to explore the concentration of the dispersion solution of the chitin nanofibers when the optimal emulsification effect is achieved.The emulsion obtained in this case has high stability and is not easy to break the milk.Then,the emulsion is mixed with chitin nanofibers and filtered.At this time,the chitin nanofibers added during the recombination act as a supporting matrix for material molding on the one hand,and can be regarded as the second protective mechanism to prevent the leakage of octadecane in the shell on the other hand.Secondly,the obtained phase change membrane was placed in an environment of 60 ℃ for drying and wetting training,and the training process was repeated for10 times to obtain high internal phase change composite materials.In addition,the above method can also be applied to alkanes with different carbon chain lengths,and the volume fraction of internal phase can reach more than 93%.It can also be applied to different materials according to the difference of crystallization temperature.For example,when teteecane is used as the internal phase,the obtained high-internal phase phase change composite can be used as the thermal management material during the cold chain transportation of drugs.There is a significant delay in the heating of drugs containing high interior phase change composites to ensure that vaccines remain at low temperatures and avoid failure.Finally,the required information can be encrypted and decrypted by taking advantage of the different light transmittance of the composite phase change material during crystallization and melting.