Natural microtubule encapsulated phase-change materials and preparation thereof

Abstract

Microtubule encapsulated microcapsules of a phase-change material and preparation thereof are provided. The microcapsules of a phase-change material consist of a phase-change material, truncated microtubules, and a polymer. The truncated microtubules are formed by truncating hollow tubular natural fibers into fiber segments with a length of 0.1 mm-5 cm. The diameter of the hollow tubular natural fiber is 0.1-1000 μm. The phase-change material is encapsulated in the truncated microtubules and the truncated microtubules are covered with the polymer. The microtubules have high energy storage density due to high hollowness, and can transfer energy stably due to the closed structure, transfer heat rapidly due to the very fine micro-tubular structures, and may be used for a long term in view of the heat and chemical stability.

Description

FIELD OF THE INVENTION[0001]The present invention relates to natural microtubule encapsulated microcapsules of a phase-change material and the preparation thereof.DESCRIPTION OF THE PRIOR ART[0002]Generally, phase-change materials (PCM), also called as latent thermal energy storage (LTES) materials, refer to materials that are capable of absorb or release energy upon phase change while the temperature of the material does not change or change a little. When serving as an energy storage carrier, the phase-change materials have the advantages of high thermal storage density, small equipment volume, and high thermal efficiency, and heat absorption or release is a constant temperature process, thus the energy utilization can be improved, and the problem of energy crisis can be solved to some extent. Presently, phase-change materials have been widely used in refrigeration and cool storage of refrigerators and air-conditioners, automatic thermostatic control of smart buildings, energy sto...

AI Technical Summary

Benefits of technology

[0027]1. The encapsulation tubules used in the present invention are cheap and easily available natural microfibers. For example, kapok fiber is a natural fiber having a large specific surface area and a high hollowness up to 80-90%, which is difficult to be realized by current artificial preparation methods, thus being more suitable for manufacturing phase-change energy material than man-made fibers. Further, kapok fiber has a high thermostability and substantially will not be thermally degraded at 250° C. Also, kapok fiber has a high chemical stability, and will only be dissolved in high-concentration strong acids.

[0028]2. The truncated natural microfibers having micropore structure with large specific surface area are used as supporting materials, and through the capillary force of the micropores, the liquid organic phase-change energy storage material or the inorganic phase-change energy storage material (at a temperature higher than the phase change temperature) is absorbed into the micropores, so as to form an organic phase-change energy storage material, inorganic phase-change energy storage material, or a composite of an organic and inorganic phase-change energy storage materials. When a solid-liquid phase change of the phase-change energy storage material occurs in the micropores, due to the capillary force, the liquid phase-change energy storage material will not easily overflow from the micropores.

[0029]3. Although the capillary force solves the fluidity problem of the solid-liquid phase-change material to some extent, it is still an “open” package system. Thus the microcapsulated microtubules with the phase-change material adsorbed therein can be further closed and terminated with a polymer.

[0030]4. The microfibers have a high hollowness and therefore a high energy storage density, and can transfer energy stably due to the closed structure, and transfer heat rapidly due to the very fine micro-tubular structures, and may be used for a long term in view of the heat and chemical stability. Further, the special lipophilic and hydrophobic wetting performance can be utilized during the processing.

[0031]5. The microcapsulated form of the phase-change material can be better dispersed in a matrix material during practical technical process. After being mixed with the matrix material, the micron-level size of the encapsulated phase-change material can make the appearance of the product be maintained and not be affected.

Problems solved by technology

A large amount of gas exists during the phase change process of the later two materials, so that the volume change of the material is great, thus the two materials are rarely used in practical application.

This disadvantage greatly limits the application of the solid-liquid phase-change energy storage materials in practice.

As the physical effect of the shaped phase-change material is relatively small, after being used repeatedly, the solid-liquid phase-change material may be easily desorbed from the carrier, and leakage and exudation, and two-phase separation may occur.

However, the strength of the microcapsule wall is insufficient, the leakage and heat resistance of the phase-change material still need to be improved, and particularly, the cost is high, which are the problems in urgent need to be solved in the industry presently.

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