U.S. patent application number 12/565504 was filed with the patent office on 2010-03-25 for natural microtubule encapsulated phase-change materials and preparation thereof.
This patent application is currently assigned to ETERNAL CHEMICAL CO., LTD.. Invention is credited to NING CHAO, JIAN XU, XIAOLI ZHANG, XIAOYAN ZHANG.
Application Number | 20100071882 12/565504 |
Document ID | / |
Family ID | 41720059 |
Filed Date | 2010-03-25 |
United States Patent
Application |
20100071882 |
Kind Code |
A1 |
ZHANG; XIAOYAN ; et
al. |
March 25, 2010 |
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 .mu.m. 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.
Inventors: |
ZHANG; XIAOYAN; (BEIJING,
CN) ; CHAO; NING; (BEIJING, CN) ; ZHANG;
XIAOLI; (BEIJING, CN) ; XU; JIAN; (BEIJING,
CN) |
Correspondence
Address: |
SHIMOKAJI & ASSOCIATES, P.C.
8911 RESEARCH DRIVE
IRVINE
CA
92618
US
|
Assignee: |
ETERNAL CHEMICAL CO., LTD.
KAOHSIUNG
TW
|
Family ID: |
41720059 |
Appl. No.: |
12/565504 |
Filed: |
September 23, 2009 |
Current U.S.
Class: |
165/110 ;
165/104.17; 29/890.03; 29/890.034 |
Current CPC
Class: |
B01J 13/22 20130101;
Y10T 29/4935 20150115; C09K 5/063 20130101; Y10T 29/49357 20150115;
C09K 5/14 20130101; F28D 20/023 20130101; B01J 13/04 20130101 |
Class at
Publication: |
165/110 ;
165/104.17; 29/890.03; 29/890.034 |
International
Class: |
F28D 17/00 20060101
F28D017/00; F28D 15/00 20060101 F28D015/00; B21D 53/02 20060101
B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2008 |
CN |
200810222787.0 |
Claims
1. Microcapsules of a phase-change material, comprising: a
phase-change material, truncated microtubules, and a polymer;
wherein the truncated microtubules are formed by truncating hollow
tubular natural fibers into fiber segments having a length of 0.1
mm-5 cm, and the hollow tubular natural fibers have a diameter of
0.1-1000 .mu.m; the phase-change material is encapsulated in the
truncated microtubules, and the truncated microtubules are
encapsulated by the polymer.
2. The microcapsules of a phase-change material according to claim
1, wherein the natural fiber is at least one of the following
natural fibers: kapok fiber, milkweed fiber, luffa fiber, bamboo
fiber, tex bamboo fiber, flax fiber, wool, and down.
3. The microcapsules of a phase-change material according to claim
1, wherein the polymer is any one of the following polymers or
copolymers or blends thereof: urea-formaldehyde resin,
melamine-formaldehyde resin, melamine-urea-formaldehyde resin,
polyurethane, polymethylmethacrylate, poly(ethyl methacrylate),
phenolic resin, epoxy resin, polyacrylonitrile, and cellulose
acetate.
4. The microcapsules of a phase-change material according to claim
1, wherein the phase-change material is at least one of 1) a
solid-liquid phase-change material and 2) a solid-solid
phase-change material; the solid-liquid phase-change material is at
least one of a) an inorganic phase-change material and b) an
organic phase-change material; the inorganic phase-change material
is a crystalline hydrated salt and/or molten salt; the organic
phase-change material is any one of the following materials: higher
aliphatic hydrocarbons, higher fatty acids, higher fatty acid
esters, salts of higher fatty acids, higher aliphatic alcohols,
aromatic hydrocarbons, aromatic ketones, aromatic amides,
fluorochloroalkanes, multicarbonyl carbonic acids, and crystalline
polymers; and the solid-solid phase-change material is an inorganic
salt, a polyol, or a cross-linked polymer resin.
5. The microcapsules of a phase-change material according to claim
4, wherein the crystalline hydrated salt is selected from: alkali
metal halides, alkaline-earth metal halides, sulfates, phosphates,
nitrates, acetates, carbonates, and combinations thereof; the
molten salt is K.sub.2WO.sub.4 and/or K.sub.2MoO.sub.4; the
inorganic salt is Li.sub.2SO.sub.4 and/or KHF.sub.2; the higher
aliphatic hydrocarbon is selected from: n-octacosane,
n-heptacosane, n-hexacosane, n-pentacosane, n-tetracosane,
n-tricosane, n-docosane, n-henicosane, n-icosane, n-nonadecane,
n-octadecane, n-heptadecane, n-hexadecane, n-pentadecane,
n-tetradecane, n-tridecane, and combinations thereof; the
crystalline polymer is high density polyethylene, polyvinylidene,
or crystalline polyvinyl chloride having a density of higher than
0.94 g/cm.sup.3; the polyol is selected from: pentaerythritol,
2,2-bis(hydroxymethyl)propanol, neopentyl glycol,
2-amino-2-methyl-1,3-propanediol, trimethylolethane, and
tris(hydroxymethyl)aminomethane; the cross-linked polymer resin is
a cross-linked polyolefin, a cross-linked polyacetal, a copolymer
of a cross-linked polyolefin and cross-linked polyacetal, a blend
of a cross-linked polyolefin and cross-linked polyacetal, and
combinations thereof.
6. A method for preparing the microcapsules of a phase-change
material according to one of claims 1 to 5, comprising: 1) heating
a phase-change material to above the melting point, or dissolving
it with a solvent, so as to obtain a liquid phase-change material;
2) dispersing and immersing truncated microtubules into the liquid
phase-change material obtained in Step 1), so as to make the
microfibers filled with the liquid phase-change material through
capillary absorption; and 3) encapsulating the truncated
microtubules filled with the phase-change material obtained in Step
2) with a polymer, so as to obtain the microcapsules of the
phase-change material.
7. The method according to claim 6, further comprising washing off
the phase-change material adsorbed on the surface of the obtained
microcapsules of the phase-change material.
8. The method according to claim 6, wherein the solvent is selected
from: deionized water, N,N'-dimethylformamide,
N,N'-dimethylacetamide, tetrahydrofurane, methylene chloride,
trichloromethane, cyclohexane, methanol, ethanol, acetone, and
mixtures thereof.
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 storage and exchange technology
in solar energy application, peak load shifting in power supply,
recovery and reuse of waste heat and residual heat, and
commodities. Due to simple and convenient use without energy
consumption, the phase-change materials have wide application
prospect and broad market.
[0003] In view of the phase change process of the material, the
phase-change materials are mainly divided into solid-liquid
phase-change material, solid-solid phase-change material, solid-gas
phase-change material, and liquid-gas phase-change material. 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. Due to small volume change, high latent heat, good
energy storage, and wide phase-change temperature range, the
solid-liquid phase-change material has been widely used in
practice. However, as liquid phase is generated during the
phase-change process, the material must be packed in a sealed
container, so as to prevent leakage and environment pollution, and
the container must be inert to the phase-change material. This
disadvantage greatly limits the application of the solid-liquid
phase-change energy storage materials in practice. Recently, with
the development of technology and the requirement of application,
people try to perform shape stabilization to convert the
solid-liquid phase-change energy storage materials into solid-solid
phase-change materials in form. However, solid-liquid phase change
still occurs in practice, which solves the melting problem of the
phase-change materials, and greatly facilitates the practical
application. Presently, the method for performing shape
stabilization process on the phase-change materials mainly includes
shaped and microcapsulation.
[0004] The shaped phase-change materials are substantially
composite phase-change energy storage materials, and refer to
phase-change material having non-fluidity and capable of
maintaining solid form formed by combining the phase-change
material and the carrier material, which can substitute solid-solid
phase-change materials. The phase-change materials contains two
main components: one is working material component, that is,
phase-change material, for storing and releasing energy through
phase change, including various phase-change materials, with
solid-liquid phase-change materials being mostly used; and the
other is carrier material component, for maintaining the
non-fluidity and processability of the phase-change material.
Therefore, the melting temperature of the carrier material is
required to be higher than the phase-change temperature of the
phase-change material, such that the working material can maintain
the solid shape and material performance in the phase change range.
From the development of the compounding of the shaped composite
phase-change materials in recent years, the main preparation method
substantially includes: co-blending, grafting, sintering, in-situ
intercalation, and sol-gel method. 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.
[0005] The microcapsulated phase-change materials are composite
phase-change materials having a core-shell structure formed by
covering the surface of the solid-liquid phase-change material
particles with a layer of polymer membrane or inorganic material
with stable performance by using microcapsule technology. During
the phase change process, solid-liquid phase change occurs in the
core of the microcapsulated phase-change material, while the outer
layer polymer membrane maintains solid form, so the phase-change
materials present as solid particles at macroscopic. The chemical
preparation method of the microcapsules of a phase-change material
mainly includes: in-situ polymerization, interfacial
polymerization, reaction phase separation, and complex
coacervation, and the shell performance obtained by different
preparation methods is different. With the development of the
polymer science, microcapsulation technology gets mature gradually,
thus the phase-change energy storage microcapsule materials are
widely concerned and researched due to the special performance and
usage. The energy storage principle of heat absorption and release
of the phase-change microcapsule is equivalent to that of a thermal
battery. The encapsulation by the micro container makes the
phase-change material converted into numerous small working units,
thus significantly expanding the application field and situation of
the phase-change material. The product with phase-change
microcapsule blended therein will establish a microclimate
environment in the melting point range of the phase-change material
used, so as to meet the requirement for comfort on temperature. The
microcapsulated phase-change materials can well solve the serious
problems of easily melting and flowing, penetration and migration,
phase separation, and corrosion during the solid-liquid phase
change process, and after being encapsulated and protected with the
shell material, the phase-change material is separated from the
external environment to be stabilized. Also, the polymer shell
material or the modified shell material significantly increases the
compatibility of the phase-change material and the matrix material,
thus significantly improving the practicality of the phase-change
material. 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.
SUMMARY OF THE INVENTION
[0006] Accordingly, the present invention is directed to a
phase-change microcapsule of a truncated natural microtubule
encapsulated phase-change material and the preparation thereof.
[0007] The microcapsules of a phase-change material of the present
invention comprise 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 to 5 cm. The hollow tubular natural fibers have a diameter
in the range from 0.1 .mu.m to 1000 .mu.m. The phase-change
material is encapsulated in the truncated microtubules, and the
truncated microtubules are then encapsulated by the polymer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a DSC curve diagram of microcapsules of a
phase-change material according to Example 1 under cyclic
temperature rise and drop.
[0009] FIG. 2 is a scanning electron microscope photo of the
microcapsules of a phase-change material according to Example 1, in
which (A) is truncated natural kapok tubule; (B) and (C) are
encapsulated kapok microtubules filled with paraffin; (D) is
encapsulated paraffin-filled kapok tubule further encapsulated with
urea-formaldehyde resin.
DETAILED DESCRIPTION OF THE INVENTION
[0010] According to the present invention, useful natural fiber can
be selected from kapok fiber, milkweed fiber, luffa fiber, bamboo
fiber, tex bamboo fiber, flax fiber, wool, and down.
[0011] The phase-change material may be at least one of 1)
solid-liquid phase-change material and 2) solid-solid phase-change
material.
[0012] The solid-liquid phase-change material may be at least one
of a) an inorganic phase-change material and b) an organic
phase-change material.
[0013] According to the present invention, the inorganic
phase-change material can be a crystalline hydrated salt and/or
molten salt. The crystalline hydrated salt may be any one of
alkaline metal or alkaline-earth metal halides, sulfates,
phosphates, nitrates, acetates, or carbonates, or any combination
thereof, such as, Na.sub.2SO.sub.4.10H.sub.2O,
Na.sub.2HPO.sub.4.12H.sub.2O, CaCl.sub.2.6H.sub.2O, and
SnCl.6H.sub.2O and a combination thereof. The molten salt can be
K.sub.2WO.sub.4 and/or K.sub.2MoO.sub.4.
[0014] The organic phase-change material can be any one of the
following materials: higher aliphatic hydrocarbons, higher fatty
acids, higher fatty acid esters, salts of higher fatty acids or
esters, higher aliphatic alcohols, aromatic hydrocarbons, aromatic
ketones, aromatic amides, fluorochloroalkanes, multicarbonyl
carbonic acids, and crystalline polymers.
[0015] The higher aliphatic hydrocarbons are generally aliphatic
hydrocarbons having 6 or more carbon atoms, preferably 6-36 carbon
atoms. The higher fatty acids generally refer to C6-C26
mono-carboxylic acids.
[0016] The higher aliphatic hydrocarbon can be any of the following
16 substances or a combination thereof: n-octacosane,
n-heptacosane, n-hexacosane, n-pentacosane, n-tetracosane,
n-tricosane, n-docosane, n-henicosane, n-icosane, n-nonadecane,
n-octadecane, n-heptadecane, n-hexadecane, n-pentadecane,
n-tetradecane, and n-tridecane.
[0017] The crystalline polymer is high density polyethylene,
polyvinylidene, or crystalline polyvinyl chloride having a density
higher than 0.94 g/cm.sup.3.
[0018] The solid-solid phase-change material is an inorganic salt,
a polyol, or a cross-linked polymer resin. The inorganic salt may
be Li.sub.2SO.sub.4 and/or KHF.sub.2. The polyol may be any of the
following 6 substances or a combination thereof: pentaerythritol
(PE), 2,2-bis(hydroxymethyl) propanol, neopentyl glycol (NPG),
2-amino-2-methyl-1,3-propanediol, trimethylolethane, and
tris(hydroxymethyl)aminomethane. The cross-linked polymer resin may
be a cross-linked polyolefin, a cross-linked polyacetal, a
co-polymer of a cross-linked polyolefin and cross-linked
polyacetal, or a blend of a cross-linked polyolefin and
cross-linked polyacetal.
[0019] The polymer in the polymer layer of the microcapsules of
phase-change a material of the present invention is any of the
following 10 polymers or copolymers or blends thereof:
urea-formaldehyde resin, melamine-formaldehyde resin,
melamine-urea-formaldehyde resin, polyurethane,
polymethylmethacrylate, poly(ethyl methacrylate), phenolic resin,
epoxy resin, polyacrylonitrile, cellulose acetate.
[0020] According to the present invention, the truncated
microtubule encapsulated phase-change microcapsules can be prepared
by the method comprising the following steps:
1) Liquefying the Phase-Change Material:
[0021] heating the phase-change material to above the melting point
or dissolving it with a solvent, so as to obtain a liquid
phase-change material; 2) Filling Truncated Natural Microtubules
with the Liquid Phase-Change Material: [0022] dispersing and
immersing truncated natural microfibers into the liquid
phase-change material obtained in 1), so as to make the
microtubules filled with the liquid phase-change material through
capillary absorption; and
3) Encapsulating the Phase-Change Material:
[0022] [0023] encapsulating the microtubules filled with the
phase-change material obtained in Step 2) with a polymer, so as to
obtain the microcapsules of the phase-change material.
[0024] Optionally, the method further comprises washing off the
phase-change material adsorbed on the surface of the resultant
microcapsules of the phase-change material.
[0025] The solvent may be any one of the following 10 solvents or a
mixture thereof: deionized water, N,N'-dimethylformamide,
N,N'-dimethylacetamide, tetrahydrofurane, methylene chloride,
trichloromethane, cyclohexane, methanol, ethanol, and acetone.
[0026] Compared with the existing microcapsulated phase-change
material encapsulation technology, the present invention has the
following advantageous effects:
[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.degree. 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.
EXAMPLES
Example 1
Preparation of Natural Kapok Fiber Encapsulated Paraffin and
Urea-Formaldehyde Resin Encapsulated Microcapsules of a
Phase-Change Material
[0032] (1) Liquefaction of Phase-Change Material:
[0033] The organic phase-change material paraffin was heated to
above the melting point of 60.degree. C. to obtain a liquid
paraffin phase-change material.
[0034] (2) Filling Truncated Natural Microtubules with the Liquid
Phase-Change Material:
[0035] 1 g natural kapok fiber (truncated microtubules) having a
length of 10-50 .mu.m was dispersed into 10 mL liquid phase-change
material obtained in Step (1), and immersed to make the capillary
absorption reach a balance, such that the kapok fiber was fully
filled with the liquid phase-change material.
[0036] (3) Encapsulation of Microcapsulated Phase-Change
Material:
[0037] 2 g urea-formaldehyde prepolymer (obtained by adding 1 g
urea into 2 ml 36% volume fraction aqueous formaldehyde solution
and stirring until the mixture was fully dissolved, heating to
60.degree. C., and maintaining at this temperature for 15 min) was
directly added dropwise into the melt of the phase-change material
filled natural kapok fiber obtained in Step (2), the temperature of
the melt was raised to 97-98.degree. C. and the reaction lasted for
1 h. Urea-formaldehyde resin polymer was generated around the kapok
fiber, and thus phase separation and deposition occurred, such that
the microcapsulated phase-change material was encapsulated by the
urea-formaldehyde resin.
[0038] (4) Purification of the Microcapsulated Phase-Change
Material:
[0039] The urea-formaldehyde resin encapsulated and phase-change
material fully filled microtubules obtained in Step (3) were taken
out, and placed in hot water to wash off the phase-change material
adsorbed on the surfaces of the tubules, and dried, so as to form
the microcapsulated phase-change material.
[0040] The DSC curve of the phase-change material under cyclic
temperature rise and drop is as shown in FIG. 1, and the scanning
electron microscope photo of the phase-change material is shown in
FIG. 2.
[0041] It can be seen from FIG. 1 that the microcapsules of a
phase-change material have a good cyclic phase-change energy
storage effect under cyclic temperature rise and drop.
[0042] It can be seen from FIG. 2 that the encapsulated kapok
microtubules filled with paraffin form encapsulated phase-change
materials after being encapsulated with the urea-formaldehyde
resin.
Example 2
Preparation of Natural Milkweed Fiber Encapsulated Pentaerythritol
and Cellulose Acetate Encapsulated Microcapsules of a Phase-Change
Material
[0043] (1) Liquefaction of Phase-Change Material:
[0044] Organic phase-change material pentaerythritol (PE) was
dissolved in a small amount of ethanol, to obtain a liquid
pentaerythritol (PE) solution phase-change material.
[0045] (2) Filling Truncated Natural Microtubules with the Liquid
Phase-Change Material:
[0046] 1 g natural milkweed fiber having a length of 0.5-10 .mu.m
was dispersed into 10 mL liquid phase-change material obtained in
Step (1), and immersed to make the capillary absorption reach a
balance, such that the milkweed fiber was fully filled with the
liquid phase-change material.
[0047] (3) Encapsulation of Microcapsulated Phase-Change
Material:
[0048] The ethanol in the phase-change material microcapsule
containing ethanol solvent obtained in Step (2) was vaporized, the
phase-change material pentaerythritol (PE) solution was
concentrated and solidified, and then immersed in 5 mL of 5 wt %
cellulose acetate solution in methylene chloride, such that the
microcapsulated phase-change material was encapsulated by cellulose
acetate through interfacial deposition.
[0049] (4) Purification of Microcapsulated Phase-Change
Material:
[0050] The cellulose acetate encapsulated and phase-change material
filled milkweed fiber obtained in Step (3) was taken out and dried,
so as to form the microcapsulated phase-change material.
[0051] The microcapsules of a phase-change material prepared
according to this method have a good cyclic phase-change energy
storage effect under cyclic temperature rise and drop, and the
encapsulated milkweed microfibers filled with pentaerythritol (PE)
form the encapsulated phase-change material with good dispersion
after being encapsulated by cellulose acetate.
Example 3
Preparation of Natural Bamboo Fiber Encapsulated
CaCl.sub.2.6H.sub.2O and Cellulose Acetate Encapsulated
Microcapsules of Phase-Change a Material
[0052] (1) Liquefaction of Phase-Change Material:
[0053] 1 g inorganic phase-change material CaCl.sub.2.6H.sub.2O was
dissolved in 10 mL deionized water, to obtain a liquid
CaCl.sub.2.6H.sub.2O solution phase-change material.
[0054] (2) Filling Truncated Natural Microtubules with the Liquid
Phase-Change Material:
[0055] 1 g natural bamboo fiber having a length of 500-1000 .mu.m
was dispersed in 10 mL liquid phase-change material obtained in
Step (1), and immersed to make the capillary absorption reach a
balance, such that the bamboo fiber was fully filled with the
liquid phase-change material.
[0056] (3) Encapsulation of Microcapsulated Phase-Change
Material:
[0057] The deionized water in the phase-change material
microcapsules containing deionized water obtained in Step (2) was
vaporized, the phase-change material CaCl.sub.2.6H.sub.2O solution
was concentrated and solidified, and then immersed in 10 mL of 5 wt
% cellulose acetate solution in methylene chloride, such that the
microcapsulated phase-change material was encapsulated by cellulose
acetate through interfacial deposition.
[0058] (4) Purification of Microcapsulated Phase-Change
Material:
[0059] The cellulose acetate encapsulated and phase-change material
filled bamboo fiber obtained in Step (3) was taken out and dried,
so as to form the microcapsulated phase-change material.
[0060] The microcapsules of a phase-change material prepared
according to this method have a good cyclic phase-change energy
storage effect under cyclic temperature rise and drop, and the
encapsulated bamboo microfibers filled with inorganic phase-change
material CaCl.sub.2.6H.sub.2O form the encapsulated phase-change
material with good dispersion after being encapsulated by cellulose
acetate.
Example 4
Preparation of Natural Flax Fiber Encapsulated Pentaerythritol and
Li.sub.2SO.sub.4 and Polyacrylonitrile Encapsulated Microcapsules
of a Phase-Change Material
[0061] (1) Liquefaction of Phase-Change Material:
[0062] 10 g organic phase-change material pentaerythritol (PE) and
10 g inorganic phase-change material Li.sub.2SO.sub.4 were
dissolved in 10 mL mixed solution of deionized water and alcohol
(50:50 v/v), to get a liquid organic/inorganic mixed phase-change
material.
[0063] (2) Filling Truncated Natural Microtubules with the Liquid
Phase-Change Material:
[0064] 5 g natural flax fiber having a length of 100-500 .mu.m was
dispersed in 10 mL liquid phase-change material obtained in Step
(1), and immersed to make the capillary absorption reach a balance,
such that the flax fiber was fully filled with the liquid
phase-change material.
[0065] (3) Encapsulation of Microcapsulated Phase-Change
Material:
[0066] The deionized water and alcohol in the phase-change material
microcapsule containing deionized water and alcohol solvent
obtained in Step (2) were vaporized, the mixed pentaerythritol (PE)
and Li.sub.2SO.sub.4 solution phase-change material was
concentrated and solidified, and immersed into 5 mL of 5 wt %
polyacrylonitrile solution in N,N'-dimethylformamide, such that the
microcapsulated phase-change material was encapsulated by
polyacrylonitrile through interfacial deposition.
[0067] (4) Purification of Microcapsulated Phase-Change
Material:
[0068] The polyacrylonitrile encapsulated and phase-change material
filled flax fiber obtained in Step (3) was taken out and immersed
in deionized water to solidify the polyacrylonitrile, and then
dried.
[0069] The microcapsules of a phase-change material prepared
according to this method have a good cyclic phase-change energy
storage effect under cyclic temperature rise and drop, and the
encapsulated natural flax microfibers filled with the phase-change
material pentaerythritol (PE) and Li.sub.2SO.sub.4 form the
encapsulated phase-change material with good dispersion after being
encapsulated by polyacrylonitrile.
* * * * *