WO2008044815A1

WO2008044815A1 - Two-way shape memory material, method of manufacturing same, and heat insulating product employing same

Info

Publication number: WO2008044815A1
Application number: PCT/KR2007/000878
Authority: WO
Inventors: Eun-Ae Kim; Shin-Jung Yoo; Jung-Hee Yeo
Original assignee: Industry Academic Cooperation Foundation of Yonsei University
Current assignee: Industry Academic Cooperation Foundation of Yonsei University
Priority date: 2006-10-12
Filing date: 2007-02-20
Publication date: 2008-04-17
Anticipated expiration: 2009-04-12
Also published as: KR100834554B1; KR20080032956A

Abstract

Conventionally, a thermal-shielding material (for example, clothes for fire fighters) that can shield an excessive heat using a one-way shape memory effect have been developed, however, the thermal-shielding effect is for single-use and the shape of the material must be recovered manually after being used. In addition, most of the smart materials require a sensor, an operating device, and an electric power, and thus, there are some problems in supplying the electric power and washing the material. According to the present invention, a shape memory material is formed as a spiral coil in consideration of a non-contracted portion due to a permanent transformation. Unlike a cylindrical coil, the spiral coil can expand both in (+) direction and (-) direction. Therefore, when the spiral coil that is expanded in the (-) direction is fabricated and trained, even if the permanent transformation occurs, the portion that is expanded in the (-) direction is not contracted in the (+) direction, and thus, a height of the coil that is in a maximum expansion state can be minimized.

Description

TWO-WAY SHAPE MEMORY MATERIAL, METHOD OF MANUFACTURING SAME, AND HEAT INSULATING PRODUCT EMPLOYING SAME

TECHNICAL FIELD

5 The present invention relates to a semi-permanent intelligent thermal insulating device operating by itself after sensing an environment temperature and providing a thermal insulating property without an additional electric power supply, and more particularly, to a two-way shape memory material contracting or expanding according to a change of a temperature and recovering an original state, a method of manufacturing io the two-way shape memory material, and a thermal insulating product using the two-way shape memory material.

BACKGROUND ART Shape memory alloys (SMA) are transformed at a low temperature, and then,

I? heated to recover their original states. In addition, when the SMAs are cooled down again, there is no change in the shape of the SMAs. This phenomenon is referred to as a one-way shape memory effect. Meanwhile, a phenomenon that the shape of the SMA is changed both at the high temperature and at the low temperature is a two-way shape memory effect or a reversible shape memory effect. In order to reveal the 0 two-way shape memory effect, a specialized treatment must be performed.

FIG. 1 illustrates an example of a method of manufacturing a two-way shape memory material that expands at a low temperature and contracts at a high temperature according to the conventional art. The two-way shape memory material is formed as a cylindrical coil spring. A cylindrical coil 10 of contraction state (0) expands at the low 5 temperature (A). When the cylindrical coil 10 is heated to a transformation temperature or higher (B), the cylindrical coil 10 should contract completely to the original state (state 10), however, the cylindrical coil 10 actually contracts to a lesser degree (state 20) due to the permanent transformation. After that, when the cylindrical coil 10 is cooled down, the cylindrical coil 10 expands (C). As described above, when the cylindrical coil 10 is0 trained by repeatedly being heated and cooled (B <-> C), the cylindrical coil having the two-way shape memory effect that can be transformed at the low temperature and the high temperature can be fabricated. When the transformation and the heating are repeated a transformation amount of the two-way shape memory material can be increased.

The permanent transformation is generated by a defect such as an electron displacement during the transformation process, and the defect causes the two-way shape memory effect. Therefore, in order to reveal the two-way shape memory effect, the permanent transformation must be performed. Therefore, when the two-way shape memory material is formed using the cylindrical coil shown in FIG. 1 , a volume of the two-way shape memory material is larger than desired at the high temperature due to the portion that is not contracted due to the permanent transformation and the length of the cylindrical coil, and thus, when the two-way shape memory material is applied to thermal insulating products such as clothes, utility of the products may be degraded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a state view illustrating a method of manufacturing a two-way shape memory material according to the conventional art; FIG. 2 is graphs showing various shapes of a two-way shape memory material according to an embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method of manufacturing the two-way shape memory material according to the embodiment of the present invention;

FIG. 4 is a state view illustrating a method of manufacturing the two-way shape memory material according to the embodiment of the present invention;

FIG. 5 is a diagram of an example of clothing in which the two-way shape memory material of the embodiment is applied; and

FIG. 6 is a detailed view of a part of the clothing, in which the two-way shape memory material is applied, according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL PROBLEM

Conventionally, a thermal-shielding material (for example, clothes for fire fighters) that can shield an excessive heat using a one-way or two-way shape memory effect has been developed, however, the thermal-shielding effect is for single-use and the shape of the material must be recovered manually after being used. In addition, most smart materials require a sensor, an operating device, and electric power, and thus, there are some problems in supplying the electric power and washing the material. The inventors of the present invention developed a material that expands when a temperature decreases and contracts when the temperature increases using a two-way shape memory effect, and attached the material to thermal insulating products such as clothes so that an air layer expands to increase a thermal insulating effect when the temperature decreases and the air layer is contracted to reduce the thermal insulating effect when the temperature increases.

Thus, the present invention provides a thermal insulating material that can contract and expand automatically without an additional operation in an environment in which the temperature changes.

TECHNICAL SOLUTION

According to an aspect of the present invention, there is provided a two-way shape memory material that is formed as a spiral coil spring in consideration of a portion that cannot be contracted due to a permanent transformation. Unlike the cylindrical coil, the spiral coil can expand both in (+) direction and (-) direction. Therefore, when the spiral coil that is expanded in the (-) direction is fabricated and trained, even if the permanent transformation occurs, the portion that is expanded in the (-) direction is not contracted in the (+) direction, and thus, a height of the coil that is in a maximum expansion state can be minimized. This will be described in more detail later. The present invention applies a two-way shape memory effect based on temperature to products (clothes) requiring thermal insulating properties using an alloy or a polymer so that the product can sense the temperature change and operate by itself without an additional sensor, an operating device, or an electric power supply to adjust the usage environment by controlling an air layer in the product. The present invention also provides a shape memory material technology using a shape memory alloy that expands when the temperature drops to increase the air layer, and contracts when the temperature increases to reduce the air layer. Most smart materials requires a sensor, an operating device, and an electric power, and thus, there are some problems in supplying the electric power and washing the material. However, the shape memory material of the present invention has a large displacement according to temperature change and can be used repeatedly, and thus, the present invention has a lot of advantages.

The present invention provides an intelligent smart material that can control the thermal insulating property by controlling the air layer automatically according to temperature without an additional electric power supply or the controlling device, and the intelligent smart material can be applied to functional sports wear, leisure wear, functional clothes, interior materials, and thermal insulating materials. A three-dimensional shape after being expanded can be returned to the original flat state when the temperature is out of the operating temperature range, and thus, the volume of the product can be reduced when the thermal insulating function is not required.

The two-way shape memory material of the present invention can be mounted onto the thermal insulating products, or can be attached onto the outermost portion of the product as an accessory, and thus, the shape memory device can be detached when the products are washed or when it is determined that the shape memory device is unnecessary. In addition, the shape memory device can be partially attached to the required portion. A three-dimensional knitting structure formed of the two-way shape memory alloy can be fabricated and used as the thermal insulating material, and thus, the knitting structure contracts or expands according to the temperature change to adjust the air layer.

ADVANTAGEOUS EFFECTS According to the present invention, the shape memory material is an environmental-friendly material having a lifespan longer than the conventional intelligent thermal insulating material using electric power, and thus, the shape memory material of the present invention can be suitable for lifestyles of health and sustainability (LOHAS). In addition, the shape memory material of the present invention can be entirely or partially applied in high value-added fabric products such as military uniform, specialized clothes, sports and leisure wear, sleeping bags, and thermal insulating products for infants and elderly people, and can be commercialized in fields requiring intelligent thermal insulating functions such as interior materials.

DESCRIPTION OF THE DRAWINGS

BEST MODE A method of manufacturing a shape memory material that expands at a low temperature of the present invention will be described as follows. A spring of spiral shape shown in FIG. 2 is fabricated. The spring can be fabricated using a wire having a diameter of 1mm, which is formed of a Ti-Ni alloy (for example, Ti-50.2 at.% Ni).

FIGS. 2(a) through 2(d) show the shape of the spiral coil spring that is changed during the two-way shape memory effect, that is, expanding when a temperature decreases and contracting when the temperature increases. The two-way shape memory material having a minimum height at a high temperature can be fabricated using the spiral coil spring shown in FIG. 2.

The two-way shape memory material can be fabricated by a method shown in FIGS. 3 and 4. Referring to FIGS. 3 and 4, a spiral coil 40 formed using a wire of Ti-Ni alloy (for example, Ti-50.2 at.% Ni) (100) is slightly expanded (height -H1), in a natural state, in a first direction (hereinafter, referred to as (-) direction). The spiral coil 40 is expanded in an opposite direction (that is, (+) direction) at a low temperature (A) to a height of H2 so that the spiral coil becomes the shape 50 in FIG. 4 (200). When the spiral coil 50 is heated at a high temperature (B in FIG. 4), the spiral coil is contracted, and the spiral coil 50 is contracted so that a height H3 is nearly 0 like the coil 60 of FIG. 4 using the property that the original state cannot be recovered due to the permanent transformation (300). If the initial expansion is controlled, the spiral coil 60 of flat shape having the lowest height can be formed. After that, the spiral coil 60 is cooled down to form the spiral coil 70 expanded to a height H4 at point C of FIG. 4 (where H4<H2). When the heating and cooling operations are repeated, the two-way shape memory material, the shape of which is repeatedly changed at the points B and C of FIG. 4, can be obtained.

The cooling and heating operations in the section of B<-->C are repeatedly performed until the two-way shape memory effect is obtained. For example, a cycle of training includes reducing the temperature to the point of Mf=-43 or lower, that is, to a martensitic state, to expand the spiral coil, and heating the spiral coil to a point of Af=22, that is, to an austenite state, to recover the original state of the spiral coil. When this training is repeated 10 to 20 times in a constant directions, the spiral coil spring automatically changes to the state that is repeatedly trained when the temperature decreases. Then, the maximum transformation amount can be controlled, and the spiral coil spring is returned to the original state when the spiral coil spring is heated. According to this principle, the spiral coil 60 that is flat at a normal temperature expands when the temperature decreases under the operating temperature (70 of FIG. 4). In the austenite state, the spiral coil must be maintained at the flat state so as not to provide the thermal insulating property (that is, not to be expanded) if the thermal insulating property is not required. In the present specification, the low temperature and the high temperature are relative. That is, degrees of expanding and contracting the coil and temperature range will be determined according to the usage of the thermal insulating product or the field in which the thermal insulating product will be used, and thus, the one of ordinary skill in the art can train the spiral coil after setting the degrees of the contraction and expansion of the spiral coil.

FIG. 5 shows the two-way shape memory material employed in a thermal insulating product 60 according to the present invention. FIG. 6 illustrates an intelligent thermal insulating operation according to the present invention. In FIG. 6, the clothing 80 includes a first layer and a second layer, and the two-way shape memory material 90 is disposed between the first and second layers. When the temperature is low, the two-way shape memory material 90 expands to form a space between the clothing and the human body to increase the thermal insulating property. In addition, when the temperature increases, the two-way shape memory material 90 contracts to reduce the space between the clothing and the human body to reduce the thermal insulating property.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

1. A method of manufacturing a two-way shape memory material that expands due to temperature decrease and contracts due to temperature increase, the method comprising: forming a spiral coil that is expanded to a predetermined height H1 in a first direction in a natural state thereof; training the spiral coil to have a two-way shape memory effect, so that the height of the spiral coil can be nearly 0 when a maximum contraction occurs and can be expanded in a second direction that is opposite to the first direction when an expansion occurs.

2. The method of claim 1 , wherein the spiral coil is formed of a Ti-Ni alloy.

3. The method of claim 1 , wherein the training of the spiral coil comprises: expanding the spiral coil in the second direction; heating the expanded spiral coil to contract the spiral coil so that the height of the spiral coil is nearly 0 after contraction; and cooling the spiral coil to expand to a predetermined height and repeating the heating and cooling operations to allow the spiral coil to have the two-way shape memory effect.

4. A two-way shape memory material formed as a spiral coil expanding in a first direction due to temperature decrease and contracting in a second direction due to temperature increase, wherein when a maximum contraction of the spiral coil occurs the spiral coil becomes flat.

5. The two-way shape memory material of claim 4, wherein the two-way shape memory material formed as a spiral coil is formed of a Ti-Ni alloy.

6. The two-way shape memory material of claim 4, wherein the two-way shape memory material formed as a spiral coil is fabricated by forming a spiral coil that is expanded to a predetermined height H1 in a first direction in a natural state thereof, and by performing a training of the spiral coil to allow the spiral coil to have a two-way shape memory effect, so that the height of the spiral coil can be nearly 0 when a maximum contraction occurs due to temperature increase and can be expanded in a second direction that is opposite to the first direction when an expansion occurs.

7. A thermal insulating product comprising: a first layer; a second layer; and a two-way shape memory material formed having a spiral coil shape, when a maximum contraction amount of which occurs the spiral coil becomes flat, expanding in a first direction due to temperature decrease and contracting in a second direction due to temperature increase between the first layer and the second layer, wherein the two-way shape memory material expands to increase the distance between the first layer and the second layer when the temperature decreases, and contracts to reduce the distance between the first layer and the second layer when the temperature increases.