JP2019089306A - Shape memory composite - Google Patents

Abstract

To provide a shape memory composite comprising a shape memory polymer and a shape memory alloy, which performs actions in two directions when heated.SOLUTION: The shape memory composite comprises: a shape memory polymer in which a certain shape recovery action is memorized; and a shape memory alloy in which a shape recovery action is memorized, the recovery action being in a direction different from the recovery action of the shape memory polymer, where (1) a shape recovery temperature (glass transition temperature, Tg) of the shape memory polymer is higher than room temperature, (2) a shape recovery temperature (reverse martensitic transformation temperature, Af) of the shape memory alloy is higher than the Tg temperature, and (3) the Mf point or Rf point of the shape memory alloy is equal to or higher than room temperature and, when heating is performed to a temperature just below the Tg temperature, the shape of the shape memory composite changes gradually from a shape memorized by the shape memory polymer to a different shape memorized by the shape memory alloy and, when heating is performed to a temperature equal to or higher than the Tg temperature, the shape of the shape memory composite recovers once the shape memorized by the shape memory polymer and, thereafter, recovers the shape memorized by the shape memory alloy.SELECTED DRAWING: Figure 1

Description

      The present invention relates to a shape memory complex that performs two-direction operations by heating only the shape memory complex.

      Many polymers and alloys having a shape memory effect are known. Among them, as a shape memory polymer (hereinafter referred to as "SMP"), polyurethane, polyisoprene, styrene butadiene copolymer, polyethylene, polynorbornene, and as a shape memory alloy (hereinafter "SMA"), Ti-Ni based, Ti Free-type, copper-type and iron-type are put to practical use. A composite consisting of SMP and SMA (see Patent Document 1) discloses a shape memory composite which changes to a memory shape of SMA upon heating and cooling and changes to a memory shape of SMP upon cooling.

JP-A-8-199080

    Many polymers and alloys having a shape memory effect are known. Among them, as a shape memory polymer (hereinafter referred to as "SMP"), polyurethane, polyisoprene, styrene butadiene copolymer, polyethylene, polynorbornene, and as a shape memory alloy (hereinafter "SMA"), Ti-Ni based, Ti Free-type, copper-type and iron-type are put to practical use. In a composite composed of SMP and SMA (Japanese Patent Application Laid-Open No. 8-199080), a shape memory composite is disclosed, which changes to a memory shape of SMA upon heating and cooling and operates to a memory shape of SMP upon cooling. This shape memory composite is a content that performs shape recovery in two directions by cooling and heating, and does not perform shape recovery in two directions only by heating of the present invention. The shape memory composite shown in Patent Document 1 has a disadvantage that the cooling rate is slow because cooling can not be performed efficiently, and the response at the time of cooling is poor.

      Thus, the present invention is to operate the shape memory complex in different directions by heating alone.

      The present invention comprises a shape memory polymer storing a certain shape recovery operation and a shape memory alloy storing a shape recovery operation in a direction different from that of the shape memory polymer recovery operation. (1) Shape recovery temperature of shape memory polymer (Glass transition temperature, Tg) is higher than room temperature, (2) shape recovery temperature of shape memory alloy (martensitic reverse transformation temperature, Af) is higher than Tg temperature, and (3) shape memory alloy has Mf point or Rf point When heating to a temperature just above room temperature to just before the Tg temperature, the shape memory polymer gradually changes from a memorized shape to another memorized shape memory alloy, and when it is heated to a temperature above Tg, the shape once It is characterized in that it recovers to the memorized shape of the memory polymer and then the shape memory alloy recovers to the memorized shape.

      According to the present invention, it is possible to improve the disadvantages of shape memory composites that have poor responsiveness during cooling due to slow cooling rates.

      If the shape memory complex of the present invention is applied to a robot hand, the robot hand can be grasped with only heating and the moved object can be released, so that the robot hand can be miniaturized.

      The SMP used in the present invention can be used without particular limitation as long as it is currently used as an SMP. For example, polyurethane, polyisoprene, styrene butadiene copolymer, polyethylene, polynorbornene and the like can be mentioned. Above all, polyurethane is desirable from the viewpoint of being able to arbitrarily set the glass transition temperature (hereinafter referred to as "Tg") by changing the combination of the constituent components.

      Shape memory polyurethane is a block copolymer containing, as a main component, a polyol constituting a soft segment, a chain extender constituting a hard segment and a diisocyanate. The polyurethane is free to change the shape recovery temperature Tg from -30.degree. C. to 60.degree. C. according to the molar ratio of the components.

      The SMA used in the present invention can be used without particular limitation as long as it is equal to or less than the shaping temperature of the SMP. For example, Ti-Ni based SMA and copper based SMA are preferred, where the shape recovery temperature of the SMA is much lower than the shaping temperature of the SMP.

      As Ti—Ni-based SMA, Ti—Ni binary system, Ti—Ni—Cu alloy, Ti—Ni—Nb alloy, Ti—Ni—Fe alloy, Ti—Ni—Pd alloy, Ti—Ni—Hf alloy, Ti— Ni-Zr alloy etc. are mentioned. The shape recovery temperature of the Ti—Ni binary alloy is −10 ° C. to 100 ° C.

      The Ti-Ni-based SMA is a material having a structure of martensite phase (hereinafter referred to as "M phase") or R phase at a low temperature, and is phase-transformed to a structure of a matrix phase (austenite phase) above a certain temperature. The shape recovery effect utilizes this phase transformation. When the Ti-Ni-based SMA of M phase or R phase is heated, transformation to the parent phase (martensitic reverse transformation) occurs gradually, and eventually becomes the complete parent phase. Generally, the temperature at which this matrix transformation starts is referred to as the As point, and the temperature at which it ends is referred to as the Af point. Usually, point Af is taken as the shape recovery temperature of the shape memory alloy. Conversely, when cooling from the temperature range which is the parent phase, martensitic transformation occurs gradually and eventually becomes the complete M phase. Similar to the matrix transformation, the start temperature of martensitic transformation is called Ms point, and the end temperature is called Mf point. The Ti-Ni binary alloy has such a property that this Mf point is lower by about 30 ° C. than the Af point. This is called temperature systemization, but when operating Ti—Ni by temperature change, it is necessary to consider this temperature hysteresis. When Ti-Ni is thermomechanically treated under specific conditions, a phase called R phase (rhombohedral structure) appears between the M phase and the matrix phase. While the R phase has a small temperature hysteresis of about 3 ° C. while the amount of shape recovery between normal M phase and the parent phase is 6% at maximum, when response to a temperature change is required, The phase-R phase transformation is often utilized. The temperature hysteresis of the Ti—Ni—Cu-based SMA is about 12 ° C., which is smaller than that of the Ti—Ni binary alloy, while that of the Ti—Ni—Nb SMA is about 150 ° C., which is larger than that of the Ti—Ni binary alloy. Therefore, it can be used properly according to each use.

      Examples of copper-based SMA include a Cu-Zn-Al alloy, a Cu-Al-Ni alloy, and a Cu-Al-Mn alloy. The martensitic reverse transformation temperature of copper system is -100 ° C to 150 ° C. The shape memory mechanism of the copper-based SMA is almost the same as that of the Ti-Ni system. The Ti-Ni-based SMA is superior in terms of strength, corrosion resistance and reliability, but the copper-based SMA is superior in terms of processability and economical efficiency.

      The complex of the present invention can be arbitrarily selected and combined from the above-mentioned SMP and SMA. However, the Tg temperature has to be higher than room temperature because it is necessary to recover the memory shape of SMP by heating. In addition, the Af point of SMA needs to be higher than the Tg of SMP since the SMP must have a higher resiliency than the SMA at around the Tg temperature. Furthermore, since the SMA needs to reduce the shape recovery at room temperature and does not prevent the deformation of the SMP, the Mf point and the Rf point must be higher than the room temperature.

      The difference between the shape recovery temperatures of SMP and SMA is not particularly limited, but in consideration of practicality, it is preferable that Tg is 10 ° C. or more higher than Ms, preferably 20 ° C. or more higher.

      Preferred SMP and SMA combinations include shape memory polyurethanes having a Tg of 40 ° C. to 60 ° C. and TI-Ni binary SMAs having an Af of 80 ° C. to 100 ° C.

      As described above, in the composite of the present invention, the shape-fixing effect of the SMP is weakened by the temperature rise due to heating from room temperature to just below the Tg temperature, so that the generation force of the SMP decreases and conversely, the recovery force of the SMA is The increase gradually transforms to the SMA memory shape. When the temperature exceeds the Tg temperature, the shape of the SMP rapidly recovers to the shape stored by the SMP. When the temperature of the complex exceeds the Af temperature of the SMA, it deforms rapidly into the shape stored by the SMA.

      There is no particular limitation on the specific combination of SMP and SMA. The SMP needs to store the shape in advance. For example, as shown in FIG. 1, SMA 1 may be coated directly with SMP2. The SMA 1 may be stored in a bent shape, stretched and straightened, and the SMP 2 may be coated thereon.

      As described above, according to the present invention, it is possible to form a shape memory complex that operates in two directions only by heating, and to solve the problem of slow response speed at the time of cooling of the shape memory complex. In this case, the application to the field which could not be applied due to the problem of response speed is expanded, and also space saving and cost reduction are realized.

It is a figure which shows one embodiment of the shape memory complex of this invention. It is a figure explaining the mechanism of the robot hand using the shape memory complex of this invention.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.
Example 1
(Af point: 74 ° C., Rf point: 42 ° C.) was memorized in a linear shape in the SMA wire rod of a 0.3 mm diameter Ti-Ni binary alloy. The SMA was elongated into a linear state, and polyurethane-based SMP (Tg: 55 ° C.) was formed into a strip shape (longitudinal: 60 mm, width: 10 mm, thickness: 0.25 mm) using a 3D printer. Shape memory processing was applied to the SMP in a spiral shape. A linear memorized 0.3 mm diameter SMA was sandwiched between two SMPs and coated by hot pressing at 130 ° C. The height of the complex was 1.1 mm at room temperature. When this composite is heated, the height of the composite is approximately linear shape at 40 ° C. 0.8 mm, 50 ° C., 0.75 mm, 0.5 mm at 60 ° C., 0.75 mm at 70 ° C., 80 ° C. 0 mm), i.e. the stored shape of the SMA. Although it repeated 10 times, the fall of deformation was not seen.

      A robot hand is created as shown in FIG. 2 using a pair of curved shape shape memory complexes. The robot hand opens once in accordance with heating, and the robot hand is closed by further heating. If heating is continued further, the robot hand opens. By performing this operation, it is possible to hold an object with the robot hand, move it while holding it, move it away, and carry the object by the robot hand only by continuing to heat the shape memory complex.

1 SMA
2 SMP
3 Robot hand fixing tool

Claims (5)

    The shape recovery temperature of the shape memory polymer (glass transition temperature) (glass transition temperature) comprising a shape memory polymer storing a certain shape recovery operation and a shape memory alloy storing a shape recovery operation of the shape memory polymer and a shape recovery operation in another direction. , Tg) is higher than room temperature, (2) shape recovery temperature (martensitic reverse transformation temperature, Af) of shape memory alloy is higher than Tg temperature, and Mf point or Rf point of shape memory alloy is higher than room temperature, When heated to just before the Tg temperature, the shape of the shape memory polymer gradually changes from the memorized shape of the shape memory polymer to another shape memorized by the shape memory alloy. A shape memory composite characterized in that the shape memory alloy recovers to the shape memorized thereafter.     The shape memory composite according to claim 1, wherein the shape memory polymer is a polymer selected from polyurethane, polyisoprene, styrene butadiene copolymer, polyethylene and polynorbornene.     The shape memory composite according to claim 1, wherein the shape memory alloy is a Ti-Ni based shape memory alloy, a Ti-Nb based shape memory alloy, a Ti-Mo based shape memory alloy, or a copper based shape memory alloy.     The shape memory composite according to claim 1, wherein the shape memory alloy is coated with a shape memory polymer of which shape is stored in advance.     A method for producing a shape memory composite, comprising hot pressing a shape memory polymer having a shape stored in advance in a shape memory alloy.

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