Adhesive and structure, and adhesion method

Abstract

Provided is an adhesive that can provide quick bonding between thermoplastic resins and excellent bond strength, a structure having adhesion provided by the adhesive, and an adhesion method using the adhesive. The adhesive bonds a first member (11) containing a thermoplastic resin or a carbon fiber reinforced thermoplastic resin and a second member (12) containing the thermoplastic resin or the carbon fiber reinforced thermoplastic resin. The adhesive includes a thermoplastic resin as a main component containing a metal nano material that absorbs electromagnetic waves and generates heat.

Claims

1. An adhesive for bonding between a first member containing a thermoplastic resin or a carbon fiber reinforced thermoplastic resin and a second member containing the thermoplastic resin or the carbon fiber reinforced thermoplastic resin, the adhesive comprising: a thermoplastic resin containing a metal nano material that absorbs electromagnetic waves and generates heat, wherein the nano material is nanocoils.

2. The adhesive according to claim 1, wherein a frequency of the electromagnetic waves is 3 MHz or more and 3 GHz or less.

3. The adhesive according to claim 1, wherein the metal is platinum or gold.

4. The adhesive according to claim 1, wherein the adhesive is in a sheet form, and the amount of the nano material added to the thermoplastic resin is 30 g/cm.sup.2 or less.

5. A structure comprising the first member and the second member bonded to each other with the adhesive according to claim 1.

6. The structure according to claim 5, wherein the thermoplastic resin in the adhesive and the thermoplastic resin in at least one of the first member and the second member are the same material.

7. An adhesion method comprising the steps of: placing the adhesive according to claim 1 in a portion of the first member to be bonded; placing the second member on the adhesive; and irradiating the adhesive with the electromagnetic waves to bond the first member and the second member with the adhesive.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view of a structure according to one embodiment of the present invention.

(2) FIG. 2 is a schematic view for explaining a method of irradiation with electromagnetic waves.

(3) FIG. 3 is a schematic view for explaining another method of irradiation with electromagnetic waves.

(4) FIG. 4 is a graph showing variations in the temperatures of the substrates of Example 1 and a comparative example with time.

(5) FIG. 5 is a graph showing the amounts of nano material in a main component and variations in the temperatures of the substrates with time.

DESCRIPTION OF EMBODIMENTS

(6) FIG. 1 is a schematic view of a bonding portion of a structure according to one embodiment of the present invention. A structure 10 has a first member 11 and a second member 12 overlapped each other and bonded to each other at the overlap through an adhesive layer 13. To be specific, the structure 10 is an aircraft, a wind turbine blade, or the like.

(7) The first member 11 and the second member 12 are composed of thermoplastic resins or carbon fiber reinforced thermoplastics (CFRTPs).

(8) In other words, the first member 11 and the second member 12 are a combination of members of thermoplastic resins, members of CFRTPs, or a member of a thermoplastic resin and a member of a CFRTP. Taking an aircraft as an example, the first member 11 and the second member 12 are a skin and a stringer, a floor beam and a bracket, or the like.

(9) The adhesive layer 13 is made of an adhesive mainly composed of a thermoplastic resin containing a metal nanomaterial that absorbs electromagnetic waves and generates heat.

(10) Examples of a thermoplastic resin serving as the main component of the adhesive include polyether ether ketone (PEEK), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon 6 (PA6), nylon 66 (PA66), polyphenylene sulfide (PPS), polyetherimide (PEI), and polyetherketoneketone (PEKK). It is preferable that the main component be the same as the materials for the first member 11 and the second member 12 to provide excellent bond strength of the adhesive layer 13. If the first member 11 and the second member 12 are composed of different thermoplastic resins, the adhesive is preferably composed of the same material as one of the first member 11 and the second member 12.

(11) A nano material refers to a material having a nano-scale two-dimensional or three-dimensional size (one to several hundred nanometers). To be specific, a nano material is, for example, a nanofiber (which has a nano-scale cross-sectional diameter), a nanocoil (which has a nano-scale cross-sectional diameter and is formed in a coil form in the longitudinal direction), nanoparticles (which have a nano-scale grain size), a nanotube (which is a hollow fiber having a nano-scale cross-sectional diameter), or the like. Nanocoils and nanofibers are particularly preferable as they have a high electromagnetic wave absorption efficiency.

(12) When a large amount of nano material is added to the main component, a crack occurs in the adhesive layer 13 during use. For this reason, the amount of nano material added to the main component is 0.1 mg/cm.sup.2 or less, preferably 30 g/cm.sup.2 or less in mass per adhesive unit area. This nano material, which has a high electromagnetic wave absorption efficiency, yields a large calorific value even at a low addition amount. Meanwhile, considering easy management of the addition amount, dispersion of the nano material, the calorific value, and the like, the lower limit of the addition amount is preferably 0.1 g/cm.sup.2.

(13) Although any metal can be used, a preferred metal has a high electromagnetic wave absorption efficiency at the frequency of electromagnetic waves which the metal is irradiated with. Specific examples are Pt, Au, Ni, and Cu.

(14) The metal is oxidized in a step of forming nanocoils or nanofiber described later. Pt and Au, which are resistant to oxidization, have electrical conductivity even when they are oxidized; thus, Pt and Au are most suitable for nano materials.

(15) A metal nanofiber is fabricated by the electrospinning method.

(16) A metal acetate is dissolved in a polymer solution (e.g., a polyvinyl alcohol aqueous solution). The obtained solution is sprayed onto a substrate by the electrospinning method, thereby forming nanofibers containing a metal. The obtained nanofibers are subjected to heat treatment in a reduced atmosphere, thus producing metal nanofibers.

(17) Metal nanocoils are obtained by forming metal thin films on the surface of nanofibers as core members, the nanofibers being fabricated by the electrospinning method. In this case, the core members may be composed of a metal or polymer. The nanocoils may be solid or hollow. An example method of forming hollow nanocoils uses a polymer core member which is provided with a metal thin film formed thereon and then subjected to heat treatment for vaporization of the polymer.

(18) The adhesive may be in the liquid state or a sheet form (having a thickness of about 150 m). An adhesive in a sheet form is easily applicable to the members and the thickness of the adhesive layer 13 can be made generally uniform.

(19) A method of bonding the first member 11 and the second member 12 with the adhesive of this embodiment will now be explained.

(20) A predetermined amount of aforementioned adhesive is applied to a portion of the first member 11 to be bonded. To use the adhesive in a sheet form, it is cut into a predetermined size of adhesive sheet and then placed on the first member 11. A portion of the second member 12 to be bonded is brought into contact with the adhesive on the first member 11, and the second member 12 is placed on the first member 11.

(21) The first member 11 and the second member 12 are overlapped each other, and the adhesive is irradiated with electromagnetic waves. The electromagnetic waves may have any frequency but are preferably not electromagnetic waves, such as X-rays, which require special management. They are preferably electromagnetic waves having a frequency that the metal in the nano material absorbs at a high absorption efficiency. Considering this, preferred is irradiation with high frequency (HF, 3 MHz or more and 30 MHz or less), very high frequency (VHF, 30 MHz or more and 300 MHz or less), or ultrahigh frequency (300 MHz or more and 3 GHz or less). To be specific, electromagnetic waves in the ISM band can be used.

(22) Electromagnetic waves for irradiation are required to be able to pass through the first member 11 and the second member 12; thus, an appropriate frequency of electromagnetic waves is selected.

(23) FIG. 2 is a schematic view for explaining a method of irradiation with electromagnetic waves. In the method shown in FIG. 2, a member composed of the first member 11 and the second member 12 overlapped through the adhesive 14 is accommodated in a chamber 15. Upon irradiation of the member with electromagnetic waves in the chamber 15, the electromagnetic waves reach the adhesive 14. The nano material (metal nanocoils or metal nanofibers) in the adhesive 14 absorbs electromagnetic waves and generates heat. The heat generated by the nano material heats and melts the main component (thermoplastic resin). When the electromagnetic waves are blocked, the adhesive is cooled, thereby forming an adhesive layer.

(24) FIG. 3 is a schematic view for explaining another method of irradiation with electromagnetic waves. In the method shown in FIG. 3, an irradiator 16 is provided above the adhesive 14 between the members. At this time, the center of the area to which the adhesive 14 is applied generally coincides with the center of the irradiator 16. In the method shown in FIG. 3, the members do not need to be accommodated in a container such as a chamber. When the irradiator 16 is operated to irradiate the members with electromagnetic waves from the irradiator 16, electromagnetic waves are absorbed in the nano material and the nano material generates heat as described above, so that the main component of the adhesive 14 melts. Subsequently, stopping the irradiator 16 blocks the electromagnetic waves, thereby cooling the adhesive and forming an adhesive layer.

(25) The irradiance and irradiation time of electromagnetic waves are set such that the main component melts and the shape during adhesive application or the sheet shape is maintained so that it cannot flow into the portions other than the portions to be bonded.

Example 1

(26) As a sample of this example, prepared was a PPS resin substrate (produced by TORAY industries, Inc., model number: A900, 10 mm high10 mm wide2 mm thick) with Pt nanocoils (solid coils with a diameter of 250 nm and a coil pitch of 3.2 m) placed thereon. The substrate was placed on an electronic scale, and the Pt nanocoils were placed on the substrate. This measurement result showed that the value was below the lower measurement limit (0.1 mg). Accordingly, the amount of Pt nanocoils on the substrate was below 0.1 mg/cm.sup.2.

(27) As a sample of a comparative example, prepared was a PPS resin (produced by TORAY industries, Inc., model number: A900) containing 60 wt % (1.3 g/cm.sup.3) of a NiZn-based ferrite (produced by JFE Chemical Corporation, model number: JN-350) mixed thereinto, molded on a substrate of 10 mm high10 mm wide2 mm thick. It should be noted that the ferrite material is a material traditionally known to exhibit high electromagnetic wave absorption efficiency.

(28) Each substrate was irradiated with microwaves (2.45 GHz, 20 W) from above, and variations in the temperature of the substrate surfaces with time were measured using an infrared thermography. FIG. 4 shows the results.

(29) In this example, the temperature sharply increased within about 20 seconds from the initiation of the irradiation. Then, the rate of increase in temperature decreased. The temperature reached 282.2 C. in 20 seconds from the initiation of the irradiation, and then 300 C. in about 33 seconds. The melting point of a PPS resin is about 280 C. Hence, the method of this example enabled heating to above the melting point of the PPS resin.

(30) In the comparative example, the temperature gradually increased from the initiation of the irradiation and reached 72.2 C. in five minutes. In the comparative example, the temperature does not reach the melting point of the PPS resin and thus cannot melt the PPS resin. In other words, the members cannot be bonded to each other with the PPS resin.

(31) For this reason, Pt nanocoils can be said to be a material having a very high electromagnetic wave absorption efficiency compared with ferrite. For this reason, it can be said that the use of only a slight amount of Pt nanocoils can melt the PPS resin and bond the members to each other, thereby providing adequate bond strength.

Example 2

(32) As a sample, prepared was a polyether ether ketone (=PEEK) resin substrate (produced by Victrex Japan, Inc., model number: 450G, 10 mm high10 mm wide3 mm thick) with Pt nanocoils (solid coils with a diameter of 250 nm and a coil pitch of 3.2 m) placed thereon.

(33) Here, the amounts of nano materials placed thereon were 7.2 g/cm.sup.2, 12 g/cm.sup.2, and 24 g/cm.sup.2.

(34) As a sample of a comparative example, the same polyetheretherketone resin substrate as in the aforementioned example was prepared and was irradiated with microwaves from above without Pt nanocoils placed thereon as in the aforementioned example. Variations in the temperature of the substrate surfaces with time were measured using an infrared thermography. FIG. 5 shows the results.

(35) The surface temperature of the sample without a nano material placed thereon (the PEEK resin substrate) barely increased. In contrast, as the amount of nano material placed thereon increased, the surface temperature of the substrate increased. The melting point of the PEEK resin is in the range of about 340 to 380 C. In other words, any method of this example enabled heating to above the melting point of the PEEK resin. In reality, any PEEK resin substrate with the nano material of this example placed thereon had the melting of the substrate surface. Referring to FIG. 5, even small amounts of 30 g/cm.sup.2 or less of nano material placed thereon obtained large calorific values.

REFERENCE SIGNS LIST

(36) 10 structure 11 first member 12 second member 13 adhesive layer 14 adhesive 15 chamber 16 irradiator