Preparation and use methods of epoxy structure adhesive capable of being peeled off as required during electrification
Technical Field
The invention relates to the technical field of advanced material preparation, in particular to a preparation method and a use method of an epoxy structure adhesive capable of being peeled off as required when electrified.
Background
The epoxy structure adhesive is a substance which is formed by compounding an epoxy resin matrix, a filler and an auxiliary agent and bonds two base materials together by utilizing interfacial adhesion and molecular cohesion. The epoxy structural adhesive can bear larger load, mainly plays a role in bonding and fixing, is mainly used for bonding structural members, and has very wide application in industries such as aerospace, home buildings, automobiles and ships and the like.
Most of the epoxy structural adhesive is non-permanent adhesive in a plurality of use occasions, and many adhesive scenes are often required to be stripped and disassembled, so that the adhesive parts are convenient to maintain or recycle. This requires that the epoxy structural adhesive have sufficiently excellent adhesion reliability within the life cycle and be quickly and safely peeled off as needed (i.e., peeled off as needed) after maintenance is required or the life cycle is completed. However, the epoxy structural adhesive forms a strong adhesive force with the adhered substrate through mechanical interlocking, van der waals force, electrostatic adsorption, chemical bond and other interactions, the body strength of the epoxy resin adhesive is high, an effective on-demand peeling method is not available at present, and the epoxy structural adhesive is actually used in a mode of mechanical peeling, solvent-assisted mechanical peeling or laser ablation-assisted mechanical peeling, is time-consuming and labor-consuming, can damage adhered parts, and is very unfavorable for long-term sustainable development of structural adhesion.
Disclosure of Invention
The invention aims to develop a novel epoxy structure adhesive which can be peeled off as required when being electrified so as to realize the repair or recycling of adhered parts, aiming at the problem that the conventional epoxy structure adhesive cannot be peeled off as required during repair and disassembly after being adhered.
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
In order to achieve the objects and other advantages, according to the present invention, a method for preparing an epoxy adhesive with an epoxy structure capable of being peeled off as required by being energized is provided, wherein a metal lithium salt and a coordination polymer are added to an epoxy resin prepolymer, and a curing agent is added to the epoxy resin prepolymer, and the mixture is uniformly mixed by a certain mixing process to obtain the epoxy adhesive with a certain ionic conductivity.
Preferably, the epoxy structural adhesive is a one-component or two-component structural adhesive material before curing, which is a single-component or two-component structural adhesive materialThe bulk viscosity at room temperature is less than or equal to 200 Pa.s; the ionic conductivity refers to that the ionic conductivity of the cured epoxy structural adhesive is more than or equal to 1 multiplied by 10-7S/cm; the crystallinity of the cured epoxy structural adhesive is less than or equal to 30 percent, and the glass transition temperature is less than or equal to 50 ℃; the certain mixing process is any one of high-speed stirring, rolling and open milling, rolling and banburying and screw extrusion.
Preferably, the epoxy resin prepolymer is a high molecular oligomer which contains two or more epoxy groups, takes an aliphatic, alicyclic or aromatic organic compound as a skeleton, can react through the epoxy groups to form a chemical crosslinking structure, and has the bulk viscosity of less than or equal to 40 Pa-s.
Preferably, the epoxy resin prepolymer is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, polyphenol epoxy resin, aliphatic glycidyl ether epoxy resin and alicyclic glycidyl ether epoxy resin;
preferably, the metal lithium salt is an organic salt or an inorganic salt composed of lithium ions and anions; the anion is CF3SO3 -、[C(SO2CF3)3]-、(CF3CF2SO2)2N-、[(SO2C4F9)N]2 2-Any one of the above;
the metal lithium salt added into the epoxy resin prepolymer is one or more of compounds formed by lithium ions and anions; the mass fraction of the metal lithium salt in the epoxy structural adhesive is less than or equal to 40 wt%.
Preferably, the coordination polymer can perform coordination complexing action with metal lithium salt, and can effectively promote the dissolution of lithium salt in the polymer; the coordination polymer is a homopolymer of one of polyoxymethylene, polyethylene oxide, polypropylene oxide, polyoxetane, poly beta-propiolactone, polyepichlorohydrin, polyvinyl acetate, polyacrylonitrile, polyethylene succinate, polymethyl methacrylate, polyvinyl amide, polyethylene adipate, polymethyl ethylene carbonate and poly sulfide or a copolymer formed by the repeating units of the polymer;
the number average molecular weight of the coordination polymer is not more than 8000 g/mol-1One or more coordination polymers are introduced into the epoxy resin prepolymer; the mass fraction of the coordination polymer in the epoxy structural adhesive is less than or equal to 40 wt%.
Preferably, the curing agent is one or more of polyamine curing agent, modified polyamine curing agent, anhydride curing agent and high polymer prepolymer; wherein the polymer prepolymer is a polymer prepolymer with one or more of amino, phenolic hydroxyl and carboxyl active groups.
Preferably, the curing agent is one or more of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylpentamine, isophoronediamine, diethylaminopropylamine, triethanolamine, m-phenylenediamine, dicyandiamide, benzyldimethylamine, adipic dihydrazide, maleic anhydride, phthalic anhydride, pyromellitic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, a condensation product of m-phenylenediamine and phenyl ether (590 curing agent), a condensation product of diethylenetriamine and butyl ether (593 curing agent), a phenol formaldehyde hexamethylenediamine condensation product (701 curing agent), low molecular weight polyamide, a condensation product of linoleic acid dimer and diethylenetriamine, a condensation product of linoleic acid dimer and triethylenetetramine, and a condensation product of linoleic acid dimer and tetraethylenepentamine.
The invention also provides a use method of the electrified and on-demand peelable epoxy structural adhesive, which is characterized in that the adhesive is applied to a bonded base material through a sizing process, and plays a role in bonding and fixing after being cured, and when repairing and disassembling are needed, voltage is applied to two sides of the bonded base material to realize on-demand peeling and disassembling; the bonded substrate is a metal interface or a conductive surface.
Preferably, the curing mode is one or more of normal-temperature standing curing, heating curing or UV curing; wherein the temperature for heating and curing is less than or equal to 180 ℃;
the glue applying process is any one of manual glue gun glue applying, pneumatic glue applying, screw extrusion glue applying and jet glue applying;
the bonded base material is any one of gold, silver, copper, iron, magnesium, zinc, nickel, beryllium, tungsten, stainless steel, metal alloy and polymer conductive composite material; if the surface of the bonded base material is non-conductive, the surface of the bonded base material needs to be subjected to conductive treatment;
the applied voltage is direct current voltage or alternating current voltage; the applied voltage is 1-100V, and the electrifying time is 1-60 s; the tensile shear strength of the adhesive bonded and cured on the bonded base material is less than or equal to 0.1 MPa.
The invention at least comprises the following beneficial effects: the preparation method is simple and effective, solves the problem that the conventional epoxy structural adhesive cannot be peeled off as required after being bonded, and has wide application prospect.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Description of the drawings:
FIG. 1 is a schematic diagram of the on-demand peel-off energization of the bonding system of the present invention.
The specific implementation mode is as follows:
the present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Example 1:
the number average molecular weight of the polymer in 40g is 400 g/mol-125g of [ C (SO) was added to polyethylene oxide (PEO400)2CF3)3]Stirring Li at the rotating speed of 200rpm for 1h at 50 ℃ until the lithium tetrafluoroborate is completely dissolved; then 100g of bisphenol F epoxy resin F46 (industrial grade) and 20g of dicyandiamide are added, and the mixture is stirred at the room temperature for 1h at the rotating speed of 200rpm to obtain the epoxy structural adhesive which can be peeled off as required by electrification. When in use, the spray type point is adoptedThe glue process is used for gluing, and heating curing is carried out after gluing; taking aluminum alloy as a bonded base material, and heating at 160 ℃ for 1h until the adhesive is completely cured; and applying 90V direct current voltage to two ends of the aluminum alloy, so that the bonding system can be completely peeled within 5 s.
Example 2:
20g (CF)3CF2SO2)2NLi is added to a reactor composed of 50g of a mixture having a number-average molecular weight of 400 g.mol-1In polyethylene oxide (PEO400), stirring at a rotation speed of 200rpm for 1h at 50 ℃ to obtain a uniform solution; then 50g of bisphenol A epoxy resin E51 (industrial grade), 50g of bisphenol A epoxy resin E44 (industrial grade) and 15g of 593 amine curing agent (industrial grade) are added, and the mixture is stirred in ice bath for 1 hour to obtain the epoxy structural adhesive which can be peeled off as required after being electrified. When in use, the glue is applied by adopting a line-marking type glue-applying process, and then is kept stand and cured at normal temperature; taking an aluminum sheet as a substrate to be bonded, standing at room temperature for 48h to complete bonding, applying 60V direct current voltage to two ends of the aluminum sheet for 10s continuously, and completely stripping a bonding system.
Example 3:
20g of a polymer having a number average molecular weight of 400 g/mol-1Polypropylene oxide (PPO400) and 20g of a mixture of polypropylene oxide and polypropylene oxide having a number-average molecular weight of 800 g.mol-1Stirring the polypropylene oxide (PPO800) at the rotating speed of 200rpm for 30min at room temperature until the mixture is completely and uniformly mixed; then 30g of lithium trifluoromethanesulfonyl (LiCF) were added3SO3) Stirring was continued at 60 ℃ for 1h at 200rpm to LiCF3SO3Completely dissolving; then 100g of bisphenol A epoxy resin E51 (industrial grade) and 10g of ethylenediamine are added, and the mixture is stirred in ice bath at the rotating speed of 200rpm for 1h to obtain the electrified peelable epoxy structural adhesive. When in use, the glue is applied by adopting a line-marking type glue-applying process, and then is kept stand and cured at normal temperature; and (3) taking the copper sheet as a substrate to be bonded, standing at room temperature for 48h to complete bonding, applying 30V direct current voltage to two ends of the copper sheet for 30s continuously, and completely stripping the bonding system.
Example 4:
25g of [ (SO)2C4F9)N]2Li2Adding 30g of the mixture into the reactor, wherein the number average molecular weight of the mixture is 800g & mol-1The mixed solution of polyethylene oxide (PEO800) is stirred at a rotating speed of 200rpm for 1 hour at 60 ℃ to obtain a uniform solutionThe solution of (1); then 100g of bisphenol A epoxy resin E54 (industrial grade) and 20g of dicyandiamide are added, and the mixture is stirred at the rotating speed of 200rpm for 1 hour at room temperature to obtain the epoxy structural adhesive which can be peeled off as required by electrification. When in use, the glue is applied by adopting a line-marking type glue-applying process, and then is heated for crosslinking and curing; taking a stainless steel sheet as a substrate to be bonded, and heating and curing at 160 ℃ for 1h to complete bonding; and applying 60V direct current voltage to two ends of the stainless steel sheet for 10s, so that the bonding system can be completely peeled off.
Example 5:
15g of a polymer having a number average molecular weight of 600 g/mol-110g of polyethylene oxide (PEO600) having a number average molecular weight of 400 g.mol-1Mixing polypropylene oxide (PPO400) and 20g of trifluoromethyl sulfonyl lithium methide (LiTFSM), and stirring at the rotating speed of 200rpm and the temperature of 60 ℃ for 1 hour to form a uniform and transparent solution; then 60g of bisphenol A epoxy resin E51 (industrial grade), 40g of bisphenol F epoxy resin F46 (industrial grade) and 15g of dicyandiamide are added, and the mixture is stirred at the rotating speed of 200rpm for 1 hour at room temperature to obtain the epoxy structural adhesive which can be peeled off as required after being electrified. When in use, the glue is applied by adopting a jet type glue-applying process, and is cured by heating after the glue is applied; taking an aluminum sheet as a bonded substrate, and heating at 160 ℃ for 1h until the adhesive is completely cured; and applying 60V direct current voltage to two ends of the aluminum sheet for 10s, so that the bonding system can be completely peeled.
Example 6:
3.5g of [ C (SO)2CF3)3]Li and 5g number average molecular weight of 400 g.mol-1Mixing the polyethylene oxide (PEO400), and stirring at the rotating speed of 200rpm for 1h at the temperature of 60 ℃; then 10g of bisphenol A epoxy resin E54 (industrial grade) and 2g of 593 curing agent (industrial grade) are added, and the mixture is stirred at the rotating speed of 200rpm for 1 hour at room temperature to obtain the epoxy structural adhesive which can be peeled off as required after electrification. When in use, the glue is applied by adopting a line-marking type glue-applying process, and is heated and cured after being applied; and (3) taking a stainless steel sheet as a substrate to be bonded, and heating and curing at 160 ℃ for 1h to complete bonding.
The adhesive system prepared in example 6 was peeled off as needed by applying a voltage across the stainless steel sheets (fig. 1), and the higher the applied voltage value was, the longer the energization time was, and the more remarkable the effect of peeling off as needed was. As shown in Table 1 (note: all data in the table are averages of 5 test specimens), the average shear bond strength of the above adhesive system when not energized was 15.3 MPa. When 15V direct current voltage lasts for 15s, 30V direct current voltage lasts for 8s, 60V direct current voltage lasts for 8s or 90V direct current voltage lasts for 1s is applied to the two ends of the stainless steel sheet, the average bonding strength of the bonding system can be attenuated to 0 MPa; when 30V direct current voltage is applied to the two ends of the stainless steel sheet for 2s or 60V direct current voltage for 1s, the average bonding strength of the bonding system is reduced to be less than 0.1 MPa; the effectiveness of the preparation method of the adhesive with the epoxy structure peeled off as required is shown.
TABLE 1
Example 7:
the number average molecular weight of the polymer in 30g is 1000 g/mol-1To the polyoxycyclobutane of (2) was added 15g (CF)3CF2SO2)2NLi, stirring at the rotating speed of 200rpm for 1h at 60 ℃ until the lithium salt is dissolved; then 90g of bisphenol F epoxy resin F46 (technical grade) and 10g of epoxy resin with a number-average molecular weight of approximately 10000g mol are added-1Stirring the bisphenol S diglycidyl ether (industrial grade) at the rotating speed of 200rpm at 60 ℃ for 12 hours until the epoxy resin is fully dissolved; then adding 18g of diethylenetriamine, and stirring at the rotating speed of 200rpm for 1 hour at room temperature to obtain an epoxy structural adhesive which can be peeled off as required after being electrified; when in use, the glue is applied by adopting a marking-off type glue-applying process, and then the heating and the solidification are carried out after the glue is applied; taking stainless steel as a bonded substrate, and heating for 1h at 100 ℃ until the adhesive is completely cured; and applying 50V direct current voltage to two ends of the stainless steel sheet for 10s, so that the bonding system can be completely peeled.
The adhesive system prepared in example 7 was peeled off as needed by applying a voltage across the stainless steel sheets, and the higher the voltage value applied, the longer the energization time, and the more remarkable the effect of peeling off as needed. As shown in Table 2 (note: all data in the table are the average values obtained from 5 test specimens), the average shear bond strength of the above adhesive system when not energized was 18.5 MPa. When 15V direct current voltage lasts for 30s, 30V direct current voltage lasts for 15s, 60V direct current voltage lasts for 15s, or 90V direct current voltage lasts for 2s, the average bonding strength of the bonding system can be attenuated to 0 MPa.
TABLE 2
Example 8:
10g of a polymer having a number average molecular weight of 1000 g/mol-110g of a polyoxyalkylene having a number average molecular weight of 600 g.mol-110g of polymethyl methacrylate having a number average molecular weight of 400 g/mol-1And 15g (CF) of3CF2SO2)2NLi mixing, stirring at the rotating speed of 200rpm at 60 ℃ for 1h until the lithium salt is dissolved; then 90g of bisphenol F epoxy resin F46 (technical grade) and 10g of epoxy resin with a number-average molecular weight of approximately 10000g mol are added-1Stirring the bisphenol S diglycidyl ether (industrial grade) at the rotating speed of 200rpm at 60 ℃ for 12 hours until the epoxy resin is fully dissolved; then adding 18g of diethylenetriamine, and stirring at the rotating speed of 200rpm for 1 hour at room temperature to obtain an epoxy structural adhesive which can be peeled off as required after being electrified; when in use, the glue is applied by adopting a marking-off type glue-applying process, and then the heating and the solidification are carried out after the glue is applied; taking stainless steel as a bonded substrate, and heating for 1h at 100 ℃ until the adhesive is completely cured; and applying 50V direct current voltage to two ends of the stainless steel sheet for 10s, so that the bonding system can be completely peeled.
TABLE 3
The adhesive system prepared in example 8 was peeled off as needed by applying a voltage across the stainless steel sheets, and the higher the voltage value applied, the longer the energization time, and the more remarkable the effect of peeling off as needed. As shown in Table 3 (note: all data in the table are the average values obtained from 5 test specimens), the average shear bond strength of the above adhesive system when not energized was 18.55 MPa. When 15V direct current voltage lasts for 8s, 30V direct current voltage lasts for 4s, 60V direct current voltage lasts for 4s, or 90V direct current voltage lasts for 1s is applied to the two ends of the stainless steel sheet, the average bonding strength of the bonding system can be attenuated to 0 MPa; it is shown that the combination of the coordination polymer of this example can significantly improve the peeling efficiency and realize peeling at a relatively low voltage.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.