CN113502139A - Low-temperature-resistant slow-bonding prestressed tendon - Google Patents
Low-temperature-resistant slow-bonding prestressed tendon Download PDFInfo
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- CN113502139A CN113502139A CN202110993892.XA CN202110993892A CN113502139A CN 113502139 A CN113502139 A CN 113502139A CN 202110993892 A CN202110993892 A CN 202110993892A CN 113502139 A CN113502139 A CN 113502139A
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Abstract
The invention provides a low-temperature-resistant slow-bonding prestressed tendon, which comprises a prestressed steel bar, a low-temperature-resistant slow-bonding agent and a sheath, and is characterized in that a filler in the low-temperature-resistant slow-bonding agent is polymer graft modified Al2O3Fine particles, polymer graft-modified Al2O3The particles are in Al2O3The particles are modified by a coupling agent containing vinyl silane and then are coated on porous Al2O3The surface of the particle is polymerized in situ to graft acrylamide, methylene bisacrylamide and styrene-butadiene-styrene block copolymer (SBS). The low-temperature-resistant slow-bonding prestressed tendon filler provided by the invention uses polymer-grafted modified Al2O3Microparticles which significantly improve the low temperature resistance, especially toughness, of the slow-release binder and improve the cycling of the slow-release binder at high and low temperaturesThe mechanical property retention rate is high. Polymer graft modified Al in the invention2O3The addition amount of the particles is small relative to that of the epoxy resin, so that the condition that the mechanical property is reduced because a large amount of inorganic filler is added to improve the fluidity of the slow adhesive in the prestressed tendon is avoided.
Description
Technical Field
The invention relates to the technical field of prestress, in particular to a low-temperature-resistant slow-bonding prestressed tendon.
Background
Compared with common reinforced concrete, prestressed concrete can fully exert material performance, improve the crack resistance and structural rigidity of members, has smaller self weight and better durability, and is one of the most common civil engineering structural forms in the world today. The prestressed concrete technology, i.e. slow-bonding prestressed concrete technology, is a prestressed form which can implement gradual transition from non-bonding to bonding between prestressed reinforcement and concrete by means of curing of slow-bonding agent, and at the same time possesses the characteristics of bonding prestressed reinforcement and non-bonding prestressed reinforcement. Almost no binding force exists between the early prestressed tendons and the slow binding material, and the early prestressed tendons and the slow binding material are the same as a non-binding system; and the later-stage slow curing of the bonding material can achieve the effect similar to that of a bonding system. The slow-bonding prestressed concrete system has the advantages of convenience in construction of a non-bonding system and flexibility in rib arrangement, and has the characteristics of high strength utilization rate and corrosion resistance of the bonding system concrete.
The slow-bonding prestressed tendon consists of three parts, namely a prestressed tendon, a slow-bonding agent and an outer sheath, wherein the slow-bonding agent has certain fluidity and good adhesiveness to steel before the prestressed tendon tensioning construction is completed so as to meet the index requirement of the tensioning construction. After the tensioning construction is finished, the delayed coagulation adhesive is gradually solidified, the solidified delayed coagulation adhesive is firmly bonded with the prestressed tendon and the outer sheath, and is tightly occluded with concrete through concave-convex indentation of the outer sheath, so that the integral mechanical effect is generated.
The slow bonding material used between the steel beam and the sheath in the slow bonding prestressed system at present comprises two types, namely slow setting mortar and epoxy resin, wherein the slow bonding material is a cement-based material, and the slow bonding material is an epoxy-based material. The epoxy resin system has higher strength and certain micro-expansibility, so the construction performance and the mechanical property of the retarded mortar before and after solidification are better. The slow-binding material using epoxy resin as main component is made up by using epoxy resin providing main adhesive property, diluent for regulating viscosity, solidifying agent for controlling solidifying period, filler and other modifying material through the processes of physical process and uniformly mixing them. Before consolidation, the epoxy resin has better thixotropy, and the prestressed steel strand almost has no friction when sliding in the sheath; after a certain period of time, the epoxy resin is solidified and then firmly bonded with the prestressed tendons and the wrapped polyethylene sheath, and is bonded with the concrete into a whole. Meanwhile, the epoxy resin slow-bonding material has better stability and good environmental adaptability. Epoxy resins are gaining increasing attention due to their significant advantages.
The epoxy resin has high crosslinking density, is brittle in nature and more brittle at low temperature, usually has large using amount of the filler, and when an epoxy adhesive system with excessive filler is stressed, strong stress concentration is easily generated, large cracks or gaps are caused during working at low temperature, intermolecular chemical bonds are broken or directly lose entanglement, a crosslinking structure is damaged, the toughness is greatly reduced, and the application of the slow-bonding reinforcing steel bar prepared by the slow-bonding reinforcing steel bar in low-temperature engineering is limited, so that the slow-bonding prestressed bar capable of resisting low temperature has important significance and application value.
Patent CN200910086949.7 discloses a delayed coagulation adhesive for retarded adhesive prestressed tendons, which comprises conventional main polymer epoxy resin of retarded adhesive, curing agent polyamide and diluent, and also comprises thixotropic agent fumed silica or organic bentonite, wherein although fumed silica or bentonite has thixotropy, the epoxy adhesive system is a strong polar system, fumed silica or organic bentonite cannot be well dispersed in the epoxy adhesive system, and a coupling bond is difficult to form, the fumed silica or organic bentonite is agglomerated or subjected to other reactions along with the time extension, so that the thixotropic effect cannot be well exerted, the thixotropic index of the retarded adhesive system is reduced, and due to the reason, the thixotropic agent added into the retarded adhesive for improving the thixotropy of the adhesive is not widely popularized and applied, and a large amount of filler is still required to be matched for use. The flocculation structure is damaged in the coating or tensioning process, the viscosity is reduced, the fluidity is enhanced, and after the external force is cancelled, the delayed coagulation adhesive can gradually recover to a static state. For example, patent CN201510187551.8 discloses a slow-bonding agent for slow-bonding prestressed tendons and a preparation method thereof, wherein thixotropic agents are not used in the patent, and the rheological property of an adhesive system is improved only by adding a large amount of fillers.
The inventor's former patent CN202010382926.7 discloses a bond-retarded prestressed steel bar, which comprises a prestressed steel bar, a bond-retarded agent and a sheath, and is characterized in that the bond-retarded agent comprises a main resin, a curing agent, a diluent and a modified filler, wherein the modifying agent of the modified filler is an epoxy silane coupling agent, and the curing agent is a compound of fluorine-containing polyamide and low molecular weight polyamide. But its low temperature resistance is insufficient. Another prior patent CN202110847572.3 by the inventor discloses a low temperature resistant slow-release adhesive, which is prepared from the following raw materials in parts by weight: 100 parts of epoxy resin and polymer graft modified Al2O317-25 parts of particles, 10-15 parts of diluent, 3-5 parts of curing agent and 1-3 parts of toughening agent; the polymer is grafted and modified with Al2O3The particles are Al2O3The particles are modified by a coupling agent containing vinyl silane and then are coated on porous Al2O3In-situ polymerization on the surface of microparticles, polymerization monomer packageIncluding methyl (meth) acrylate and acrylamide. Al (Al)2O3The particles provide good compressive strength as a filler, and because the copolymer of MMA and AM is grafted on the surfaces of the particles, amide groups and ester groups can generate large interaction force with epoxy resin, and when the particles are stressed, crazing can be initiated and microcrack can be stopped, and energy can be absorbed to achieve the purpose of toughening. However, the durability after curing is not enough, the strength is reduced more under high and low temperature alternating cycle, and the applicant finds that the mechanical property of the slow-bonding prestressed material is not enough under the high and low temperature alternating condition, and particularly, the toughness is reduced more quickly because the added toughening agent is not good in affinity under repeated high and low temperature change, particularly in freeze-thaw cycle, and is easy to precipitate and migrate. In addition, the viscosity of the epoxy resin rapidly decreases at low temperature and Al2O3The compatibility of the particles and the grafted polymer is poor, so that the mechanical property, particularly the toughness, of the slow-bonding prestressed tendon at low temperature still needs to be improved continuously. At low temperature, especially at subzero temperature, the material cannot be normally coagulated and hardened, if the material is frozen and expanded, the material is heated and thawed, and the prestressed pipeline can crack after repeated times, which is a serious safety hazard.
In summary, there is a need to develop a slow-bonding prestressed tendon with low temperature resistance, which has excellent mechanical properties at low temperature, especially improved toughness, and can ensure that the mechanical strength is not reduced basically after repeated high-low temperature alternating cycles, thereby ensuring smooth construction of engineering.
Disclosure of Invention
In order to overcome the defect of insufficient mechanical property of the slow bonding prestressed tendon in the prior art at low temperature or under the condition of repeated high-low temperature alternating circulation, the invention aims to provide the low-temperature resistant slow bonding prestressed tendon. The low-temperature-resistant slow-bonding prestressed tendon filler provided by the invention uses polymer-grafted modified Al2O3The microparticles reduce the cross-linking density of the epoxy resin, thereby reducing the glass transition temperature of the epoxy adhesive, improving the low-temperature resistance and the strength at low temperature, and simultaneously, the copolymer of SBS and AM is grafted on the surface of the microparticles, so that amide groups and the epoxy resin can generate great mutual effectActing force, when the particles are stressed, the crazing can be initiated and the microcrack can be stopped, and the energy can be absorbed to achieve the aim of toughening; the SBS chain segment can obviously improve the mechanical property, particularly the toughness of the material at low temperature. For Al2O3After the polymer grafted on the surface of the particle is crosslinked to a certain degree, the mechanical property retention rate of the slow adhesive in high and low temperature alternating circulation is obviously improved. Further, in the present invention, polymer graft-modified Al2O3The addition amount of the particles is small relative to that of the epoxy resin, so that the condition that the mechanical property is reduced because a large amount of inorganic filler is added to improve the fluidity of the slow adhesive in the prestressed tendon is avoided.
The technical scheme of the invention is realized as follows:
the low-temperature-resistant slow-bonding prestressed tendon comprises a prestressed steel bar, a low-temperature-resistant slow-bonding agent and a sheath, and is characterized in that a filler in the low-temperature-resistant slow-bonding agent is polymer graft modified Al2O3Fine particles, polymer graft-modified Al2O3The particles are in Al2O3The particles are modified by a coupling agent containing vinyl silane and then are coated on porous Al2O3The surface of the particle is polymerized in situ to graft acrylamide, methylene bisacrylamide and styrene-butadiene-styrene block copolymer (SBS).
The coating of prestressing steel surface has slow binder, and slow binder outside cladding protective sheath, solidification back prestressing steel, slow binder and protective sheath zonulae occludens are a whole.
In the SBS, the styrene content is 25-35 wt%, and the viscosity of a 15 wt% toluene solution is 400-700cps at 25 ℃.
The vinyl silane coupling agent is at least one selected from vinyl trimethoxy silane, vinyl triethoxy silane, vinyl triisopropoxy silane, methyl vinyl dimethoxy silane, methyl vinyl diethoxy silane and vinyl tri (2-methoxyethoxy) silane.
Further, the low-temperature-resistant slow-bonding prestressed tendon is prepared from the following raw materials in parts by weight: 100 parts of epoxy resin and polymer graft modification Al2O320-30 parts of particles, 10-15 parts of diluent, 5-8 parts of curing agent and 1-1.5 parts of toughening agent.
Further, Al is grafted and modified on the polymer2O3In the fine particles, Al2O3The mass ratio of the particles to the vinyl-containing silane coupling agent to the acrylamide, the methylene bisacrylamide and the styrene-butadiene-styrene block copolymer is 100: 3-5: 10-14: 0.6-1: 34-45.
The inventors have unexpectedly found that polymer graft-modified Al prepared from the above-mentioned materials2O3The particles are used as the filler, have the functions of a thixotropic agent and the filler, can obviously improve the toughness of the prestressed material at low temperature, can reduce the using amount of the toughening agent, basically cannot lose the toughness under the high-low temperature alternating condition, cannot generate the toughening failure condition caused by precipitation, migration and the like of the toughening agent due to the extreme condition (such as negative temperature or high-low temperature alternating) of the physically blended toughening agent, can greatly reduce the risk, and improve the high efficiency and reliability of the slow-bonding prestressed material in severe or extreme weather frequent areas.
Further, the diluent is selected from at least one of dibutyl phthalate, butyl glycidyl ether, phenyl glycidyl ether, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene and n-butanol; the toughening agent is selected from at least one of DOP, DBP, TCP and TPP.
Further, the curing agent is at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylene tetramine, aniline trimer and isophorone diamine, preferably the ratio of aniline trimer to isophorone diamine is 1-2: 1, compounding.
Further, the epoxy resin is at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin, and the epoxy value of the epoxy resin is 0.42-0.50mol/100 g.
In one embodiment of the present invention, the polymer is graft-modified with Al2O3The microparticles are obtained by a preparation method comprising the following steps:
s1, dissolving trialkyl aluminate in a first organic solvent to obtain an oil phase;
s2, dissolving a first emulsifier and a pore-foaming agent in water to obtain a water phase;
s3, mixing the water phase and the oil phase, emulsifying to obtain emulsion, dropwise adding ammonia water to adjust the pH value to 9-11, reacting for 5-7h, centrifuging, drying, and calcining to obtain porous Al2O3Microspheres;
S4.Al2O3modifying the surface of the microsphere: uniformly mixing a silane coupling agent containing vinyl with an alcohol aqueous solution, and adding Al2O3Drying the microspheres to constant weight to obtain surface modified Al2O3Microspheres are reserved;
s5, graft modification: in inert gas atmosphere, the surface modified Al2O3Adding the microspheres and SBS into a second organic solvent, performing ultrasonic dispersion, adding an oil-soluble initiator, heating, and reacting at constant temperature;
s6, cooling, adding an aqueous solution of acrylamide and methylene bisacrylamide, adding a second emulsifier and a water-soluble initiator, stirring and emulsifying, heating again, reacting at a constant temperature, pouring a third organic solvent after the reaction is finished, filtering, washing and drying to obtain the polymer grafted modified Al2O3And (3) microparticles.
Further, Al is graft-modified to the above polymer2O3The preparation method of the particles comprises the following steps:
in step S1, the trialkyl aluminate is selected from at least one of triisopropyl aluminate and tribenzyl aluminate; the first organic solvent is at least one selected from the group consisting of toluene, ethylbenzene, xylene, n-decane, n-hexane, n-propylbenzene, isopropylbenzene and diphenylmethane, and the amount of the first solvent added is not particularly limited, and is generally 2 to 5 times the volume of the trialkyl aluminate in terms of mass, in L/kg;
in step S2, the first emulsifier is an anionic emulsifier, and is specifically selected from at least one of potassium stearate, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium dodecylsulfate, sodium hexadecylsulfonate, sodium hexadecylbenzenesulfonate, sodium hexadecylsulfate, sodium octadecylbenzenesulfonate, and sodium octadecylsulphonate; the pore-foaming agent is at least one of polyoxyethylene sorbitan fatty acid ester and polyethylene glycol octyl phenyl ether; the mass ratio of the trialkyl aluminate to the emulsifier to the pore-forming agent is 100: (6-10): (10-15).
In step S3, the emulsification condition is that emulsification is carried out for 2-5min at the rotating speed of 2000-4000 r/min; the centrifugation condition is centrifugation for 10-20min at the rotating speed of 5000-10000 r/min; the drying condition is drying for 2-4h at 50-90 ℃; the calcination condition is preheating for 1-2h at the temperature of 100-150 ℃ and then calcining for 3-5h at the temperature of 500-700 ℃.
In step S4, the vinyl-containing silane coupling agent and the alcohol-water solution are uniformly mixed according to the weight ratio of 1:15-25, the alcohol-water solution is a mixed solution prepared by mixing alcohol and water according to the volume ratio of 3-6:1, and the alcohol is at least one of methanol, ethanol and propanol.
In step S5, the second organic solvent is at least one selected from cyclohexane, toluene, benzene, methyl ethyl ketone, ethyl acetate and dichloroethane, and the amount of the second organic solvent added is not particularly limited, but is generally surface-modified Al2O32-5 times of the mass of the microspheres, and the unit is L/kg; the oil-soluble initiator is AIBN and/or BPO, and the using amount of the oil-soluble initiator is 0.1-0.3 wt% of SBS; the ultrasonic power is 0.5kW to 1.5kW, the frequency is 40 kHz to 60kHz, and the ultrasonic dispersion time is 0.5h to 1 h; s5, heating to 60-80 ℃, and reacting for 1-2h at a constant temperature of 60-80 ℃.
In step S6, the second emulsifier is a nonionic emulsifier with HLB of 3-6, such as at least one of ethylene glycol fatty acid ester, sorbitan sesquioleate, polyoxyethylene sorbitol, propylene glycol monolaurate, sorbitan monooleate, oleyl alcohol polyoxyethylene ether, and glyceryl monostearate, and the amount of the second emulsifier is 4-7 wt% of the total mass of acrylamide and methylene acrylamide; the water-soluble initiator is a persulfate salt, such as potassium persulfate, ammonium persulfate, and, where appropriate, a bicarbonate salt, such as sodium bicarbonate. The amount of the water-soluble initiator added is 0.5 to 1 wt% of the total mass of acrylamide and methylene acrylamide. The temperature rise constant-temperature reaction is carried out for 3 to 5 hours when the temperature rises to 60 to 70 ℃; the third organic solvent is at least one selected from acetone, benzene and absolute ethyl alcohol; filtration, washing and drying are well known in the art, for example, filtration by suction filtration or centrifugation, washing with acetone or ethanol, and drying in an oven at 70-90 deg.C to constant weight.
According to the preparation method, the obtained polymer is grafted and modified with Al2O3The particle size of the fine particles is 2 to 5 μm, preferably 2.4 to 2.8. mu.m.
Further, the low-temperature resistant slow-release binder is obtained by a preparation method comprising the following steps:
t1, grafting polymer to modify Al2O3Dispersing the particles in a solvent, adding epoxy resin, and uniformly dispersing by ultrasonic;
and T2, mixing the diluent, the toughening agent and the curing agent, adding the mixture obtained in the step (1), stirring and mixing uniformly, and placing the mixture in a closed container for vacuumizing and defoaming treatment to obtain the low-temperature-resistant slow-bonding agent.
The invention also provides a preparation method of the low-temperature-resistant slow-bonding prestressed tendon, which comprises the following steps:
p1. coating the low-temperature resistant slow-bonding agent on the surface of the prestressed reinforcement, wherein the coating thickness is 1.0-3.0mm
And P2, melting, heating and extruding the sheath raw material to wrap the surface of the prestressed reinforcement obtained in the step S1, embossing and cooling to obtain the low-temperature-resistant slow-bonding prestressed reinforcement.
The invention has the following beneficial effects:
the polymer prepared by the invention is grafted and modified Al2O3The microparticles can reduce the crosslinking density of the epoxy resin, thereby reducing the glass transition temperature of the epoxy adhesive, improving the low-temperature resistance and the strength at low temperature, and having the function of improving the thixotropic property of the low-temperature resistant slow-bonding agent due to the mutual effect of hydrogen bonds between amide groups and the epoxy resin because SBS chain segments and polyacrylamide chain segments with amino groups with a certain crosslinking degree are grafted on the surfaces of the microparticles; the SBS chain segment can absorb a large amount of deformation energy, so that the sensitivity of mechanical properties to temperature is reduced, particularly the sensitivity at low temperature, and the slow bonding is realizedThe agent still maintains good mechanical properties at low temperature. In particular, the toughness at low temperatures is significantly improved.
In addition, the toughening effect of SBS is chemical modification, and compared with physical blending effect of adding toughening agent, it has good stability. The reduction degree of mechanical property under the high-low temperature alternating circulation is obviously improved.
In the low-temperature-resistant slow-bonding prestressed tendon, polymer graft modified Al2O3The addition amount of the particles is small relative to that of the epoxy resin, so that the condition that the mechanical property is reduced because a large amount of inorganic filler is added to improve the fluidity of the slow adhesive in the prestressed tendon is avoided.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
SBS is purchased from Kraton, JapanTM6152, styrene content 27.5-29%, solution viscosity 500cps (15% toluene solution at 25 ℃).
Preparation example Polymer graft-modified Al2O3Preparation of microparticles
Preparation example 1
S1, dissolving 10 parts of triisopropyl aluminate into 50 parts of dimethylbenzene to obtain an oil phase;
s2, dissolving 0.6 part of potassium stearate and 1.0 part of polyoxyethylene sorbitan fatty acid ester (Tween 20) in 50mL of water to obtain a water phase;
s3, mixing the water phase and the oil phase, emulsifying, stirring for 2min under the emulsifying condition of 2000r/min to obtain emulsion, dropwise adding ammonia water to adjust the pH value to 9, reacting for 5h, centrifuging for 10min under the centrifuging condition of 8000r/min, drying at 70 ℃ for 2h, calcining at 120 ℃ for 2h, heating to 500 ℃ and calcining for 3h to obtain porous Al2O3Microspheres(ii) a Subjecting the obtained porous Al to laser particle size analyzer2O3The particles are tested and characterized, and the average particle size is 2.26 mu m;
s4, uniformly mixing 3 parts of vinyl trimethoxy silane and 50 parts of alcohol-water solution (ethanol: water: 4:1, v/v), and adding 100 parts of porous Al2O3Stirring the microspheres for reaction for 4 hours, and drying the microspheres in an oven at 80 ℃ to constant weight to obtain surface modified Al2O3Microspheres are reserved;
s5, filling nitrogen into the reaction system to remove oxygen, and modifying 100 parts of surface modified Al2O3Adding the microspheres into 360 parts of toluene solution containing 40 parts of SBS, starting ultrasound, wherein the ultrasound power is 1kW, the frequency is 60kHz, the ultrasound dispersion time is 0.5h, adding 0.1 part of BPO as an initiator after the ultrasound dispersion is uniform, heating to 80 ℃, and keeping constant temperature for reaction for 1 h;
s6, cooling the system to room temperature, adding 65 parts of aqueous solution in which 10 parts of acrylamide and 0.6 part of methylene bisacrylamide are dissolved and 0.5 part of ethylene glycol fatty acid ester (HLB is 3.7), stirring and emulsifying, slowly dropwise adding 1.1 part of aqueous solution containing 0.12 part of sodium persulfate, heating to 60 ℃ under stirring for reaction for 5 hours, cooling to room temperature after the reaction is finished, performing suction filtration, washing with absolute ethyl alcohol for 2 times, and drying in an oven at 80 ℃ to constant weight to obtain the polymer graft modified Al2O3And (3) microparticles. Polymer graft modified Al obtained by laser particle analyzer test2O3The average particle size of the fine particles was 2.45 μm, and the average particle size was increased, probably because of Al2O3The surface of the particles is formed with a polymer layer.
Preparation example 2
The other conditions and operations were the same as in example 1 except that SBS was used in an amount of 34 parts in step S5.
Preparation example 3
The other conditions and operations were the same as in example 1 except that SBS was used in an amount of 45 parts in step S5.
Preparation example 4
The other conditions and operations were the same as in example 1 except that SBS was used in an amount of 28 parts in step S5.
Preparation example 5
The other conditions and operations were the same as in example 1 except that SBS was used in an amount of 50 parts in step S5.
Preparation example 6
The other conditions and operation were the same as in example 1 except that in step S6, acrylamide was used in an amount of 14 parts and methylene bisacrylamide was used in an amount of 1 part.
Comparative preparation example 1
The other conditions and operation were the same as in example 1 except that step S5 was omitted and step S4 gave vinyltrimethoxysilane surface-modified Al2O3After the microspheres, step S6 is performed directly, i.e. Al2O3SBS is not grafted on the surface of the microsphere.
Comparative preparation example 2
The other conditions and the operation are the same as the example 1, except that the step S6 is omitted, after the reaction of the step S5 is finished, the mixture is cooled to room temperature, filtered, washed by absolute ethyl alcohol for 2 times, and then dried in an oven at the temperature of 80 ℃ to constant weight to obtain the polymer grafted modified Al2O3And (3) microparticles.
Comparative preparation example 3
The other conditions and operations were the same as in example 1 except that methylene bisacrylamide was not added in step S6, that is, no crosslinking agent was added.
Example 1
(1) 20 parts of the Polymer obtained in preparation example 1 was graft-modified with Al2O3Dispersing the particles in 200 parts of acetone, adding 100 parts of bisphenol A epoxy resin E42, and uniformly dispersing by ultrasonic, wherein the ultrasonic power is 2000W, the frequency is 60Hz, and the ultrasonic time is 1.5 h;
(2) mixing 12 parts of diluent dibutyl phthalate, 0.8 part of flexibilizer DOP and 4 parts of curing agent (the curing agent is aniline trimer and isophorone diamine which are mixed and compounded according to the mass ratio of 3: 2), adding the mixture into the system in the step (1), stirring and mixing uniformly, wherein the stirring speed is 600r/min, the stirring time is 1.5h, and placing the mixture in a closed container for vacuum degassing treatment to obtain the low-temperature resistant slow-bonding agent.
Examples 2 to 6
Other operations and conditions were the same as in example 1, zoneOther than polymer graft-modified Al2O3The fine particles were obtained in preparation examples 2 to 6, respectively.
Example 7
The other operations and conditions were the same as in example 1 except that the polymer was graft-modified with Al2O3The amount of the fine particles is 30 parts.
Comparative examples 1 to 3
The other operations and conditions were the same as in example 1 except that the polymer was graft-modified with Al2O3The fine particles were obtained in comparative preparation examples 1 to 3, respectively.
Application example
The low temperature resistant slow-release binder prepared in the examples and the comparative examples of the present invention and the commercially available slow-release binder were subjected to performance tests, and the results are shown in table 1.
Thixotropic index TI: according to the specification of B/T2794-.
Mechanical properties: the mechanical properties are tested on a universal tester, the curing time is 3 months, the testing temperature is-20 ℃, and the reference is made to the standard B/T2567-.
High and low temperature alternation performance: and (3) testing by referring to the standard JG/T370-.
TABLE 1
The table shows that the low-temperature-resistant slow-setting adhesive prepared by the embodiment of the invention has good slow-setting thixotropic property, does not change the thixotropic index after 60 days, maintains good mechanical property at the low temperature of-20 ℃, and has good low-temperature resistance.
The compound curing agent of aniline trimer and isophorone diamine can be cured to reach ideal mechanical strength in a short time, and has stable chemical structure and multiple functionality under the conditions of low temperature resistance and high and low temperature alternation resistance, so that the compound curing agent of two different amine curing agents has stable chemical structure and multiple functionality, the crosslinking degree of epoxy resin is reduced after the compound curing agent reacts with the epoxy resin, and the stability of the epoxy resin is improved, thereby improving the low temperature resistance of the epoxy resin.
Claims (10)
1. The low-temperature-resistant slow-bonding prestressed tendon comprises a prestressed steel bar, a low-temperature-resistant slow-bonding agent and a sheath, and is characterized in that a filler in the low-temperature-resistant slow-bonding agent is polymer graft modified Al2O3Fine particles, polymer graft-modified Al2O3The particles are in Al2O3The particles are modified by a coupling agent containing vinyl silane and then are coated on porous Al2O3The surface of the particle is polymerized in situ to graft acrylamide, methylene bisacrylamide and styrene-butadiene-styrene block copolymer (SBS).
2. The low temperature resistant slow-bonding tendon as claimed in claim 1, wherein the SBS has a styrene content of 25-35 wt% and a 15 wt% toluene solution viscosity of 400-700cps at 25 ℃; and/or
The vinyl silane coupling agent is at least one selected from vinyl trimethoxy silane, vinyl triethoxy silane, vinyl triisopropoxy silane, methyl vinyl dimethoxy silane, methyl vinyl diethoxy silane and vinyl tri (2-methoxyethoxy) silane.
3. The low temperature resistant slow-bonding prestressed tendon as claimed in claim 1, which is prepared from the following raw materials in parts by weight: 100 parts of epoxy resin and polymer graft modified Al2O320-30 parts of particles, 10-15 parts of diluent, 5-8 parts of curing agent and 1-1.5 parts of toughening agent.
4. The low temperature resistant slow-bonded tendon as claimed in claim 1Characterized in that the polymer is grafted and modified with Al2O3In the fine particles, Al2O3The mass ratio of the particles to the vinyl-containing silane coupling agent to the acrylamide, the methylene bisacrylamide and the styrene-butadiene-styrene block copolymer is 100: 3-5: 10-14: 0.6-1: 34-45.
5. The low temperature resistant slow-bonding tendon as claimed in claim 1, wherein the diluent is at least one selected from dibutyl phthalate, butyl glycidyl ether, phenyl glycidyl ether, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, n-butanol; the toughening agent is selected from at least one of DOP, DBP, TCP and TPP; and/or
The curing agent is at least one of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylene tetramine, aniline trimer and isophorone; and/or
The epoxy resin is at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin, and the epoxy value of the epoxy resin is 0.42-0.50mol/100 g.
6. The low temperature resistant slow-bonding prestressed tendon as claimed in claim 5, wherein the curing agent is aniline trimer and isophorone diamine according to a mass ratio of 1-2: 1, compounding.
7. The low temperature resistant slow-bonding tendon as claimed in claim 1, wherein the polymer graft-modified Al2O3The microparticles are obtained by a preparation method comprising the following steps:
s1, dissolving trialkyl aluminate in a first organic solvent to obtain an oil phase;
s2, dissolving a first emulsifier and a pore-foaming agent in water to obtain a water phase;
s3, mixing the water phase and the oil phase, emulsifying to obtain emulsion, dropwise adding ammonia water to adjust the pH value to 9-11, reacting for 5-7h, centrifuging, drying, and calcining to obtain porous Al2O3Microspheres;
S4.Al2O3modifying the surface of the microsphere: uniformly mixing a silane coupling agent containing vinyl with an alcohol aqueous solution, and adding Al2O3Drying the microspheres to constant weight to obtain surface modified Al2O3Microspheres are reserved;
s5, graft modification: in inert gas atmosphere, the surface modified Al2O3Adding the microspheres and SBS into a second organic solvent, performing ultrasonic dispersion, adding an oil-soluble initiator, heating, and reacting at constant temperature;
s6, cooling, adding an aqueous solution of acrylamide and methylene bisacrylamide, adding a second emulsifier and a water-soluble initiator, stirring and emulsifying, heating again, reacting at a constant temperature, pouring a third organic solvent after the reaction is finished, filtering, washing and drying to obtain the polymer grafted modified Al2O3And (3) microparticles.
8. The low temperature resistant slow-bonding tendon as claimed in claim 7, wherein in step S1, the trialkyl aluminate is selected from at least one of triisopropyl aluminate and tribenzyl aluminate; the first organic solvent is at least one selected from toluene, ethylbenzene, xylene, n-decane, n-hexane, n-propylbenzene, isopropylbenzene and diphenylmethane; and/or
In step S2, the first emulsifier is an anionic emulsifier; the pore-foaming agent is at least one of polyoxyethylene sorbitan fatty acid ester and polyethylene glycol octyl phenyl ether; the mass ratio of the trialkyl aluminate to the emulsifier to the pore-forming agent is 100: (6-10): (10-15); and/or
In step S3, the emulsification condition is that emulsification is carried out for 2-5min at the rotating speed of 2000-4000 r/min; the centrifugation condition is centrifugation for 10-20min at the rotating speed of 5000-10000 r/min; the drying condition is drying for 2-4h at 50-90 ℃; the calcination condition is preheating for 1-2h at the temperature of 100-150 ℃ and then calcining for 3-5h at the temperature of 500-700 ℃; and/or
In step S4, uniformly mixing a vinyl-containing silane coupling agent and an alcohol-water solution according to a weight ratio of 1:15-25, wherein the alcohol-water solution is a mixed solution prepared by mixing alcohol and water according to a volume ratio of 3-6:1, and the alcohol is at least one of methanol, ethanol and propanol; and/or
In step S5, the second organic solvent is at least one selected from cyclohexane, toluene, benzene, methyl ethyl ketone, ethyl acetate, and dichloroethane; the oil-soluble initiator is AIBN and/or BPO; heating to 60-80 ℃, keeping the temperature of 60-80 ℃ and reacting for 1-2h at constant temperature; and/or
In step S6, the second emulsifier is a nonionic emulsifier, the HLB is 3-6, and the addition amount of the second emulsifier is 4-7 wt% of the total mass of acrylamide and methylene acrylamide; the water-soluble initiator is persulfate, and the addition amount of the water-soluble initiator is 0.5-1 wt% of the total mass of acrylamide and methylene acrylamide; the temperature rise constant-temperature reaction is carried out for 3 to 5 hours when the temperature rises to 60 to 70 ℃; the third organic solvent is at least one selected from acetone, benzene and absolute ethyl alcohol;
according to the preparation method, the obtained polymer is grafted and modified with Al2O3The particle size of the fine particles is 2 to 5 μm, preferably 2.4 to 2.8. mu.m.
9. The low temperature resistant slow-bonding prestressed tendon as claimed in claim 1, wherein the low temperature resistant slow-bonding agent is obtained by a preparation method comprising the following steps:
t1, grafting polymer to modify Al2O3Dispersing the particles in a solvent, adding epoxy resin, and uniformly dispersing by ultrasonic;
and T2, mixing the diluent, the toughening agent and the curing agent, adding the mixture obtained in the step (1), stirring and mixing uniformly, and placing the mixture in a closed container for vacuumizing and defoaming treatment to obtain the low-temperature-resistant slow-bonding agent.
10. The method for preparing the low temperature resistant slow-bonding prestressed tendon of any one of claims 1-9, characterized by comprising the following steps:
p1, coating the low-temperature resistant slow-bonding agent on the surface of the prestressed reinforcement, wherein the coating thickness is 1.0-3.0mm
And P2, melting, heating and extruding the sheath raw material to wrap the surface of the prestressed reinforcement obtained in the step S1, embossing and cooling to obtain the low-temperature-resistant slow-bonding prestressed reinforcement.
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