CN114805971A - High-filling dynamic bond crosslinked polymer magnetic composite material and preparation method thereof - Google Patents
High-filling dynamic bond crosslinked polymer magnetic composite material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof, belonging to the technical field of high polymer materials. The material has excellent processing performance, mechanical property and self-repairing effect under the condition of realizing high filling (up to 90 wt%) of modified magnetic powder particles, and has excellent initial mechanical property (the tensile strength can reach more than 23MPa under the condition of high filling amount); meanwhile, the material can be recycled. The invention also discloses a preparation method of the material and application of the material in preparation of precision instruments.
Description
Technical Field
The invention relates to the technical field of high polymer materials, in particular to a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof.
Background
With the rapid development of modern industry in recent years, magnetic materials are widely applied, and the social demand for high-performance permanent magnetic materials is increased dramatically year by year. The method has very important significance in researching the magnetism of the substance, developing a novel magnetic material, optimizing the preparation process and improving the recovery of the magnetic material. The bonded magnet material obtained by mixing the magnetic powder into plastic or rubber has light relative density, can be molded by injection and is easy to process into a product with a complex shape with high dimensional precision, and overcomes the defects that the original ferrite magnet and rare earth magnet have high hardness and large brittleness and cannot be prepared into a complex shape.
The binder is an important component for bonding the magnet material, and the binder can form a continuous phase in the bonded magnet material, so that the flowability of magnetic powder particles in the material and the bonding strength among the particles are improved, and meanwhile, the material is endowed with excellent mechanical properties (the mechanical properties of the material are mainly determined by the binder) and corrosion resistance.
In order to further improve the usability of the material, the technical scheme that a self-repairing function is introduced into the adhesive and the magnetic powder particles through a bionic design to prepare the cross-linked bonded magnet material with the self-repairing capability and the recycling capability exists in the prior art, the obtained material is longer in service life, more reliable in performance and higher in production cost performance. However, these materials have a low loading of magnetic powder particles and are not satisfactory in terms of use effect and recyclability; if the filling amount of the magnetic powder particles is increased, the processing performance and the mechanical property of the material can be influenced.
Disclosure of Invention
Based on the defects in the prior art, the invention aims to provide a high-filling dynamic bond crosslinked polymer magnetic composite material which has excellent processing performance, mechanical property, self-repairing effect and repeatable recyclability under the condition of realizing high filling of modified magnetic powder particles.
In order to achieve the purpose, the invention adopts the technical scheme that:
a high-filling dynamic bond crosslinked polymer magnetic composite material comprises the following components in parts by weight:
100 parts of polymer binder and 150-910 parts of modified magnetic powder;
the polymer binder is a reversible DA-bond crosslinked linear polymer;
the modified magnetic powder contains functional groups that react with reversible DA bonds in the polymer binder.
In the components of the high-filling dynamic bond crosslinked polymer magnetic composite material, because a large number of DA bond reversible crosslinking points exist among linear polymers crosslinked by reversible DA bonds (a dynamic bond), and the modified magnetic powder also contains functional groups capable of forming the reversible bonds with the crosslinking points, on one hand, the interaction between the modified magnetic powder and a polymer binder is effectively enhanced due to the DA bond reversible crosslinking, the dispersibility of the modified magnetic powder in the polymer binder is improved, and the filling amount of the modified magnetic powder is up to 90 wt%; on the other hand, in the product processing process, the reversible DA bonds between linear polymers have partial crosslinking decomposition, so that the processing viscosity of the whole material is quickly reduced, the fluidity and the processability of the material are improved, the continuous production can be realized even under common processing equipment, and meanwhile, the processed material has good self-repairing capability and excellent mechanical property due to the matching of the two components. Meanwhile, the inventor finds through experiments that the same lifting effect can be achieved by not any polymer binder, and if the polymer binder is not used in proper types, the problem that the obtained material is difficult to process even though magnetic powder particles are agglomerated can occur.
Preferably, the high-filling dynamic bond crosslinked polymer magnetic composite material comprises the following components in parts by weight:
100 parts of polymer binder and 500-910 parts of modified magnetic powder.
Preferably, the reversible DA bond is any one of a reversible DA bond formed by reacting furan with maleimide, a reversible DA bond formed by reacting furan with maleic anhydride, and a reversible DA bond formed by reacting cyclopentadiene with maleic anhydride.
Preferably, the number average molecular weight of the linear polymer is 3000-5000.
More preferably, the linear polymer is a modified diol polymer, more preferably a modified polybutadiene.
When the preferable linear polymer is adopted, reversible DA bond crosslinking points generated by reactants are mainly concentrated on side chains of the linear polymer, and the crosslinking performance and the crosslinking amount are far greater than the types of polymers generated by some reversible DA bonds at end groups, so that ideal modified magnetic powder dispersibility and material processability can be realized only by adopting one single polymer without matching with other polymers; meanwhile, the inventor finds that, taking modified polybutadiene as an example, if the molecular weight of the linear polymer is too small, the production cost of raw materials is high, and the production cost is difficult to optimize, and meanwhile, if the molecular weight is too small, the material becomes hard and brittle, so that the performance of the polymer magnetic composite material is reduced; if the molecular weight is too large, the modified magnetic powder has high viscosity even though the reversible DA bond is subjected to crosslinking decomposition in the processing process when being used as a polymer binder, so that the dispersion degree of the modified magnetic powder is reduced, and the mechanical properties such as tensile strength and the like of the obtained material are reduced; the polymer binders of the above kind are selected for optimum performance.
Preferably, the preparation method of the polymer binder comprises the following steps:
(1) mixing and dissolving a linear oligomer, a modified compound a and a catalyst in a solvent, and reacting the obtained mixed solution in an inert atmosphere to obtain a modified polymer;
(2) mixing and dissolving a modified polymer and a modified compound b in a solvent, and reacting the obtained mixed solution in an inert atmosphere to obtain a polymer binder;
the modified compound a and the modified compound b react and form a reversible DA bond.
More preferably, the linear oligomer is a glycol polymer, more preferably polybutadiene.
In the method for preparing the polymer binder of the present invention, a raw material for forming a reversible DA bond is first introduced into a linear oligomer, and then the crosslinking of the reversible DA bond is directionally induced by adding a modifying compound b, wherein the modifying compound a or b may be selected from the reversible DA bond formed by reacting furan with maleimide, the reversible DA bond formed by reacting furan with maleic anhydride, and the reversible DA bond formed by reacting cyclopentadiene with maleic anhydride. Meanwhile, the modified compounds a and b of the present invention are not limited to the above-mentioned preferred groups and can form reversible DA bonds, and other compounds that can achieve the same effects can be used.
More preferably, the modified compound a is a furan compound, and the furan compound is at least one of furfuryl mercaptan and furfuryl methacrylate; the modified compound b is a maleimide compound, and the maleimide compound is at least one of N, N ' - (4,4 ' -methylenediphenyl) bismaleimide, N ' - (1, 4-phenylene) bismaleimide, 1, 4-bis (maleimide) butane or 1, 2-bis (maleimide) ethane.
Preferably, the catalyst of step (1) is azobisisobutyronitrile.
Preferably, the polymer binder in the step (2) further contains at least one of a chain extender, an end capping agent and an anti-aging agent.
The skilled person can introduce catalysts, chain extenders, blocking agents and/or anti-ageing agents as appropriate to achieve optimum product properties depending on the actual conditions and the reaction conditions of the linear polymer.
More preferably, the chain extender is at least one of diphenylmethane diisocyanate and hexamethylene diisocyanate.
More preferably, the blocking agent is a fluorine-containing blocking agent, and the fluorine-containing blocking agent is 4-trifluoromethyl phenyl isocyanate.
The inventor tests that when the polymer binder contains fluorine, the dispersion degree of the modified magnetic powder in the obtained material is improved to a certain extent, and the mechanical property of the material is improved accordingly.
More preferably, the anti-aging agent is at least one of 4-isopropylaminodiphenylamine and N-phenyl-2-naphthylamine.
Preferably, the solvent in steps (1) and (2) is at least one of tetrahydrofuran, chloroform, ethyl acetate, absolute ethyl alcohol and toluene.
Preferably, the method for preparing the modified magnetic powder comprises the following steps:
mixing and dissolving the magnetic powder, the silane coupling agent, the modified compound and the catalyst in a solvent, and obtaining the modified magnetic powder after full reaction.
In order to make the modified magnetic powder reversibly cross-linked with the polymer binder, corresponding to the polymer binder, the inventor introduces a modifying compound into the surface of the magnetic powder through a silane coupling agent to complete modification, and it is noted that the modifying compound and the modifying compound b mentioned in the preparation method of the polymer binder can be the same or other available compounds which react with the modifying compound a to form reversible DA bonds; meanwhile, the modified compound may be a compound which reacts with a silane coupling agent to produce a substance corresponding to the modified compound b.
More preferably, the magnetic powder is at least one of neodymium iron boron, barium ferrite, strontium ferrite and ferroferric oxide.
More preferably, the magnetic powder has an average particle diameter of 10 to 150 μm.
When the particle size of the magnetic powder is increased, the specific surface area of the magnetic powder is relatively reduced, the magnetic powder loading of the final material is increased, the mechanical properties of the final material are enhanced, and a person skilled in the art can select the magnetic powder with a proper particle size according to actual conditions.
More preferably, the silane coupling agent is KH550, and the modifying compound is maleic anhydride.
Since maleic anhydride can react with KH550 and form maleimide, it can be used as a modification of magnetic powder.
More preferably, the catalyst is a mixture of zinc chloride and hexamethyldisilazane.
The invention also aims to provide a preparation method of the high-filling dynamic bond crosslinked polymer magnetic composite material, which comprises the following steps:
and carrying out melt blending, extrusion and injection molding on the components to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material.
The preparation method of the high-filling dynamic bond crosslinked polymer magnetic composite material has simple operation steps, and can realize industrial mass production without adopting special equipment.
Preferably, the temperature of the melt blending is 120-140 ℃.
Preferably, the rotating speed during melt blending is set to be 70-100 rpm, and the time is 10-20 min.
The invention further aims to provide application of the high-filling dynamic bond crosslinked polymer magnetic composite material in preparation of precise instruments.
Preferably, the precision instrument comprises a motor, a communicator, a sensor and a relay.
The high-filling dynamic bond crosslinked polymer magnetic composite material can realize high filling amount of magnetic powder particles, can ensure excellent mechanical property and processing property, has a self-repairing effect, and can realize repeated recovery, so that the high-filling dynamic bond crosslinked polymer magnetic composite material is particularly suitable for preparing precise instruments such as small precise motors, stepping motors, communication equipment sensors, relays and the like with higher requirements on the mechanical property, the processing property, the service performance and the economic benefit of the prepared material.
The invention has the beneficial effects that the invention provides a high-filling dynamic bond crosslinked polymer magnetic composite material, which has excellent processing performance, mechanical property and self-repairing effect under the condition of realizing high filling (up to 90 wt%) of modified magnetic powder particles, and has excellent initial mechanical property (the tensile strength can reach more than 23MPa under the condition of high filling amount); meanwhile, the material can be recycled. The invention also provides a preparation method of the material and application of the material in preparation of precision instruments.
Drawings
Fig. 1 is an infrared spectrum of before-modified ndfeb, after-modified ndfeb, and after DA reaction of the modified ndfeb with furan used in example 1 of the present invention; wherein 1 is a spectrogram of neodymium iron boron before modification, 2 is a spectrogram of modified neodymium iron boron, and 3 is a spectrogram of modified neodymium iron boron after DA reaction with furan;
FIG. 2 is an apparent morphology of a product of example 3 after scratch treatment and before heat treatment in effect example 1 of the present invention;
FIG. 3 is an apparent morphology of a product of example 3 after heat treatment in effect example 1 of the present invention.
Detailed Description
In order to better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples and comparative examples, which are intended to be understood in detail, but not intended to limit the invention. All other embodiments obtained by a person skilled in the art without making any inventive step are within the scope of protection of the present invention. The experimental reagents and instruments designed for the practice of the present invention and the comparative examples are common reagents and instruments unless otherwise specified.
Example 1
The invention relates to an embodiment of a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) mixing 100g of linear oligomer polybutadiene 2700, 26g of modified compound alpha-furfurylthiol and 5g of catalyst azobisisobutyronitrile, dissolving in 300mL of tetrahydrofuran, reacting the obtained mixed solution at 80 ℃ for 12h under a nitrogen atmosphere, concentrating the product, precipitating with methanol, and drying to obtain a modified polymer;
(2) mixing and dissolving 40g of modified polymer and 15g of modified compound b N, N '- (4, 4' -methylene diphenyl) bismaleimide in 300mL of tetrahydrofuran, reacting the obtained mixed solution at 70 ℃ for 10 hours under a nitrogen atmosphere, adding 0.8g of age resister 4-isopropylaminodiphenylamine (age resister 4010NA), pouring the mixture into a polytetrafluoroethylene mold, and drying the mixture at 60 ℃ to form a film, thereby obtaining a polymer binder, namely HTPB-DA;
(3) mixing and dissolving 13.2g of silane coupling agent KH550, 5.9g of maleic anhydride, 8.2g of catalyst zinc chloride and 9.7g of catalyst hexamethyldisilazane in 100mL of toluene, reacting at 80 ℃ for 12h under a nitrogen atmosphere, filtering, adding 300mL of absolute ethanol into the obtained filtrate, adjusting the pH of the solution to 3-4 by using anhydrous oxalic acid, adding 120g of neodymium iron boron with the average particle size of 10 mu m, reacting at 100 ℃ for 4h under the nitrogen atmosphere completely, washing the obtained product by using absolute ethanol, and drying to obtain modified magnetic powder (namely the modified neodymium iron boron);
(4) taking 75g of modified magnetic powder, carrying out vacuum drying at 80 ℃ for 12h, taking 13.2g of HTPB-DA particles, and carrying out vacuum drying at 60 ℃ for 12 h; and then mixing the two raw materials, adding the mixture into a torque rheometer, melting and mixing the mixture at the rotating speed of 120 ℃ and 70rpm, banburying the mixture for 15min, granulating the obtained product, transferring the granulated product into a double-screw extruder, and performing injection molding at the rotating speed of 120 ℃ and 70rpm and the injection pressure of 0.7MPa to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material, namely the neodymium iron boron/HTPB-DA polymer bonded magnet.
The infrared analysis is performed on the modified neodymium iron boron, the modified neodymium iron boron and the modified DA reactant of neodymium iron boron and furan, and the results are shown in fig. 1, which shows that the modified magnetic powder successfully introduces a maleimide group compared with the modified neodymium iron boron before modification, and further performs a reversible DA crosslinking reaction with furan small molecules, which proves that the maleimide on the surface of the neodymium iron boron still has good reactivity.
Example 2
The invention relates to an embodiment of a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) mixing 100g of linear oligomer polybutadiene 2700, 26g of modified compound alpha-furfurylthiol and 5g of catalyst azobisisobutyronitrile, dissolving in 300mL of tetrahydrofuran, reacting the obtained mixed solution at 80 ℃ for 12h under a nitrogen atmosphere, concentrating the product, precipitating with methanol, and drying to obtain a modified polymer;
(2) mixing 53g of modified polymer and 0.8g of chain extender hexamethylene diisocyanate, dissolving the mixture in 400mL of tetrahydrofuran, reacting the obtained mixed solution at 60 ℃ for 2h under a nitrogen atmosphere, adding 22g of modified compound b N, N '- (4, 4' -methylenediphenyl) bismaleimide, mixing, heating to 70 ℃, reacting for 10h, adding 1g of age resister 4-isopropylaminodiphenylamine (age resister 4010NA), pouring into a polytetrafluoroethylene mold, and drying at 60 ℃ to form a film, thereby obtaining a polymer binder, namely HTPB-NCO-DA;
(3) mixing and dissolving 13.2g of silane coupling agent KH550, 5.9g of maleic anhydride, 8.2g of catalyst zinc chloride and 9.7g of catalyst hexamethyldisilazane in 100mL of toluene, reacting at 80 ℃ for 12 hours under nitrogen atmosphere, filtering, adding 300mL of absolute ethanol into obtained filtrate, adjusting the pH of the solution to 3-4 by adopting anhydrous oxalic acid, adding 120g of neodymium iron boron with the average particle size of 10 mu m, reacting at 100 ℃ for 4 hours under nitrogen atmosphere completely, washing the obtained product by adopting absolute ethanol, and drying to obtain modified magnetic powder;
(4) 75g of modified magnetic powder is taken to be dried in vacuum at 80 ℃ for 12h, 13.2g of HTPB-NCO-DA is taken to be cut into granules, and the granules are placed at 60 ℃ for vacuum drying for 12 h; and then mixing the two raw materials, adding the mixture into a torque rheometer, melting and mixing the mixture at the rotating speed of 120 ℃ and 70rpm, banburying the mixture for 15min, granulating the obtained product, transferring the granulated product into a double-screw extruder, and performing injection molding at the rotating speed of 120 ℃ and 50rpm and the injection pressure of 0.7MPa to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material, namely the neodymium iron boron/HTPB-NCO-DA polymer bonded magnet.
Example 3
The invention relates to an embodiment of a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) mixing 100g of linear polymer polybutadiene 2700, 26g of modified compound alpha-furfurylthiol and 5g of catalyst azobisisobutyronitrile, dissolving in 300mL of tetrahydrofuran, reacting the obtained mixed solution at 80 ℃ for 12h under a nitrogen atmosphere, concentrating the product, precipitating with methanol, and drying to obtain a modified polymer;
(2) 30g of the modified polymer, 3.1g of a fluorine blocking agent 4-trifluoromethylphenylisocyanate were mixed and dissolved in 400mL of tetrahydrofuran, and the resulting mixed solution was reacted at 60 ℃ for 2 hours under a nitrogen atmosphere, followed by12.1g N, heating N '- (4, 4' -methylenediphenyl) bismaleimide to 70 ℃ to react for 10h, adding 0.6g of age resister 4-isopropylaminodiphenylamine (age resister 4010NA), pouring into a polytetrafluoroethylene mold, drying at 60 ℃ to form a film, and obtaining the polymer binder named as HTPB-F 3 -DA；
(3) Mixing and dissolving 13.2g of silane coupling agent KH550, 5.9g of maleic anhydride, 8.2g of catalyst zinc chloride and 9.7g of catalyst hexamethyldisilazane in 100mL of toluene, reacting at 80 ℃ for 12h under a nitrogen atmosphere, filtering, adding 300mL of absolute ethanol into the obtained filtrate, adjusting the pH of the solution to 3-4 by using absolute oxalic acid, adding 120g of neodymium iron boron with the average particle size of 10 mu m, reacting at 100 ℃ for 4h under the nitrogen atmosphere completely, washing the obtained product by using absolute ethanol, and drying to obtain modified magnetic powder;
(4) vacuum drying 75g modified magnetic powder at 80 deg.C for 12h, and collecting 13.2g HTPB-F 3 Cutting the particles into DA pellets, and vacuum drying the pellets for 12 hours at the temperature of 60 ℃; then mixing the two raw materials, adding the mixture into a torque rheometer, melting and mixing the mixture at the rotating speed of 120 ℃ and 70rpm, banburying the mixture for 15min, granulating the obtained product, transferring the granulated product into a double-screw extruder, and performing injection molding at the rotating speed of 120 ℃ and 50rpm and the injection pressure of 0.7MPa to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material, namely the neodymium iron boron/HTPB-F material is named as NdFeB/HTPB-F 3 -DA polymer bonded magnets.
Example 4
The invention relates to an embodiment of a high-filling dynamic bond crosslinked polymer magnetic composite material and a preparation method thereof, wherein the preparation method comprises the following steps:
(1) mixing 100g of linear polymer polybutadiene 2700, 26g of modified compound alpha-furfurylthiol and 5g of catalyst azobisisobutyronitrile, dissolving in 300mL of tetrahydrofuran, reacting the obtained mixed solution at 80 ℃ for 12h under a nitrogen atmosphere, concentrating the product, precipitating with methanol, and drying to obtain a modified polymer;
(2) 30g of the modified polymer, 3.1g of a fluorine blocking agent 4-trifluoromethylphenylisocyanate were mixed and dissolved in 400mL of tetrahydrofuran, and the resulting mixed solution was reacted at 60 ℃ for 2 hours under a nitrogen atmosphere, followed by 12.1g N,heating N '- (4, 4' -methylene diphenyl) bismaleimide to 70 ℃ for reaction for 10 hours, adding 0.6g of age resister 4-isopropylaminodiphenylamine (age resister 4010NA), pouring into a polytetrafluoroethylene mold, drying at 60 ℃ to form a film, and obtaining a polymer binder named as HTPB-F 3 -DA；
(3) Mixing and dissolving 13.2g of silane coupling agent KH550, 5.9g of maleic anhydride, 8.2g of catalyst zinc chloride and 9.7g of catalyst hexamethyldisilazane in 100mL of toluene, reacting at 80 ℃ for 12h under a nitrogen atmosphere, filtering, adding 300mL of absolute ethanol into the obtained filtrate, adjusting the pH of the solution to 3-4 by using anhydrous oxalic acid, adding 60g of neodymium iron boron with the average particle size of 10 mu m and 60g of neodymium iron boron with the average particle size of 150 mu m, reacting at 100 ℃ for 4h under the nitrogen atmosphere till the solution is complete, washing the obtained product by using absolute ethanol, and drying to obtain modified magnetic powder;
(4) vacuum drying 75g modified magnetic powder at 80 deg.C for 12h, and collecting 8.3g HTPB-F 3 Cutting the particles into DA pellets, and vacuum drying the pellets for 12 hours at the temperature of 60 ℃; then mixing the two raw materials, adding the mixture into a torque rheometer, melting and mixing the mixture at the rotating speed of 120 ℃ and 70rpm, banburying the mixture for 15min, granulating the obtained product, transferring the granulated product into a double-screw extruder, and performing injection molding at the rotating speed of 120 ℃ and 50rpm and the injection pressure of 0.7MPa to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material, namely the neodymium iron boron/HTPB-F material is named as NdFeB/HTPB-F 3 -DA polymer bonded magnets.
Comparative example 1
This comparative example differs from example 3 only in that the modified magnetic powder was replaced with neodymium iron boron powder having an average particle size of 10 μm in the same mass.
Comparative example 2
A magnet composite material, the method of making the material comprising the steps of:
13.2g of butadiene rubber (purchased from Shanghai Mingtian Biotechnology Co., Ltd., molecular weight of 50000g/mol), 0.9g of dicumyl peroxide, 0.3g of anti-aging agent 4010NA and 75g of modified magnetic powder (the modified magnetic powder is prepared as in example 1) are mixed and added into a torque rheometer to be melted and mixed under the conditions of 100 ℃ and 100rpm, after banburying for 20min, the obtained product is cut into particles and then transferred into a double screw extruder to be subjected to injection molding under the conditions of 130 ℃ and 50rpm and 0.7MPa injection pressure, and the magnet composite material is obtained.
Effect example 1
To verify the performance of the highly filled dynamically bonded cross-linked polymer magnetic composite of the present invention, the following tests were performed on each of the examples and comparative examples:
(1) the processing performance is as follows: selecting balance torque representation, balancing each product for 15min by using a Haake torque rheometer at the temperature of 120 ℃ and the rotating speed of 70rpm, and taking a torque value as a balance torque value when banburying mixing is finished;
(2) tensile property: measuring according to ISO 527-2 standard, processing each product into a dumbbell shape, testing at 25 ℃ and 5mm/min of tensile rate, testing the tensile strength, tensile modulus and elongation at break of a sample, preparing three samples for each product, and averaging the results;
the test results are shown in table 1.
TABLE 1
As can be seen from Table 1, the products of the examples have good processability, and the modified magnetic powder loading of the products can reach 90 wt% at the most, and the tensile strength can reach 23.6%; on the other hand, the elongation at break of the product can also be adjusted to 22% according to the formulation. Wherein, the product of the example 3 contains a fluorine end-capping agent, so that the tensile strength is better than that of the product of the example 1 under the same filling amount; the final molecular weight of the polymer binder in the product of example 2 is larger than that in example 1, so that the viscosity during processing is also improved, and the tensile strength of the material is relatively reduced; the average particle size of the modified magnetic powder in the product of example 4 is relatively increased, and it can be seen that the tensile strength of the obtained material is also increased, but the elongation at break is relatively decreased, which indicates that the high-filling dynamic bond crosslinked polymer magnetic composite material of the present invention can effectively adjust the rigidity and toughness of the material by adjusting different component parameters according to the actual use requirements. In contrast, the magnetic powder in the product of comparative example 1 is not modified at all, and has poor dispersibility and relatively poor mechanical properties in the product; the polymer in the product of the comparative example 2 adopts butadiene rubber with larger molecular weight, so the viscosity during processing is too high, the polymer is difficult to be uniformly mixed with modified magnetic powder, the compatibility is poor, and all the performances can not meet the use requirements.
To further verify other properties of the example products, the following properties were continuously tested on each example product:
(3) the recyclability: cutting each product into pieces, performing injection molding again by adopting the same method in the preparation method, repeating for 3 times, and then performing the same test in the step (2), wherein the test results are shown in table 2;
(4) self-repairability: scratching the surface of each product until obvious scratches appear, then keeping the surface at the temperature of 120-140 ℃ for 0.1-1 h, and keeping the surface at the temperature of 60-80 ℃ for 6-12 h; and (4) characterizing the surface appearance of the product by using a super-depth-of-field microscope, and observing the surface scratch appearance of the material before and after heat treatment.
TABLE 2
| Sample (I) | Tensile Strength (MPa) | Tensile Strength holding ratio (%) |
| Example 1 | 18.8 | 103.8 |
| Example 2 | 16.1 | 93.6 |
| Example 3 | 19.4 | 95.1 |
| Example 4 | 22.5 | 95.3 |
As can be seen from Table 2, the tensile strength of the products of the examples is almost unchanged after 3 times of repeated recycling and injection molding, and the retention rate can reach more than 93%, which indicates that the products can maintain good mechanical properties even after being processed for many times due to reversible crosslinking among the polymer binders and between the polymer binders and the modified magnetic powder. And the appearance observation of the heat-treated product with each scratch shows that the scratch can be completely recovered, and taking the product of example 3 as an example, the appearance graphs before and after the heat treatment are shown in fig. 2 and 3, so that the product has a self-repairing effect without doubt.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. The high-filling dynamic bond crosslinked polymer magnetic composite material is characterized by comprising the following components in parts by weight:
100 parts of polymer binder and 150-910 parts of modified magnetic powder;
the polymer binder is a reversible DA-bond crosslinked linear polymer;
the modified magnetic powder contains functional groups that react with reversible DA bonds in the polymer binder.
2. The highly filled dynamically bonded crosslinked polymer magnetic composite material according to claim 1, comprising the following components in parts by weight:
100 parts of polymer binder and 500-910 parts of modified magnetic powder.
3. The highly filled dynamically bonded cross-linked polymer magnetic composite of claim 1, wherein said reversible DA bond is any one of a reversible DA bond formed by reacting furan with maleimide, a reversible DA bond formed by reacting furan with maleic anhydride, and a reversible DA bond formed by reacting cyclopentadiene with maleic anhydride.
4. The highly filled dynamically bonded crosslinked polymer magnetic composite material according to claim 1, wherein the linear polymer has a number average molecular weight of 3000 to 5000;
preferably, the linear polymer is a modified glycol polymer.
5. The preparation method of the high-filling dynamic bond crosslinked polymer magnetic composite material as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
carrying out melt blending, extrusion and injection molding on the polymer binder and the modified magnetic powder to obtain the high-filling dynamic bond crosslinked polymer magnetic composite material;
preferably, the temperature of the melt blending is 120-140 ℃, the rotating speed during the melt blending is set to be 70-100 rpm, and the time is 10-20 min.
6. The method of preparing a highly filled dynamically bonded cross-linked polymer magnetic composite as claimed in claim 5, wherein said polymer binder is prepared by a method comprising the steps of:
(1) mixing and dissolving a linear oligomer, a modified compound a and a catalyst in a solvent, and reacting the obtained mixed solution in an inert atmosphere to obtain a modified polymer;
(2) mixing and dissolving a modified polymer and a modified compound b in a solvent, and reacting the obtained mixed solution in an inert atmosphere to obtain a polymer binder;
the modified compound a and the modified compound b react and form a reversible DA bond;
preferably, the linear oligomer is a glycol polymer.
7. The method for preparing a high-filled dynamic bond crosslinked polymer magnetic composite material according to claim 6, wherein the modified compound a is a furan compound, and the furan compound is at least one of furfuryl mercaptan and furfuryl alcohol methacrylate; the modified compound b is a maleimide compound, and the maleimide compound is at least one of N, N ' - (4,4 ' -methylenediphenyl) bismaleimide, N ' - (1, 4-phenylene) bismaleimide, 1, 4-bis (maleimide) butane or 1, 2-bis (maleimide) ethane.
8. The method for preparing a highly filled dynamically bonded crosslinked polymer magnetic composite material according to claim 6, wherein the polymer binder in the step (2) further contains at least one of a chain extender, a capping agent and an anti-aging agent;
preferably, the chain extender is at least one of diphenylmethane diisocyanate and hexamethylene diisocyanate; the end-capping reagent is a fluorine-containing end-capping reagent which is 4-trifluoromethyl phenyl isocyanate; the anti-aging agent is at least one of 4-isopropylaminodiphenylamine and N-phenyl-2-naphthylamine.
9. The method of preparing a highly filled dynamically bonded cross-linked polymer magnetic composite material according to claim 5, wherein the method of preparing the modified magnetic powder comprises the steps of:
mixing and dissolving magnetic powder, a silane coupling agent, a modified compound and a catalyst in a solvent, and obtaining modified magnetic powder after full reaction;
preferably, the magnetic powder is at least one of neodymium iron boron, barium ferrite, strontium ferrite and ferroferric oxide; the silane coupling agent is KH 550; the catalyst is a mixture of zinc chloride and hexamethyldisilazane.
10. The use of the highly filled dynamically bonded crosslinked polymer magnetic composite material according to any one of claims 1 to 5 for the preparation of precision instruments;
preferably, the precision instrument comprises a motor, a communicator, a sensor and a relay.
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