CN117844225A - Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof - Google Patents
Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof Download PDFInfo
- Publication number
- CN117844225A CN117844225A CN202311709281.3A CN202311709281A CN117844225A CN 117844225 A CN117844225 A CN 117844225A CN 202311709281 A CN202311709281 A CN 202311709281A CN 117844225 A CN117844225 A CN 117844225A
- Authority
- CN
- China
- Prior art keywords
- polyaryletherketone
- nano tube
- carbon nano
- composite powder
- carbon
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 149
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 140
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 140
- 239000002131 composite material Substances 0.000 title claims abstract description 88
- 229920006260 polyaryletherketone Polymers 0.000 title claims abstract description 84
- 239000000843 powder Substances 0.000 title claims abstract description 66
- 239000000463 material Substances 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 239000006185 dispersion Substances 0.000 claims abstract description 26
- 239000000243 solution Substances 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000011259 mixed solution Substances 0.000 claims abstract description 17
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 238000001035 drying Methods 0.000 claims abstract description 16
- 239000000701 coagulant Substances 0.000 claims abstract description 14
- 239000002798 polar solvent Substances 0.000 claims abstract description 14
- 238000007873 sieving Methods 0.000 claims abstract description 8
- 238000005406 washing Methods 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims description 41
- 229920001652 poly(etherketoneketone) Polymers 0.000 claims description 32
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 29
- 229920002530 polyetherether ketone Polymers 0.000 claims description 29
- 239000007788 liquid Substances 0.000 claims description 15
- 229910021642 ultra pure water Inorganic materials 0.000 claims description 14
- 239000012498 ultrapure water Substances 0.000 claims description 14
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 12
- 239000002904 solvent Substances 0.000 claims description 12
- KEQGZUUPPQEDPF-UHFFFAOYSA-N 1,3-dichloro-5,5-dimethylimidazolidine-2,4-dione Chemical group CC1(C)N(Cl)C(=O)N(Cl)C1=O KEQGZUUPPQEDPF-UHFFFAOYSA-N 0.000 claims description 11
- XTHPWXDJESJLNJ-UHFFFAOYSA-N chlorosulfonic acid Substances OS(Cl)(=O)=O XTHPWXDJESJLNJ-UHFFFAOYSA-N 0.000 claims description 11
- 238000000967 suction filtration Methods 0.000 claims description 10
- 239000000725 suspension Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 7
- 238000010298 pulverizing process Methods 0.000 claims description 7
- 229960000583 acetic acid Drugs 0.000 claims description 6
- 239000012362 glacial acetic acid Substances 0.000 claims description 6
- 239000002048 multi walled nanotube Substances 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 5
- 238000003828 vacuum filtration Methods 0.000 claims description 4
- 239000002109 single walled nanotube Substances 0.000 claims description 3
- 238000003760 magnetic stirring Methods 0.000 claims description 2
- 229920000642 polymer Polymers 0.000 abstract description 8
- 238000013329 compounding Methods 0.000 abstract description 7
- 239000000203 mixture Substances 0.000 abstract description 6
- 238000010146 3D printing Methods 0.000 abstract description 3
- 230000005611 electricity Effects 0.000 abstract description 2
- 230000003014 reinforcing effect Effects 0.000 abstract description 2
- 238000001914 filtration Methods 0.000 abstract 1
- 239000007791 liquid phase Substances 0.000 abstract 1
- 239000012071 phase Substances 0.000 abstract 1
- 239000002244 precipitate Substances 0.000 abstract 1
- 229920001643 poly(ether ketone) Polymers 0.000 description 34
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 9
- 229920000049 Carbon (fiber) Polymers 0.000 description 8
- 239000004917 carbon fiber Substances 0.000 description 8
- 230000008569 process Effects 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 6
- 238000005054 agglomeration Methods 0.000 description 6
- 230000002776 aggregation Effects 0.000 description 6
- 229910021389 graphene Inorganic materials 0.000 description 5
- -1 polytetrafluoroethylene Polymers 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000002238 carbon nanotube film Substances 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 239000012779 reinforcing material Substances 0.000 description 3
- 239000004642 Polyimide Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- JUPQTSLXMOCDHR-UHFFFAOYSA-N benzene-1,4-diol;bis(4-fluorophenyl)methanone Chemical class OC1=CC=C(O)C=C1.C1=CC(F)=CC=C1C(=O)C1=CC=C(F)C=C1 JUPQTSLXMOCDHR-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000007580 dry-mixing Methods 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 229920002492 poly(sulfone) Polymers 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 230000005588 protonation Effects 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000009827 uniform distribution Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- XMWRBQBLMFGWIX-UHFFFAOYSA-N C60 fullerene Chemical compound C12=C3C(C4=C56)=C7C8=C5C5=C9C%10=C6C6=C4C1=C1C4=C6C6=C%10C%10=C9C9=C%11C5=C8C5=C8C7=C3C3=C7C2=C1C1=C2C4=C6C4=C%10C6=C9C9=C%11C5=C5C8=C3C3=C7C1=C1C2=C4C6=C2C9=C5C3=C12 XMWRBQBLMFGWIX-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004734 Polyphenylene sulfide Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 239000007822 coupling agent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 229910003472 fullerene Inorganic materials 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012770 industrial material Substances 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 239000011256 inorganic filler Substances 0.000 description 1
- 229910003475 inorganic filler Inorganic materials 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000011859 microparticle Substances 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 239000005543 nano-size silicon particle Substances 0.000 description 1
- 229910021392 nanocarbon Inorganic materials 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000002064 nanoplatelet Substances 0.000 description 1
- 239000002667 nucleating agent Substances 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 239000004597 plastic additive Substances 0.000 description 1
- 239000011160 polymer matrix composite Substances 0.000 description 1
- 229920013657 polymer matrix composite Polymers 0.000 description 1
- 229920000069 polyphenylene sulfide Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Landscapes
- Compositions Of Macromolecular Compounds (AREA)
- Carbon And Carbon Compounds (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Abstract
The invention discloses a carbon nano tube/polyaryletherketone composite powder material and a preparation method thereof, wherein the method comprises the following steps: respectively dissolving polyaryletherketone and a dispersed carbon nanotube by adopting a strong polar solvent, and mixing the two homogeneous phases to obtain a carbon nanotube/polyaryletherketone mixed solution; transferring the mixed solution into a coagulant to coagulate and separate out the carbon nano tube/polyaryletherketone, washing, filtering and drying the precipitate at constant temperature to obtain a carbon nano tube/polyaryletherketone composite dry material; and then crushing and sieving the mixture in turn to obtain the carbon nano tube/polyaryletherketone composite powder. The invention uses the liquid phase compounding method, not only solves the technical problem that mechanical mixing is difficult to realize full compounding of the polymer and the carbon nano tube, but also ensures that the polymer and the carbon nano tube are uniformly distributed through full dispersion of the carbon nano tube in the solution, fully utilizes the reinforcing effect of the carbon nano tube, and obtains the composite powder with excellent performances such as force, electricity, heat and the like. The composite powder prepared by the invention meets the performance requirement of 3D printing.
Description
Technical Field
The invention relates to a carbon nano tube/polyaryletherketone composite powder material and a preparation method thereof, in particular to the dispersion of carbon nano tubes and the full and uniform composition of the carbon nano tubes and the polyaryletherketone, belonging to the technical field of additive manufacturing materials.
Background
With the improvement of the performance requirements of industrial materials, thermoplastic engineering plastics gradually attract the attention of scientific researchers due to the good mechanical, high temperature resistance, chemical resistance and other performances, such as polyaryletherketone, polyphenylene sulfide, polyimide, polysulfone and the like. Among them, the polyaryletherketone family is a polymer formed by connecting rigid chains such as benzene rings and carbonyl groups, and has been shown to have certain excellent properties in applications in fields of home textiles, transportation, aerospace and the like in recent years. In order to make the polyaryletherketone be widely applied and meet the more severe performance requirements of mechanics, electric conduction, heat conduction and the like, the reinforcing material is compounded with the polyaryletherketone as a common means. The nanoscale material has a remarkable reinforcing effect due to a large specific surface area, and becomes an important reinforcing material. The nano carbon material (such as fullerene, graphene, carbon nano tube, active carbon and the like) has good heat, force, electricity and other performances, is a light high-performance nano reinforced material with great potential, and is widely used as a reinforcement in a polymer matrix composite material to improve the material performance. Because the polyaryletherketone is difficult to dissolve, the preparation process of the carbon nanotube reinforced polyaryletherketone composite material at present mainly adopts melt mixing and mechanical mixing, and the research of the polyether-ether-ketone is relatively more.
Dry mixing is the simplest, common preparation process. Such as: 1) The Chinese patent 201910712468.6 comprises the steps of mixing graphene oxide, carbon nano tubes, polyether-ether-ketone, polyaryletherketone coupling agent, high-temperature-resistant antioxidant and compatilizer in a high-speed mixer, extruding and granulating, and performing injection molding; 2) Chinese patent No. 202211192703.X mixes polyether-ether-ketone and functionalized carbon nano tube and then granulates, mixes the composite material and polyether-ether-ketone to obtain a mixed material, and then further extrudes and forms the antistatic polyether-ether-ketone composite material; 3) European patent EP2023/053221 uses a roller to mix polyaryletherketone, polysulfone, inorganic filler, nucleating agent and plastic additive, then the mixture is subjected to composite granulation by a double-screw extruder, and finally an electric insulation film is prepared by injection molding; and 4) mixing graphene, carbon nano tubes and polyether ether ketone according to a certain proportion by adopting a mechanical mixing method in the document M.F.Arif, H.Alhashmi, K.M.Varadarajan, J.H.Koo, A.J.Hart, S.Kumar.Multifunctional performance of carbon nanotubes and graphene nanoplatelets reinforced PEEK composites enabled via FFF additive manufacturing. Composites Part B2020,184,107625, and preparing the 3D printing wire rod through screw extrusion. In general, the powder prepared by the dry mixing means is simply mixed, and the powder is difficult to be fully compounded with the reinforcement body in the subsequent processing due to high viscosity and high surface tension of the polymer melt, and has the structural problem of uneven distribution of different components.
For this reason, a wet-process-based compounding process has been developed, and has been widely used for thermoplastic resins such as polyimide and polyvinylidene fluoride. However, due to the solubility of polyaryletherketones, current wet processing is still inherently a simple mechanical mix. Such as: 1) The Chinese patent No. 201610859934.X disperses polyether-ether-ketone and functionalized carbon nano-tube in ethanol water solution added with dispersing agent, ultrasonic treatment and stirring to obtain uniform dispersion, and rotary heating evaporation, vacuum drying, grinding and sieving to obtain composite powder for laser selective sintering; 2) Chinese patent 201710438033.8 is to mix and stir ethanol dispersion of polyether-ether-ketone and dimethylformamide dispersion of carbon nanotube, and dry to obtain mixed powder of carbon nanotube/polyether-ether-ketone; 3) Chinese patent 201810699727.1 comprises mixing polyether-ether-ketone, graphene, carbon nanotube, polytetrafluoroethylene, nano silicon dioxide and para-polyphenol in ethanol solution, ultrasonic stirring, oven drying, pulverizing, and sieving to obtain composite powder; 4) Literature A.M.Di.z-Pascal, M.Naffakh, M.A.G, mez, C.Marco, G.Ellis, M.T.Mart i.nez, A.Ans ban, J.M.Gonz lez-domi.nguez, Y.Mart i nez-Rubi, B.Simarong.development and characterization of PEEK/carbon nanotubes, carbon 2009,47,3079, first dispersing single-walled carbon nanotubes and polyetheretherketone in ethanol, mixing them by a micro extruder, melt blending the carbon nanotubes with polyetheretherketone, and then preparing them into a film in a press; and 5) document M.Umesh, P.Meghashree, B.Jayashree.Carbon nanotubes-APowerful nano-filler for enhancing the performance properties of Polyetherketoneketone composites and additives. Composites Science and Technology 2021,210,108813, after ultrasonic dispersion of polyetherketoneketone and hydroxylated carbon nanotubes in deionized water, drying them, developed a carbon nanotube reinforced polyetherketoneketone adhesive. Although these techniques all fall under the wet preparation, the polyaryletherketone forms suspended microparticles in solution, resulting in techniques that are essentially solely based on wet mechanical mixing and do not achieve the desired complexing effect.
Therefore, the existing composite of the carbon nano tube and the polyaryletherketone, especially the powder mainly comprising the polyether-ether-ketone, the polyether-ketone and the carbon nano tube, is basically mixed. How to develop fully compounded carbon nano tube/polyaryletherketone powder material, and improve the performance of the compound powder, is a breakthrough work to further expand the application of the compound powder material in the fields of 3D printing and the like. Wherein, whether the dissolution of the polyaryletherketone can be realized or not, and the realization of the efficient combination and the uniform distribution of the polyaryletherketone and the polyaryletherketone by using a real wet process are key.
In recent years, polyetherketoneketone has received attention as an important member of the polyaryletherketone family. The polyether ketone has high molecular polarity due to rich ketone bonds, so that the polyether ketone has high solubility, and can be dissolved by adopting fluorine-based and/or chlorine-based solvents. There are several articles and patents disclosing the preparation of composites based on polyetherketoneketone solutions: 1) The Chinese patent 202111055042.1 discloses a long carbon fiber/polyether ketone composite material prepared based on polyether ketone solution, and provides a wet preparation method; 2) B.L.Li, F.Zhang, M.X.Jiao, Y.B.Li, X.Wang, X.H.Zhang.Carbon fiber/polyetherkeytone Composites, part I An ideal and uniform composition via solution-based processing Polymer Composites 2022,43 (5), 2803 utilize polar solvents containing fluorine and/or chlorine to dissolve polyetherketoneketone, thus realizing the impregnation of long carbon fiber bundles in polyetherketoneketone solution, and preparing carbon fiber/polyetherketoneketone composite; 3) The long Carbon fiber/polyetherketoneketone composite material interface obtained by the document F.Zhang, B.L.Li, M.X.Jiao, Y.B.Li, X.Wang, Y.Yang, Y.Q.Yang, X.H.Zhang.Wet-composition-induced amorphous adhesion toward a high interfacial shear strength between Carbon fiber and polyethyleneketoneketone Materials, doi:10.1016/S1872-5805 (22) 60646-2 based on polyetherketoneketone solution has strong bonding and excellent interlaminar shear performance; and 4) Chinese patent 202210401927.0 discloses a preparation method of chopped carbon fiber/polyether ketone composite powder: dissolving polyetherketoneketone in fluorine-based and/or chlorine-based polar solvent, adding chopped carbon fiber, stirring thoroughly, adding coagulant to coagulate and separate out chopped carbon fiber/polyetherketoneketone, and sequentially drying, cooling, pulverizing, and sieving to obtain composite powder. The technology can be called a processing technology based on a solution method, can realize sufficient pre-compounding between the reinforcing material and the polyether ketone, obtain composite powder with excellent performance, and provides good inspiration for preparing the carbon nano tube/polyether ketone composite powder. However, whether or not carbon nanotubes can be sufficiently dispersed on the basis of being able to dissolve polyetherketoneketone is a key to achieving their pre-compounding, subject to agglomeration of carbon nanotubes in solution. The solvent capable of dissolving the polyetherketoneketone in the disclosed technology is difficult to overcome the problem of agglomeration among the carbon nanotubes, so that a proper solvent needs to be found to dissolve the polyetherketoneketone and well disperse the carbon nanotubes.
Furthermore, we find some places to be used for reference in a few prior art. For example, in chinese patent nos. 201610441363.8 and 202210836636.4, modified polyaryletherketone and functionalized carbon nanotubes are dispersed and mixed, so that a similar work is performed for achieving uniform dispersion of carbon nanotubes in the polyaryletherketone matrix and combination of the two, but the real dissolution of the polyaryletherketone is still not achieved, and thus the real compounding is not achieved.
In summary, although there is a solvent capable of effectively dissolving polyetherketoneketone in the prior art, the dispersion effect of the solvent on the carbon nanotubes is limited, so we need to find a solvent which can dissolve the polyaryletherketone and uniformly disperse the carbon nanotubes, so that the two components are fully compounded and uniformly distributed in the solution.
Disclosure of Invention
The invention solves the technical problems that: how to realize the efficient compounding and uniform distribution of the carbon nano tube and the polyaryletherketone, and improve the performance of the composite powder.
In order to solve the technical problems, it is critical to solve the problems to dissolve the polyaryletherketone and disperse the carbon nanotubes, an effective reagent is required to be found, and the carbon nanotubes can be uniformly dispersed while the polyaryletherketone is dissolved, so that the carbon nanotube/polyaryletherketone composite powder material is developed by using a wet process. After a series of researches, the inventor finds that the strong polar solvent can realize the dispersion of the carbon nano-tube by utilizing protonation, meanwhile, based on similar compatibility, the solvent can realize the effective dissolution of the polyaryletherketone, and experiments prove that the solvent can not only disperse the carbon nano-tube, but also can well dissolve the polyaryletherketone such as polyether ketone, polyether ether ketone and the like, and can not cause chemical modification. Based on the above, the invention provides a preparation method of a carbon nano tube/polyaryletherketone composite powder material, which comprises the following steps:
step 1: dissolving polyaryletherketone by using a strong polar solvent, and dispersing carbon nanotubes by using the solvent to respectively obtain a homogeneous polyaryletherketone solution and a carbon nanotube dispersion;
wherein the strong polar solvent is chlorosulfonic acid; the concentration of the polyaryletherketone solution is 5-20wt%; the concentration of the carbon nano tube dispersion liquid is 0.2-2.0wt%;
step 2: mixing the two homogeneous phases according to a certain mass ratio, and stirring to obtain a stable carbon nano tube/polyaryletherketone homogeneous mixed solution;
step 3: slowly transferring the mixed solution into a beaker containing a coagulant, stirring, fully replacing the strong polar solvent, and pouring ultrapure water with the same mass as the dispersion liquid into the beaker to dilute the coagulant to obtain a suspension;
step 4: carrying out vacuum suction filtration on the suspension in the beaker, dispersing the obtained solid in ultrapure water, stirring and washing, carrying out vacuum suction filtration again, and repeating the steps for a plurality of times to obtain a carbon nano tube/polyaryletherketone composite wet material;
step 5: drying the obtained wet material in an oven at constant temperature to obtain a carbon nano tube/polyaryletherketone composite dry material;
step 6: and (3) fully crushing the carbon nano tube/polyaryletherketone composite dry material obtained in the step (5) in a crusher, and sieving to obtain the carbon nano tube/polyaryletherketone composite powder.
Preferably, the polyaryletherketone in the step 1 is polyetherketoneketone or polyetheretherketone, and powder with the particle size less than or equal to 300 μm is selected.
More preferably, the molar ratio of the para-to ortho-structure (abbreviated as para-to ortho-structure ratio, or T/I ratio) of the polyetherketoneketone is 50:50, 60:40, 70:30, 80:20, or 100:0.
Preferably, the carbon nanotubes in the step 1 are single-walled carbon nanotubes, multi-walled carbon nanotubes or carbon nanotube assembly materials (fibers, films or arrays).
Preferably, the mass ratio of the carbon nano tube to the polyaryletherketone in the mixed solution in the step 2 is 1:4-80; the stirring process conditions are as follows: stirring at 25-50 deg.c and 1200-1800 rpm for 1-8 hr.
Preferably, the coagulant in the step 3 is glacial acetic acid and/or glacial ultrapure water.
More preferably, the coagulant is glacial acetic acid.
Preferably, the mass of the coagulant in the step 3 is 3-8 times of that of the mixed solution.
Preferably, the stirring in the step 4 adopts low-rotation-speed magnetic stirring or manual stirring; the diameter of filter paper used for vacuum filtration is 110mm, the aperture is 3-6 mu m, and the vacuum negative pressure is-97 kPa; the repetition number in the step 5 is 2-5.
Preferably, the constant temperature drying process parameters in the step 5 are as follows: drying temperature is 100-200 ℃ and drying time is 1-8 h.
More preferably, the constant temperature drying temperature in the step 5 is 150 ℃ and the drying time is 5h.
Preferably, the process parameters of the crushing in the step 6 are as follows: the rotation speed of the pulverizer is 20000rpm, the distance between the cutter blade of the pulverizer and the bottom of the pulverizer is 1cm, the pulverizing temperature is 25-50 ℃, and the pulverizing time is 5-25 min; the mesh size of the screen is 40 mesh.
Compared with the prior art, the invention has the following beneficial effects:
based on the technological breakthrough of polyaryletherketone (polyether ketone or polyether ether ketone) being soluble in a strong polar solvent, the invention innovatively utilizes the polyaryletherketone solution to prepare the carbon nanotube/polyaryletherketone composite powder, wherein the technological path is to firstly dissolve the polyaryletherketone and disperse the carbon nanotubes in a protonated manner, and then fully and uniformly combine and distribute the two, which is different from the simple mixing process of the dispersion liquid of the two in the prior art (Chinese patent invention patent 201610859934.X, 201710438033.8 and the like).
The invention uses chlorosulfonic acid solvent, which not only can fully disperse the carbon nano-tube, but also can fully dissolve the poly (arylene ether ketone), solves the problems of difficult dissolution of the poly (arylene ether ketone) and easy agglomeration of the carbon nano-tube faced by the preparation of the carbon nano-tube/poly (arylene ether ketone) composite powder by using a solution method, and overcomes the defect that the prior solvent capable of dissolving the poly (arylene ether ketone) can not fully disperse the carbon nano-tube. Unlike the irreversible graft dispersion adopted by the prior art (Chinese patent invention 201610441363.8, 202210836636.4, etc.) on the carbon nanotubes, the protonation dispersion of the carbon nanotubes can be deprotonated in the solidification process after the carbon nanotubes are fully compounded, and the excellent performance of the carbon nanotubes is not affected.
Drawings
FIG. 1 is a polyether ketone/chlorosulfonic acid solution as described in example 1;
FIG. 2 is an infrared spectrum of chlorosulfonic acid treated polyetherketoneketone;
FIG. 3 is a photograph of the mixed liquor prepared in example 1;
FIG. 4 is a photograph of the carbon nanotube/polyether ketone composite powder prepared in example 1;
FIG. 5 is a scanning electron microscope image of the carbon nanotube/polyether ketone composite powder prepared in example 1;
FIG. 6 is a carbon nanotube/polyaryletherketone composite sheet prepared by high temperature hot press molding of the composite powder obtained in examples 1 to 3;
FIG. 7 is a cross-sectional scanning electron microscope image of a carbon nanotube/polyetherketoneketone composite sheet prepared by high temperature hot-press molding of the composite powder obtained in example 1.
Detailed Description
In order to make the invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Example 1
The embodiment provides a preparation method of a carbon nano tube/polyaryletherketone composite powder material, which comprises the following steps:
step 1: dissolving polyetherketoneketone (powder with the T/I ratio of 60:40 and the particle diameter of less than or equal to 300 mu m) in chlorosulfonic acid at room temperature (25 ℃) and the concentration of 8wt%, dispersing the multi-wall carbon nanotube film in chlorosulfonic acid and the concentration of 0.3wt%, and stirring at 1500rpm for 6 hours to respectively obtain a homogeneous polyetherketoneketone solution and a carbon nanotube dispersion;
step 2: mixing and stirring the two homogeneous phases at 25 ℃ at a mass ratio of carbon nano tubes to polyether ketone of 1:9, wherein the stirring speed is 1500rpm, and the stirring time is 1h, so as to obtain a carbon nano tube/polyether ketone homogeneous phase mixed solution;
step 3: slowly transferring the mixed solution into a beaker containing glacial acetic acid with the mass which is 3 times that of the dispersion liquid, stirring to fully displace the strong polar solvent, pouring ultrapure water with the mass which is equal to that of the dispersion liquid into the beaker to dilute the coagulant, and obtaining suspension liquid;
step 4: carrying out vacuum suction filtration on the suspension in the beaker, dispersing the obtained solid in ultrapure water, stirring and washing, then carrying out vacuum suction filtration again, and repeating the steps for 3 times to obtain a carbon nano tube/polyether ketone composite wet material, wherein the diameter of the filter paper is 110mm, the aperture is 3 mu m, and the vacuum negative pressure is-97 kPa;
step 5: drying the obtained wet material in an oven at 150 ℃ for 5 hours at constant temperature to obtain a carbon nano tube/polyether ketone composite dry material;
step 6: fully crushing the carbon nano tube/polyether ketone composite dry material obtained in the step 5 in a crusher, wherein the rotating speed of the crusher is 20000rpm, the distance between the cutter blade of the crusher and the bottom of the crusher is 1cm, the crushing temperature is 40 ℃, the crushing time is 10min, and the carbon nano tube/polyether ketone composite dry material passes through a 40-mesh screen, so that the carbon nano tube/polyether ketone composite powder is obtained, and the carbon nano tube/polyether ketone composite powder is shown in figure 4; the electron microscope Scanning (SEM) results are shown in fig. 5, and it can be seen that the surfaces of the carbon nanotubes are fully coated with the polyether ketone polymer, and there is no obvious agglomeration of the carbon nanotube bundles.
Example 2
The embodiment provides a preparation method of a carbon nano tube/polyaryletherketone composite powder material, which comprises the following steps:
step 1: dissolving polyetherketoneketone (powder with the T/I ratio of 50:50 and the particle diameter of less than or equal to 300 mu m) in chlorosulfonic acid at room temperature (25 ℃) and the concentration of the polyetherketoneketone powder is 12wt%, dispersing the multi-wall carbon nanotube powder in the chlorosulfonic acid and the concentration of the multi-wall carbon nanotube powder is 1.0wt%, and stirring at 1200rpm for 8 hours to respectively obtain a homogeneous polyetherketoneketone solution and a carbon nanotube dispersion;
step 2: mixing and stirring the two homogeneous phases at 25 ℃ at the mass ratio of the carbon nano tube to the polyether ketone of 1:19, wherein the stirring speed is 1200rpm, and the stirring time is 3 hours, so as to obtain a carbon nano tube/polyether ketone homogeneous phase mixed solution;
step 3: slowly transferring the mixed solution into a beaker containing glacial acetic acid with the mass which is 5 times that of the dispersion liquid, stirring to fully replace a strong polar solvent, pouring ultrapure water with the mass which is equal to that of the dispersion liquid into the beaker to dilute the coagulant, and obtaining a suspension liquid;
step 4: carrying out vacuum suction filtration on the suspension in the beaker, dispersing the obtained solid in ultrapure water, stirring and washing, then carrying out vacuum suction filtration again, and repeating the steps for 5 times to obtain a carbon nano tube/polyether ketone composite wet material, wherein the diameter of the filter paper is 110mm, the aperture is 5 mu m, and the vacuum negative pressure is-97 kPa;
step 5: drying the obtained wet material in an oven at 180 ℃ for 4 hours at constant temperature to obtain a carbon nano tube/polyether ketone composite dry material;
step 6: and (3) fully crushing the carbon nano tube/polyether ketone composite dry material obtained in the step (5) in a crusher, wherein the rotating speed of the crusher is 20000rpm, the distance between the cutter blade of the crusher and the bottom of the crusher is 1cm, the crushing temperature is 40 ℃, the crushing time is 10min, and the carbon nano tube/polyether ketone composite powder is obtained by sieving the carbon nano tube/polyether ketone composite dry material with a 40-mesh screen.
SEM characterization analysis shows that the carbon nanotube/polyether ketone composite powder material has carbon nanotube surface coated with polyether ketone polymer and no obvious agglomeration.
Example 3
The embodiment provides a preparation method of a carbon nano tube/polyaryletherketone composite powder material, which comprises the following steps:
step 1: 4.5g of polyether-ether-ketone (powder with the particle size less than or equal to 300 mu m) is dissolved in chlorosulfonic acid at room temperature (25 ℃) and the concentration is 8wt%, 0.2g of multi-wall carbon nano tube film is dispersed in chlorosulfonic acid, the concentration is 0.3wt%, the stirring speed is 1800rpm, and the stirring time is 5 hours, so that a homogeneous polyether-ether-ketone solution and a carbon nano tube dispersion liquid are respectively obtained;
step 2: mixing and stirring the two homogeneous phases at 25 ℃ at a stirring speed of 1800rpm for 1h according to the mass ratio of the carbon nano tube to the polyether-ether-ketone of 1:4 to obtain a carbon nano tube/polyether-ether-ketone homogeneous phase mixed solution;
step 3: slowly transferring the mixed solution into a beaker containing glacial acetic acid/ice ultrapure water mixed solution (the mass ratio is 1:1) with the mass of 8 times of the dispersion liquid, stirring to fully replace a strong polar solvent, and pouring ultrapure water with the mass equal to the mass of the dispersion liquid into the beaker to dilute the coagulant to obtain a suspension liquid;
step 4: carrying out vacuum suction filtration on the suspension in the beaker, dispersing the obtained solid in ultrapure water, stirring and washing, then carrying out vacuum suction filtration again, and repeating the steps for 4 times to obtain a carbon nano tube/polyether-ether-ketone composite wet material, wherein the diameter of the filter paper is 110mm, the aperture is 4 mu m, and the vacuum negative pressure is-97 kPa;
step 5: drying the obtained wet material in an oven at 200 ℃ for 3 hours at constant temperature to obtain a carbon nano tube/polyether-ether-ketone composite dry material;
step 6: and (3) fully crushing the carbon nano tube/polyether-ether-ketone composite dry material obtained in the step (5) in a crusher, wherein the rotating speed of the crusher is 20000rpm, the distance between the cutter blade of the crusher and the bottom of the crusher is 1cm, the crushing temperature is 40 ℃, the crushing time is 10min, and the carbon nano tube/polyether-ether-ketone composite powder is obtained by sieving the carbon nano tube/polyether-ether-ketone composite dry material with a 40-mesh screen.
SEM characterization analysis shows that the carbon nanotube/polyether-ether-ketone composite powder material prepared through the steps has carbon nanotube surface fully coated with polyether-ether-ketone polymer and no obvious agglomeration.
Performance test:
the carbon nano tube/polyaryletherketone composite powder obtained in examples 1 to 3 was subjected to powder performance test, and at the same time, the carbon nano tube/polyaryletherketone composite powder obtained in examples 1 to 3 was subjected to conventional high-temperature hot press molding to prepare a thermoformed part, namely, after preheating for 1h at 380 ℃ in a muffle furnace, molding under a pressure of 50MPa at 380 ℃ in a hot press, and naturally cooling to obtain a carbon nano tube/polyaryletherketone composite sheet with a diameter of 90×10x1mm, as shown in fig. 6. The SEM of the cross section of the carbon nanotube/polyetherketoneketone composite sheet prepared by using the composite powder obtained in example 1 is shown in fig. 7, and it can be seen that the carbon nanotubes and the polyetherketoneketone resin matrix are uniformly and sufficiently compounded. The above composite sheet was subjected to mechanical and electrical property tests, and the results are shown in table 1. From the results shown in Table 1, the obtained carbon nanotube/polyaryletherketone composite sheet has excellent tensile and flexural mechanical properties.
TABLE 1 Performance test results of carbon nanotube/polyaryletherketone composite materials
Comparative example 1
Step 1: dissolving polyether ketone (powder with the T/I ratio of 60:40 and the particle size of less than or equal to 300 mu m) in trifluoroacetic acid at room temperature (25 ℃) with the concentration of 8wt%, and stirring at 1500rpm for 6 hours to obtain a homogeneous polyether ketone solution;
step 2: adding carbon nanotube powder into the homogeneous phase polyether ketone solution according to the mass ratio of the carbon nanotube to the polyether ketone of 1:9, stirring for 8 hours at 30 ℃ and 1500rpm, wherein the carbon nanotube is difficult to disperse in the solution, and a uniform carbon nanotube/polyarylether ketone composite dispersion liquid cannot be formed.
Comparative example 2
Step 1: at room temperature (25 ℃), dissolving polyetherketoneketone (powder with the T/I ratio of 60:40 and the particle size less than or equal to 300 mu m) in trifluoroacetic acid, wherein the concentration is 8wt%, the stirring speed is 1500rpm, and the stirring time is 6 hours, so as to obtain a homogeneous polyetherketoneketone solution, dispersing the carbon nano tube film in the trifluoroacetic acid under the same stirring condition, wherein the concentration is 0.2wt%, the carbon nano tube film is difficult to disperse, the film shape is always maintained, and the carbon nano tube/polyaryletherketone composite powder cannot be prepared by taking the carbon nano tube film as a raw material.
While the invention has been described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. The preparation method of the carbon nano tube/polyaryletherketone composite powder material is characterized by comprising the following steps:
step 1: dissolving polyaryletherketone by using a strong polar solvent, and dispersing carbon nanotubes by using the solvent to respectively obtain a homogeneous polyaryletherketone solution and a carbon nanotube dispersion;
wherein the strong polar solvent is chlorosulfonic acid; the concentration of the polyaryletherketone solution is 5-20wt%; the concentration of the carbon nano tube dispersion liquid is 0.2-2.0wt%;
step 2: mixing the two homogeneous phases, and stirring to obtain a stable carbon nano tube/polyaryletherketone homogeneous phase mixed solution;
step 3: slowly transferring the mixed solution into a beaker containing a coagulant, stirring, fully replacing the strong polar solvent, and pouring ultrapure water into the beaker to dilute the coagulant to obtain a suspension;
step 4: carrying out vacuum suction filtration on the suspension in the beaker, dispersing the obtained solid in ultrapure water, stirring and washing, carrying out vacuum suction filtration again, and repeating the steps for a plurality of times to obtain a carbon nano tube/polyaryletherketone composite wet material;
step 5: drying the obtained wet material in an oven at constant temperature to obtain a carbon nano tube/polyaryletherketone composite dry material;
step 6: and (3) fully crushing the carbon nano tube/polyaryletherketone composite dry material obtained in the step (5) in a crusher, and sieving to obtain the carbon nano tube/polyaryletherketone composite powder.
2. The method for preparing the carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the polyaryletherketone in the step 1 is polyetherketoneketone or polyetheretherketone, and the molar ratio of the para-benzene structure to the ortho-benzene structure in the polyetherketoneketone is 50:50, 60:40, 70:30, 80:20 or 100:0, and the polyaryletherketone is powder with the particle size less than or equal to 300 μm.
3. The method for preparing a carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the carbon nanotubes in the step 1 are single-walled carbon nanotubes, multi-walled carbon nanotubes or carbon nanotube assembly materials.
4. The method for preparing the carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the mass ratio of the carbon nanotubes to the polyaryletherketone in the mixed solution in the step 2 is 1:4-80.
5. The method for preparing a carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the stirring condition in the step 2 is 25 to 50 ℃ and 1200 to 1800rpm; the stirring time is 1-8 h.
6. The method for preparing a carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the coagulant in the step 3 is glacial acetic acid and/or glacial ultrapure water; the mass of the coagulant is 3-8 times of that of the mixed solution.
7. The method for preparing the carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the stirring in the step 4 is magnetic stirring at a low rotation speed or manual stirring; the diameter of filter paper used for vacuum filtration is 110mm, the aperture is 3-6 mu m, and the vacuum negative pressure is-97 kPa; the repetition times of the vacuum filtration, the ultrapure water washing and the vacuum filtration are 2 to 5 times.
8. The method for preparing the carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the constant temperature drying process parameters in the step 5 are as follows: drying temperature is 100-200 ℃ and drying time is 1-8 h.
9. The method for preparing the carbon nanotube/polyaryletherketone composite powder material according to claim 1, wherein the technological parameters of the pulverizing in the step 6 are as follows: the rotation speed of the pulverizer is 20000rpm, the distance between the cutter blade of the pulverizer and the bottom of the pulverizer is 1cm, the pulverizing temperature is 25-50 ℃, and the pulverizing time is 5-25 min; the mesh size of the screen is 40 mesh.
10. The carbon nanotube/polyaryletherketone composite powder material prepared by the method for preparing a carbon nanotube/polyaryletherketone composite powder material according to any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311709281.3A CN117844225A (en) | 2023-12-12 | 2023-12-12 | Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311709281.3A CN117844225A (en) | 2023-12-12 | 2023-12-12 | Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117844225A true CN117844225A (en) | 2024-04-09 |
Family
ID=90533590
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311709281.3A Pending CN117844225A (en) | 2023-12-12 | 2023-12-12 | Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117844225A (en) |
-
2023
- 2023-12-12 CN CN202311709281.3A patent/CN117844225A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Sui et al. | The dispersion of CNT in TPU matrix with different preparation methods: solution mixing vs melt mixing | |
| CN1263596C (en) | Method of forming conductive polymeric nanocomposite materials and materials produced thereby | |
| Jogi et al. | Dispersion and performance properties of carbon nanotubes (CNTs) based polymer composites: a review | |
| CN100549070C (en) | A kind of preparation method of carbon nano-tube/polymer conducing composite material | |
| CN106674825B (en) | A kind of preparation method and masterbatch of graphene/PVC composite material masterbatch | |
| TWI810162B (en) | In situ bonding of carbon fibers and nanotubes to polymer matrices | |
| CN103739903B (en) | A kind of High-conductivity carbon nanotube/rubber nanocomposite and preparation method thereof | |
| KR20140009139A (en) | Process for producing polymer-cnt composites | |
| CN103937234A (en) | Thermal conductive plastic applying modified carbon material, and preparation method thereof | |
| CN104629276A (en) | Preparation method for nanocrystal cellulose composite material, product and application thereof | |
| Liu et al. | Constructing a double-percolated conductive network in a carbon nanotube/polymer-based flexible semiconducting composite | |
| CN104987659A (en) | Heat-resistant antistatic conductive polymer composite material and preparation method therefor and application thereof | |
| CN103709744A (en) | Carbon fiber/carbon nanotube reinforced nylon composite material and preparation method thereof | |
| CN109735064A (en) | A kind of conductive agglomerate and preparation method thereof | |
| JP6996770B2 (en) | In situ binding of carbon fibers and nanotubes to the polymer matrix | |
| KR100851431B1 (en) | A method to align carbon nanotubes by electrospining process with a immiscible polymer blend | |
| CN117844225A (en) | Carbon nano tube/polyaryletherketone composite powder material and preparation method thereof | |
| KR20080020462A (en) | Fabrication method of nano particle aligned channel and the nano particle aligned channel using continuous shear force and phase separation behavior of immiscible binary polymer blend nano particle composite | |
| KR101654638B1 (en) | Hybrid filler composite and preparing method of the same | |
| CN101328276B (en) | Preparation of single wall carbon nanotube-polymer conductive composite film | |
| CN105111701A (en) | Conductive carbon/polymer based composite material and preparation method thereof | |
| KR101122610B1 (en) | Carbon fiber-containing resin dispersion solution and resin composite material | |
| CN101484237A (en) | Ultrasound assisted continuous process for dispersion of nanofibers and nanotubes in polymers | |
| Zhang et al. | Flexural properties and micromorphologies of wood flour/carbon nanofiber/maleated polypropylene/polypropylene composites | |
| CN114685971B (en) | Chopped carbon fiber/polyether ketone composite powder material and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |