CN114276158A - Preparation method of short carbon fiber composite material - Google Patents
Preparation method of short carbon fiber composite material Download PDFInfo
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- CN114276158A CN114276158A CN202111634827.4A CN202111634827A CN114276158A CN 114276158 A CN114276158 A CN 114276158A CN 202111634827 A CN202111634827 A CN 202111634827A CN 114276158 A CN114276158 A CN 114276158A
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Abstract
The invention mainly aims at the problem of recycling and reusing resources in the production process of a carbon/carbon composite material, and mainly relates to a method for preparing a carbon fiber composite material by using a turning material of the carbon/carbon composite material as a main raw material and using commercial short carbon fibers as a reinforcing phase. The method takes turning materials and leftover materials generated in the turning process of a workpiece as main raw materials, and the carbon/carbon composite material with high mechanical property is prepared by the steps of pretreatment modification, wet mixing, drying, cold press molding, heat treatment and the like of the raw materials. The invention not only realizes the effective utilization of resources and reduces the production cost, but also effectively reduces the solid waste generated in the production process and well improves the problem of environmental pollution.
Description
Technical Field
The invention relates to a method for preparing a carbon fiber composite material by taking turning materials and leftover materials of workpieces as main materials and commercial chopped carbon fibers as a reinforcing phase.
Background
With the continuous improvement of the technical level and the continuous consumption of resources, the development of the circular economy is required to be more and more urgent. In China, tens of thousands of tons of carbon/carbon composite materials are produced every year, and meanwhile, a large amount of processing waste materials containing carbon fibers are generated in the preparation process. If these carbon fiber composite materials are directly discarded, the waste treatment and utilization difficulty is large due to the characteristics of high mechanical strength, excellent heat resistance, excellent friction property, good corrosion resistance and the like, and the carbon fiber composite material waste has attracted much attention to the environmental pollution. Therefore, how to recycle these materials becomes an important issue to be solved urgently in the development of the carbon/carbon composite material industry.
At present, the method for recycling carbon fiber composite waste commonly used at home and abroad mainly comprises three modes of chemical recycling, energy recycling and physical recycling, wherein the economic benefit can be maximized by using the physical recycling method. The turning material and the leftover material mainly consist of carbon fiber and carbon powder, and the physical method is to use the carbon materials as a reinforcement and a filling material, then mix the carbon materials with resin, and prepare the carbon fiber reinforced resin (CFRP) composite material through hot-press molding. The chopped carbon fiber composite material can be prepared into a high-temperature-resistant furnace material and a heat-insulating photovoltaic material through heat treatment, and has wide application in the field of anti-friction materials.
Patent 201910284823.4 describes a technology for producing carbon-carbon composite board by using rim charge in detail, mainly realizes recycling of rim charge through the processes of preform weaving, rim charge filling and hot pressing, but this method needs to weave the preform, is time-consuming and labor-consuming, and the hot pressing process is carried out by adopting a mode of directly mixing powder resin and rim charge, which not only can generate a large amount of dust, but also can cause uneven mixing of partial materials, resulting in large product performance difference of each batch.
Patent 201180007837.3 describes a method for producing molded articles from carbon material by using recycled carbon fibers, but the method is characterized in that the liquid-phase impregnation treatment is carried out during the production process, the operation process is complicated, the produced waste liquid causes serious environmental pollution, and a large amount of dust is generated during the production process of the molded articles, which has a great influence on the environment.
Disclosure of Invention
In order to solve the technical problems in the background, the invention provides a method for preparing a carbon fiber composite material, which has the advantages of effective recycling of resources and friendly working environment. In particular to a method for preparing a carbon fiber composite material by taking turning materials and leftover materials in the processing process of the carbon/carbon composite material as main materials, commercial short carbon fibers as a reinforcing phase and thermosetting resin as a forming agent through pretreatment modification, material mixing, drying, cold press molding and heat treatment.
The invention specifically comprises the following steps
Step one), pre-treatment of solid waste materials:
crushing and screening → acid and alkali washing → drying → oxidation treatment → surface mechanical modification
Firstly, crushing and screening raw materials (turning materials and leftover materials in the processing process of a carbon/carbon composite material), then removing impurities generated in the collecting process through acid-base washing, carrying out surface activation, drying and surface oxidation treatment after washing, and finally obtaining a pretreatment recycled material through mechanical modification, wherein the pretreatment recycled material is resin-modified coated carbon powder and/or resin-modified coated chopped carbon fiber powder;
step two), wet mixing: putting the material obtained in the step one, the commercial chopped carbon fibers, the thermosetting resin and the dissolving agent into a mixer according to a certain proportion and uniformly mixing;
step three), drying: drying the material obtained in the step two in a drying box to obtain a dry mixed material;
step four), cold press molding: filling the dried mixed material obtained in the step three into a mould, putting the mould into a mould press, and carrying out cold press molding under the room temperature environment by controlling the pressing pressure and the pressure maintaining time in a segmented manner;
step five), performing high-temperature heat treatment on the cold-pressed compact obtained in the step four;
and step six) machining treatment.
Further, in the step one, the size of the used screen is 20-100 meshes, the screening time is 5-30min, and the average length of the fibers of the screened material is less than 0.5mm, and the diameter of the screened material is less than 0.8 mm.
Further, in the first step, the time for acid-base washing is 5-30 min; the drying temperature is 100-; the oxidant in the oxidation treatment process is air or ozone, the treatment temperature is 200-; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9: 0.8-1.5, preferably 9: 1. When the mixture is uniform, the mixture can be mixed in a high-speed mechanical mixer at a speed of 650-1300 rpm.
Further, in the second step, in the mixing, the recycled carbon fiber, the commercial carbon fiber bundle and the thermosetting resin are taken as a whole; the mass ratio of the recycled carbon fiber is 55-80 wt%, the commercial carbon fiber bundle is 5-10 wt%, the thermosetting resin is 15-35 wt%, and the mass ratio of the dissolving agent to the resin is 1/1-3/1.
Further, in the second step, the average length of the used commercial carbon fiber bundle is 5-30mm, and the diameter is less than 1 mm; the thermosetting resin is one or more of phenolic resin and epoxy resin, and the wetting agent is one or more of methanol, ethanol or furfuryl alcohol.
Further, in the third step, the drying temperature is 120-200 ℃, and the heat preservation time is 2-6 h.
Further, in the fourth step, the pressure in the cold pressing process is 100-200MPa, and the pressure maintaining time is 2-5 min. The cold pressing process is segmented and pressure maintaining, and specifically comprises the following steps: keeping the pressure for 1-2 minutes when the pressing pressure is 5-10 MPa; keeping the pressure for 1-2 minutes when the pressing pressure is 10-20 MPa; keeping the pressure for 1-2 minutes when the pressing pressure is 100-200 MPa. The air among the raw material particles can be removed by the sectional pressure maintaining, the stress is eliminated, and the better molding is facilitated.
Further, in the fifth step, the high-temperature heat treatment includes carbonization, CVD chemical vapor deposition, and graphitization (whether graphitization is performed is determined according to product requirements), specifically: the carbonization temperature is 800-1200 ℃, and the required time is 2-10 h; the chemical vapor deposition temperature is 1200-1800 ℃, and the required time is 8-20 h; the graphitization temperature is 2400-3000 ℃, and the heat preservation time is 2-10 h.
Further, the density of the prepared carbon fiber composite material is 1.4-1.7g/cm3The bending strength is more than 60MPa, the compressive strength is more than 120MPa, and the high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high-toughness high-strength high.
As a preferred scheme:
in the first step, the time of acid-base washing is 5 min; the drying temperature is 150 ℃, and the drying time is 2 hours; the oxidant in the oxidation treatment process is air, the treatment temperature is 300 ℃, and the time is 2 hours; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9:1 in a high-speed mechanical mixer to obtain resin modified and coated carbon powder and chopped carbon fiber powder; (ii) a
In the second step, the mass ratio of the recovered carbon fiber in the mixed material is 70 wt%, the mass ratio of the commercial carbon fiber bundle is 5 wt%, the mass ratio of the thermosetting resin is 25 wt%, and the mass ratio of the resin to the dissolving agent is 1: 2; in the second step, the average length of the used commercial chopped carbon fibers is 12mm, the diameter of the commercial chopped carbon fibers is 0.5mm, the used thermosetting resin is phenolic resin, and the used wetting agent is ethanol;
in the third step, the temperature during drying is 120 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1.5 minutes when the pressing pressure is 5 MPa; keeping the pressure for 1.5 minutes when the pressing pressure is 10 MPa; keeping the pressure for 2 minutes when the pressing pressure is 100 MPa.
In the fifth step, the temperature for carbonizing the material is 900 ℃, and the required time is 5 hours;
step five, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and the material is densified 3 times by the same method;
the green compact density of the prepared chopped carbon fiber composite board is 1.42g/cm3The density of the densified material is 1.53g/cm3，The bending strength is 73.4MPa, the compressive strength is 131.4MPa,
as a preferred scheme:
in the first step, the time of acid-base washing is 5 min; the drying temperature is 150 ℃, and the drying time is 2 hours; the oxidant in the oxidation treatment process is air, the treatment temperature is 300 ℃, and the time is 2 hours; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a weight ratio of 9:1 in a high-speed mechanical mixer to obtain resin modified and coated carbon powder and chopped carbon fiber powder; (ii) a
In the second step, the mass ratio of the recovered carbon fibers in the mixed material is 60 wt%, the mass ratio of the commercial chopped carbon fibers is 10 wt%, and the mass ratio of the modified suspension resin is 1: 2.5;
in the second step, the average length of the used commercial carbon fiber is 12mm, the diameter of the commercial carbon fiber is 0.5mm, the used thermosetting resin is phenolic resin, and the used dissolving agent is methanol;
in the third step, the temperature during drying is 140 ℃, and the heat preservation time is 3 hours;
in the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 2 minutes when the pressing pressure is 8 MPa; keeping the pressure for 2 minutes when the pressing pressure is 15 MPa; keeping the pressure for 1 minute when the pressing pressure is 200 MPa;
in the fifth step, the carbonization temperature of the material is 1000 ℃, and the required time is 5 hours;
step five, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and the material is densified 3 times by the same method;
the green compact density of the prepared chopped carbon fiber composite board is 1.52g/cm3The density of the densified material is 1.54g/cm3The flexural strength was 75.42MPa, and the compressive strength was 148.4 MPa.
Compared with the prior art, the invention has the beneficial effects that:
firstly, the carbon fiber raw material is from turning materials and leftover materials in the production process of the carbon/carbon composite material, so that a large amount of cost is saved, the emission of carbon waste is reduced, and the problems of resource waste and environmental pollution are effectively reduced.
Secondly, the invention adopts a series of early-stage treatment works to modify the solid waste reclaimed materials, firstly, acid-base solutions with different concentrations are used for treatment, hydrophobic pollutants on the surface of the carbon fiber can be removed, the specific surface area of the fiber is increased, the bonding strength of the fiber and the resin can be improved by oxidation modification, the dispersity and the stability of the pretreatment powder coated by resin modification are greatly improved, and the mechanical strength of the synthetic material can be further improved.
Thirdly, the invention adopts a wet mixing method, so that the raw materials are mixed more uniformly and fully, powder and dust are avoided, and the working environment is friendly.
Fourthly, the invention adopts a segmented cold pressing method for compression molding, can more rapidly process raw materials, and has simple process and short preparation period.
Fifthly, in order to further improve the product performance of the composite material, the commercial chopped carbon fibers are used as a reinforcing phase, so that the mechanical property of the product is greatly improved.
Finally, the invention greatly improves the thermal physical property and the mechanical property of the chopped carbon fiber composite material by a heat treatment mode, and the material can be widely applied to the fields of photovoltaics, heat treatment, friction and the like.
Drawings
FIG. 1 is a process flow diagram for preparing a carbon fiber composite material according to the present invention;
FIG. 2 is a structural diagram of the appearance of a turning scrap electron microscope used in the invention;
FIG. 3 is a metallographic microstructure of the product obtained in example 1;
fig. 4 is a schematic representation of the carbon fiber composite synthesized in example 1.
Detailed Description
Example 1
A certain amount of turning material of the carbon/carbon composite material is taken, and the carbon fiber composite material is obtained through the following preparation process.
Step one), pre-treatment of solid waste materials:
crushing and screening → acid and alkali washing → drying → oxidation treatment → surface mechanical modification
Firstly, crushing and screening the turned solid waste materials, wherein the size of a screen is 50 meshes, then removing impurities generated in the collection process through acid-base washing, carrying out surface activation, carrying out drying and surface oxidation treatment after washing, and finally carrying out final treatment through a mechanical modification method to obtain resin modified and coated carbon powder and chopped carbon fiber powder;
step two), wet mixing: putting the screened short carbon fiber reclaimed material, the commercial short carbon fibers, the thermosetting resin and the dissolving agent into a mixer according to a certain proportion and uniformly mixing;
step three), drying: putting the mixture into a drying box for drying to obtain a dry mixture;
step four), cold press molding: putting the dried mixed material into a mould, then putting the mould into a cold press, and carrying out cold press molding on the mixed material under the room temperature environment by controlling certain pressure and time;
step five), carrying out carbonization and CVD high-temperature heat treatment;
and step six) machining treatment.
According to the preparation method of the chopped carbon fiber composite material, in the first step, the acid-base washing time is 5 min; the drying temperature is 150 ℃, and the drying time is 2 hours; the oxidant in the oxidation treatment process is air, the treatment temperature is 300 ℃, and the time is 2 hours; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9:1 in a high-speed mechanical mixer at 850 rpm to obtain resin modified and coated carbon powder and chopped carbon fiber powder;
according to the preparation method of the chopped carbon fiber composite material, in the second step, the mass ratio of the recovered carbon fibers in the mixed material is 70%, the mass ratio of the commercial carbon fiber bundles is 5%, the mass ratio of the thermosetting resin is 25%, and the mass ratio of the resin to the dissolving agent is 1: 2.
according to the above preparation method of the chopped carbon fiber composite material, in the second step, the average length of the used commercial chopped carbon fibers is 12mm, the diameter of the commercial chopped carbon fibers is 0.5mm, the thermosetting resin used is phenolic resin, and the wetting agent used is ethanol.
According to the preparation method of the chopped carbon fiber composite material, in the third step, the drying temperature is 120 ℃, and the heat preservation time is 3 hours.
According to the preparation method of the chopped carbon fiber composite material, in the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1.5 minutes when the pressing pressure is 5 MPa; keeping the pressure for 1.5 minutes when the pressing pressure is 10 MPa; keeping the pressure for 2 minutes when the pressing pressure is 100 MPa.
According to the preparation method of the chopped carbon fiber composite material, in the fifth step, the material is carbonized at the temperature of 900 ℃ for 5 hours.
According to the preparation method of the chopped carbon fiber composite material, in the fifth step, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and the material densification is carried out 3 times by the same method.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the pressed compact density of 1.42g/cm3The density of the densified material is 1.53g/cm3，The bending strength is 73.4MPa, the compressive strength is 131.4MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
Comparative example 1:
keeping other test parameters unchanged in all test processes in example 1, only changing the difference of the mixing ratio, not adding commercial carbon fibers in the mixed material, wherein the ratio of the recycled carbon fibers is 75 percent, the ratio of the phenolic resin is 25 percent, and the mass ratio of the phenolic resin to the dissolving agent is 1: 2. the final density of the prepared chopped carbon fiber composite board is 1.51g/cm3，The flexural strength was 58.2MPa and the compressive strength was 115.3 MPa.
Example 2
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of the solid waste treatment is the same as that of the example 1.
In the second step, the proportion of the recovered carbon fibers in the mixed material is 60%, the proportion of the commercial chopped carbon fibers in the mixed material is 10%, the proportion of the modified suspension resin in the mixed material is 30%, and the mass ratio of the resin to the dissolving agent is 1: 2.5, the average length of the commercial carbon fiber used was 12mm, the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 140 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 2 minutes when the pressing pressure is 8 MPa; keeping the pressure for 2 minutes when the pressing pressure is 15 MPa; keeping the pressure for 1 minute when the pressing pressure is 200 MPa.
In the fifth step, the carbonization temperature of the material is 1000 ℃, the required time is 5 hours, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and densification is carried out for 3 times by the same method.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the pressed compact density of 1.52g/cm3The density of the densified material is 1.54g/cm3，The bending strength is 75.42MPa, the compressive strength is 148.4MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
Comparative example 2:
keeping other test parameters unchanged in all test processes in example 2, only changing the difference of the mixing ratio, not adding commercial carbon fibers in the mixed material, wherein the ratio of the recycled carbon fibers is 70 percent, the ratio of the phenolic resin is 30 percent, and the mass ratio of the phenolic resin to the dissolving agent is 1: 2.5. the final density of the prepared chopped carbon fiber composite board is 1.58g/cm3，The flexural strength was 52.37MPa, and the compressive strength was 110.2 MPa.
Example 3
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of solid waste treatment is the same as that of the example 1;
in the second step, the proportion of the pre-treated recycled carbon fiber in the mixed material is 60%, the proportion of the commercial chopped carbon fiber is 5%, the proportion of the modified suspension resin is 35%, and the mass ratio of the resin to the dissolving agent is 1: 3. the average length of the commercial carbon fiber used was 12mm and the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 140 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1 minute when the pressing pressure is 10 MPa; keeping the pressure for 1 minute when the pressing pressure is 20 MPa; keeping the pressure for 1 minute when the pressing pressure is 150 MPa.
In the fifth step, the carbonization temperature of the material is 950 ℃, the required time is 6 hours, the chemical vapor deposition temperature for material densification is 1500 ℃, the required time is 15 hours, and densification is carried out for 2 times by the same method.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the density of 1.49g/cm3，The bending strength is 67.29MPa, the compressive strength is 122.1MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
Comparative example 3:
keeping other test parameters unchanged in all test processes in the example 3, only changing the mould pressing mode of the composite material, and pressing by adopting a hot pressing mode, wherein the pressing temperature is 120 ℃, the time is 3min, and the pressure is 150 MPa. The final density of the prepared chopped carbon fiber composite board is 1.46g/cm3，The flexural strength was 49.55MPa, and the compressive strength was 89.2 MPa.
Example 4
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of solid waste treatment is the same as that of the example 1;
in the second step, the ratio of the pre-treated recycled carbon fiber in the mixed material is 65%, the commercial chopped carbon fiber is 10%, the modified suspension resin is 25%, and the mass ratio of the resin to the dissolving agent is 1: 2. the average length of the commercial carbon fiber used was 12mm and the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 120 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 2 minutes when the pressing pressure is 5 MPa; keeping the pressure for 2 minutes when the pressing pressure is 15 MPa; keeping the pressure for 2 minutes when the pressing pressure is 180 MPa.
In the fifth step, the carbonization temperature of the material is 1100 ℃, the required time is 5 hours, the chemical vapor deposition temperature for material densification is 1600 ℃, the required time is 18 hours, and the densification is carried out for 2 times by the same method.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the density of 1.52g/cm3，The bending strength is 69.78MPa, the compressive strength is 130.7MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
Comparative example 4:
the other test parameters in all the test processes in the example 4 are kept unchanged, only the mould pressing mode of the composite material is changed, and the composite material is pressed by adopting a one-step cold press forming mode, wherein the pressing time is 6min, and the pressure is 180 MPa. The final density of the prepared chopped carbon fiber composite board is 1.24g/cm3，The flexural strength was 38.7MPa and the compressive strength was 76.4 MPa.
Example 5
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of solid waste treatment is the same as that of the example 1;
in the second step, the ratio of the pre-treated recycled carbon fiber in the mixed material is 70%, the ratio of the commercial chopped carbon fiber is 5%, the ratio of the modified suspension resin is 25%, and the mass ratio of the resin to the dissolving agent is 1: 2. the average length of the commercial carbon fiber used was 12mm and the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 120 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1 minute when the pressing pressure is 8 MPa; keeping the pressure for 2 minutes when the pressing pressure is 12 MPa; keeping the pressure for 2 minutes when the pressing pressure is 150 MPa.
In the fifth step, the carbonization temperature of the material is 1000 ℃, the required time is 4 hours, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 15 hours, the densification is performed 3 times by the same method, and the graphitization treatment temperature is 2300 ℃ and the time is 3 hours.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the density of 1.58g/cm3，The bending strength is 61.45MPa, the compressive strength is 128.6MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
Comparative example 5
All other test parameters were kept unchanged for the test procedure in example 5, but the raw material solid waste was not treated with any mechanical and coating modification. The final density of the prepared chopped carbon fiber composite board is 1.31g/cm3，The flexural strength was 72.9MPa and the compressive strength was 41.3 MPa.
Example 6
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of solid waste treatment is the same as that of the example 1;
in the second step, the ratio of the pre-treated recycled carbon fiber in the mixed material is 75%, the commercial chopped carbon fiber is 10%, the modified suspension resin is 15%, and the mass ratio of the resin to the dissolving agent is 1: 1. the average length of the commercial carbon fiber used was 12mm and the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 120 ℃, and the heat preservation time is 2 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1 minute when the pressing pressure is 10 MPa; keeping the pressure for 2 minutes when the pressing pressure is 15 MPa; keeping the pressure for 2 minutes when the pressing pressure is 180 MPa.
In the fifth step, the carbonization temperature of the material is 1000 ℃, the required time is 5 hours, the chemical vapor deposition temperature for material densification is 1500 ℃, the required time is 16 hours, the densification is carried out 3 times by the same method, and the graphitization treatment temperature is 2300 ℃ and the time is 3 hours.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the density of 1.60g/cm3，The bending strength is 59.68MPa, the compression strength is 122.7MPa, the heat resistance and the mechanical strength are very excellent, and the material can be effectively utilized in the fields of photovoltaic heat-insulating materials and friction-resistant materials
Example 7
A method of making a chopped carbon fiber composite according to example 1
In the first step, the pretreatment process of solid waste treatment is the same as that of the example 1;
in the second step, the proportion of the pre-treated recycled carbon fiber in the mixed material is 80%, the proportion of the commercial chopped carbon fiber is 5%, the proportion of the modified suspension resin is 15%, and the mass ratio of the resin to the dissolving agent is 1: 1. the average length of the commercial carbon fiber used was 12mm and the diameter was 0.5mm, the thermosetting resin used was phenol resin, and the solvent used was methanol.
In the third step, the temperature during drying is 120 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1.5 minutes when the pressing pressure is 8 MPa; keeping the pressure for 2 minutes when the pressing pressure is 12 MPa; keeping the pressure for 2 minutes when the pressing pressure is 150 MPa.
In the fifth step, the carbonization temperature of the material is 950 ℃, the required time is 5 hours, the chemical vapor deposition temperature for material densification is 1600 ℃, the required time is 12 hours, the densification is carried out 3 times by the same method, and the graphitization treatment temperature is 2300 ℃ and the time is 3 hours.
According to the preparation method of the chopped carbon fiber composite material, the prepared chopped carbon fiber composite board has the density of 1.57g/cm3，The bending strength is 57.22MPa, the compressive strength is 121.2MPa,has excellent heat resistance and mechanical strength, and can be effectively used in the fields of photovoltaic heat-insulating materials and friction-resistant materials.
TABLE 1
Claims (10)
1. A preparation method of a carbon fiber composite material is characterized by comprising the following steps: the method comprises the steps of taking turning materials and leftover materials in the processing process of the carbon/carbon composite material as raw materials, taking commercial chopped carbon fibers as a reinforcing phase, taking thermosetting resin as a forming agent, adding a certain amount of dissolving agent during mixing, and drying, cold press molding and heat treatment to obtain the carbon fiber composite material; the method mainly comprises the following steps:
firstly, pre-treatment of solid waste materials:
crushing and screening → acid and alkali washing → drying → oxidation treatment → surface mechanical modification
Firstly, crushing and screening raw materials, then removing impurities generated in the collection process through acid-base washing, carrying out surface activation, drying and surface oxidation treatment after washing, and finally obtaining a pretreatment recycled material through mechanical modification, wherein the pretreatment recycled material is resin modified and coated carbon powder and/or resin modified and coated chopped carbon fiber powder;
step two, wet mixing
Putting the pretreated reclaimed material obtained in the step one, the commercial chopped carbon fibers, the thermosetting resin and the dissolving agent into a mixer according to a certain proportion and uniformly mixing;
drying in step three
Putting the mixed material obtained in the step two into a drying box for drying to obtain a dried mixed material;
step four cold press molding
Putting the dried mixed material obtained in the step three into a mould, then putting the mould into a cold press, and carrying out cold press molding on the mixed material by controlling the pressure and time in sections under the room temperature environment;
step five, carrying out high-temperature heat treatment on the cold-pressed green compact obtained in the step four;
and step six, machining treatment.
2. The method of making a chopped carbon fiber composite of claim 1, wherein: in the first step, the time of acid-base washing is 5-30 min; the drying temperature is 100-; the oxidant in the oxidation treatment process is air or ozone, the treatment temperature is 200-; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9: a ratio of 0.8 to 1.5, preferably 9:1, is mixed homogeneously in a high-speed mechanical mixer at a speed of 650 and 1300 rpm.
3. The method for preparing a chopped carbon fiber composite according to claim 1, wherein in the second step, recycled carbon fibers, commercial carbon fiber bundles and thermosetting resin are taken as a whole in the mixing; the proportion of the recycled carbon fiber is 55-80 wt%, the commercial carbon fiber bundle is 5-10 wt%, and the thermosetting resin is 15-35 wt%; the mass ratio of the resin to the dissolving agent is 1: 3-1: 1.
4. The method as claimed in claim 1, wherein in the second step, the average length of the used commercial carbon fiber bundles is 10-30mm, and the diameter is less than 1 mm; the thermosetting resin is one or more of phenolic resin and epoxy resin, and the dissolving agent is one or more of methanol, ethanol or furfuryl alcohol.
5. The method for preparing a chopped carbon fiber composite material according to claim 1, wherein in the third step, the drying temperature is 120-200 ℃ and the holding time is 2-6 h.
6. The preparation method of the chopped carbon fiber composite material according to claim 1, wherein in the fourth step, the cold pressing process is performed by segmented pressure maintaining, and specifically comprises the following steps: keeping the pressure for 1-2 minutes when the pressing pressure is 5-10 MPa; keeping the pressure for 1-2 minutes when the pressing pressure is 10-20 MPa; keeping the pressure for 1-2 minutes when the pressing pressure is 100-200 MPa.
7. The method for preparing a chopped carbon fiber composite according to claim 1, wherein in the fifth step, the high-temperature heat treatment comprises carbonization, CVD chemical vapor deposition and graphitization, and specifically comprises the following steps: the carbonization temperature is 800-1200 ℃, and the required time is 2-10 h; the chemical vapor deposition temperature is 900-1800 ℃, and the required time is 8-20 h; the graphitization temperature is 2400-3000 ℃, and the heat preservation time is 2-10 h.
8. The carbon fiber composite material produced by the method according to any one of claims 1 to 7, wherein the carbon fiber composite material is produced to have a density of 1.4 to 1.7g/cm3The bending strength is more than 60MPa, and the compressive strength is more than 120 MPa.
9. The carbon fiber composite material prepared according to any one of claims 1 to 7, wherein in the first step, the time for acid-base washing is 5 min; the drying temperature is 150 ℃, and the drying time is 2 hours; the oxidant in the oxidation treatment process is air, the treatment temperature is 300 ℃, and the time is 2 hours; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9:1 to obtain resin modified and coated carbon powder and/or chopped carbon fiber powder;
in the second step, the mass ratio of the pretreatment recycled material carbon fiber in the mixed material is 70%, the mass ratio of the commercial carbon fiber bundle is 5%, the mass ratio of the thermosetting resin is 25%, and the mass ratio of the resin to the dissolving agent is 1: 2; in the second step, the average length of the used commercial chopped carbon fibers is 12mm, the diameter of the commercial chopped carbon fibers is 0.5mm, the used thermosetting resin is phenolic resin, and the used wetting agent is ethanol;
in the third step, the temperature during drying is 120 ℃, and the heat preservation time is 3 hours.
In the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 1.5 minutes when the pressing pressure is 5 MPa; keeping the pressure for 1.5 minutes when the pressing pressure is 10 MPa; keeping the pressure for 2 minutes when the pressing pressure is 100 MPa.
In the fifth step, the temperature for carbonizing the material is 900 ℃, and the required time is 5 hours;
step five, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and the material is densified 3 times by the same method;
the green compact density of the prepared chopped carbon fiber composite board is 1.42g/cm3The density of the densified material is 1.53g/cm3，The flexural strength was 73.4MPa, and the compressive strength was 131.4 MPa.
10. The carbon fiber composite material produced by the method according to any one of claims 1 to 6, characterized in that:
in the first step, the time of acid-base washing is 5 min; the drying temperature is 150 ℃, and the drying time is 2 hours; the oxidant in the oxidation treatment process is air, the treatment temperature is 300 ℃, and the time is 2 hours; the mechanical modification method specifically comprises the following steps of mixing oxide powder and resin according to a mass ratio of 9:1 to obtain resin modified and coated carbon powder and short carbon fiber powder;
in the second step, the mass ratio of the reclaimed carbon fibers in the mixed material is 60%, the mass ratio of the commercial chopped carbon fibers is 10%, the mass ratio of the modified suspension resin is 1: 2.5;
in the second step, the average length of the used commercial carbon fiber is 12mm, the diameter of the commercial carbon fiber is 0.5mm, the used thermosetting resin is phenolic resin, and the used dissolving agent is methanol;
in the third step, the temperature during drying is 140 ℃, and the heat preservation time is 3 hours;
in the fourth step, the cold pressing process comprises the following specific steps: keeping the pressure for 2 minutes when the pressing pressure is 8 MPa; keeping the pressure for 2 minutes when the pressing pressure is 15 MPa; keeping the pressure for 1 minute when the pressing pressure is 200 MPa;
in the fifth step, the carbonization temperature of the material is 1000 ℃, and the required time is 5 hours;
step five, the chemical vapor deposition temperature for material densification is 1400 ℃, the required time is 12 hours, and the material is densified 3 times by the same method;
the green compact density of the prepared chopped carbon fiber composite board is 1.52g/cm3The density of the densified material is 1.54g/cm3，The flexural strength was 75.42MPa, and the compressive strength was 148.4 MPa.
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