CN115847693A - Forming process of high-strength polytetrafluoroethylene sheet - Google Patents
Forming process of high-strength polytetrafluoroethylene sheet Download PDFInfo
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- CN115847693A CN115847693A CN202211274030.2A CN202211274030A CN115847693A CN 115847693 A CN115847693 A CN 115847693A CN 202211274030 A CN202211274030 A CN 202211274030A CN 115847693 A CN115847693 A CN 115847693A
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Abstract
The invention provides a molding process of a high-strength polytetrafluoroethylene sheet, and belongs to the technical field of polytetrafluoroethylene composite materials. The method comprises the following steps: 1) Mixing materials: uniformly mixing polytetrafluoroethylene resin powder and mica powder according to a certain proportion; 2) And single-piece forming: adding the mixture obtained in the step 1) into a mould for pressure forming, wherein during the pressure forming, the mould is in a centrifugal rotating state; 3) And sheet combination: grouping the single sheet blanks prepared in the step 2) in pairs, and taking the mica powder deposition side as a composite surface to form a composite blank; 4) And sintering: heating the composite blank material prepared in the step 3) to bond the composite surfaces to prepare a polytetrafluoroethylene composite sheet; 5) And cooling: and rapidly cooling the polytetrafluoroethylene composite sheet formed after sintering to obtain a finished polytetrafluoroethylene sheet. The invention has the advantages of high strength, smooth appearance, stable performance and the like.
Description
Technical Field
The invention belongs to the technical field of polytetrafluoroethylene composite materials, and relates to a molding process of a high-strength polytetrafluoroethylene sheet.
Background
Polytetrafluoroethylene, commonly known as "plastic king", is a high molecular polymer prepared by polymerization using tetrafluoroethylene as a monomer. Because of its high temperature resistance, low friction coefficient, strong acid and alkali resistance, etc., it is widely used in the electrical industry, in the fields of spaceflight, aviation, electronics, instruments, computers, etc.
According to application scenes and performance requirements, the polytetrafluoroethylene is used as a base material and is compounded with other materials to strengthen the performance of the sheet, so that the polytetrafluoroethylene has wider application prospects and market values. The polytetrafluoroethylene has very good mechanical property, environmental resistance and electrical property, but the dimensional stability of the polytetrafluoroethylene is relatively poor, the polytetrafluoroethylene is difficult to be directly applied when the dimensional stability has higher requirements, and the mechanical strength of the polytetrafluoroethylene is correspondingly influenced by the better ductility of the polytetrafluoroethylene.
Disclosure of Invention
The invention aims to provide a forming process of a high-strength polytetrafluoroethylene sheet aiming at the problems in the prior art, and the technical problem to be solved is to prepare a polytetrafluoroethylene composite sheet with better integrity.
The purpose of the invention can be realized by the following technical scheme: a molding process of a high-strength polytetrafluoroethylene sheet is characterized by comprising the following steps:
1) Mixing materials: uniformly mixing polytetrafluoroethylene resin powder and mica powder according to a certain proportion;
2) And single-piece forming: adding the mixture obtained in the step 1) into a mould for pressure forming, wherein during the pressure forming, the mould is in a centrifugal rotating state;
3) And sheet combination: grouping the single sheet blanks prepared in the step 2) in pairs, and taking one side deposited with mica powder as a composite surface to form a composite blank;
4) And sintering: heating the composite blank material prepared in the step 3) to bond the composite surfaces to prepare a polytetrafluoroethylene composite sheet;
5) And cooling: and rapidly cooling the polytetrafluoroethylene composite sheet formed after sintering to obtain a finished polytetrafluoroethylene sheet.
Because the density of mica powder is greater than polytetrafluoroethylene powder, under the effect of centrifugal force, mica powder and polytetrafluoroethylene powder have relatively obvious layering, because the difference in density between them is not big, consequently, under the effect of appropriate centrifugal force, the layering is not thorough, but have each other the debris, and be gradual change state, specifically speaking, the inboard polytetrafluoroethylene proportion of centrifugal force is far greater than the centrifugal force outside, make veneer polytetrafluoroethylene one side level and smooth, the no burr, after the piece that closes, both promoted the mechanical properties of sheet, simultaneously, its outer wall is smooth and flat, the condition of falling powder, desludging is controlled, and the three layer construction who forms compares the compound three layer construction of viscose, its peel strength is higher, compound wholeness is better, prevent permeating, deformation resistance is stronger.
Further, the mass ratio of the mica powder in the step 1) is less than 15%.
Further, in the step 2), before pressing, the mixed material in the mold cavity is maintained in a relaxed state for 1-3 minutes, and a centrifugal rotation state is maintained, then, the air is exhausted and the pressure is applied for 15-60 minutes, the pressure is applied under 0.5MPa for 3-20 minutes, finally, the pressure is increased to 25-40 MPa, the rest time is maintained, and the mold is maintained in a centrifugal rotation state all the time in the pressing process.
Further, the rotation speed of centrifugal rotation of the die is not less than 3000r/min.
Further, the heating temperature in the step 4) is 300-36 ℃, and the heating time is 2-8 h.
Further, rapid cooling is carried out at the heating temperature of the step 4), and the rapid cooling medium is normal temperature water.
Further, the mica powder is calcined mica powder.
The equipment for making the mould in the centrifugal rotation state comprises a frame, a protective cylinder, a centrifugal cylinder, a motor, a rotating rod and a plurality of moulds, wherein the protective cylinder, the centrifugal cylinder, the motor, the rotating rod and the moulds are fixed on the frame, the centrifugal cylinder is arranged outside the rotating rod, an output shaft of the motor is connected with one end of the rotating rod, a bidirectional hydraulic cylinder is arranged in the middle of the rotating rod, a swing arm is arranged between each two push rods of the bidirectional hydraulic cylinder and the centrifugal cylinder, the moulds are circumferentially and uniformly distributed on the inner wall of the centrifugal cylinder, the centrifugal cylinder is positioned on the inner side of the protective cylinder, the two ends of the swing arm are respectively hinged with the push rods of the bidirectional hydraulic cylinder and the movable mould plates of the moulds, and the protective cylinder is fixed on the frame.
Further, the number of the molds exceeds 12.
Furthermore, a shutter is arranged on the protective cylinder.
Drawings
FIG. 1 is a sheet compounding flow chart in the process.
Fig. 2 is a schematic view of the structure of the centrifugal apparatus.
Fig. 3 is a schematic view of the internal structure of the centrifugal apparatus.
Fig. 4 is a schematic view showing a layered state of a single sheet before compounding.
In the figure, 1, a frame; 2. protecting the cylinder; 3. a centrifugal cylinder; 4. a motor; 5. a rotating rod; 6. a mold; 7. a bidirectional hydraulic cylinder; 8. and (4) swinging arms.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
As shown in fig. 1, the molding process of the high-strength polytetrafluoroethylene sheet comprises the following steps:
1. mixing materials: uniformly mixing polytetrafluoroethylene resin powder and calcined mica powder according to a certain proportion; the mass ratio of the mica powder is less than 15%, the proportion of the mica powder is properly adjusted according to the application of the composite material, and if the composite sheet material is required to have better buffer performance or the surface flatness of the sheet material is required to be higher, the using amount of the mica powder can be properly reduced.
2. Single-piece forming: adding the mixture obtained in the step (1) into a mould (6) for pressure forming, wherein during the pressure forming, the mould (6) is in a centrifugal rotation state; before pressing, the mixed material in the die cavity is maintained in a relaxed state for 1-3 minutes, a centrifugal rotation state is maintained, then the pressing is carried out for 15-60 minutes under the pressure of 0.5MPa for 3-20 minutes, finally the pressure is increased to 25-40 MPa for the rest time, the die 6 is always maintained in the centrifugal rotation state in the pressing process, and the rotation speed of the centrifugal rotation is not less than 3000r/min. The maintaining time of the pre-pressing is correspondingly changed when the rotating speed is different, and the material relaxation state before pressing is to ensure that the powder is better layered under lower pressure. The small pressure is used to make the lamination more uniform without any significant difference in the thickness of the mica powder in the longitudinal direction, and the subsequent pressure is used to perform, and the sheet is obtained as shown in fig. 4.
3. Sheet combination: grouping the single sheet blanks prepared in the step 2 in pairs, and taking the mica powder deposition side as a composite surface to form a composite blank;
4. and (3) sintering: heating the composite blank material prepared in the step (3) to bond the composite surfaces to prepare a polytetrafluoroethylene composite sheet, wherein the heating temperature is 300-36 ℃, and the heating time is 2-8 h;
5. and (3) cooling: and rapidly cooling the polytetrafluoroethylene composite sheet formed after sintering to obtain a finished polytetrafluoroethylene sheet, wherein the cooling medium is normal-temperature circulating water.
Because the density of mica powder is greater than polytetrafluoroethylene powder, under the effect of centrifugal force, mica powder and polytetrafluoroethylene powder have relatively obvious layering, because the difference in density between them is not big, consequently, under the effect of appropriate centrifugal force, the layering is not thorough, but have each other the debris, and be gradual change state, specifically speaking, the inboard polytetrafluoroethylene proportion of centrifugal force is far greater than the centrifugal force outside, make veneer polytetrafluoroethylene one side level and smooth, the no burr, after the piece that closes, both promoted the mechanical properties of sheet, simultaneously, its outer wall is smooth and flat, the condition of falling powder, desludging is controlled, and the three layer construction who forms compares the compound three layer construction of viscose, its peel strength is higher, compound wholeness is better, prevent permeating, deformation resistance is stronger.
As shown in fig. 2 and fig. 3, the apparatus for making the mold 6 in a centrifugal rotation state includes a frame 1, a protective cylinder 2 fixed on the frame 1, a centrifugal cylinder 3, a motor 4, a rotating rod 5 and a plurality of molds 6, the centrifugal cylinder 3 is arranged outside the rotating rod 5, an output shaft of the motor 4 is connected with one end of the rotating rod 5, a bidirectional hydraulic cylinder 7 is arranged in the middle of the rotating rod 5, a swing arm 8 is arranged between two push rods of the bidirectional hydraulic cylinder 7 and the centrifugal cylinder 3, each mold 6 is circumferentially and uniformly distributed on the inner wall of the centrifugal cylinder 3, the centrifugal cylinder 3 is located inside the protective cylinder 2, two ends of the swing arm 8 are respectively hinged with a push rod of the bidirectional hydraulic cylinder 7 and a movable mold plate of the mold 6, and the protective cylinder 2 is fixed on the frame 1. The number of the moulds 6 exceeds 12, and the larger number can reduce the centrifugal distance difference of the sheets in the moulds 6 and improve the uniformity of the sheets; the protective cylinder 2 is provided with a stop door, the mold 6 can be disassembled and assembled when the protective cylinder is opened, and the centrifugal cylinder 3 has a certain operation space in the longitudinal direction. The bidirectional hydraulic cylinder synchronously stretches the two push rods, so that the die synchronously applies pressure, and the reverse action can release pressure or remove the die.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments, or alternatives may be employed, by those skilled in the art, without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (10)
1. A molding process of a high-strength polytetrafluoroethylene sheet is characterized by comprising the following steps:
1) Mixing materials: uniformly mixing polytetrafluoroethylene resin powder and mica powder according to a certain proportion;
2) And single piece forming: adding the mixture obtained in the step 1) into a mould (6) for pressing and forming, wherein the mould (6) is in a centrifugal rotating state during the pressing and forming;
3) And sheet combination: grouping the single sheet blanks prepared in the step 2) in pairs, and taking the mica powder deposition side as a composite surface to form a composite blank;
4) And sintering: heating the composite blank material prepared in the step 3) to bond the composite surfaces to prepare a polytetrafluoroethylene composite sheet;
5) And cooling: and rapidly cooling the polytetrafluoroethylene composite sheet formed after sintering to obtain a finished polytetrafluoroethylene sheet.
2. The forming process of high-strength polytetrafluoroethylene sheet according to claim 1, wherein the mass ratio of mica powder in step 1) is less than 15%.
3. The process for molding a high-strength polytetrafluoroethylene sheet according to claim 1, wherein the mixture in the mold cavity is maintained in a relaxed state for 1-3 minutes before the step 2) of pressing, and is kept in a centrifugal rotation state, then the mixture is subjected to pressure application for 15-60 minutes by exhausting air, the pressure application pressure is 0.5Mpa, the mixture is kept for 3-20 minutes, finally the pressure is increased to 25-40 Mpa, the rest time is kept, and the mold (6) is kept in the centrifugal rotation state all the time during the pressure application process.
4. The process for molding high-strength polytetrafluoroethylene sheet according to claim 1, wherein the rotational speed of centrifugal rotation of the mold (6) is not less than 3000r/min.
5. The process for molding a high-strength polytetrafluoroethylene sheet according to claim 1, wherein the heating temperature in step 4) is 300-36 ℃ and the heating time is 2-8 h.
6. The process for forming a high-strength polytetrafluoroethylene sheet according to claim 1, wherein the rapid cooling is performed at the heating temperature in step 4), and the rapid cooling medium is normal-temperature water.
7. The process for forming a high strength polytetrafluoroethylene sheet according to claim 1, wherein said mica powder is calcined mica powder.
8. The forming process of the high-strength polytetrafluoroethylene sheet according to claim 1, wherein the device for enabling the mold (6) to be in a centrifugal rotation state comprises a frame (1), a protective cylinder (2) fixed on the frame (1), a centrifugal cylinder (3), a motor (4), a rotating rod (5) and a plurality of molds (6), wherein the centrifugal cylinder (3) is arranged outside the rotating rod (5), an output shaft of the motor (4) is connected with one end of the rotating rod (5), a bidirectional hydraulic cylinder (7) is arranged in the middle of the rotating rod (5), a swing arm (8) is arranged between each of two push rods of the bidirectional hydraulic cylinder (7) and the centrifugal cylinder (3), the molds (6) are circumferentially and uniformly distributed on the inner wall of the centrifugal cylinder (3), the centrifugal cylinder (3) is located on the inner side of the protective cylinder (2), two ends of the swing arm (8) are respectively hinged with the push rod of the bidirectional hydraulic cylinder (7) and a movable mold plate of the mold (6), and the protective cylinder (2) is fixed on the frame (1).
9. The process for molding high-strength polytetrafluoroethylene sheet according to claim 8, wherein the number of said molds (6) is more than 12.
10. The forming process of the high-strength polytetrafluoroethylene sheet according to claim 8, wherein a shutter is arranged on the casing (2).
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211274030.2A CN115847693B (en) | 2022-10-18 | 2022-10-18 | Forming process of high-strength polytetrafluoroethylene sheet |
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| CN202211274030.2A CN115847693B (en) | 2022-10-18 | 2022-10-18 | Forming process of high-strength polytetrafluoroethylene sheet |
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Denomination of invention: Forming process of high-strength polytetrafluoroethylene sheets Effective date of registration: 20230922 Granted publication date: 20230530 Pledgee: Industrial and Commercial Bank of China Limited Zhejiang Yangtze River Delta integration demonstration zone sub branch Pledgor: Jiashan Yide longfluorine Technology Co.,Ltd. Registration number: Y2023980058551 |
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