CN106867160B

CN106867160B - PTFE composite material and preparation method thereof

Info

Publication number: CN106867160B
Application number: CN201710147025.8A
Authority: CN
Inventors: 阳世清
Original assignee: National University of Defense Technology
Current assignee: National University of Defense Technology
Priority date: 2017-03-13
Filing date: 2017-03-13
Publication date: 2020-12-01
Anticipated expiration: 2037-03-13
Also published as: CN106867160A

Abstract

The invention relates to a PTFE composite material and a preparation method thereof, wherein the PTFE composite material is prepared from the following raw materials in percentage by mass: 2-30% of continuous fiber, 30-98% of PTFE powder and 0-50% of filler powder. The PTFE composite material utilizes continuous fibers and filler powder in a certain proportion to modify polytetrafluoroethylene, the continuous fibers serve as a framework, internal stress concentration points are reduced, when the PTFE composite material is subjected to external load, force is transmitted to the continuous fibers, the continuous fibers can play a bearing role, the mechanical property of the PTFE composite material is effectively improved, the highest tensile strength can reach 272.4MPa, the PTFE composite material in the shape of a large-size thin-wall cylinder can also obtain excellent mechanical property, and the radial rigidity of the PTFE composite material in the shape of a cylinder can be further improved by arranging the annular reinforcing ribs on the PTFE composite material in the shape of a cylinder.

Description

PTFE composite material and preparation method thereof

Technical Field

The invention relates to the field of composite materials, in particular to a PTFE composite material and a preparation method thereof.

Background

Polytetrafluoroethylene (PTFE), an artificially synthesized polymer material using fluorine to replace all hydrogen atoms in polyethylene, has the characteristics of acid and alkali resistance and resistance to various organic solvents, and is almost insoluble in all solvents. With the development of science and technology, the application of polytetrafluoroethylene in engineering is rapidly increased, and the polytetrafluoroethylene becomes one of indispensable important materials in advanced science and modern industry, and is widely used as high and low temperature resistant and corrosion resistant materials, insulating materials and the like in industries such as atomic energy, national defense, aerospace, electronics, electrical, chemical engineering, machinery, instruments, buildings, textiles, metal surface treatment, pharmacy, medical treatment, food, metallurgical smelting and the like, and has bright development prospect.

However, the mechanical properties of polytetrafluoroethylene are poor, which limits its practical application to some extent.

Disclosure of Invention

Therefore, a PTFE composite material with better mechanical properties is needed.

The specific technical scheme is as follows:

the PTFE composite material is prepared from the following raw materials in percentage by mass:

2 to 20 percent of continuous fiber

30 to 98 percent of PTFE powder

0-50% of filler powder.

In one embodiment, the PTFE powder is a suspension-process polytetrafluoroethylene powder.

In one embodiment, the continuous fibers are selected from PBO fibers, aramid fibers, carbon fibers, SiC fibers, or metal fibers.

In one embodiment, the filler powder is inorganic powder or metal powder, and the inorganic powder is selected from metal or nonmetal oxides, carbides, silicides or borides; the metal powder is selected from metal powder of Al, Mg, Ti, Zr, Fe and Cu or metal alloy powder thereof.

In one embodiment, the PTFE composite is in the shape of a cylinder, and a plurality of annular reinforcing ribs are arranged on the cylinder.

In one embodiment, the diameter of the cylinder body is 50-1000mm, the wall thickness is 1-20mm, and the distance between every two adjacent reinforcing ribs is 10-100 mm.

The invention also aims to provide a preparation method of the PTFE composite material, which comprises the following steps:

mixing the PTFE powder and the filler powder to obtain composite material powder, and wrapping the continuous fibers with the composite material powder to obtain a fiber powder belt;

winding the fiber powder belt to form a fiber powder belt cylinder;

and sintering the fiber powder belt cylinder to obtain the PTFE composite material.

In one embodiment, the fiber powder belt is wound by a winding roller, the shape of the winding roller is matched with that of the fiber powder belt barrel, an annular groove is formed in the winding roller, and the fiber powder belt is filled in the annular groove (to form a reinforcing rib).

In one embodiment, the continuous fibers are dispersed through a detwister.

In one embodiment, the sintering treatment is carried out under the conditions of raising the temperature from 15-30 ℃ to 320-400 ℃ within 400min of 380-400 ℃, and then lowering the temperature after heat preservation for 0.5-1.5 h.

The principle and the beneficial effects of the invention are as follows:

according to the PTFE composite material, the polytetrafluoroethylene is modified by utilizing the continuous fibers and the filler powder in a certain proportion, the continuous fibers are used as frameworks, internal stress concentration points are reduced, when the PTFE composite material is subjected to external load, force is transmitted to the continuous fibers, the continuous fibers can play a bearing role, the mechanical property of the PTFE composite material is effectively improved, the highest tensile strength can reach 272.4MPa, the PTFE composite material in the shape of a large-size thin-wall cylinder can also obtain excellent mechanical property, and the radial rigidity of the PTFE composite material in the shape of a cylinder can be further improved by arranging the annular reinforcing ribs on the PTFE composite material in the shape of a cylinder.

Drawings

FIG. 1 is a photograph of a PTFE composite prepared in example 22;

FIG. 2 is a stress-strain plot of three circumferential sections of a PTFE composite prepared in example 22;

FIG. 3 is a stress-strain plot of three axial slices of a PTFE composite prepared in example 22;

FIG. 4 is a photograph of a PTFE composite prepared in example 23.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

2 to 20 percent of continuous fiber

30 to 98 percent of PTFE powder

0-50% of filler powder.

Preferably, the PTFE powder is polytetrafluoroethylene powder prepared by a suspension method.

Preferably, the continuous fibers are selected from PBO fibers, aramid fibers, carbon fibers, SiC fibers or metal fibers, most preferably PBO fibers.

Preferably, the filler powder is inorganic powder or metal powder, and the inorganic powder is selected from metal or nonmetal oxides, carbides, silicides or borides; the metal powder is selected from metal powder of Al, Mg, Ti, Zr, Fe, Cu or metal alloy powder thereof.

Preferably, the PTFE composite material is in the shape of a cylinder, and a plurality of annular reinforcing ribs are arranged on the cylinder.

Preferably, the diameter of the cylinder body is 50-1000mm, the wall thickness is 1-20mm, and the distance between every two adjacent reinforcing ribs is 10-100 mm.

The preparation method of the PTFE composite material comprises the following steps:

and S10, mixing the PTFE powder and the filler powder to obtain composite material powder, and wrapping the continuous fibers with the composite material powder to obtain the fiber powder belt.

And S20, winding the fiber powder strip to form a fiber powder strip cylinder.

And S30, sintering the fiber powder belt cylinder to obtain the PTFE composite material.

Preferably, the metal wrapping plate with the demolding material attached to the inner wall is wrapped on the surface of the fiber powder belt cylinder before the sintering treatment, so that the PTFE composite material in the sintering process can be supported and protected, and deformation or damage can be avoided.

Preferably, the demolding material is graphite powder or PTFE glass fiber cloth, has the characteristics of high temperature resistance, abrasion resistance, chemical resistance and lubricity, and still has a good demolding effect after high temperature.

Preferably, the sintering treatment is carried out under the conditions of raising the temperature from 15-30 ℃ to 320-400 ℃ within 380-400min, and then cooling is carried out after heat preservation for 0.5-1.5 h.

Preferably, the continuous fibers are dispersed through a tool such as a detwister to be fluffed so as to be sufficiently contacted with the composite powder.

Preferably, the composite material powder is dried in vacuum at 50-200 ℃ for 0.5-3h, and then is used after being cooled to room temperature or is sealed in a dryer for standby, so that the influence of moisture or agglomeration on the performance of the prepared PTFE composite material after the composite material powder is not used for a long time is avoided.

Preferably, the fiber powder belt is wound by a winding roller, the shape of the winding roller is matched with that of the fiber powder belt barrel, an annular groove is formed in the winding roller, and the fiber powder belt is filled in the annular groove.

Preferably, the fiber powder band is hoop-wound and longitudinally-wound to form a fiber powder band cylinder.

The invention is further illustrated by the following specific examples.

Examples 1 to 19

The PTFE composite material was prepared according to the component ratios in Table 1 as follows:

the PTFE powder and the Al metal powder were put into a mixer and sufficiently and uniformly mixed to obtain composite material powder, in which the continuous fibers in examples 1 to 11 and 14 were dispersed with a tool or by hand to be fluffy, and in example 14, the continuous fibers were dispersed by using a back-twist machine. And mixing the composite material powder with the continuous fibers to enable the composite material powder to wrap the continuous fibers and then gathering the continuous fibers to obtain the powder belt.

The surface of the winding roller is coated with a demolding material, the compression roller is adjusted to be in close contact with the winding roller, then the fiber powder belt is fed from one end surface between the two rollers, the winding roller is rotated, the compression roller presses the fiber powder belt to be coated on the winding roller, the fiber powder belt is wound in a gapless annular mode until the other end of the winding roller is reached, then the compression roller is used for repeatedly rolling, the fiber powder belt is tightly attached to the winding roller, and one-time annular winding is completed. And then winding the fiber powder belt on the winding roller along the axial direction, and repeatedly rolling the fiber powder belt by using a pressing roller after the fiber powder belt covers the whole winding roller along the axial direction, so that the fiber powder belt is tightly attached to the winding roller. And (4) repeatedly winding, feeding the powder belt from the middle in subsequent hoop winding, and increasing the thickness of the winding layer until the formed fiber powder belt cylinder body reaches the preset thickness.

After winding, the winding roller is detached, the metal wrapping plate with the inner wall attached with the demolding material is wrapped on the surface of the fiber powder belt cylinder, then the fiber powder belt cylinder is placed into a furnace for sintering treatment, the temperature is increased from 25 ℃ to 380 ℃ within 390min, the temperature is kept for 1h, and then the temperature is reduced to obtain the PTFE composite material, wherein atmosphere protection is not needed in the process.

TABLE 1

*: sample slippage: untwisting method

Example 20

The PTFE powder, Al powder, and PBO fibers were 68.9%, 24.8%, and 6.3% by mass, respectively, and the PTFE composite was prepared according to the procedure of example 1 except that only hoop winding was performed. The height of the prepared PTFE composite material was 155mm, the inner diameter was 155mm, the mass of the cylinder was 316g, the thickness of the cylinder at different measurement positions was as shown in Table 2, the thickness of the cylinder at a distance of about 10mm from the edge was measured every 60 degrees, the average thickness at one end was 2.05mm and the average thickness at the other end was 2.08mm, both sides of the cylinder were measured. The slices were sampled and tested for tensile strength, the tensile strength in the fiber direction (hoop) was 53.6MPa and the tensile strength in the fiber perpendicular direction (axial) was 6.56 MPa.

TABLE 2

Measuring orientation (°)	One end thickness (mm)	Thickness of the other end (mm)
			0°	2.03	2.12
60°	2.05	2.13
			120°	2.02	2.06
180°	2.08	2.04
			240°	2.08	2.05
Average	2.05	2.08

Example 21

The mass percentages of the PTFE powder, Al powder, and PBO fiber were 66.5%, 24.0%, and 9.5%, and the PTFE composite was prepared according to the procedure of example 1. The prepared PTFE composite material had a height of 155mm, an inner diameter of 155mm, a mass of 224.7g, and cylinder thicknesses at different measurement positions as shown in Table 3, wherein the cylinder thickness was measured at intervals of 60 degrees at positions of about 10mm from the edge, and the average thickness was 1.98mm at one end and 1.91mm at the other end of the cylinder at both sides. The slices were sampled and subjected to tensile strength testing, with a fiber direction (hoop) tensile strength of 95.49MPa and a fiber perpendicular direction (axial) tensile strength of 35.56 MPa.

TABLE 3

Measuring orientation (°)	One end thickness (mm)	Thickness of the other end (mm)
			0°	1.80	1.78
60°	1.98	1.92
			120°	1.98	1.98
180°	1.90	1.88
			240°	2.26	2.00
Average	1.98	1.91

Example 22

The mass percentages of the PTFE powder, Al powder, and PBO fiber were 66.15%, 23.85%, and 10%, and the PTFE composite material was prepared according to the procedure of example 1. The prepared PTFE composite material had a height of 179.5mm, an inner diameter of 300mm, a mass of 571g, and cylinder thicknesses at different measurement positions as shown in Table 4, and the cylinder thickness at a distance of about 10mm from the edge was measured every 60 degrees, and the average thickness at one end was 1.89mm and the average thickness at the other end was 2.01mm at both sides of the cylinder. The slices were sampled and tested for tensile strength, and as shown in FIG. 2, the stress-strain curves of the three slices in the hoop direction were shown, and the average tensile strength in the fiber direction (hoop direction) was 68.8 MPa. As shown in FIG. 3, the stress-strain curves of the three sliced samples in the axial direction were found to have an average tensile strength of 41.7MPa in the fiber perpendicular direction (axial direction). The radial stiffness of the PTFE composite of this example was measured to be less than 10N/mm.

TABLE 4

Measuring orientation (°)	One end thickness (mm)	Thickness of the other end (mm)
			0°	1.86	2.02
60°	1.67	2.23
			120°	1.96	1.80
180°	1.86	2.16
			240°	2.10	1.86
Average	1.89	2.01

Example 23

A PTFE composite was prepared according to the procedure of example 1, except that a winding roll having five circumferential grooves on the surface was used, the fiber powder tape was wound in the circumferential grooves until the circumferential grooves were filled with the fiber powder tape, and then the fiber powder tape was wound to form a fiber powder tape cylinder, thereby obtaining a PTFE composite with a ring-shaped reinforcing rib. As shown in figure 4, the prepared PTFE composite material has the height of 180mm, the inner diameter of 300mm and the cylinder mass of 1020g, wherein PBO fiber accounts for 11.75 percent, the balance is composite material powder, the composite material powder proportion for forming the shell is PTFE/Al (73.5 percent/26.5 percent), and the composite material powder proportion for forming the reinforcing rib is PTFE/TiB₂(60%/40%). The thickness of the cylinder at different measurement positions is shown in Table 5, the thickness of the cylinder at a distance of about 10mm from the edge is measured every 60 degrees, both ends of the cylinder are measured, the average thickness of one end is 2.71mm, the average thickness of the other end is 2.70mm, the average thickness of the reinforcing ribs is 2.62mm, the width is 3.57mm, and the average calculated density of the cylinder is 2.02g/cm³The radial stiffness of the PTFE composite of this example was 16.75N/mm.

TABLE 5

From examples 1 to 23, it can be seen that the PTFE composite material of the present invention has good mechanical properties, the tensile strength in the fiber direction is up to 272.4MPa, and the PTFE composite material in the shape of a large-sized thin-walled cylinder also has very excellent mechanical properties, and it can be seen that compared with other fibers, the mechanical properties of the PBO fiber-reinforced PTFE composite material are significantly better than those of other fibers. Example 11 sample slip occurred during the tensile strength test with a practical strength above 241.3 MPa.

The glass fiber is used in examples 12 to 13, the carbon fiber or the silicon carbide fiber is used in examples 15 to 19, the continuous fiber is not dispersed, the tensile strength is 24.1MPa at most, the glass fiber is used in example 12, the continuous fiber is dispersed by a detwisting method, the tensile strength reaches 115MPa, and the mechanical property of the PTFE composite material is reduced due to the poor mixing effect of the continuous fiber and the composite material powder caused by the fact that the continuous fiber is not dispersed, and the continuous fiber cannot be fully wrapped by the composite material powder.

From examples 22 to 23, it can be seen that by providing the annular reinforcing rib on the PTFE composite material having the cylindrical shape, the radial stiffness can be increased by more than 50%, the support performance is significantly improved, and the mechanical properties are better. From examples 20 to 21, it is understood that the hoop tensile strength of the PTFE composite material can be further improved by winding the fiber powder tape into a fiber tape cylinder by a combination of hoop winding and longitudinal winding, and the axial tensile strength is also significantly enhanced, so that the PTFE composite material has more excellent overall mechanical properties.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The PTFE composite material is characterized by comprising the following raw materials in percentage by mass:

12.7 percent of continuous fiber

PTFE powder 64.17%

23.13 percent of filler powder;

the continuous fibers are selected from PBO fibers, and the continuous fibers are continuous fibers dispersed by a back-twisting machine; the PTFE powder is polytetrafluoroethylene powder prepared by a suspension method, and the filler powder is Al;

the PTFE composite material is in the shape of a cylinder, and a plurality of annular reinforcing ribs are arranged on the cylinder;

the diameter of the cylinder body is 50-1000mm, the wall thickness is 1-20mm, and the distance between every two adjacent reinforcing ribs is 10-100 mm.

2. The method of preparing the PTFE composite of claim 1, comprising the steps of:

winding the fiber powder belt to form a fiber powder belt cylinder;

3. The preparation method according to claim 2, wherein the fiber powder tape is wound by a winding roller, the shape of the winding roller is matched with that of the fiber powder tape cylinder, an annular groove is formed in the winding roller, and the fiber powder tape is filled in the annular groove.

4. The method as claimed in claim 2, wherein the sintering treatment is carried out under the conditions of raising the temperature from 15-30 ℃ to 320-400 ℃ within 400min at 380-400 ℃, and lowering the temperature after heat preservation for 0.5-1.5 h.