High silica cloth reinforced polytetrafluoroethylene composite material, preparation method and application thereof
阅读说明：本技术 高硅氧布增强聚四氟乙烯复合材料、其制备方法及应用 (High silica cloth reinforced polytetrafluoroethylene composite material, preparation method and application thereof ) 是由 肖沅谕 李松 石广兴 沙晓涵 高龙飞 武元娥 何志华 于 2021-10-20 设计创作，主要内容包括：本发明涉及一种高硅氧布增强聚四氟乙烯复合材料、其制备方法及应用；包括如下制备步骤：在真空条件下,将高硅氧布浸渍于固体含量为35%-61%的聚四氟乙烯分散液中；浸渍后烘干,将浸渍有聚四氟乙烯分散液的高硅氧布平铺,将固体含量为35%-61%的聚四氟乙烯分散液涂刷于浸渍有聚四氟乙烯分散液的高硅氧布上,涂刷后烘干,获得预浸布；将预浸布热处理,获得高硅氧布增强聚四氟乙烯预浸布；将高硅氧布增强聚四氟乙烯预浸布剪裁、铺覆于模具中,在180-375℃和2-20MPa模压成型,获得高硅氧布增强聚四氟乙烯预浸布复合材；获得的高硅氧布增强聚四氟乙烯复合材料,力学性能好,无“黑心”问题,介电常数和损耗低。(The invention relates to a high silica cloth reinforced polytetrafluoroethylene composite material, a preparation method and application thereof; the preparation method comprises the following preparation steps: under the vacuum condition, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with the solid content of 35-61%; drying after impregnation, flatly paving the high silica cloth impregnated with the polytetrafluoroethylene dispersion liquid, coating the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% on the high silica cloth impregnated with the polytetrafluoroethylene dispersion liquid, and drying after coating to obtain the prepreg cloth; carrying out heat treatment on the prepreg cloth to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth; cutting and paving the high-silica cloth reinforced polytetrafluoroethylene prepreg in a mold, and carrying out compression molding at 180-375 ℃ and 2-20MPa to obtain a high-silica cloth reinforced polytetrafluoroethylene prepreg composite material; the obtained high silica cloth reinforced polytetrafluoroethylene composite material has good mechanical property, no 'black core' problem and low dielectric constant and loss.)
1. A preparation method of a high silica cloth reinforced polytetrafluoroethylene composite material is characterized by comprising the following steps: the preparation method comprises the following preparation steps:
under the vacuum condition, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with the solid content of 35-61%; drying after dipping, and repeating the above process for 1-5 times; spreading the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid, brushing the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% on the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid by adopting a brushing process, and drying for 30-120min at the temperature of 130-220 ℃ after brushing to obtain pre-soaked cloth;
carrying out heat treatment on the prepreg cloth at the temperature of 280-320 ℃ for 30-120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
cutting and paving the high-silica cloth reinforced polytetrafluoroethylene prepreg in a mold, and carrying out compression molding at 180-375 ℃ and 2-20MPa to obtain a high-silica cloth reinforced polytetrafluoroethylene prepreg composite material;
wherein, the coating weight of the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% is calculated according to the formula (I), and the polytetrafluoroethylene dispersion liquid is completely brushed on the prepreg cloth after being weighed, and the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg.
2. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: gradient heating is adopted in the process of drying at the temperature of 130-; the gradient temperature rise process is as follows: heating to 130 deg.C, maintaining the temperature for 30min, heating to 190 deg.C, maintaining the temperature for 60min, heating to 220 deg.C, and maintaining the temperature for 60 min; the heating rate is 2-10 ℃/min.
3. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: in the process of drying at the temperature of 280 plus 320 ℃ for 30-120min, gradient temperature rise is adopted, and the gradient temperature rise process is as follows: heating to 280 deg.C, maintaining the temperature for 20-60min, heating to 320 deg.C, maintaining the temperature for 30-120min at a heating rate of 2-10 deg.C/min.
4. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mould, and adopting gradient temperature rise and gradient pressurization in the compression molding process of 180-375 ℃ and 2-20MPa, wherein the gradient temperature rise and gradient pressurization processes are as follows:
after the temperature is increased to 180 ℃ and the pressure is increased to 2MPa, the temperature is kept for 30-60min, the temperature is increased to 280 ℃, the pressure is increased to 4MPa, and the temperature is kept for 60-120 min; raising the temperature to 330 ℃, raising the pressure to 6MPa, and keeping the temperature for 60-120 min; the temperature is increased to 375 ℃, the pressure is increased to 10MPa, and the temperature is kept for 360 min.
5. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: the mass fraction of the polytetrafluoroethylene in the high silica cloth reinforced polytetrafluoroethylene prepreg cloth is 40-60%.
6. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: the solid content of the polytetrafluoroethylene dispersion is 45-61%.
7. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: under the vacuum condition, soaking the high silica cloth in the prepared polytetrafluoroethylene dispersion liquid; the soaking time is 20-60 min.
8. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material according to claim 1, characterized by comprising the following steps: the high silica cloth is one of plain weave, twill weave and forged grain; the thickness of the high silica cloth is 0.26-1.35 mm.
9. A high silica cloth-reinforced polytetrafluoroethylene composite material produced based on the method for producing a high silica cloth-reinforced polytetrafluoroethylene composite material according to any one of claims 1 to 8.
10. Use of the high silica cloth reinforced polytetrafluoroethylene composite according to claim 9 in a radome.
Technical Field
The invention relates to the technical field of special materials, in particular to a high silica cloth reinforced polytetrafluoroethylene composite material, and a preparation method and application thereof.
Background
The antenna housing has the main functions of ensuring the necessary pneumatic appearance, bearing the pneumatic heating and various loads in the flying process and reducing the influence of the flying environment on electronic equipment in the housing in the high-speed flying process of the missile. Meanwhile, the radome must have good electromagnetic wave transmission characteristics.
Research shows that the traditional radome is made of glass fiber reinforced polytetrafluoroethylene composite materials, and pre-impregnated cloth is prepared by adopting a method of Torontis impregnation, so that the preparation period is long; the preparation process of cold pressing and sintering is adopted in the forming process, the preparation process is complex, and time and labor are consumed; and the composite material has low mechanical strength, black core in the product, and large dielectric constant and loss.
Therefore, in order to solve the above problems, the present invention urgently needs to provide a high silica cloth reinforced polytetrafluoroethylene composite material, a preparation method and an application thereof.
Disclosure of Invention
The invention aims to provide a high silica cloth reinforced polytetrafluoroethylene composite material, a preparation method and application thereof, and the design of the high silica cloth reinforced polytetrafluoroethylene composite material is used for solving the problems that the existing antenna housing in the prior art adopts a glass fiber reinforced polytetrafluoroethylene composite material and adopts a Torontis impregnation method to prepare pre-impregnated cloth, so that the preparation period is long; the preparation process of cold pressing and sintering is adopted in the forming process, the preparation process is complex, and time and labor are consumed; and the composite material has low mechanical strength, and the product has black core and large dielectric constant and loss.
The invention provides a preparation method of a high silica cloth reinforced polytetrafluoroethylene composite material, which comprises the following preparation steps:
under the vacuum condition, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with the solid content of 35-61%; drying after dipping, and repeating the above process for 1-5 times; spreading the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid, brushing the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% on the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid by adopting a brushing process, and drying for 30-120min at the temperature of 130-220 ℃ after brushing to obtain pre-soaked cloth;
carrying out heat treatment on the prepreg cloth at the temperature of 280-320 ℃ for 30-120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
cutting and paving the high-silica cloth reinforced polytetrafluoroethylene prepreg in a mold, and carrying out compression molding at 180-375 ℃ and 2-20MPa to obtain a high-silica cloth reinforced polytetrafluoroethylene prepreg composite material;
wherein, the coating weight of the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% is calculated according to the formula (I), and the polytetrafluoroethylene dispersion liquid is completely brushed on the prepreg cloth after being weighed, and the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg.
Preferably, gradient temperature rise is adopted in the process of drying at 130-220 ℃ for 30-120 min; the gradient temperature rise process is as follows: heating to 130 deg.C, maintaining the temperature for 30min, heating to 190 deg.C, maintaining the temperature for 60min, heating to 220 deg.C, and maintaining the temperature for 60 min; the heating rate is 2-10 ℃/min.
Preferably, in the process of drying at 280-320 ℃ for 30-120min, gradient temperature rise is adopted, and the gradient temperature rise process is as follows: heating to 280 deg.C, maintaining the temperature for 20-60min, heating to 320 deg.C, maintaining the temperature for 30-120min at a heating rate of 2-10 deg.C/min.
Preferably, the high silica cloth reinforced polytetrafluoroethylene prepreg cloth is cut and paved in a mould, and gradient temperature rise and gradient pressurization are adopted in the compression molding process at 180-375 ℃ and 2-10MPa, wherein the gradient temperature rise and gradient pressurization process comprises the following steps:
after the temperature is increased to 180 ℃ and the pressure is increased to 2MPa, the temperature is kept for 30-60min, the temperature is increased to 280 ℃, the pressure is increased to 4MPa, and the temperature is kept for 60-120 min; raising the temperature to 330 ℃, raising the pressure to 6MPa, and keeping the temperature for 60-120 min; the temperature is increased to 375 ℃, the pressure is increased to 10MPa, and the temperature is kept for 360 min.
Preferably, the mass fraction of the polytetrafluoroethylene in the high silica cloth reinforced polytetrafluoroethylene prepreg cloth is 40-60%.
Preferably, the polytetrafluoroethylene dispersion has a solids content of 45% to 61%.
Preferably, soaking the high-silica cloth in the prepared polytetrafluoroethylene dispersion liquid under the vacuum condition; the soaking time is 20-60 min.
Preferably, the high silica cloth is one of plain weave, twill weave and forged grain; the thickness of the high silica cloth is 0.26-1.35 mm.
The invention also provides a high silica cloth reinforced polytetrafluoroethylene composite material prepared by the preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material.
The invention also provides an application of the high silica cloth reinforced polytetrafluoroethylene composite material in an antenna housing.
Compared with the prior art, the high silica cloth reinforced polytetrafluoroethylene composite material, the preparation method and the application thereof provided by the invention have the following advantages:
1. the preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material provided by the invention adopts a method combining dipping and brushing, so that the resin content can be controlled, and the preparation period can be greatly shortened; through two-step high-temperature heat treatment of the prepreg cloth, impurities in the prepreg cloth are fully removed, the problem of 'black core' in the forming process of the composite material is avoided, and the dielectric constant and the loss of the composite material are reduced.
2. The preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material provided by the invention adopts a compression molding process to replace the previous cold pressing and sintering preparation process, simplifies the preparation process, improves the production efficiency and improves the mechanical property of the composite material.
3. The high silica cloth reinforced polytetrafluoroethylene composite material prepared by the preparation method provided by the invention has excellent comprehensive performance, and the density of the composite material is 1.9-2.3g/cm3The compressive strength is more than or equal to 60MPa, the tensile strength is more than or equal to 40MPa, the dielectric constant is between 2.7 and 3.1, and the dielectric loss is less than or equal to 0.01, so that the preparation method can be used for preparing the antenna housing.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a high silica cloth reinforced polytetrafluoroethylene composite material, which comprises the following preparation steps:
s1) under the vacuum condition, soaking the high silica cloth in polytetrafluoroethylene dispersion liquid with the solid content of 35-61%; drying after dipping, and repeating the above process for 1-5 times; spreading the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid, brushing the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% on the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid by adopting a brushing process, and drying for 30-120min at the temperature of 130-220 ℃ after brushing to obtain pre-soaked cloth;
s2) carrying out heat treatment on the prepreg cloth at the temperature of 280-320 ℃ for 30-120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
s3) cutting and paving the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mould, and carrying out compression molding at 180-375 ℃ and 2-20MPa to obtain the high silica cloth reinforced polytetrafluoroethylene prepreg cloth composite material;
wherein, the coating weight of the polytetrafluoroethylene dispersion liquid with the solid content of 35-61% is calculated according to the formula (I), and the polytetrafluoroethylene dispersion liquid is completely brushed on the prepreg cloth after being weighed, and the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg.
Specifically, gradient temperature rise is adopted in the process of drying at 130-220 ℃ for 30-120 min; the gradient temperature rise process is as follows: heating to 130 deg.C, maintaining the temperature for 30min, heating to 190 deg.C, maintaining the temperature for 60min, heating to 220 deg.C, and maintaining the temperature for 60 min; the heating rate is 2-10 ℃/min.
Specifically, in the process of drying at 280-320 ℃ for 30-120min, gradient temperature rise is adopted, and the gradient temperature rise process is as follows: heating to 280 deg.C, maintaining the temperature for 20-60min, heating to 320 deg.C, maintaining the temperature for 30-120min at a heating rate of 2-10 deg.C/min.
Specifically, cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mold, and adopting gradient temperature rise and gradient pressurization in the compression molding process of 180-375 ℃ and 2-20MPa, wherein the gradient temperature rise and gradient pressurization process comprises the following steps:
after the temperature is increased to 180 ℃ and the pressure is increased to 2MPa, the temperature is kept for 30-60min, the temperature is increased to 280 ℃, the pressure is increased to 4MPa, and the temperature is kept for 60-120 min; raising the temperature to 330 ℃, raising the pressure to 6MPa, and keeping the temperature for 60-120 min; the temperature is increased to 375 ℃, the pressure is increased to 10MPa, and the temperature is kept for 360 min.
Specifically, the mass fraction of the polytetrafluoroethylene in the high silica cloth reinforced polytetrafluoroethylene prepreg cloth is 40-60%.
Specifically, the solid content of the polytetrafluoroethylene dispersion is 45% to 61%.
Specifically, under the vacuum condition, soaking high silica cloth in the prepared polytetrafluoroethylene dispersion liquid; the soaking time is 20-60 min.
Specifically, the high silica cloth is one of plain weave, twill weave and forged grain; the thickness of the high silica cloth is 0.26-1.35 mm.
The invention also provides a high silica cloth reinforced polytetrafluoroethylene composite material prepared by the preparation method of the high silica cloth reinforced polytetrafluoroethylene composite material.
The invention also provides an application of the high silica cloth reinforced polytetrafluoroethylene composite material in an antenna housing.
The invention adopts a method combining dipping and coating, strictly controls the resin content, can greatly shorten the preparation period, fully removes impurities in the prepreg by two-step high-temperature heat treatment of the prepreg, avoids the problem of 'black core' in the forming process of the composite material, reduces the dielectric constant and loss of the composite material, replaces the traditional cold pressing and sintering preparation process by a compression molding process after the heat treatment of the prepreg, simplifies the preparation process, improves the production efficiency and improves the mechanical property of the composite material; the obtained composite material has a density of 1.9-2.3g/cm3The compressive strength is more than or equal to 60MPa, the tensile strength is more than or equal to 40MPa, the dielectric constant is between 2.7 and 3.1, and the dielectric loss is less than or equal to 0.01, so that the preparation method can be used for preparing the antenna housing.
Example one
Sample 1 preparation:
high silica cloth is used as a reinforcing material, the fabric weave structure is plain weave, and the thickness is 0.26mm;
101) under vacuum condition, the pressure in the tank is less than or equal to-0.07 MPa, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with solid content of 40%, drying for 20min at 130 deg.C for 30min, 190 deg.C for 60min,220 deg.C for 60min, and repeating the above steps for 1 time; spreading the high silica cloth impregnated with the polytetrafluoroethylene dispersion, coating the polytetrafluoroethylene dispersion with a solid content of 60% on the high silica cloth impregnated with the polytetrafluoroethylene dispersion by a coating process, drying at 130 ℃ for 30min, 190 ℃ for 60min and 220 ℃ for 60min after coating, and obtaining the prepreg cloth containing 60% of polytetrafluoroethylene by mass fraction;
weighing 60% of polytetrafluoroethylene dispersion liquid by weight, calculating the weighed weight according to a formula (I), and brushing the weighed polytetrafluoroethylene dispersion liquid on a prepreg cloth completely after weighing, wherein the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg;
102) carrying out heat treatment on the prepreg cloth at 280 ℃ for 60min, and carrying out heat treatment at 320 ℃ for 120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
103) cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mold, and keeping the temperature at 180 ℃ for 30min on a press under the pressure of 2 MPa; keeping the temperature at 280 ℃ for 60min and keeping the pressure at 4 MPa; keeping the temperature at 330 ℃ for 60min and the pressure at 6 MPa; keeping the temperature at 375 ℃ for 180min, keeping the pressure at 10MPa, and carrying out compression molding to obtain the high silica cloth reinforced polytetrafluoroethylene prepreg composite material (sample 1).
The density of sample 1 was tested according to GB/T1463; the tensile strength of sample 1 was tested according to GB/T1447; the compressive strength of sample 1 was tested according to GB/T1449; sample 1 was tested for linear expansion coefficient according to GB/T10295; sample 1 was tested for specific heat capacity according to GJB330A method; measuring the dielectric constant by adopting a strip line resonant cavity method; measuring dielectric loss by adopting a strip line resonant cavity method; the parameters obtained are shown in Table 1.
Control sample 1 was prepared, and control sample 1 was prepared identically to samples 101 and 103 without the 102 step, i.e., without the heat treatment at 280 ℃ for 60min and at 320 ℃ for 120 min.
In preparing control sample 2, control sample 2 was prepared in the same manner as sample 1 in steps 101 and 102, and in step 103, control sample 2 was prepared by a cold pressing and sintering process.
Compared with the control sample 1 and the control sample 2, the compressive strength and the tensile strength of the sample 1 are obviously higher than those of the control sample 1 and the control sample 2, and the expansion coefficient, the dielectric constant and the dielectric loss are obviously lower than those of the control sample 1 and the control sample 2, so that the performance of the high-silica cloth reinforced polytetrafluoroethylene prepreg composite material is effectively improved in the heat treatment process, the gradient temperature rise and the pressure increase die pressing.
Example two
Sample 2 preparation:
101) under vacuum condition, the pressure in the tank is less than or equal to-0.07 MPa, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with solid content of 40%, drying for 20min at 130 deg.C for 30min, 190 deg.C for 60min,220 deg.C for 60min, and repeating the above steps for 1 time; spreading the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid flatly, coating the polytetrafluoroethylene dispersion liquid with the solid content of 60% on the high silica cloth soaked with the polytetrafluoroethylene dispersion liquid by adopting a coating process, drying for 30min at 130 ℃, drying for 60min at 190 ℃ and drying for 60min at 220 ℃ after coating, and obtaining the prepreg cloth containing the polytetrafluoroethylene with the mass fraction of 50%;
weighing 60% of polytetrafluoroethylene dispersion liquid by weight, calculating the weighed weight according to a formula (I), and brushing the weighed polytetrafluoroethylene dispersion liquid on a prepreg cloth completely after weighing, wherein the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg;
202) carrying out heat treatment on the prepreg cloth at 280 ℃ for 60min, and carrying out heat treatment at 320 ℃ for 120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
203) cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mold, and keeping the temperature at 180 ℃ for 30min on a press under the pressure of 2 MPa; keeping the temperature at 280 ℃ for 60min and keeping the pressure at 4 MPa; keeping the temperature at 330 ℃ for 60min and the pressure at 6 MPa; keeping the temperature at 375 ℃ for 180min, keeping the pressure at 10MPa, and carrying out compression molding to obtain the high silica cloth reinforced polytetrafluoroethylene prepreg composite material (sample 2).
The density of sample 2 was tested according to GB/T1463; the tensile strength of sample 2 was tested according to GB/T1447; the compressive strength of sample 2 was tested according to GB/T1449; sample 2 was tested for linear expansion coefficient according to GB/T10295; sample 2 was tested for specific heat capacity according to GJB330A method; measuring the dielectric constant by adopting a strip line resonant cavity method; measuring dielectric loss by adopting a strip line resonant cavity method; the parameters obtained are shown in Table 1.
The difference between the sample 2 and the sample 1 is that the prepreg cloth contains different mass fractions of polytetrafluoroethylene, the mass fraction of the polytetrafluoroethylene in the prepreg cloth of the sample 1 is 60%, and the mass fraction of the polytetrafluoroethylene in the prepreg cloth of the sample 2 is 50%, which shows that the mechanical property and the dielectric property of the composite material are affected by changing the mass fraction of the polytetrafluoroethylene in the prepreg cloth, and the mass fraction of the polytetrafluoroethylene in the prepreg cloth of the sample 1 is 60%, so that the performance is better.
EXAMPLE III
Sample 3 preparation:
high silica cloth is used as a reinforcing material, the fabric weave structure is plain weave, and the thickness is 0.26mm;
301) under vacuum condition, the pressure in the tank is less than or equal to-0.07 MPa, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with solid content of 40%, drying for 20min at 130 deg.C for 30min, 190 deg.C for 60min,220 deg.C for 60min, and repeating the above steps for 1 time; spreading the high silica cloth impregnated with the polytetrafluoroethylene dispersion, coating the polytetrafluoroethylene dispersion with a solid content of 60% on the high silica cloth impregnated with the polytetrafluoroethylene dispersion by a coating process, drying at 130 ℃ for 30min, 190 ℃ for 60min and 220 ℃ for 60min after coating, and obtaining the prepreg cloth containing 60% of polytetrafluoroethylene by mass fraction;
weighing 60% of polytetrafluoroethylene dispersion liquid by weight, calculating the weighed weight according to a formula (I), and brushing the weighed polytetrafluoroethylene dispersion liquid on a prepreg cloth completely after weighing, wherein the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg;
302) carrying out heat treatment on the prepreg cloth at 280 ℃ for 60min, and carrying out heat treatment at 320 ℃ for 120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
303) cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mold, and keeping the temperature at 180 ℃ for 30min on a press under the pressure of 2 MPa; keeping the temperature at 280 ℃ for 60min and keeping the pressure at 4 MPa; keeping the temperature at 310 ℃ for 60min and the pressure at 6 MPa; the temperature is kept at 350 ℃ for 180min, the pressure is 10MPa, and the high silica cloth reinforced polytetrafluoroethylene prepreg composite material (sample 3) is obtained by compression molding.
Sample 3 was tested for density according to GB/T1463; the tensile strength of sample 3 was tested according to GB/T1447; the compressive strength of sample 3 was tested according to GB/T1449; sample 3 was tested for linear expansion coefficient according to GB/T10295; sample 3 was tested for specific heat capacity according to GJB330A method; measuring the dielectric constant by adopting a strip line resonant cavity method; measuring dielectric loss by adopting a strip line resonant cavity method; the parameters obtained are shown in Table 1.
The difference between the sample 3 and the sample 1 is that the temperature of the gradient temperature rise during the hot pressing on the press is lower than that of the sample 1, and the obtained compressive strength and tensile strength of the sample 3 are slightly lower than those of the sample 1, so that the temperature of the gradient temperature rise during the hot pressing needs to be controlled.
Example four
Sample 4 preparation:
high silica cloth is used as a reinforcing material, the fabric weave structure is plain weave, and the thickness is 0.26mm;
401) under vacuum condition, the pressure in the tank is less than or equal to-0.07 MPa, soaking high silica cloth in polytetrafluoroethylene dispersion liquid with solid content of 40%, drying for 20min at 130 deg.C for 30min, 190 deg.C for 60min,220 deg.C for 60min, and repeating the above steps for 1 time; spreading the high silica cloth impregnated with the polytetrafluoroethylene dispersion, coating the polytetrafluoroethylene dispersion with a solid content of 60% on the high silica cloth impregnated with the polytetrafluoroethylene dispersion by a coating process, drying at 130 ℃ for 30min, 190 ℃ for 60min and 220 ℃ for 60min after coating, and obtaining the prepreg cloth containing 60% of polytetrafluoroethylene by mass fraction;
weighing 60% of polytetrafluoroethylene dispersion liquid by weight, calculating the weighed weight according to a formula (I), and brushing the weighed polytetrafluoroethylene dispersion liquid on a prepreg cloth completely after weighing, wherein the formula (I) is as follows:
(formula one)
Wherein m isClothThe weight of the high silica cloth before impregnation; m isBefore brushingThe weight of the impregnated high silica cloth is shown; omega is the solid content of the polytetrafluoroethylene dispersion liquid for impregnation; eta is the mass fraction of the polytetrafluoroethylene in the prepreg;
402) carrying out heat treatment on the prepreg cloth at 280 ℃ for 60min, and carrying out heat treatment at 320 ℃ for 120min to obtain high silica cloth reinforced polytetrafluoroethylene prepreg cloth;
403) cutting and spreading the high silica cloth reinforced polytetrafluoroethylene prepreg cloth in a mold, and keeping the temperature at 180 ℃ for 30min on a press under the pressure of 4 MPa; keeping the temperature at 280 ℃ for 60min and the pressure at 6 MPa; keeping the temperature at 330 ℃ for 60min and the pressure at 10 MPa; the temperature is kept at 375 ℃ for 180min, the pressure is 15MPa, and the high silica cloth reinforced polytetrafluoroethylene prepreg composite material (sample 4) is obtained by compression molding.
Sample 4 was tested for density according to GB/T1463; the tensile strength of sample 4 was tested according to GB/T1447; the compressive strength of sample 3 was tested according to GB/T1449; sample 4 was tested for linear expansion coefficient according to GB/T10295; sample 4 was tested for specific heat capacity according to GJB330A method; measuring the dielectric constant by adopting a strip line resonant cavity method; measuring dielectric loss by adopting a strip line resonant cavity method; the parameters obtained are shown in Table 1.
The difference between the sample 4 and the sample 1 is that the gradient pressure rise is different in the molding process, the gradient pressure rise value of the sample 4 is higher than that of the sample 1, and the mechanical property of the sample 4 is obviously higher than that of the sample 1, which shows that the control of the pressure has a certain influence on the mechanical property in the molding process, but the dielectric constant and the dielectric loss of the sample 4 are inferior to those of the sample 1.
Based on the above analysis, the temperature control in the drying process and the temperature control in the heat treatment process have a large influence on the mechanical properties; the temperature control and the pressure control in the molding process have certain influence on the mechanical properties of the material; the mass fraction of the polytetrafluoroethylene contained in the prepreg has certain influence on the dielectric constant and the dielectric loss performance, so that each parameter of the preparation steps needs to be reasonably controlled, and the parameter of each step can be adjusted according to the requirement of a customer on the product performance, thereby obtaining the high-performance high-silica cloth reinforced polytetrafluoroethylene prepreg composite material.
TABLE 1 high silica cloth reinforced Polytetrafluoroethylene prepreg composite Performance test results
Sample (I)
Density (g/cm)3）
Compressive Strength (MPa)
Tensile Strength (MPa)
Coefficient of linear expansion/° C (RT-200 ℃ C.)
Specific heat capacity/° C (RT-200 ℃ C.)
Dielectric constant
Dielectric loss
Sample 1
2.01
119
83
3.5×10-6
1.01
2.9
0.017
Comparative sample 1
2.00
113
79
3.9×10-6
0.98
3.15
0.028
Comparative sample 2
2.00
89
63
4.1×10-6
1.00
2.92
0.018
Sample 2
2.01
118
83
3.7×10-6
1.01
3.17
0.034
Sample 3
2.01
96
65
4.1×10-6
0.98
2.98
0.027
Sample No. 4
2.08
135
97
3.7×10-6
1.03
3.01
0.028
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
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