High-temperature low-dielectric-loss liquid crystal polymer composite material as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature low-dielectric-loss liquid crystal polymer composite material as well as a preparation method and application thereof. The composite material comprises the following components in parts by weight: 100 parts of liquid crystal polymer resin; 30 to 250 parts of polytetrafluoroethylene; 3 to 150 parts of wollastonite; wherein the mass ratio of the wollastonite to the polytetrafluoroethylene is (0.1-0.6): 1. The wollastonite and the polytetrafluoroethylene in a specific weight ratio are added into the liquid crystal polymer to improve the high-temperature dielectric loss of the liquid crystal polymer, meanwhile, the wollastonite can play a role in enhancement, the prepared composite material has good high-frequency and high-temperature dielectric loss performance and mechanical performance, the bending strength is not lower than 60 MPa, and the tensile strength is not lower than 30 MPa. And the dielectric loss is not higher than 0.008 under the high-temperature condition of high frequency (10GHz) and high temperature (150 DEG C).

Description

Technical Field

[0001] The present invention relates to the field of special modified plastics, and more specifically, to a liquid crystal polymer composite material with high temperature and low dielectric loss, a preparation method thereof, and an application thereof. Background Art

[0002] Liquid crystal polymers are widely used in electronic connectors due to their excellent fluidity, dimensional stability, and self-flame retardant properties. Also, because liquid crystal polymers have stable dielectric properties at high frequencies, they are widely used in communication connector products in the rapidly developing high-speed communication technology field in recent years. As the application scenarios increase, higher requirements are put forward for the dielectric properties of liquid crystal polymer materials, including low dielectric constant, low dielectric loss, etc.

[0003] In an alternating electric field, a material will consume part of the electrical energy, causing the temperature of the material to rise, and finally dissipating in the form of heat. The performance index characterizing the magnitude of the electrical energy dissipation of the material is the dielectric loss. The greater the dielectric loss of the material, the more heat will be generated during use, resulting in an increase in the temperature of the component. A high dielectric loss of the material will lead to a decline in the performance of the material.

[0004] It has been found through research that the dielectric loss of liquid crystal polymers increases with the increase in temperature, which will lead to a vicious cycle during application, that is, the temperature of the component rises, the dielectric loss changes, the generated heat further increases, resulting in a further increase in the temperature of the component, thus having a great negative impact on the performance of the component, such as signal transmission distortion, a decrease in the service life of the material, etc. The prior art CN 113121962A improves the dielectric loss of liquid crystal polymers by adding polytetrafluoroethylene to liquid crystal polymers, but its dielectric loss is still relatively high under high temperature conditions. Generally, the industry requires that the dielectric loss under high temperature does not exceed 0.008. Therefore, there is an urgent need in the art for a liquid crystal polymer with a lower dielectric loss in a high temperature environment. Summary of the Invention

[0005] The purpose of the present invention is to provide a liquid crystal polymer composite material with high temperature and low dielectric loss to overcome the defect or deficiency of the large dielectric loss of liquid crystal polymer materials in a high temperature environment in the above-mentioned prior art.

[0006] Another purpose of the present invention is to provide a preparation method of the liquid crystal polymer composite material with high temperature and low dielectric loss.

[0007] Another purpose of the present invention is to provide an application of the liquid crystal polymer composite material with high temperature and low dielectric loss.

[0008] To achieve the above purposes, the present invention is realized through the following technical solutions:

[0009] A high-temperature and low-dielectric-loss liquid crystal polymer composite material, comprising the following components calculated by weight:

[0010] 100 parts of liquid crystal polymer resin;

[0011] 30 - 250 parts of polytetrafluoroethylene;

[0012] 3 - 150 parts of wollastonite;

[0013] Wherein, the mass ratio of the wollastonite to the polytetrafluoroethylene is (0.1 - 0.6):1.

[0014] In the present invention, a high-temperature and low-dielectric-loss liquid crystal polymer composite material is provided. The inventors have found through a large number of experimental studies that adding polytetrafluoroethylene to the liquid crystal polymer can reduce its dielectric loss. However, due to the poor dispersion performance of polytetrafluoroethylene, the dielectric loss is still relatively high under high-temperature conditions, and the addition of a large amount of polytetrafluoroethylene will cause the mechanical properties of the composition to decline. High-frequency electronic components have relatively high requirements for the material strength, usually requiring a flexural strength ≥ 60 MPa. Therefore, adding wollastonite can microscopically improve the dispersion of polytetrafluoroethylene and improve the phase interface, thereby reducing the dielectric loss in a high-temperature environment and having a relatively high flexural strength of the material. However, since the dielectric loss of wollastonite itself is higher than that of polytetrafluoroethylene, it is necessary to control the appropriate ratio of wollastonite to polytetrafluoroethylene to obtain a liquid crystal polymer material with good high-temperature dielectric loss.

[0015] It should be noted that those skilled in the art should understand that the liquid crystal polymer described in the present invention is a high-molecular substance composed of rigid molecular chains and can exhibit both the fluidity of a liquid and the regularity of a crystal under certain physical conditions.

[0016] Specifically, the melting point of the liquid crystal polymer resin is above 270 °C.

[0017] In the present invention, the proportion of the liquid crystal polymer resin in the liquid crystal polymer composite material is not less than 20 wt%.

[0018] In the present invention, the mass ratio of the wollastonite to the polytetrafluoroethylene is (0.1 - 0.6):1. For example, but not limited to, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, and 0.6:1, etc., can all achieve the present invention. Further, the mass ratio of the wollastonite to the polytetrafluoroethylene is (0.2 - 0.5):1. Within this range, the high-temperature dielectric loss of the prepared liquid crystal polymer composite material is lower and the performance is better.

[0019] Further, the high-temperature and low-dielectric-loss liquid crystal polymer composite material comprises the following components calculated by weight:

[0020] 100 parts of liquid crystal polymer resin;

[0021] 70 - 120 parts of polytetrafluoroethylene;

[0022] 7 - 70 parts of wollastonite.

[0023] Furthermore, the aspect ratio of the wollastonite is (8 - 40):1. For example, but not limited to, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1 and 40:1 etc. can all achieve the present invention. Selecting an appropriate aspect ratio of wollastonite enables the wollastonite to better transfer stress, has a better strengthening effect and can simultaneously reduce the high-temperature dielectric loss of the material.

[0024] Even further, the aspect ratio of the wollastonite is (12 - 25):1.

[0025] Specifically, the aspect ratio is obtained by measurement with a polarized light microscope.

[0026] Furthermore, the weight-average molecular weight of the polytetrafluoroethylene is 10 3 - 6×10 7 .

[0027] Even further, the weight-average molecular weight of the polytetrafluoroethylene is 10 4 - 10 5 .

[0028] Specifically, the weight-average molecular weight is measured by gel permeation chromatography.

[0029] In the present invention, the high-temperature low-dielectric-loss liquid crystal polymer composite material further comprises 0.1 - 1 part of processing aid.

[0030] In some specific embodiments, the processing aid is one or more of metal stearate, linear low-density polyethylene, ethylene-acrylic acid copolymer.

[0031] The present invention also protects a method for preparing the above-mentioned high-temperature low-dielectric-loss liquid crystal polymer composite material, comprising the following steps:

[0032] Mix the liquid crystal polymer resin, polytetrafluoroethylene, wollastonite and processing aid evenly, and then obtain the high-temperature low-dielectric-loss liquid crystal polymer composite material through melt blending and extrusion granulation by an extruder.

[0033] Furthermore, a twin-screw extruder is used for the extrusion granulation.

[0034] Furthermore, the ratio of the screw length to the diameter of the twin-screw extruder is (35 - 55):1, the temperature of the screw barrel of the twin-screw extruder is Tm ± 30 °C, where Tm is the melting point of the liquid crystal polymer resin; the screw rotation speed of the twin-screw extruder is 250 - 650 rpm.

[0035] The present invention also protects the application of the above high-temperature low-dielectric-loss liquid crystal polymer composite material in the preparation of high-frequency transmission electronic component materials, such as high-frequency high-speed connector materials.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The present invention provides a high-temperature low-dielectric-loss liquid crystal polymer composite material. By adding wollastonite and polytetrafluoroethylene with a specific ratio to the liquid crystal polymer, wollastonite can improve the dispersion performance of polytetrafluoroethylene, thereby improving the phase interface to obtain a lower high-temperature dielectric loss; and the addition of wollastonite can play a reinforcing role to help improve the mechanical properties of the material. The flexural strength of the prepared high-temperature low-dielectric-loss liquid crystal polymer composite material is not less than 60 MPa, and the dielectric loss under high-temperature conditions (150 °C) at high frequency (10 GHz) is not higher than 0.008. Detailed Embodiments

[0038] The following further illustrates the present invention in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventionally purchased raw material reagents.

[0039] Raw materials used in each embodiment and comparative example:

[0040] Liquid crystal polymer resin:

[0041] Liquid crystal polymer resin 1: Vicryst R8300, with a melting point of 350 °C, produced by Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0042] Liquid crystal polymer resin 2: Vicryst R8000, with a melting point of 280 °C, produced by Zhuhai Wantong Special Engineering Plastics Co., Ltd.;

[0043] Polytetrafluoroethylene:

[0044] Polytetrafluoroethylene 1: A-01, with a weight-average molecular weight of 5×10 3 , purchased from Shenyang Tianyu Xiang Micropowder Materials Factory;

[0045] Polytetrafluoroethylene 2: A-03, with a weight-average molecular weight of 1.5×10 4 , purchased from Shenyang Tianyu Xiang Micropowder Materials Factory;

[0046] Polytetrafluoroethylene 3: B-01, with a weight-average molecular weight of 5×10 4 , purchased from Tianyu Xiang Micropowder Materials Factory, Shenyang City;

[0047] Polytetrafluoroethylene 4: KDLJ-01, with a weight-average molecular weight of 5×10 7 , purchased from Tianyu Xiang Micropowder Materials Factory, Shenyang City;

[0048] Wollastonite:

[0049] Wollastonite 1: Model: SYW-XA450, aspect ratio of 20:1, purchased from Siyuan Mining Co., Ltd.;

[0050] Wollastonite 2: Model: SYW-XA360, aspect ratio of 15:1, purchased from Siyuan Mining Co., Ltd.;

[0051] Wollastonite 3: Model: SYW-XA180, aspect ratio of 8:1, purchased from Siyuan Mining Co., Ltd.;

[0052] Wollastonite 4: Model: SYW-XA1150, aspect ratio of 40:1, purchased from Siyuan Mining Co., Ltd.;

[0053] Glass fiber: average diameter of 10μm, grade 923, purchased from Owens Corning;

[0054] Processing aid: linear low-density polyethylene, grade DFDC 7050, purchased from PetroChina;

[0055] Examples 1-21 and Comparative Examples 1-5

[0056] The liquid crystal polymer composites described in Examples 1-21 and Comparative Examples 1-5 were prepared according to the formulations in Tables 1-3 by the following preparation method:

[0057] The liquid crystal polymer resin, polytetrafluoroethylene and wollastonite were added to a high-speed mixer in proportion and mixed evenly, and then put into a twin-screw extruder for melt blending and extrusion granulation to obtain the liquid crystal polymer composite; the screw length-diameter ratio of the twin-screw extruder is (35-55):1, the barrel temperature of the twin-screw extruder is Tm±30°C, where Tm is the melting point of the liquid crystal polymer resin; the screw speed of the twin-screw extruder is 250-650 rpm.

[0058] Table 1 Dosages of each component in the high-temperature low-dielectric-loss liquid crystal polymer composites in Examples 1-10 (unit: parts by weight)

[0059]

[0060]

[0061] Note: X represents the mass ratio of wollastonite to polytetrafluoroethylene

[0062] Table 2 Dosages of each component in the high-temperature and low-dielectric-loss liquid crystal polymer composites in Examples 11 - 21 (unit: parts by weight)

[0063]

[0064] Note: X represents the mass ratio of wollastonite to polytetrafluoroethylene

[0065] Table 3 Dosages of each component in the liquid crystal polymer composites in Comparative Examples 1 - 5 (unit: parts by weight)

[0066]

[0067] Note: X represents the mass ratio of wollastonite to polytetrafluoroethylene

[0068] Performance Test

[0069] 1. Test Method

[0070] (1) Determination of high-temperature dielectric loss: The liquid crystal polymer composites prepared in the above examples and comparative examples were molded into 100mm * 100mm * 1mm square plates using a single-screw injection molding machine. Referring to the standard IEC62562 - 2010, the sample plate and the fixture were placed in a constant-temperature oven at 150 °C for 10 min, and then the dielectric loss at 10 GHz was measured;

[0071] (2) Bending strength test: The liquid crystal polymer composites prepared in the above examples and comparative examples were molded into 100mm * 100mm * 1mm square plates using a single-screw injection molding machine. Referring to the standard ISO 178 - 2019, the bending strength of the material was measured, and the standard requires that the bending strength of the high-frequency material ≥ 60 MPa.

[0072] 2. Test Results

[0073] The test results of the bending strength and high-temperature dielectric loss of the liquid crystal polymer composites prepared in the above examples and comparative examples are shown in Table 4.

[0074] Table 4 Determination results of each example and comparative example

[0075]

[0076]

[0077] As can be seen from Table 4, the high-temperature low-dielectric-loss liquid crystal polymer composite prepared by the present invention has a low high-temperature dielectric loss and a high flexural strength. Specifically, at 10 GHz and 150 °C, the dielectric loss does not exceed 0.008, and the flexural strength is not less than 60 MPa.

[0078] As can be seen from Examples 1 to 3, when the weight ratio of wollastonite to polytetrafluoroethylene is further adjusted to (0.2 - 0.5):1, the comprehensive performance of the prepared liquid crystal polymer composite is better, its high-temperature dielectric loss is not higher than 0.006, and the flexural strength is not less than 100 MPa.

[0079] As can be seen from Examples 2, 16 to 18, as the molecular weight of polytetrafluoroethylene increases, the high-temperature dielectric loss of the prepared liquid crystal polymer composite first decreases and then increases, and the flexural strength gradually increases; when the molecular weight of polytetrafluoroethylene is 10 4 ~10 5 , the comprehensive performance of the prepared liquid crystal polymer composite is better, the high-temperature dielectric loss is not higher than 0.0057, and the flexural strength is not less than 95 MPa.

[0080] As can be seen from Examples 2, 19 to 21, as the aspect ratio of wollastonite increases, the high-temperature dielectric loss of the prepared liquid crystal polymer composite first decreases and then increases, and the flexural strength gradually increases; when the aspect ratio of wollastonite is (12 - 25):1, the comprehensive performance of the prepared liquid crystal polymer composite is better, the high-temperature dielectric loss is not higher than 0.0057, and the flexural strength is not less than 95 MPa.

[0081] As can be seen from Comparative Example 1, when too little polytetrafluoroethylene is added, the high-temperature dielectric loss of the prepared liquid crystal polymer composite is too high to meet the requirements.

[0082] As can be seen from Comparative Example 2, when too much polytetrafluoroethylene is added, the flexural strength of the prepared liquid crystal polymer composite is too low to meet the requirements.

[0083] As can be seen from Comparative Examples 3 and 4, when too much or too little wollastonite is added, the high-temperature dielectric loss of the prepared liquid crystal polymer composite is higher than 0.008 and cannot meet the requirements.

[0084] As can be seen from Comparative Example 5, when glass fiber is used to replace wollastonite, the high-temperature dielectric loss of the prepared liquid crystal polymer composite increases significantly, which is significantly higher than that of the examples and cannot meet the requirements.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A high-temperature and low-dielectric-loss liquid crystal polymer composite material, characterized in that It comprises the following components calculated by weight parts: Liquid crystal polymer resin: 100 parts; Polytetrafluoroethylene: 30 - 250 parts; Wollastonite: 3 - 150 parts; Among them, the mass ratio of the wollastonite to the polytetrafluoroethylene is (0.1 - 0.6):

1.

2. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 1, wherein It comprises the following components calculated by weight parts: Liquid crystal polymer resin: 100 parts; Polytetrafluoroethylene: 70 - 120 parts; Wollastonite: 7 - 70 parts.

3. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 1, wherein The mass ratio of the wollastonite to the polytetrafluoroethylene is (0.2 - 0.5):

1.

4. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 1, characterized in that The aspect ratio of the wollastonite is (8 - 40):

1.

5. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 4, wherein The aspect ratio of the wollastonite is (12 - 25):

1.

6. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 1, wherein The weight-average molecular weight of the polytetrafluoroethylene is 10 3 ~6×10 7 .

7. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 1, wherein The composite material further comprises 0.1 - 1 part of processing aid.

8. The high-temperature low-dielectric-loss liquid crystal polymer composite material according to claim 7, wherein The processing aid is one or more of metal stearate, linear low density polyethylene, and ethylene - acrylic acid copolymer.

9. A method for preparing the high - temperature and low - dielectric - loss liquid crystal polymer composite material according to any one of claims 1 - 8, comprising the following steps: Mix the liquid crystal polymer resin, polytetrafluoroethylene, wollastonite, and processing aid evenly, and then melt - blend and extrude - pelletize through an extruder to obtain the high - temperature and low - dielectric - loss liquid crystal polymer composite material.

10. An application of the high - temperature and low - dielectric - loss liquid crystal polymer composite material according to any one of claims 1 - 8 in preparing high - frequency transmission electronic component materials.

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