Polytetrafluoroethylene-based quartz fiber low-dielectric composite material

Abstract

When the human society enters the highly informationized era, instant uninterrupted communication between electronic devices is everywhere, which causes innovative application of the 5G / 6G communication technology in work and life, such as automobile automatic driving, virtual / augmented reality, digital logistics and the like. The development of the technologies also continuously improves the performance requirements of the low-dielectric composite material, such as high frequency, high speed and low loss, which are the key points of the current research. The invention provides preparation of a polytetrafluoroethylene-based quartz fiber low-dielectric composite material, quartz fibers and polytetrafluoroethylene resin are used as a reinforcement and a matrix, the resin content of a composite material substrate is regulated and controlled by adopting a multi-impregnation mode, and surface defects of the composite substrate are repaired through polydopamine deposition. The polytetrafluoroethylene-based quartz fiber low-dielectric composite material prepared by the invention is high in strength, has low dielectric constant and dielectric loss in a high-frequency environment, is simple in preparation process, and can meet wave-transparent performance requirements and packaging requirements of a new generation of communication technology and related equipment.

Description

Technical Field

[0001] This invention relates to the field of low-dielectric composite materials technology, and more specifically, to the preparation of a polytetrafluoroethylene quartz fiber low-dielectric composite material. Background Technology

[0002] Human society has entered a highly information-driven era, with ubiquitous, real-time, and uninterrupted communication between electronic devices. This has spurred innovative applications of 5G / 6G communication technologies in work and daily life, such as autonomous driving, virtual / augmented reality, and digital logistics. The development of these technologies is also continuously increasing the performance requirements for low-dielectric composite materials; high-frequency, high-speed, and low-loss performance are current research priorities.

[0003] Chinese patent CN116769280A discloses a method for preparing a low-dielectric composite material. It uses ultra-high molecular weight polyethylene fiber and a multifunctional epoxy resin composite system as an adhesive to prepare an organic fiber prepreg, which is then molded into a low-dielectric composite material. Chinese patent CN118620265A discloses a method for preparing an in-situ modified low-dielectric quartz fiber composite material. It uses epoxy-based POSS and polyetheramine to in-situ crosslink modified quartz fibers, utilizing the introduced polar epoxy groups to react with a cyanate ester resin matrix, thereby enhancing the chemical bond between the fiber and the resin. Both of these materials suffer from relatively cumbersome preparation processes or slightly insufficient performance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for preparing a low-dielectric composite material of polytetrafluoroethylene (PTFE) quartz fiber. Quartz fiber and PTFE resin are used as reinforcement and matrix, respectively. The resin content of the composite substrate is controlled through multiple impregnation processes, and surface defects of the composite substrate are repaired through polydopamine deposition. The PTFE quartz fiber low-dielectric composite material prepared by this invention exhibits high strength, low dielectric constant and dielectric loss in high-frequency environments, and a simple preparation process, meeting the wave transmission performance requirements and packaging needs of next-generation communication technologies and related equipment.

[0005] This invention provides a method for preparing a polytetrafluoroethylene low-dielectric composite material, comprising the following: a) High-purity silica quartz fiber was impregnated with polytetrafluoroethylene emulsion, and then subjected to thermosetting, hot pressing and polydopamine deposition treatment in sequence to obtain polytetrafluoroethylene quartz fiber low dielectric composite material.

[0006] The aforementioned silica quartz fiber is a high-purity quartz fiber, wherein the silica content is controlled to be greater than 95%, preferably greater than 98%. The high-purity quartz fiber can be fiber filament, chopped fiber, or quartz fiber cloth, preferably quartz fiber cloth, in order to balance excellent mechanical properties and more convenient composite material preparation processes.

[0007] Preferably, the high-purity quartz fiber cloth mentioned above needs to undergo pretreatment before impregnation to remove spinning auxiliaries such as wetting agents and antistatic agents from the surface of the fiber cloth. The pretreatment process can employ heat treatment or solvent elution. Heat treatment is a conventional high-temperature heat treatment at 650℃, the purpose of which is to facilitate the volatilization or thermal decomposition of surface spinning auxiliaries. Solvent elution can be carried out by acetone extraction or immersion in acidic solutions such as hydrochloric acid or sulfuric acid.

[0008] Preferably, the quartz fiber fabric after removing the surface spinning aid is subjected to a silane coupling agent surface treatment to increase the interfacial compatibility between the fiber and the polytetrafluoroethylene resin matrix. The silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH570), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), etc., and the surface treatment method is the conventional method for using such coupling agents.

[0009] The polytetrafluoroethylene body mentioned in step a) can be polytetrafluoroethylene solid powder, film, emulsion, or other forms of polytetrafluoroethylene resin, preferably a polytetrafluoroethylene emulsion. Common commercially available products can be selected as the polytetrafluoroethylene emulsion.

[0010] The impregnation process of the aforementioned polytetrafluoroethylene (PTFE) emulsion specifically includes: cutting quartz fiber fabric into unit fabrics of appropriate size as needed, and then immersing the unit fabrics in the PTFE emulsion for impregnation and heat curing. Multiple impregnation operations can be performed to control the relative content of quartz fiber and PTFE resin. The mass fraction of PTFE resin can be 15%-85%, preferably controlled at 35%-75%, and the heat curing temperature can be 270°C-400°C, preferably controlled at 300°C-350°C.

[0011] After thermosetting, the unit fabrics are stacked in a mold according to the required dimensions, and then placed in a hot press for hot pressing to obtain a polytetrafluoroethylene (PTFE) quartz fiber composite material. High-temperature hot pressing is beneficial for the molding of PTFE resin, but too high a temperature may cause PTFE decomposition. Higher pressure is beneficial for the densification of the composite material, but too high a pressure may cause the quartz fibers to break. The hot pressing pressure is 10MPa-45MPa, preferably controlled at 20MPa-30MPa; the hot pressing temperature is 300°C-400°C, preferably controlled at 320°C-340°C.

[0012] The aforementioned polytetrafluoroethylene quartz fiber composite materials often suffer from numerous defects that affect their final dielectric properties. Preferably, the polydopamine deposition described in step a) can repair surface defects and improve performance. The specific process of polydopamine deposition includes: preparing a polydopamine solution with a pH controlled between 7 and 11, preferably 7.5-10; controlling the polydopamine concentration to 0.5-10 g / L, preferably 1-8 g / L; immersing the hot-pressed composite board in the polydopamine solution; rinsing the board surface after deposition; and drying it in an oven to obtain the polytetrafluoroethylene quartz fiber low-dielectric composite material.

[0013] Compared with existing technologies, the preparation method provided by this invention uses high-purity silica quartz fiber fabric as the substrate and polytetrafluoroethylene composite resin as the adhesive. The preparation process is simple, and the obtained polytetrafluoroethylene low dielectric composite material has high strength and low dielectric constant and dielectric loss in high-frequency environments, which can meet the wave transmission performance requirements and packaging needs of next-generation communication technologies and related equipment. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0015] This invention provides a method for preparing a low-dielectric composite material of polytetrafluoroethylene quartz fiber, comprising the following steps: High-purity silica quartz fiber fabric is pretreated, surface treated with silane coupling agent, and impregnated with polytetrafluoroethylene emulsion. Then, it is successively subjected to hot pressing and polydopamine deposition to obtain polytetrafluoroethylene quartz fiber low dielectric composite material.

[0016] In this invention, the silica content in the high-purity silica quartz fiber fabric is controlled to be no less than 95%. This invention does not impose any special restrictions on the source of the high-purity silica quartz fiber fabric; commercially available products or homemade products well-known to those skilled in the art can be used.

[0017] In this invention, the surface treatment of the silane coupling agent is conventional. The silane coupling agent can be γ-methacryloyloxypropyltrimethoxysilane (KH570) or γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and other silane coupling agents.

[0018] In this invention, the polytetrafluoroethylene emulsion can be impregnated using multiple impregnation methods to control the relative mass content of polytetrafluoroethylene and quartz fiber.

[0019] In this invention, the hot pressing process includes: stacking unit fabrics in a mold according to size requirements, and then placing them into a hot press for hot pressing.

[0020] In this invention, the polydopamine deposition is performed using an alkaline dopamine immersion deposition method. After deposition, the surface of the substrate is rinsed and then dried, resulting in a polytetrafluoroethylene quartz fiber low-dielectric composite material.

[0021] The polytetrafluoroethylene quartz fiber low-dielectric composite material involved in this invention has a simple preparation process, high material strength, stable performance, low dielectric constant, and low dielectric loss, which can meet the wave transmittance requirements of next-generation communication technologies and related equipment. Compared with the prior art, this invention has the following advantages: (1) This invention uses polytetrafluoroethylene (PTFE), which has excellent low dielectric properties, temperature stability, and chemical stability, as the resin matrix. The PTFE emulsion impregnation operation is convenient. (2) High-purity silica quartz fiber is used as the reinforcing phase and the main material. Silica, with its non-polar and highly crystalline structure, plays a key role in reducing the dielectric constant and dielectric loss of the composite material. Furthermore, the high strength of the quartz fiber provides mechanical properties to the composite material, achieving the dual goals of high strength and low dielectric of the composite material. (3) By repairing defects through the surface deposition of polydopamine, the structural integrity of the composite material is improved, further enhancing the dielectric properties of the composite material. (4) The preparation process involved in this invention is simple and the performance is controllable.

[0022] To further illustrate the present invention, the following embodiments will be described in detail.

[0023] Example 1 (1) Quartz fiber cloth pretreatment: Quartz fiber cloth (Hubei Feilihua quartz fiber cloth, silica content 98%~99.5%, sizing agent content 0.5%~2%, water 0%~0.1%) is pretreated by heating to remove spinning aids on the fiber surface. The temperature is 650°C.

[0024] (2) Quartz fiber cloth impregnation-thermal curing: Quartz fiber cloth modified with coupling agent was impregnated with Japanese Daikin D210-C polytetrafluoroethylene emulsion (nonionic PTFE emulsion, solid content 60%, surfactant content 6%, average particle size 0.25μm), and the resin content was controlled at 35wt%. The thermal curing temperature was 300°C.

[0025] (3) Hot pressing: The impregnated cloth is hot pressed at a temperature of 320°C, a pressure of 20MPa, and a time of 4h to obtain the composite board.

[0026] The formulation and process parameters in other embodiments that differ from those in Example 1 are shown in Table 1. Table 1 Example Process parameters different from those in Example 1 2 Resin content 55%, thermosetting temperature 350°C, hot pressing temperature 320°C, hot pressing pressure 20MPa 3 Resin content 65%, thermosetting temperature 350°C, hot pressing temperature 340°C, hot pressing pressure 20MPa 4 Resin content 65%, thermosetting temperature 350°C, hot pressing temperature 340°C, hot pressing pressure 30MPa 5 Resin content 65%, thermosetting temperature 350°C, hot-pressing temperature 340°C, hot-pressing pressure 30MPa, PDA deposition concentration 3g / L, pH 8.5. 6 Resin content 65%, thermosetting temperature 350°C, hot-pressing temperature 340°C, hot-pressing pressure 30MPa, PDA deposition concentration 5g / L, pH 9.5 7 The resin content is 65%, the thermosetting temperature is 350°C, the hot-pressing temperature is 340°C, the hot-pressing pressure is 30 MPa, the PDA deposition concentration is 7 g / L, and the pH is 9.5. Dielectric property testing: The composite board to be tested was cut into strips 1mm thick, 3mm wide, and at least 100mm long. The dielectric constant and dielectric loss of the strips were measured using a high-frequency (microwave) dielectric constant analyzer. Tensile strength test: Cut the board to be tested into strips that are 1mm thick, 3mm wide and 100mm long. Use a universal tensile testing machine to stretch the strips in opposite directions at a stretching speed of 5mm / min.

[0027] The performance parameters of different embodiments are shown in Table 2.

[0028] Table 2 Example Dielectric constant (10 GHz) Dielectric loss (10GHz) Tensile modulus (MPa) 1 3.19 0.0066 9,12 2 3.06 0.0057 8.98 3 2.84 0.0051 8.43 4 2.77 0.0042 9.12 5 2.17 0.0041 9.19 6 1.81 0.0036 9.01 7 2.07 0.0052 9.12 The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a low-dielectric polytetrafluoroethylene composite material, characterized in that, The process includes the following steps: combining high-purity silica quartz fiber cloth with polytetrafluoroethylene resin to obtain a polytetrafluoroethylene quartz fiber low dielectric composite material.

2. According to claim 1, the characteristic is that, The high-purity quartz fiber contains no less than 95% silica by mass, and preferably more than 98%.

3. According to claim 1, the high-purity quartz fiber needs to be subjected to high-temperature heat treatment to remove spinning aids such as wetting agents from the surface of the fiber cloth.

4. According to claim 1, the characteristic is that, The silane coupling agent treatment uses common silane coupling agents, such as γ-methacryloxypropyltrimethoxysilane (KH570) or γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), etc.

5. According to claim 1, the process of multi-stage impregnation of the polytetrafluoroethylene emulsion includes: Quartz fiber fabric is cut into unit fabrics of appropriate size as needed, and the unit fabrics are then impregnated with polytetrafluoroethylene (PTFE) emulsion. This impregnation process is repeated multiple times to control the relative content of quartz fiber and PTFE resin. Preferably, the mass fraction of PTFE resin is controlled at 35%-75%.

6. According to claim 1, the characteristic is that, The hot pressing process is as follows: after heat curing, the unit fabric is stacked in a mold according to the required size, and then placed into a hot press for hot pressing. The hot pressing operation is a conventional hot pressing operation, with a hot pressing temperature of 200°C-380°C and a hot pressing pressure of 15MPa-30MPa.

7. According to claim 1, the characteristic is that, The polydopamine deposition method employed is a conventional alkaline dopamine deposition method. The specific process of polydopamine deposition includes: preparing an alkaline solution with a pH controlled at 7-11 and a dopamine concentration controlled at 0.5-10 g / L.