A surface treatment agent for silicon nitride fibers, a method for preparing the same, and an application thereof

Abstract

The application belongs to the technical field of surface treatment of silicon nitride fibers, and particularly relates to a surface treatment agent for silicon nitride fibers, a preparation method and application thereof. The raw materials of the surface treatment agent include 20-40 parts of polytetrafluoroethylene, 4-12 parts of an impregnating agent and 4-12 parts of a lubricant. The lubricant is selected from one or more of polyethylene wax, silicone oil, dimethyl silicone oil, polyphthalamide, trimethylolpropane oleate, glycerol trioleate, isooctyl acrylate and isooctyl methacrylate. The surface treatment agent prepared by the application can effectively act on the silicon nitride fibers under the synergistic effect of the lubricant and the impregnating agent. After secondary sizing, the bundle property, wear resistance, stiffness and bending resistance of the silicon nitride fibers are improved, the weaving performance requirements of the silicon nitride fibers are met, the process is simple, the cost is low, the application is suitable for industrial production, and the application can be widely applied.

Description

Technical Field

[0001] This invention belongs to the field of silicon nitride fiber surface treatment technology, specifically relating to a silicon nitride fiber surface treatment agent, its preparation method, and its application. Background Technology

[0002] Silicon nitride fiber, a high-temperature resistant ceramic fiber with excellent wave transmission properties, is an excellent material for fabricating radomes. However, due to its high stiffness and brittleness, silicon nitride fiber suffers damage during weaving due to bending, friction, shearing, and torsion caused by contact with loom components and fibers during warp feeding, shearing, weft insertion, and beating. This leads to a decline in fiber performance and, in severe cases, can affect the normal weaving process. This presents significant difficulties and challenges in the fabrication of silicon nitride fiber radome preforms. To reduce damage to the yarn during weaving, a more effective approach is to sizing the fiber to improve its weaving properties.

[0003] Chinese invention patent CN108929600A discloses a flame-retardant and wear-resistant coating material for radomes and its preparation method. The flame-retardant and wear-resistant coating material for radomes includes the following raw materials: EVA resin, thermosetting liquid polyimide pure resin, silane coupling agent, expanded graphite, potassium perfluorobutyl sulfonate, nano antimony trioxide, nano silicon nitride, polytetrafluoroethylene micro powder, polyethylene wax, dispersant, and antioxidant. The resulting flame-retardant and wear-resistant coating material for radomes has advantages such as flame retardancy and wear resistance, but the preparation method of this coating material is complex and costly. Another Chinese invention patent, CN111188195A, discloses a surface treatment agent for silicon nitride fibers and its preparation method. The surface treatment agent comprises the following raw materials in parts by weight: 34-49 parts of polytetrafluoroethylene, 17-28 parts of polydimethyldiallylammonium chloride, 9-17 parts of urea, 8-14 parts of ethoxylated aliphatic alkylamine, 2-6 parts of hydrophilic oil agent, 1.6-3.9 parts of additives, and 2-6 parts of thickener. The surface treatment agent of this invention can effectively act on silicon nitride fibers under the synergistic effect of each component, enhance the high-temperature resistance of silicon nitride fibers, prevent them from decomposing at high temperatures and causing a decrease in strength, and ensure their effective use as a high-temperature resistant material. However, the surface treatment agent of this invention cannot significantly improve the tow strength, wear resistance, and practicality of silicon nitride fibers.

[0004] The development and research of silicon nitride fibers started relatively late. Compared with high-performance fibers such as carbon fiber and glass fiber, there are fewer reports on surface modification or sizing agents. In addition, the surface of silicon nitride fibers is composed of Si-OH and Si-NH groups, which makes its affinity for organic polymer matrices weak. Furthermore, its high stiffness and brittleness make the development of sizing agents for silicon nitride fibers quite difficult.

[0005] Therefore, there is an urgent need in the field to develop a surface treatment agent that can improve the bundle properties, abrasion resistance, stiffness, and bending resistance of silicon nitride fibers. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art by providing a silicon nitride fiber surface treatment agent, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A surface treatment agent, the raw materials of which include polytetrafluoroethylene, a wetting agent, and a lubricant.

[0009] Preferably, the lubricant is selected from one or more of polyethylene wax, silicone oil, dimethyl silicone oil, polyphthalamide, trimethylolpropane oleate, trioleic acid glyceride, isooctyl acrylate and isooctyl methacrylate.

[0010] More preferably, the lubricant is selected from any one of polyethylene wax, trimethylolpropane oleate, and polyphthalamide.

[0011] Preferably, the wetting agent is selected from any one of polyethylene glycol, polyethylene glycol laurate, halogenated bisphenol A type epoxy resin, and oleylamine polyoxyethylene ether.

[0012] Preferably, the surface treatment agent comprises, by weight, 20-40 parts of polytetrafluoroethylene, 4-12 parts of wetting agent, 4-12 parts of lubricant, and the remainder water to a total of 100 parts by weight.

[0013] More preferably, the raw materials of the surface treatment agent, by weight, include 30-40 parts of polytetrafluoroethylene, 6-12 parts of wetting agent, 6-12 parts of lubricant, and the balance of water to a total of 100 parts by weight.

[0014] Most preferably, the raw materials of the surface treatment agent, by weight, include 40 parts of polytetrafluoroethylene, 12 parts of wetting agent, 12 parts of lubricant, and the balance of water to a total of 100 parts by weight.

[0015] The present invention also provides a method for preparing the above-mentioned surface treatment agent, which includes mixing polytetrafluoroethylene, a wetting agent and a lubricant in water to obtain the agent.

[0016] Preferably, the mixing temperature is 40-45°C and the mixing time is 40-50 min.

[0017] Preferably, the mixing process involves stirring, and the stirring speed is 60-180 rpm.

[0018] The present invention also provides the application of the above-mentioned surface treatment agent in the preparation of radome preforms.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The surface treatment agent prepared in this invention can effectively act on silicon nitride fibers under the synergistic effect of lubricant and wetting agent components. After secondary sizing, the bundle properties, wear resistance, stiffness and bending resistance of silicon nitride fibers are improved, and the weaving performance requirements of silicon nitride fibers are met.

[0021] (2) The formulation of the surface treatment agent prepared by this invention is scientific, the proportion is rigorous, the process is simple, the cost is low, it is suitable for industrial production, and it can be widely used. Detailed Implementation

[0022] All raw materials used in this invention are commercially available products. Specifically, polyethylene glycol was purchased from Shandong Hongtai Polymer Materials Factory, model PEG4000; polyethylene glycol laurate was purchased from Haian (Linyi) Guoli Chemical Co., Ltd., model PEG400ML; halogenated bisphenol A type epoxy resin was purchased from Hesheng (Guangdong) International Trade Co., Ltd., model EPON XY852M; and oleylamine polyoxyethylene ether was purchased from Zibo Yunchuan Chemical Co., Ltd., model ON-2.

[0023] Example 1

[0024] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 30 parts polytetrafluoroethylene, 8 parts polyethylene glycol, 8 parts polyethylene wax, and the balance water to a total of 100 parts by weight.

[0025] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, polyethylene wax and polyethylene glycol are placed in water, heated in a water bath and stirred, the temperature is set to 40℃, the time is set to 50min and the rotation speed is 120rpm, and the silicon nitride fiber surface treatment agent is obtained.

[0026] Example 2

[0027] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 20 parts polytetrafluoroethylene, 4 parts oleylamine polyoxyethylene ether, 4 parts silicone oil, and the balance being water to a total of 100 parts by weight.

[0028] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, silicone oil and oleylamine polyoxyethylene ether are placed in water, heated in a water bath and stirred, the temperature is set to 45℃, the time is set to 40min, and the rotation speed is 60rpm, thus obtaining the silicon nitride fiber surface treatment agent.

[0029] Example 3

[0030] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 40 parts polytetrafluoroethylene, 12 parts halogenated bisphenol A type epoxy resin, 12 parts trimethylolpropane oleate, and the balance being water to a total of 100 parts by weight.

[0031] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, trimethylolpropane oleate and halogenated bisphenol A type epoxy resin are placed in water, heated in a water bath and stirred. The temperature is set to 45℃, the time is set to 40min, and the rotation speed is 180rpm, thus obtaining the silicon nitride fiber surface treatment agent.

[0032] Example 4

[0033] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 25 parts polytetrafluoroethylene, 6 parts polyethylene glycol laurate, 6 parts polyphthalamide, and the balance water to a total of 100 parts by weight.

[0034] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, polyphthalamide and polyethylene glycol laurate are placed in water, heated in a water bath and stirred, the temperature is set to 45℃, the time is set to 40min, and the rotation speed is 100rpm, thus obtaining the silicon nitride fiber surface treatment agent.

[0035] Example 5

[0036] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 30 parts polytetrafluoroethylene, 2 parts silicone oil, 2 parts trimethylolpropane oleate, 4 parts polyethylene glycol, 8 parts polyethylene wax, and the balance being water to a total of 100 parts by weight.

[0037] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, silicone oil, trimethylolpropane oleate, polyethylene glycol and polyethylene wax are placed in water, heated in a water bath and stirred. The temperature is set to 40°C, the time is set to 50 min, and the rotation speed is 120 rpm to obtain the silicon nitride fiber surface treatment agent.

[0038] Example 6

[0039] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 30 parts polytetrafluoroethylene, 4 parts polyethylene wax, 2 parts polyphthalamide, 2 parts isooctyl acrylate, 8 parts halogenated bisphenol A type epoxy resin, and the balance being water added to 100 parts by weight.

[0040] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, polyethylene wax, polyphthalamide, isooctyl acrylate and halogenated bisphenol A type epoxy resin are placed in water, heated in a water bath and stirred, with the temperature set at 40℃, the time set at 50min, and the rotation speed at 120rpm, to obtain the silicon nitride fiber surface treatment agent.

[0041] Comparative Example 1

[0042] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 50 parts polytetrafluoroethylene, 8 parts polyethylene glycol, 8 parts polyethylene wax, and the balance water to a total of 100 parts by weight.

[0043] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene, polyethylene wax and polyethylene glycol are placed in water, heated in a water bath and stirred, the temperature is set to 40℃, the time is set to 50min and the rotation speed is 120rpm, and the silicon nitride fiber surface treatment agent is obtained.

[0044] Comparative Example 2

[0045] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 30 parts polytetrafluoroethylene, 16 parts polyethylene wax, and the balance water to a total of 100 parts by weight.

[0046] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene and polyethylene wax are placed in water, heated in a water bath and stirred. The temperature is set to 40℃, the time is set to 50min, and the rotation speed is 120rpm, thus obtaining the silicon nitride fiber surface treatment agent.

[0047] Comparative Example 3

[0048] A silicon nitride fiber surface treatment agent, by weight, comprises the following components: 30 parts polytetrafluoroethylene, 16 parts polyethylene glycol, and the balance water to a total of 100 parts by weight.

[0049] The preparation method of silicon nitride fiber surface treatment agent is as follows: polytetrafluoroethylene and polyethylene glycol are placed in water, heated in a water bath and stirred, with the temperature set at 40°C, the time set at 50 min, and the rotation speed at 120 rpm, to obtain the silicon nitride fiber surface treatment agent.

[0050] Test case

[0051] The surface treatment agents prepared in Examples 1-6 and Comparative Examples 1-3 were used to perform secondary sizing on silicon nitride fibers (manufacturer: Fujian Liya Company, fiber model and specification: Cansas-4103) using an oil pump, and the coating was applied at a pressure of 12KN to obtain a coating with a thickness of 150μm.

[0052] The test metrics are as follows:

[0053] Hook bond strength test: The hook bond strength test was conducted in accordance with Appendix B of standard GJB1982-94 "Method for Determination of Hook Bond Strength of Carbon Fiber". The test instrument was a Xin Sansi CMT8502 electronic universal testing machine. Each group of samples was tested 5 times and the average value was taken. The tensile speed was 10mm / min. The hook bond strength value was specified to be ≥30N.

[0054] Stiffness test: The stiffness test is conducted in accordance with GB / T7690.4-2013 "Test methods for reinforcing yarns - Part 4: Determination of stiffness". The fiber bundle sample is 500 mm long. A 50 g weight is attached to the other end and suspended for 2 minutes to allow the yarn to fully straighten. After 2 minutes, the weight is removed, and the midpoint of the fiber bundle is suspended on a steel hook. After 30 seconds, the yarn spacing at 60 mm from the suspension point is recorded. Each group of samples is tested 10 times and the average value is taken. The required stiffness value is 85-100 mm.

[0055] Abrasion resistance test: The abrasion resistance test refers to ZBW04005-89 "Test Method for Abrasion Resistance of Yarn - Reciprocating Grinding Roller Method". 180-grit sandpaper is wrapped around a stainless steel roller as a friction rod. The length of the fiber bundle sample is 450mm. A 125g weight is used to control the tension. The rotation speed of the eccentric wheel is 100r / min. Each sample is tested 10 times and the average value is taken. The abrasion resistance test is required to be ≥753 times.

[0056] Fiber bundle property test: The fiber bundle property test adopts the ruler and compass method. The fiber bundle property is measured by the size of the fiber diameter. The diameter of the fiber after passing through the roller is measured and the data is recorded. Each group of samples is tested 10 times and the average value is taken. The bundle property is required to be ≤2.4mm.

[0057] The test results are shown in Table 1.

[0058] Table 1 Test Results

[0059]

[0060] From the data in Table 1, we can obtain:

[0061] (1) The surface treatment agents prepared in Examples 1-6 were coated on the silicon nitride fibers respectively. The hook strength, stiffness and wear resistance were increased, and the bundled properties were reduced. Even if the silicon nitride fibers were twisted, their performance was improved after coating with the surface treatment agent, and the requirements of each index were met.

[0062] (2) The only difference between Comparative Example 1 and Example 1 is the content of polytetrafluoroethylene. It can be seen that after coating the silicon nitride fiber with the surface treatment agent prepared in Comparative Example 1, its stiffness did not meet the standard.

[0063] (3) The only difference between Comparative Example 2 and Example 1 is that it does not contain a wetting agent, and the only difference between Comparative Example 3 and Example 1 is that it does not contain a lubricant. It can be seen that after coating the silicon nitride fibers with the surface treatment agents prepared in Comparative Example 2 and Comparative Example 3 respectively, the hook strength and stiffness of Comparative Example 2 do not meet the standards, and the hardness of Comparative Example 3 does not meet the standards. It can be seen that it is due to the synergistic effect of the wetting agent and the lubricant that the silicon nitride fibers coated in Examples 1-6 meet the test requirements.

[0064] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A surface treatment agent, characterized by, The raw materials of the surface treatment agent include, by weight fraction, 20-40 parts of polytetrafluoroethylene, 4-12 parts of a wetting agent, 4-12 parts of a lubricant selected from any one of polyethylene wax, trimethylolpropane oleate and polyphthalamide, and the balance of water added to 100 parts by weight.

2. The surface treatment agent according to claim 1, characterized by, The raw materials of the surface treatment agent include, by weight fraction, 30-40 parts of polytetrafluoroethylene, 6-12 parts of a wetting agent, 6-12 parts of a lubricant, and the balance of water added to 100 parts by weight.

3. The surface treatment agent according to claim 2, characterized by The raw materials of the surface treatment agent include, by weight fraction, 40 parts of polytetrafluoroethylene, 12 parts of a wetting agent, 12 parts of a lubricant, and the balance of water added to 100 parts by weight.

4. A method for producing the surface treatment agent according to any one of claims 1 to 3, characterized by, The polytetrafluoroethylene, the wetting agent and the lubricant are mixed in water.

5. The production method according to claim 4, characterized by, The temperature of the mixing is 40-45℃, and the mixing time is 40-50 min.

6. The preparation method according to claim 4, characterized in that, The mixing is performed with stirring, and the stirring speed is 60-180 rpm.

7. Use of the surface treatment agent of any one of claims 1-3 or prepared by the preparation method of any one of claims 4-6 in the preparation of a radome preform.

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