Modified polyphenylene sulfide material for air preheater, preparation method and flat tube

Abstract

The invention relates to the field of air preheaters, in particular to a modified polyphenylene sulfide material for an air preheater, a preparation method of the modified polyphenylene sulfide material and a flat tube.The modified polyphenylene sulfide material for the air preheater is characterized by comprising high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide; the modified gallium nitride and the modified silicon carbide are respectively gallium nitride and silicon nitride which are subjected to surface modification treatment by adopting a silane coupling agent, and the modified gallium nitride accounts for 3-8% of the mass of the high-crystallinity polyphenylene sulfide resin; the modified silicon carbide accounts for 4-15% of the mass of the high-crystallinity polyphenylene sulfide resin; 1-10 parts by mass of a compatilizer, 1-10 parts by mass of a stabilizer, 10-20 parts by mass of toughening fibers, 20-30 parts by mass of a high-temperature crystallization thermoplastic material and 0.5-1.5 parts by mass of a high-temperature antioxidant are also added into every 100 parts by mass of the high-crystallinity polyphenylene sulfide resin. The non-metal heat-conducting material and the metal heat-conducting material are doped to improve the heat conductivity of the polyphenylene sulfide resin, so that the material which is low in heat-conducting filler consumption, high in heat conductivity and excellent in comprehensive performance is prepared.

Description

Technical Field

[0001] The invention relates to the field of air preheaters, and in particular to a modified polyphenylene sulfide material for air preheaters, a preparation method thereof, and a flat tube. Background Art

[0002] Heating furnaces and reboilers are large energy consumers and CO2 emitters in the refining industry. Their energy efficiency is directly related to the energy consumption index and CO2 emission index of the device. Especially when the heat loss of heating furnaces is generally high, it is imperative to transform the refining equipment to save energy and reduce emissions, improve quality and increase efficiency! At present, the design thermal efficiency of heating furnaces is generally below 93%, and the exhaust temperature is generally 130-160℃, and a considerable part of the waste heat can be reused.

[0003] Air preheater is a device that uses high-temperature flue gas or steam to preheat the air entering the furnace. It is widely used in the refining industry. The air preheater transfers the heat in the high-temperature flue gas or steam to the air through the principle of heat exchange, so that the air reaches a higher temperature before entering the combustion furnace, thereby saving fuel and improving combustion efficiency. Due to the chemical reactions between the chemicals contained in the cooling water (such as nitrogen oxides, acids, alkalis, salts, etc.) and the pipes, the pipe wall gradually becomes thinner and even perforated. In the cooling water system, due to the potential difference between different metals or between metals and non-metals, a primary battery is formed, resulting in electrochemical corrosion. Microorganisms (such as bacteria, fungi, etc.) in the cooling water attach and grow on the pipe wall to form a biofilm, causing the pipe wall to be biologically corroded.

[0004] Traditional metal heat exchange tubes are not corrosion-resistant. Although the heat-resistant coating technology on the metal surface improves the corrosion resistance of the metal, it greatly reduces the thermal conductivity and brings unreliability. It has poor corrosion resistance to strong acids and alkalis and is expensive, which limits its application. Although it has good corrosion resistance, it is very expensive. It has the disadvantages of poor mechanical properties and poor pressure resistance. Summary of the invention

[0005] Based on this, the present invention proposes a modified polyphenylene sulfide material for an air preheater, a preparation method and a flat tube, which have good thermal conductivity and better corrosion resistance.

[0006] According to a first aspect of the present invention, there is provided a modified polyphenylene sulfide material for an air preheater, comprising a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide;

[0007] The modified gallium nitride and the modified silicon carbide are respectively gallium nitride and silicon nitride subjected to surface modification treatment using a silane coupling agent, wherein the modified gallium nitride accounts for 3-8% of the mass of the high-crystallinity polyphenylene sulfide resin; and the modified silicon carbide accounts for 4-15% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0008] For every 100 parts of the high crystallinity polyphenylene sulfide resin, the following are added according to the mass fractions: 1-10 parts of a compatibilizer, 1-10 parts of a stabilizer, 10-20 parts of toughening fibers, 20-30 parts of a high temperature crystalline thermoplastic material and 0.5-1.5 parts of a high temperature antioxidant.

[0009] According to an embodiment of the present invention, the compatibilizer is one or both of maleic anhydride-ethylene-octene copolymer and ethylene-vinyl acetate copolymer.

[0010] According to an embodiment of the present invention, the toughening fiber is one or both of carbon fiber and graphene fiber.

[0011] According to an embodiment of the present invention, the stabilizer is one or more of polyether chain-bridged bisimidazoline nitrone nitrogen oxides, linear nitrones, and cyclic nitrones;

[0012] The high temperature crystalline thermoplastic material is one of polyetheretherketone and polypropylene.

[0013] According to a second aspect of the present invention, there is provided a method for preparing a modified polyphenylene sulfide material for an air preheater, comprising the following steps:

[0014] Using a silane coupling agent to perform surface modification treatment on gallium nitride and silicon carbide to obtain modified gallium nitride and modified silicon carbide;

[0015] Preparation of high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide;

[0016] Preparation of modified polyphenylene sulfide materials.

[0017] According to an embodiment of the present invention, the surface modification of nano-gallium nitride and nano-silicon carbide using a silane coupling agent to obtain modified gallium nitride and modified silicon carbide includes:

[0018] The nano-gallium nitride and nano-silicon carbide are prepared into a dispersion liquid, and after adding a dispersant, the dispersion liquid is stirred and ultrasonically dispersed at room temperature to obtain a gallium nitride dispersion liquid and a silicon carbide dispersion liquid respectively;

[0019] Anhydrous ethanol is added to the gallium nitride dispersion and the silicon carbide dispersion, and aminopropyltriethoxysilane is added dropwise, and the temperature is raised to 80-100° C. The reaction is centrifuged and dried to obtain the modified gallium nitride and the modified silicon carbide.

[0020] According to an embodiment of the present invention, the high temperature antioxidant may be Revonox 608 and GA-80, which can improve the oxidation resistance of PPS, and due to the good compatibility of these antioxidants with the PPS matrix, the compatibility of gallium nitride and silicon carbide with PPS can also be indirectly improved.

[0021] According to an embodiment of the present invention, the preparation of a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide comprises:

[0022] Weigh the components according to the following weight ratio: 100 parts of linear polyphenylene sulfide resin, 1-10 parts of stabilizer, 0.5-1.5 parts of high temperature antioxidant and 1-10 parts of compatibilizer;

[0023] Add the weighed linear polyphenylene sulfide resin, stabilizer, antioxidant and compatibilizer into a high-speed batching mixer and mix them evenly to obtain a first premix;

[0024] Adding the modified gallium nitride and the modified silicon carbide to the first premix, and mixing them evenly to obtain a second premix;

[0025] The second premix is ​​placed in a twin-screw machine, melt-extruded through the twin-screw machine, and then cooled, dried, and granulated to obtain a granular high-crystallinity polyphenylene sulfide resin.

[0026] According to an embodiment of the present invention, the temperature of the twin-screw machine is set as follows: first stage temperature 240-260°C, second stage temperature 255-275°C, third stage temperature 260-275°C, fourth stage temperature 265-275°C, fifth stage temperature 280-300°C.

[0027] According to an embodiment of the present invention, the preparation of the modified polyphenylene sulfide material comprises:

[0028] Add 100 parts of the high crystallinity polyphenylene sulfide resin, 10-20 parts of toughening fiber, and 20-30 parts of high temperature crystalline thermoplastic material into a high-speed batching mixer, and mix them evenly to obtain a third premix;

[0029] The third premix is ​​placed in a single screw machine, the secondary premix is ​​melt-extruded through the single screw machine, and then cooled and granulated to obtain the modified polyphenylene sulfide material;

[0030] Among them, the temperature setting of the single screw machine is: first stage temperature 260-320℃, second stage temperature 265-325℃, third stage temperature 270-330℃, fourth stage temperature 275-335℃, fifth stage temperature 280-320℃.

[0031] According to a third aspect of the present invention, there is provided a flat tube made of modified polyphenylene sulfide material for an air preheater.

[0032] The advantages of the present invention are:

[0033] In the present invention, firstly, the cross-linking problem of polyphenylene sulfide in the processing process is solved by preparing a high-crystallinity polyphenylene sulfide resin technology, thereby ensuring the regularity of its molecules and preventing the reduction of the thermal conductivity of the resin; at the same time, non-metallic thermal conductive materials and metal thermal conductive materials are used for doping to improve the thermal conductivity of the polyphenylene sulfide resin, especially the addition of gallium nitride can effectively optimize the crystal structure of the polyphenylene sulfide crystal, thereby preparing a high thermal conductivity, corrosion-resistant modified polyphenylene sulfide material with low thermal conductive filler dosage, high thermal conductivity, excellent comprehensive performance, and high thermal conductivity.

[0034] The high thermal conductivity and corrosion-resistant modified polyphenylene sulfide material provided by the present invention can effectively reduce the exhaust temperature to 90°C or even lower, and will not cause corrosion to the heat exchange tubes, thereby effectively increasing the efficiency of the heating furnace to 95+. The heat exchange tubes have a small density, and the weight of the entire air preheater equipment is lighter than that of equipment made of other materials. It is easy to install and reduces the investment in supporting steel frames and foundations. The modular design of the air preheater equipment saves time, effort, and cost for later maintenance and repair. It also solves the dew point corrosion problem in the low-temperature zone of the preheater from the source of the heat exchange tube material, further reduces the exhaust temperature of the heating furnace, increases the thermal efficiency of the heating furnace to more than 95%, reduces the energy consumption of the device, and reduces the emission of CO2 and other pollutants. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0036] According to a first aspect of the present invention, there is provided a modified polyphenylene sulfide material for an air preheater, comprising a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide;

[0037] The modified gallium nitride and the modified silicon carbide are respectively gallium nitride and silicon nitride subjected to surface modification treatment using a silane coupling agent, wherein the modified gallium nitride accounts for 3-8% of the mass of the high-crystallinity polyphenylene sulfide resin; and the modified silicon carbide accounts for 4-15% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0038] For every 100 parts of the high crystallinity polyphenylene sulfide resin, the following are added according to the mass fractions: 1-10 parts of a compatibilizer, 1-10 parts of a stabilizer, 10-20 parts of toughening fibers, 20-30 parts of a high temperature crystalline thermoplastic material and 0.5-1.5 parts of a high temperature antioxidant.

[0039] Silicon carbide and silicon nitride have high thermal conductivity. Silicon carbide and silicon nitride have smaller particle size and higher specific surface area, which is conducive to uniform dispersion in the matrix resin to form an effective thermal conductive network, thereby improving the overall thermal conductivity of the composite material. Through surface treatment, such as coating with a dispersant or coupling agent treatment, the dispersibility and thermal conductivity efficiency of aluminum nitride thermal conductive powder in the composite material can be improved.

[0040] Silane coupling agents contain two types of active groups, one is a hydrolyzable group (such as Si-X), and the other is a group that can react with organic polymers (such as Y group). During the treatment process, the groups on the surface of silicon carbide and silicon nitride will be changed, and further covalent bonds will be formed under heating conditions. This covalent bond significantly improves the compatibility of silicon carbide and silicon nitride with polyphenylene sulfide materials. It can also improve the thermal conductivity of silicon carbide and silicon nitride, making them have better effects.

[0041] In the present invention, firstly, the cross-linking problem of polyphenylene sulfide in the processing process is solved by preparing a high-crystallinity polyphenylene sulfide resin technology, thereby ensuring the regularity of its molecules and preventing the reduction of the thermal conductivity of the resin; at the same time, non-metallic thermal conductive materials and metal thermal conductive materials are used for doping to improve the thermal conductivity of the polyphenylene sulfide resin, especially the addition of gallium nitride can effectively optimize the crystal structure of the polyphenylene sulfide crystal, thereby preparing a high thermal conductivity, corrosion-resistant modified polyphenylene sulfide material with low thermal conductive filler dosage, high thermal conductivity, excellent comprehensive performance, and high thermal conductivity.

[0042] The high thermal conductivity and corrosion-resistant modified polyphenylene sulfide material provided by the present invention can effectively reduce the exhaust temperature to 90°C or even lower, and will not cause corrosion to the heat exchange tubes, thereby effectively increasing the efficiency of the heating furnace to 95+. The heat exchange tubes have a small density, and the weight of the entire air preheater equipment is lighter than that of equipment made of other materials. It is easy to install and reduces the investment in supporting steel frames and foundations. The modular design of the air preheater equipment saves time, effort, and cost for later maintenance and repair. It also solves the dew point corrosion problem in the low-temperature zone of the preheater from the source of the heat exchange tube material, further reduces the exhaust temperature of the heating furnace, increases the thermal efficiency of the heating furnace to more than 95%, reduces the energy consumption of the device, and reduces the emission of CO2 and other pollutants.

[0043] According to an embodiment of the present invention, the compatibilizer is one or both of maleic anhydride-ethylene-octene copolymer and ethylene-vinyl acetate copolymer.

[0044] According to an embodiment of the present invention, the toughening fiber is one or both of carbon fiber and graphene fiber.

[0045] Both graphene fiber and carbon fiber have excellent mechanical, electrical and thermal properties. Each carbon atom in graphene is sp2 hybridized, which makes graphene have ultra-high in-plane thermal conductivity, which can effectively improve the strength and thermal conductivity of the material.

[0046] According to an embodiment of the present invention, the stabilizer is one or more of polyether chain-bridged bisimidazoline nitrone nitrogen oxides, linear nitrones, and cyclic nitrones;

[0047] The high temperature crystalline thermoplastic material is one of polyetheretherketone and polypropylene.

[0048] According to a second aspect of the present invention, there is provided a method for preparing a modified polyphenylene sulfide material for an air preheater, comprising the following steps:

[0049] Using a silane coupling agent to perform surface modification treatment on gallium nitride and silicon carbide to obtain modified gallium nitride and modified silicon carbide;

[0050] Preparation of high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide;

[0051] Preparation of modified polyphenylene sulfide materials.

[0052] According to an embodiment of the present invention, the surface modification of nano-gallium nitride and nano-silicon carbide using a silane coupling agent to obtain modified gallium nitride and modified silicon carbide includes:

[0053] The nano-gallium nitride and nano-silicon carbide are prepared into a dispersion liquid, and after adding a dispersant, the dispersion liquid is stirred and ultrasonically dispersed at room temperature to obtain a gallium nitride dispersion liquid and a silicon carbide dispersion liquid respectively;

[0054] Anhydrous ethanol is added to the gallium nitride dispersion and the silicon carbide dispersion, and aminopropyltriethoxysilane is added dropwise, and the temperature is raised to 80-100° C. The reaction is centrifuged and dried to obtain the modified gallium nitride and the modified silicon carbide.

[0055] According to an embodiment of the present invention, the preparation of a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide comprises:

[0056] Weigh the components according to the following weight ratio: 100 parts of linear polyphenylene sulfide resin, 1-10 parts of stabilizer, 0.5-1.5 parts of high temperature antioxidant and 1-10 parts of compatibilizer;

[0057] Add the weighed linear polyphenylene sulfide resin, stabilizer, antioxidant and compatibilizer into a high-speed batching mixer and mix them evenly to obtain a first premix;

[0058] Adding the modified gallium nitride and the modified silicon carbide to the first premix, and mixing them evenly to obtain a second premix;

[0059] The second premix is ​​placed in a twin-screw machine, melt-extruded through the twin-screw machine, and then cooled, dried, and granulated to obtain a granular high-crystallinity polyphenylene sulfide resin.

[0060] According to an embodiment of the present invention, the temperature of the twin-screw machine is set as follows: first stage temperature 240-260°C, second stage temperature 255-275°C, third stage temperature 260-275°C, fourth stage temperature 265-275°C, fifth stage temperature 280-300°C.

[0061] According to an embodiment of the present invention, the preparation of the modified polyphenylene sulfide material comprises:

[0062] Add 100 parts of the high crystallinity polyphenylene sulfide resin, 10-20 parts of toughening fiber, and 20-30 parts of high temperature crystalline thermoplastic material into a high-speed batching mixer, and mix them evenly to obtain a third premix;

[0063] The third premix is ​​placed in a single screw machine, the secondary premix is ​​melt-extruded through the single screw machine, and then cooled and granulated to obtain the modified polyphenylene sulfide material;

[0064] Among them, the temperature setting of the single screw machine is: first stage temperature 260-320℃, second stage temperature 265-325℃, third stage temperature 270-330℃, fourth stage temperature 275-335℃, fifth stage temperature 280-320℃.

[0065] According to a third aspect of the present invention, there is provided a flat tube made of modified polyphenylene sulfide material for an air preheater.

[0066] Example: Preparation of samples.

[0067] The steps include:

[0068] The nano-gallium nitride and nano-silicon carbide are prepared into a dispersion liquid, and after adding a dispersant, the dispersion liquid is stirred and ultrasonically dispersed at room temperature to obtain a gallium nitride dispersion liquid and a silicon carbide dispersion liquid respectively;

[0069] Adding anhydrous ethanol to the gallium nitride dispersion and the silicon carbide dispersion, and dropping aminopropyltriethoxysilane, heating to 80-100° C., reacting and centrifugally drying to obtain modified gallium nitride and modified silicon carbide;

[0070] Weigh the components according to the following weight ratio: 100 parts of linear polyphenylene sulfide resin, 1-10 parts of stabilizer, 0.5-1.5 parts of high temperature antioxidant and 1-10 parts of compatibilizer;

[0071] Add the weighed linear polyphenylene sulfide resin, stabilizer, antioxidant and compatibilizer into a high-speed batching mixer and mix them evenly to obtain a first premix;

[0072] Adding modified gallium nitride and modified silicon carbide to the first premix, and mixing them evenly to obtain a second premix;

[0073] The second premix is ​​placed in a twin-screw machine, and the second premix is ​​melt-extruded by the twin-screw machine, and then cooled, dried, and granulated to obtain a granular high-crystallinity polyphenylene sulfide resin. The temperature of the twin-screw machine is set as follows: the first stage temperature is 240-260°C, the second stage temperature is 255-275°C, the third stage temperature is 260-275°C, the fourth stage temperature is 265-275°C, and the fifth stage temperature is 280-300°C;

[0074] Add 100 parts of high crystallinity polyphenylene sulfide resin, 10-20 parts of toughening fiber, and 20-30 parts of high temperature crystalline thermoplastic material into a high-speed batching mixer, and mix them evenly to obtain a third premix;

[0075] The third premix is ​​placed in a single screw machine, and the secondary premix is ​​melt-extruded through the single screw machine, and then cooled and granulated to obtain a modified polyphenylene sulfide material;

[0076] Among them, the temperature setting of the single screw machine is: first stage temperature 260-320℃, second stage temperature 265-325℃, third stage temperature 270-330℃, fourth stage temperature 275-335℃, fifth stage temperature 280-320℃.

[0077] Sample 1:

[0078] The modified polyphenylene sulfide material is prepared by the above method, and the modified polyphenylene sulfide material for air preheater includes a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide;

[0079] The modified gallium nitride and the modified silicon carbide are respectively gallium nitride and silicon nitride subjected to surface modification treatment using a silane coupling agent, the modified gallium nitride accounts for 3% of the mass of the high-crystallinity polyphenylene sulfide resin; the modified silicon carbide accounts for 4% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0080] For every 100 parts of the high crystallinity polyphenylene sulfide resin, 1 part of maleic anhydride-ethylene-octene copolymer, 1 part of polyether chain-bridged bis-imidazoline nitrone nitroxide, 10 parts of carbon fiber, 20 parts of polypropylene and 0.5 parts of high temperature antioxidant are added according to the mass fraction. After testing, the thermal conductivity of the prepared polyphenylene sulfide thermal conductive composite material is 6.944W / mK. The tensile strength is 89MPa.

[0081] Sample 2:

[0082] The modified polyphenylene sulfide material is prepared by the above method, wherein the modified gallium nitride accounts for 8% of the mass of the high-crystallinity polyphenylene sulfide resin; the modified silicon carbide accounts for 15% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0083] For every 100 parts of the high crystallinity polyphenylene sulfide resin, 10 parts of ethylene-vinyl acetate copolymer, 10 parts of linear nitrone, 20 parts of graphene fiber, 30 parts of polyetheretherketone and 1.5 parts of high temperature antioxidant are added according to the mass fraction. After testing, the thermal conductivity of the prepared polyphenylene sulfide thermal conductive composite material is 8.856W / mK. The tensile strength is 109MPa.

[0084] Sample 3:

[0085] The modified polyphenylene sulfide material is prepared by the above method, wherein the modified gallium nitride accounts for 4% of the mass of the high-crystallinity polyphenylene sulfide resin; the modified silicon carbide accounts for 8% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0086] For every 100 parts of the high crystallinity polyphenylene sulfide resin, 5 parts of maleic anhydride-ethylene-octene copolymer and ethylene-vinyl acetate copolymer, 4 parts of cyclic nitrone, 14 parts of carbon fiber and graphene fiber, 24 parts of polyetheretherketone and 1.2 parts of high temperature antioxidant are added according to the mass fraction. After testing, the thermal conductivity of the prepared polyphenylene sulfide thermal conductive composite material is 7.436W / mK. The tensile strength is 97MPa sample 4:

[0087] The modified polyphenylene sulfide material is prepared by the above method, wherein the modified gallium nitride accounts for 9% of the mass of the high-crystallinity polyphenylene sulfide resin; the modified silicon carbide accounts for 12% of the mass of the high-crystallinity polyphenylene sulfide resin;

[0088] For every 100 parts of the high crystallinity polyphenylene sulfide resin, 7 parts of ethylene-vinyl acetate copolymer, 8 parts of linear nitrone, 15 parts of graphene fiber, 27 parts of polyetheretherketone and 1.3 parts of high temperature antioxidant are added according to the mass fraction. After testing, the thermal conductivity of the prepared polyphenylene sulfide thermal conductive composite material is 7.877W / mK. The tensile strength is 97MPa.

[0089] Sample 5:

[0090] The modified polyphenylene sulfide material is prepared by the above method, except that modified gallium nitride and modified silicon carbide are not added;

[0091] For every 100 parts of the high crystallinity polyphenylene sulfide resin, 10 parts of ethylene-vinyl acetate copolymer, 10 parts of linear nitrone, 20 parts of graphene fiber, 30 parts of polyetheretherketone and 1.5 parts of high temperature antioxidant are added according to the mass fraction. After testing, the thermal conductivity of the prepared polyphenylene sulfide thermal conductive composite material is 3.952W / mK. The tensile strength is 92MPa.

[0092] Experimental example

[0093] 1. Corrosion resistance test

[0094] Purpose: To test the material's ability to resist chemical attack.

[0095] Method: Place the sample in a simulated cooling water environment for a period of time and then take it out for observation, or use an accelerated corrosion tester for testing. The results are shown in Table 1.

[0096] Table 1. Corrosion resistance results of the embodiments of the present invention

[0097]

[0098]

[0099] Corrosion resistance: All samples containing modified gallium nitride and modified silicon carbide (samples 1 to 4) showed no obvious signs of corrosion after long-term exposure to simulated cooling water, and the corrosion rate was extremely low. In contrast, the control sample 5 without these ingredients showed slight discoloration and a corrosion rate of 0.02mm / year.

[0100] 2. Thermal stability test

[0101] Purpose: To understand the stability of materials in high temperature environments.

[0102] Methods: The mass loss and phase change behavior of the samples during heating were studied by thermogravimetric analysis (TGA), as shown in Table 2.

[0103] Table 2. Thermal stability performance results of the embodiments of the present invention

[0104]

[0105] Thermal stability: The initial weight loss temperatures of all samples were higher than 375°C, indicating that they had good thermal stability. The samples containing modified ingredients (samples 1 to 4) showed better thermal stability, with lower maximum weight loss rates, and the thermogravimetric spectra showed a single peak and stable decomposition characteristics; while the control sample 5 showed a higher maximum weight loss rate and a double peak feature, which may mean that there is a multi-stage decomposition process.

[0106] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A modified polyphenylene sulfide material for air preheater, characterized in that: It includes a high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide; The modified gallium nitride and the modified silicon carbide are respectively gallium nitride and silicon nitride subjected to surface modification treatment using a silane coupling agent, wherein the modified gallium nitride accounts for 3-8% of the mass of the high-crystallinity polyphenylene sulfide resin; and the modified silicon carbide accounts for 4-15% of the mass of the high-crystallinity polyphenylene sulfide resin; For every 100 parts of the high crystallinity polyphenylene sulfide resin, the following are added according to the mass fractions: 1-10 parts of a compatibilizer, 1-10 parts of a stabilizer, 10-20 parts of toughening fibers, 20-30 parts of a high temperature crystalline thermoplastic material and 0.5-1.5 parts of a high temperature antioxidant.

2. The food grade silicon dioxide material according to claim 1, characterized in that The compatibilizer is one or both of maleic anhydride-ethylene-octene copolymer and ethylene-vinyl acetate copolymer.

3. The food grade silicon dioxide material according to claim 1, characterized in that: The toughening fiber is one or both of carbon fiber and graphene fiber.

4. The food grade silicon dioxide material according to claim 1, characterized in that The stabilizer is one or more of polyether chain-bridged bisimidazoline nitrone nitrogen oxides, linear nitrones, and cyclic nitrones; The high temperature crystalline thermoplastic material is one of polyetheretherketone and polypropylene.

5. A method for preparing the modified polyphenylene sulfide material for air preheater according to any one of claims 1 to 4, characterized in that: The steps include: Using a silane coupling agent to perform surface modification treatment on gallium nitride and silicon carbide to obtain modified gallium nitride and modified silicon carbide; Preparation of high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide; Preparation of modified polyphenylene sulfide materials.

6. The preparation method according to claim 5, characterized in that: The method of using a silane coupling agent to perform surface modification treatment on nano-gallium nitride and nano-silicon carbide to obtain modified gallium nitride and modified silicon carbide comprises: The nano-gallium nitride and nano-silicon carbide are prepared into a dispersion liquid, and after adding a dispersant, the dispersion liquid is stirred and ultrasonically dispersed at room temperature to obtain a gallium nitride dispersion liquid and a silicon carbide dispersion liquid respectively; Anhydrous ethanol is added to the gallium nitride dispersion and the silicon carbide dispersion, and aminopropyltriethoxysilane is added dropwise, and the temperature is raised to 80-100° C. The reaction is centrifuged and dried to obtain the modified gallium nitride and the modified silicon carbide.

7. The preparation method according to claim 5, characterized in that: The method for preparing the high-crystallinity polyphenylene sulfide resin doped with modified gallium nitride and modified silicon carbide comprises: Weigh the components according to the following weight ratio: 100 parts of linear polyphenylene sulfide resin, 1-10 parts of stabilizer, 0.5-1.5 parts of high temperature antioxidant and 1-10 parts of compatibilizer; Add the weighed linear polyphenylene sulfide resin, stabilizer, antioxidant and compatibilizer into a high-speed batching mixer and mix them evenly to obtain a first premix; Adding the modified gallium nitride and the modified silicon carbide to the first premix, and mixing them evenly to obtain a second premix; The second premix is ​​placed in a twin-screw machine, melt-extruded through the twin-screw machine, and then cooled, dried, and granulated to obtain a granular high-crystallinity polyphenylene sulfide resin.

8. The preparation method according to claim 7, characterized in that: The temperature of the twin-screw machine is set as follows: first stage temperature 240-260°C, second stage temperature 255-275°C, third stage temperature 260-275°C, fourth stage temperature 265-275°C, and fifth stage temperature 280-300°C.

9. The preparation method according to claim 5, characterized in that: The preparation of the modified polyphenylene sulfide material comprises: Add 100 parts of the high-crystallinity polyphenylene sulfide resin, 10-20 parts of toughening fibers, and 20-30 parts of high-temperature crystalline thermoplastic materials into a high-speed batching mixer, and mix them evenly to obtain a third premix; The third premix is ​​placed in a single screw machine, the secondary premix is ​​melt-extruded through the single screw machine, and then cooled and granulated to obtain the modified polyphenylene sulfide material; Among them, the temperature setting of the single screw machine is: first stage temperature 260-320℃, second stage temperature 265-325℃, third stage temperature 270-330℃, fourth stage temperature 275-335℃, fifth stage temperature 280-320℃.

10. A flat tube made of the modified polyphenylene sulfide material for air preheater according to claims 1-9.

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