Preparation method and application of multilayer polyphenylene sulfide composite film

Abstract

The present invention relates to the technical field of multilayer films, and discloses a preparation method and application of a multilayer polyphenylene sulfide composite film. The preparation method comprises the following steps: (1) premixing polyphenylene sulfide resin and silane coupling agent-modified boron nitride, and then mixing the premixed mixture with an antioxidant and a processing aid to obtain a mixture; (2) melt-extrude the mixture through a twin-screw extruder with a plurality of meshing blocks at staggered angles of 45 degrees, and then cast the mixture and irradiate cross-linking to obtain a PPS film; (3) alternately layer the PPS film and a carbon fiber-epoxy resin precured film, and then perform hot pressing to obtain a multilayer polyphenylene sulfide composite film. The present invention uses a silane coupling agent to modify the surface of the boron nitride, combines a dry premixing and melt shearing dispersion strategy, and then induces cross-linking of the PPS resin by irradiation, thereby improving the thermal conductivity and heat deformation temperature of the film, and ultimately obtaining a multilayer film material that can adapt to the harsh working conditions in the aerospace field or the automotive field.

Description

Technical Field

[0001] The present invention relates to the technical field of multilayer films, and in particular to a preparation method and application of a multilayer polyphenylene sulfide composite film. Background Art

[0002] Polyphenylene sulfide (PPS), a semi-crystalline specialty engineering plastic, has been widely used in electronic packaging, automotive components, and other fields due to its excellent chemical resistance, flame retardancy, and mechanical strength. However, in composite applications requiring stringent high-temperature resistance, such as aerospace and new energy vehicle batteries, the limitations of traditional PPS films are becoming increasingly apparent. The glass transition temperature (Tg) of pure PPS is approximately 90°C, with an upper temperature limit of 200°C for long-term use. When ambient temperatures exceed 180°C, the mobility of the PPS molecular segments increases significantly, leading to thermal shrinkage and stiffness loss in the film. Especially under cyclic thermal shock conditions, the film is prone to microcracks and ultimately failure. Although some studies have attempted to enhance heat resistance by adding glass or carbon fibers, such as publication number CN113045900A, which discloses a continuous carbon fiber-reinforced polyphenylene sulfide composite, the introduction of fibers leads to a sharp decrease in film flexibility and poor interfacial compatibility with composite matrices (such as carbon fiber / epoxy prepreg), limiting its application in interlaminar toughening of composites.

[0003] In existing technologies, hexagonal boron nitride (h-BN) is often used to improve the heat dissipation performance of PPS films due to its high thermal conductivity and insulation properties. However, when the BN addition exceeds 5 wt%, the mechanical properties deteriorate due to the following reasons: (1) Agglomeration effect: BN flakes form micron-sized agglomerates due to van der Waals forces, which become crack nucleation points under tensile stress, resulting in a decrease in impact strength; (2) Weak interface bonding: The interface adhesion between BN and PPS matrix is ​​low, which causes void defects during thermal cycling; (3) Melt fluidity deterioration: The rigid layer structure of BN hinders the slip of PPS molecular chains, resulting in a decrease in melt flow index (MFI) and extrusion fluctuations; (4) Uncontrolled thickness uniformity: In the traditional casting process, the lateral temperature difference of the melt in the die head reaches more than ±5°C, and the high viscosity melt produces shark skin phenomenon at the die lip (periodic ripples or rough textures formed on the surface of the product due to unstable melt flow during extrusion or injection molding of polymer materials, resembling shark skin, with a surface roughness Ra>1μm), which ultimately leads to uneven film thickness distribution. Summary of the Invention

[0004] To address the aforementioned technical issues, the present invention provides a method for preparing and applying a multilayer polyphenylene sulfide composite film. This method utilizes a silane coupling agent to chemically bond and modify the BN surface. This method, combined with a "dry premixing-melt shear" gradient dispersion strategy, achieves both high dissociation and directional alignment of the BN flakes. Irradiation then induces crosslinking of the PPS resin, simultaneously forming sulfur-sulfur crosslinks and BN thermal conductivity pathways, thereby improving the film's thermal conductivity and heat distortion temperature. The resulting PPS film is alternately laminated with a carbon fiber-epoxy resin precured film and then hot-pressed to form a multilayer film suitable for the demanding operating conditions of the aerospace and automotive industries.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a multilayer polyphenylene sulfide composite film, characterized in that it comprises the following steps:

[0007] (1) Premixing polyphenylene sulfide resin and silane coupling agent modified boron nitride at 60-90° C. and 2500-3500 rpm for 5-15 minutes, and then mixing the mixture with an antioxidant and a processing aid to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid is 76-91%: 8-20%: 0.5-1.5%: 0.5-2.5%;

[0008] (2) The mixture is melt-extruded through a twin-screw extruder with several meshing blocks at a staggered angle of 45°, and then cast and irradiated to obtain a PPS film;

[0009] (3) The PPS film and the carbon fiber-epoxy resin pre-cured film are alternately layered and then hot-pressed to obtain a multilayer polyphenylene sulfide composite film.

[0010] This invention addresses the problems of high boron nitride addition-modified with a silane coupling agent by adding boron nitride to the resin, which can lead to agglomeration and insufficient interfacial adhesion. Boron nitride (BN) is pretreated with a silane coupling agent, forming a grafted layer on the BN surface through chemical bonding (Si-O-B bonds), significantly improving its wettability with polyphenylene sulfide (PPS). BN and PPS are then dry-premixed at 60-90°C and high rotational speed, where shear forces are used to exfoliate the BN flakes, achieving initial dispersion and oriented alignment of the BN. Furthermore, a twin-screw extruder with intermeshing blocks staggered at 45° angles creates a high shear zone, applying localized, high-intensity longitudinal shear forces to further achieve high dissociation and oriented alignment of the BN flakes, significantly improving BN dispersibility in the PPS material. Consequently, this invention allows the addition of BN to the PPS resin to exceed 5 wt% without degrading mechanical properties. Furthermore, the highly oriented BN flakes form a continuous thermally conductive network, thereby improving the thermal conductivity of the film.

[0011] The film obtained by melt extrusion is then subjected to electron beam irradiation to induce sulfur-sulfur crosslinks between PPS molecules. This crosslinked structure can reduce the melt index and simultaneously increase the high-temperature heat distortion temperature. As a result, the compatibility of the PPS film produced by the present invention with the carbon fiber-epoxy resin precured film is significantly improved. The silane coupling agent reacts with the epoxy groups during the hot pressing process to form covalent bonds, thereby increasing the interlaminar shear strength. The carbon fiber, as the skeleton structure of the multilayer film, can provide tensile strength and rigidity, while the epoxy resin provides adhesion. Combined with the modification of the PPS film by the present invention, the overall structural stability of the multilayer film is further improved, while ensuring good thermal conductivity and mechanical strength.

[0012] Preferably, in step (1), the boron nitride modified with the silane coupling agent has a hexagonal crystal structure, a particle size of 0.1-2 μm, and a particle size distribution of: D50 of 0.5-1.2 μm, and D90 ≤ 1.8 μm.

[0013] Preferably, in step (1), in the silane coupling agent-modified boron nitride, the modification ratio of the silane coupling agent is 1-3% of the mass of the boron nitride, and the silane coupling agent is an aminosilane coupling agent, more preferably KH-550 or KH-560.

[0014] Preferably, in step (1), the preparation method of the silane coupling agent modified boron nitride comprises the following steps: adding the silane coupling agent to an ethanol-water mixed solvent to obtain a silane solution; drying the boron nitride powder, adding the dried boron nitride powder to the silane solution, ultrasonically dispersing the powder, and then reacting the powder in a water bath; after the reaction is completed, centrifuging, washing, and drying the powder.

[0015] Preferably, the water bath reaction is carried out by stirring in a water bath at 70-80° C. for 3-4 hours.

[0016] Preferably, in step (1), the processing aid is at least one of calcium stearate, paraffin wax and polytetrafluoroethylene powder.

[0017] Preferably, the antioxidant includes a primary antioxidant and a secondary antioxidant; the primary antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1010) and 2,6-di-tert-butyl-p-cresol (BHT, antioxidant 264); the secondary antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168) and distearyl pentaerythritol diphosphite (antioxidant 626).

[0018] Preferably, in step (2), the temperature of the twin-screw extruder is set to: zone 1 300-310°C; zone 2 315-325°C; zone 3 330-340°C; and die head 325-335°C.

[0019] Preferably, in step (2), the twin screw has 2-4 meshing blocks with a staggered angle of 45°.

[0020] Preferably, in step (2), the die head used in the twin-screw extruder is a T-type die head with zoned temperature control. The T-type die head adopts a "wedge-shaped cavity + fishtail diversion" structure, is divided into 6 zones in the horizontal direction, and has a three-layer structure in the vertical direction. The temperature of the central zone is set at 325-335°C, and the edge zone is set according to the temperature of the central zone + 5°C.

[0021] The "wedge-shaped cavity + fishtail diversion" structure is used to optimize the melt flow field (shear rate variance <10%). Combined with online β-ray thickness measurement and PID closed-loop control, the film thickness fluctuation coefficient (CV value <1.5%) and surface roughness (Ra <0.2 μm) can be controlled, thereby improving processing efficiency and reducing energy consumption.

[0022] Preferably, in step (2), the tape casting is tape casting and stretching on a cooling roller, the temperature of the first cooling roller is 120-130°C, the temperature of the second cooling roller is 70-80°C, and the pulling speed is 3-5 m / min.

[0023] The product adopts a two-stage gradient cooling system, which passes through the first and second cooling rollers with temperature gradient settings. The first cooling roller is set at a higher temperature to extend the melt setting time and reduce internal stress. The second cooling roller is set at a lower temperature to quickly solidify the surface structure and inhibit crystallization coarsening.

[0024] Preferably, in step (2), the irradiation dose is 5-20 kGy, and the cross-linking degree of the PPS film after irradiation is controlled at 8-18%.

[0025] Excessive radiation crosslinking (such as more than 18%) will have the following negative effects on the performance of PPS film: 1. Decreased BN orientation and dispersion: Excessive crosslinking will limit the mobility of PPS molecular chains, affect the directional arrangement of BN sheets in the melt, and reduce the continuity of the thermal conductivity network; 2. Increased film brittleness: Excessive crosslinking will lead to increased material rigidity and decreased flexibility, and microcracks will easily occur under hot pressing or mechanical loads; 3. Weakened interlayer bonding: In composite material applications, excessive crosslinking will reduce the active groups on the film surface, reduce the chemical bonding ability with epoxy resin, and affect the interlayer shear strength; 4. Deterioration of processing performance: Excessive crosslinking will reduce melt fluidity, resulting in difficulties in extrusion and cast molding, and may cause shark skin phenomenon or uneven thickness; 5. Reduced thermal cycling stability: Excessively high crosslinking structure may accelerate fatigue failure due to stress concentration during thermal cycling, affecting the long-term reliability of composite materials in aerospace environments.

[0026] Preferably, in step (3), the method for preparing the carbon fiber-epoxy resin precured film comprises the following steps: coating or impregnating the carbon fiber with epoxy resin prepreg, and precuring the carbon fiber at 60-120° C. for 20-40 minutes.

[0027] Pre-curing only partially cross-links the resin, retaining certain active groups (such as epoxy groups) to facilitate subsequent reaction with the silane amino groups in the PPS film, and also facilitates laying and enhances interlayer bonding.

[0028] Preferably, the carbon fiber is a carbon fiber fabric or a carbon fiber unidirectional tape; the ratio of the carbon fiber to the epoxy resin prepreg is 60-70%:30-40% by mass; the epoxy resin prepreg includes an epoxy resin, a curing agent and an accelerator, and the mass ratio of the epoxy equivalent weight (EEW) of the epoxy resin, the curing agent and the accelerator is 100:80-100:0.5-2.

[0029] Preferably, the curing agent includes one or more of an amine curing agent (such as DDS, DDM), an acid anhydride curing agent (such as MTHPA) and a phenolic resin curing agent; the accelerator includes one or more of an imidazole accelerator (such as 2-methylimidazole) and a tertiary amine accelerator (such as BDMA).

[0030] Preferably, in step (3), the total number of layers of the alternating layers is 8-16 layers, the total thickness is 1.5-3 mm, the adjacent layers are different films, the thickness of the PPS film is 50-150 μm, and the thickness of the carbon fiber-epoxy resin pre-cured film is 150-200 μm.

[0031] Preferably, in step (3), the temperature of the hot pressing molding is 180-220°C, the pressure is 0.5-1.5 MPa, and the time is 30-60 min.

[0032] In a second aspect, the present invention provides an application of the multilayer polyphenylene sulfide composite film prepared by the above preparation method in the aerospace field or the automotive field.

[0033] The multilayer polyphenylene sulfide composite film of the present invention can be applied to the aerospace field or the automotive field, such as aerospace high-temperature composite materials, automotive lightweight composite materials, etc.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The BN surface is modified by silane coupling agent and combined with dry premixing to break through the upper limit of BN addition in traditional processes, while achieving high dissociation and directional arrangement of BN sheets, significantly improving thermal conductivity;

[0036] (2) Irradiation induces PPS cross-linking, improving melt fluidity through controllable cross-linking degree, while forming sulfur-sulfur cross-linking bonds and BN continuous networks to construct dual-mechanism heat conduction channels, thereby increasing high-temperature heat deformation temperature and taking into account high heat resistance and creep resistance;

[0037] (3) Silane amino groups participate in epoxy curing to form covalent bonds (CN bonds), which improves the interlaminar shear strength and prevents delamination after thermal cycling, making it suitable for harsh working conditions such as aerospace composite materials or automotive lightweight composite materials. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] The method for preparing the multilayer polyphenylene sulfide composite film of the present invention comprises the following steps:

[0040] (1) Adding a silane coupling agent (KH-550 or KH-560) to an ethanol-water mixed solvent to obtain a silane solution; drying boron nitride powder (particle size 0.1-2 μm, D50 0.5-1.2 μm, D90 ≤ 1.8 μm), adding it to the silane solution, ultrasonically dispersing it, and then stirring it in a 70-80°C water bath for 3-4 hours. After the reaction is completed, centrifuging, washing, and drying it to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent is 1-3% of the mass of the boron nitride.

[0041] (2) premixing polyphenylene sulfide resin and silane coupling agent modified boron nitride at 60-90° C. and 2500-3500 rpm for 5-15 minutes, and then mixing the mixture with an antioxidant and a processing aid to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid is 76-91%: 8-20%: 0.5-1.5%: 0.5-2.5%;

[0042] (3) The mixture is melt-extruded through a twin-screw extruder, the twin-screw has several meshing blocks with a staggered angle of 45 degrees, and the temperature segment of the twin-screw extruder is set to: 300-310℃ for zone 1; 315-325℃ for zone 2; 330-340℃ for zone 3; 325-335℃ for T-die; then cast and stretch formed on a cooling roller, the temperature of the first cooling roller is 120-130℃, the temperature of the second cooling roller is 70-80℃, and the pulling speed is 3-5 m / min; then irradiation cross-linking is carried out, the irradiation dose is 5-20 kGy, and the cross-linking degree of the film after irradiation is controlled at 8-18%, obtaining a PPS film with a thickness of 50-150 μm;

[0043] (4) coating or impregnating carbon fiber (carbon fiber fabric or carbon fiber unidirectional tape) with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 60-70%:30-40%, and then precuring at 60-120°C for 20-40 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 150-200 μm;

[0044] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film are alternately layered, with a total number of layers of 8-16 layers, and the actual total thickness tested is 1.5-3 mm; then hot pressing is performed at a temperature of 180-220 ° C and a pressure of 0.5-1.5 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0045] In a specific embodiment of the present invention, a method for preparing silane coupling agent-modified boron nitride includes the following steps: adding a silane coupling agent (KH-550) to an ethanol-water mixed solvent (the volume ratio of ethanol to water is 95:5) to obtain a silane solution; drying boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) in vacuum at 100° C. for 2 hours to remove surface adsorbed water, and then adding the powder to the silane solution. The powder is ultrasonically dispersed at a power of 300 W for 20 minutes, and then stirred in a 70° C. water bath for 4 hours to hydrolyze the silane (Si-OR→Si-OH) and condense with the -OH groups on the BN surface (Si-OB); after the reaction is completed, the powder is centrifuged at 8000 rpm for 10 minutes, washed with ethanol three times to remove free silane coupling agent, and dried in vacuum at 80° C. for 6 hours to obtain silane coupling agent-modified boron nitride.

[0046] In a specific embodiment of the present invention, the processing aid is at least one of calcium stearate, paraffin wax and polytetrafluoroethylene powder.

[0047] In a specific embodiment of the present invention, the antioxidant includes a primary antioxidant and a secondary antioxidant. The primary antioxidant includes at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Antioxidant 1010) and 2,6-di-tert-butyl-p-cresol (BHT, Antioxidant 264). The secondary antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite (Antioxidant 168) and distearyl pentaerythritol diphosphite (Antioxidant 626).

[0048] In a specific embodiment of the present invention, the T-die employs a "wedge-shaped cavity + fishtail diversion" structure and employs zoned temperature control. The die is divided into six zones horizontally and a three-layer structure vertically. The center zone temperature is set at 325-335°C, while the edge zones are set at the same temperature +5°C. Furthermore, combining online β-ray thickness measurement with PID closed-loop control, the film thickness fluctuation coefficient (CV value <1.5%) and surface roughness (Ra <0.2 μm) can be controlled.

[0049] In a specific embodiment of the present invention, the epoxy resin prepreg includes epoxy resin, a curing agent and an accelerator, the mass ratio of the epoxy equivalent weight (EEW) of the epoxy resin, the curing agent and the accelerator is 100:80:0.5-2, the curing agent is an amine curing agent (DDS), and the accelerator is an imidazole accelerator (2-methylimidazole).

[0050] Example 1

[0051] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0052] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0053] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were each equipped with a 45° staggered meshing block. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0054] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0055] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0056] Example 2

[0057] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0058] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 80℃ and 3000 rpm for 15 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 83.5%:15%:0.5%:1%;

[0059] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. A 45° staggered meshing block was provided in each of the second and third zones of the twin-screw. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0060] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0061] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0062] Example 3

[0063] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0064] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 90℃ and 3500 rpm for 15 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 77%:20%:1%:2%;

[0065] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were each equipped with a 45° staggered meshing block. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0066] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0067] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0068] Example 4

[0069] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 3% of the mass of the boron nitride.

[0070] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0071] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were each equipped with a 45° staggered meshing block. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0072] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 60%:40%, and then precured at 120°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 160±1μm;

[0073] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0074] Example 5

[0075] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0076] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0077] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were each equipped with a 45° staggered meshing block. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 12 kGy. The cross-linking degree of the film after irradiation was controlled at 13%, and a PPS film with a thickness of 120±1 μm was obtained.

[0078] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 190±1μm;

[0079] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 16 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the rotation speed of premixing the polyphenylene sulfide resin and the silane coupling agent-modified boron nitride is too low.

[0082] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0083] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 1000 rpm for 30 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0084] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were each equipped with a 45° staggered meshing block. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0085] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0086] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0087] Comparative Example 2

[0088] The difference from Example 1 is that the twin screws have meshing blocks with a staggered angle of 30°.

[0089] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0090] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0091] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. Zones 2 and 3 of the twin-screw were equipped with two meshing blocks with a staggered angle of 30°. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0092] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0093] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0094] Comparative Example 3

[0095] The difference from Example 1 is that the boron nitride is not modified with a silane coupling agent.

[0096] (1) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and boron nitride powder (particle size of 0.1-2μm, D50 of 1μm, D90 of 1.5μm) were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, boron nitride, antioxidant and processing aid is 88.5%:10%:0.5%:1%;

[0097] (2) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. A 45° staggered meshing block was provided in each of the second and third zones of the twin-screw. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 10 kGy. The cross-linking degree of the film after irradiation was controlled at 11%, and a PPS film with a thickness of 100±1 μm was obtained.

[0098] (3) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0099] (4) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0100] Comparative Example 4

[0101] The difference from Example 1 is that after electron beam irradiation, the cross-linking degree of the PPS film is too large.

[0102] (1) Boron nitride powder (particle size 0.1-2 μm, D50 1 μm, D90 1.5 μm) was modified with a silane coupling agent (KH-550) to obtain silane coupling agent-modified boron nitride. The modification ratio of the silane coupling agent was 1.5% of the mass of the boron nitride.

[0103] (2) Polyphenylene sulfide resin (melt index 120 g / 10min, T m =285℃) and silane coupling agent modified boron nitride were premixed at 70℃ and 3000 rpm for 10 min, and then mixed with antioxidants (antioxidant 1010 and antioxidant 168) and a processing aid (calcium stearate) to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant and processing aid was 88.5%:10%:0.5%:1%;

[0104] (3) The mixture was melt-extruded through a twin-screw extruder. The temperature of the twin-screw extruder was set to: 300°C in zone 1; 320°C in zone 2; 335°C in zone 3; and 335°C in the T-die. A 45° staggered meshing block was provided in each of the second and third zones of the twin-screw. The mixture was then cast and stretched on a cooling roller. The temperature of the first cooling roller was 120°C, the temperature of the second cooling roller was 70°C, and the pulling speed was 4 m / min. The mixture was then cross-linked by electron beam irradiation. The irradiation dose was 20 kGy. The cross-linking degree of the film after irradiation was controlled at 22%, and a PPS film with a thickness of 100±1 μm was obtained.

[0105] (4) The carbon fiber (carbon fiber unidirectional tape) was impregnated with epoxy resin prepreg, with the ratio of carbon fiber to epoxy resin prepreg being 70%:30%, and then precured at 100°C for 30 minutes to obtain a carbon fiber-epoxy resin precured film with a thickness of 165±1μm;

[0106] (5) The PPS film and the carbon fiber-epoxy resin pre-cured film were alternately layered, with a total of 14 layers; then hot pressing was performed at a temperature of 190°C and a pressure of 1.1 MPa to obtain a multilayer polyphenylene sulfide composite film.

[0107] Performance testing:

[0108] 1. Tensile strength (MPa)

[0109] Test method: Use a universal material testing machine to stretch a dumbbell-shaped specimen at a rate of 5 mm / min. Take the average value of 5 specimens and retain the data to one decimal place.

[0110] 2. Orientation degree (XRD half-peak width, °)

[0111] Test method: XRD patterns were measured by X-ray diffractometer, and the diffraction peak intensity of the (002) plane was analyzed. The full width at half maximum (FWHM) was calculated by Jade software fitting, with an angle accuracy of ±0.1°.

[0112] 3. Thermal conductivity (W / m•K)

[0113] Test method: Laser flash thermal conductivity meter is used to test the thermal conductivity in the thickness direction. The test temperature is 25±0.5℃.

[0114] 4. Heat deformation temperature (℃)

[0115] Test method: load 1.82 MPa, heating rate 2°C / min, sample size 127×13×3 mm, record temperature when deformation is 0.25 mm.

[0116] 5. Interlaminar shear strength (MPa)

[0117] Test method: Short beam shear test was conducted according to ASTM D2344 / ISO 14130, with a span-to-thickness ratio of 5:1, a loading rate of 1 mm / min, and specimen dimensions of 20 × 10 × 2 mm. The average value of five tests was taken.

[0118] Table 1 Performance test results of multilayer polyphenylene sulfide composite membrane

[0119]

[0120] As shown in Table 1, the multilayer polyphenylene sulfide composite films produced in Examples 1-5 exhibit high thermal conductivity, high heat distortion temperature, high tensile strength, and high interlayer bonding strength. The BN therein also exhibits a high degree of orientation. Because the composite films of the present invention are multilayered, the dispersion and orientation of the BN, as well as reactive groups such as silanylamino groups, within the PPS film significantly influence the performance of the multilayer film.

[0121] The BN orientation in Comparative Examples 1-2 is relatively low, indicating that high-speed premixing is beneficial for utilizing shear force to peel off the BN sheets, initially achieving BN dispersion and directional arrangement. The 45° staggered angle twin-screw is more conducive to the directional arrangement of the boron nitride sheets along the extrusion direction, enhancing dispersibility and forming a continuous thermal conductive network. The 30° staggered angle has a weaker effect on orientation control, possibly due to insufficient shear causing BN agglomeration. Furthermore, the synergy between the two can further achieve high dissociation and directional arrangement of the BN sheets, resulting in a highly oriented BN continuous thermal conductive network. Since the thermal conductivity of the multilayer polyphenylene sulfide composite film is an average thermal conductivity, if the BN dispersion and orientation are low, BN aggregation in some areas will occur, and the silane coupling agent is not easy to react with the polymer matrix, which will affect the thermal conductivity and interlayer bonding of the composite film.

[0122] In Comparative Example 3, BN was not modified with a silane coupling agent. Due to the cross-wetting between BN and PPS, a high degree of orientation could not be obtained even after high-speed premixing and melt shearing, thereby affecting the thermal conductivity and mechanical strength.

[0123] In Comparative Example 4, excessive cross-linking of the PPS film will lead to decreased BN orientation and dispersion, increased film brittleness, and weakened interlayer bonding, thereby affecting thermal conductivity and mechanical strength.

[0124] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a multilayer polyphenylene sulfide composite film, characterized in that: The steps include: (1) Add KH-550 or KH-560 to an ethanol-water mixed solvent to obtain a silane solution; the boron nitride is a hexagonal crystal with a particle size of 0.1-2 μm. After drying the boron nitride powder, add it to the silane solution, ultrasonically disperse it, and then react it in a water bath. After centrifugation, washing, and drying, a silane coupling agent-modified boron nitride is obtained; Premixing polyphenylene sulfide resin and silane coupling agent modified boron nitride at 60-90° C. and 2500-3500 rpm for 5-15 minutes, and then mixing the mixture with an antioxidant and a processing aid to obtain a mixture; wherein, by mass percentage, the ratio of polyphenylene sulfide resin, silane coupling agent modified boron nitride, antioxidant, and processing aid is 76-91%: 8-20%: 0.5-1.5%: 0.5-2.5%; (2) The mixture is melt-extruded through a twin-screw extruder with a plurality of meshing blocks at a staggered angle of 45°. The temperature of the twin-screw extruder is set to: 300-310°C in zone 1; 315-325°C in zone 2; 330-340°C in zone 3; and 325-335°C in the die head. The mixture is then cast and irradiated to obtain a PPS film. The crosslinking degree of the PPS film after irradiation is controlled to be 8-18%. (3) The PPS film and the carbon fiber-epoxy resin pre-cured film are alternately layered and then hot-pressed to obtain a multilayer polyphenylene sulfide composite film.

2. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein: In step (1), in the boron nitride modified with the silane coupling agent, the modification ratio of the silane coupling agent is 1-3% of the mass of the boron nitride.

3. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein: In step (2), the die head used by the twin-screw extruder is a T-die head.

4. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein In step (2), the tape casting is tape casting and stretching on a cooling roller, the temperature of the first cooling roller is 120-130°C, the temperature of the second cooling roller is 70-80°C, and the pulling speed is 3-5 m / min.

5. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein: In step (2), the irradiation dose is 5-20 kGy.

6. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein: In step (3), the method for preparing the carbon fiber-epoxy resin precured film includes the following steps: coating or impregnating the carbon fiber with epoxy resin prepreg, and precuring the carbon fiber at 60-120° C. for 20-40 minutes.

7. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, wherein: In step (3), the total number of layers of the alternating layers is 8-16 layers, the total thickness is 1.5-3 mm, the adjacent layers are different films, the thickness of the PPS film is 50-150 μm, and the thickness of the carbon fiber-epoxy resin pre-cured film is 150-200 μm.

8. The method for preparing a multilayer polyphenylene sulfide composite film according to claim 1, 6 or 7, characterized in that: In step (3), the temperature of the hot pressing molding is 180-220°C, the pressure is 0.5-1.5 MPa, and the time is 30-60 min.

9. Use of the multilayer polyphenylene sulfide composite film prepared by the preparation method according to any one of claims 1 to 8 in the aerospace field or the automotive field.

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