Large-scale preparation method of PPS-based composite material with low expansion and high dimensional stability

Abstract

The invention belongs to the technical field of polymer composite materials, and discloses a large-scale preparation method of a PPS-based composite material with low expansion and high dimensional stability. According to the method, a multi-scale synergistic enhancement system of graphene and nano silicon dioxide is constructed, a maleic anhydride grafted PPS compatilizer is introduced into melt blending, and interface chemical anchoring is achieved through amino-maleic anhydride-epoxy ternary reaction. The filler is premixed according to the mass ratio of 1: 1 after being subjected to surface functionalization, the total content is 15-30 wt%, and the composite material is obtained through twin-screw reactive extrusion and injection molding. The invention provides the large-scale preparation method of the low-expansion high-dimensional-stability PPS-based composite material which is reasonable in structural design, high in process controllability, excellent in performance index and suitable for industrial production, and the problem that thermal expansion suppression and interface strengthening are difficult to consider at the same time in the prior art is solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, and relates to a method for the large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials. Background Technology

[0002] PPS, a high-performance thermoplastic engineering plastic, has been widely used in high-end industrial fields with stringent requirements for comprehensive material performance, such as electronics, automotive manufacturing, and aerospace, due to its excellent high-temperature resistance, chemical stability, flame retardancy, and electrical insulation properties. Especially in the manufacture of precision structural components and functional parts, PPS-based composite materials, with their advantages of strong designability and good processing adaptability, have become an important alternative to traditional metals or ordinary engineering plastics.

[0003] PPS resin exhibits significant thermal expansion above its glass transition temperature, with a linear expansion coefficient typically reaching 30-50 ppm / K, far exceeding that of metal or ceramic structural materials. In applications sensitive to micron-level dimensional accuracy, such as electronic packaging, connectors, and sensor brackets, this thermal expansion can easily lead to assembly stress, interface debonding, and even functional failure.

[0004] Existing technologies mostly employ a single inorganic filler (such as glass fiber, talc, or mica) for modification, using rigid particles to restrict polymer chain segment movement and reduce overall expansion. This strategy improves dimensional stability to some extent and simultaneously enhances mechanical strength, thus achieving phased success in early industrial applications.

[0005] A single filler system cannot simultaneously meet the multiple requirements of suppressing thermal expansion, interfacial compatibility, and processing flowability. For example, while a high proportion of glass fiber can effectively reduce the coefficient of linear expansion, it can easily lead to increased anisotropic expansion of the material, inducing warping deformation in injection molded parts with complex geometries. On the other hand, nanoscale fillers such as nano-silica, although possessing high specific surface area and potential expansion suppression capabilities, have weak interfacial bonding between their surface polarity and non-polar PPS matrix, which easily forms agglomerates. This not only weakens mechanical properties but may also amplify dimensional fluctuations due to localized stress concentration.

[0006] If only two-dimensional nanomaterials such as graphene are used for modification, although their ultra-high modulus and low intrinsic expansion characteristics can be used to control thermal expansion behavior, their layered structure is prone to orientation stacking during the melting process, resulting in uneven dispersion. Furthermore, they lack effective chemical anchoring with the PPS matrix, limiting the efficiency of interfacial stress transfer and making it difficult to improve dimensional stability on a macroscopic scale. Summary of the Invention

[0007] To achieve the aforementioned objectives, this invention provides a method for the large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials. This method constructs a multi-scale synergistic reinforcement system of graphene and nano-silica, and introduces an interfacial chemical anchoring mechanism during melt blending. This effectively solves the mismatch between thermal expansion suppression efficiency and interfacial synergistic reinforcement mechanism in existing technologies. Thus, while ensuring good processing flowability, it significantly reduces the coefficient of linear expansion, improves dimensional stability and mechanical property consistency, meeting the stringent requirements for long-term reliability in high-precision applications such as electronics, electrical appliances, and automotive parts.

[0008] The method for large-scale preparation of the low-expansion, high-dimensionally stable PPS-based composite material of the present invention includes the following steps: First, PPS resin particles are vacuum dried at 120°C for 8 hours to reduce their moisture content to below 0.05%; then, surface-functionalized modified graphene and nano-silica coated with silane coupling agent are mixed at a mass ratio of (3:7)-(7:3) to form a multi-scale filler premix; next, the premix and dried PPS resin are added to a high-speed mixer at a total filler content of 15-30 wt%, and mixed at 1500 rpm and 60°C for 10 minutes to obtain a uniform dry mix; then, the premix and dried PPS resin are mixed at a total filler content of 15-30 wt% to obtain a uniform dry mix; The dry mixture is fed into a twin-screw extruder and subjected to melt blending and reactive extrusion under the following process conditions: a set temperature range of 280-320℃, a screw speed of 300 rpm, and a length-to-diameter ratio of 40:1. The twin-screw extruder has side feed ports in zones 5 to 8 for injecting 0.5-2.0 wt% maleic anhydride-grafted polyphenylene sulfide compatibilizer. The extrudate is water-cooled, stretched, and pelletized to obtain composite material masterbatch. Finally, the masterbatch is dried at 120℃ for 4 hours and then injection molded to prepare standard test specimens or structural parts. The injection temperature is 300-330℃, the die temperature is 140-160℃, and the holding time is 20-40 seconds.

[0009] The modified graphene was prepared as follows: Original graphene powder was dispersed in anhydrous ethanol at a concentration of 2 mg / mL and ultrasonically treated for 30 min at an ultrasonic power of 300 W and a frequency of 40 kHz; then, 5% (by weight of graphene) of 3-aminopropyltriethoxysilane was added, and the mixture was stirred in an oil bath at 60 °C for 6 h; after the reaction, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 80 °C for 12 h to obtain modified graphene with surface grafted aminosilane. This modified graphene has fewer than 5 layers and a specific surface area of ​​400-600 m². 2 / g, with an average tablet diameter of 1-3μm.

[0010] The nano-silica is spherical amorphous silica particles with a primary particle size of 20-50 nm and a specific surface area of ​​150-250 m².2 / g; Before use, mix it with γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:3 and stir at 100°C for 2 hours to allow the silane coupling agent to form a covalent coating layer on its surface, thereby obtaining surface epoxy-functionalized nano-silica.

[0011] In a preferred embodiment of the present invention, the maleic anhydride-grafted polyphenylene sulfide compatibilizer has a grafting rate of 0.8%-1.5% and a weight-average molecular weight of 40,000-60,000 g / mol. During melt blending, the maleic anhydride groups of this compatibilizer can undergo amidation reactions with the amino groups on the surface of modified graphene, while its main chain structure has high compatibility with the PPS matrix, thereby constructing a chemical bonding bridge at the graphene-PPS interface. On the other hand, the polar groups on its molecular chain can also undergo ring-opening addition reactions with the epoxy groups on the surface of nano-silica to form a three-dimensional cross-linked network structure, realizing spatial interlocking and stress synergistic transfer of multi-scale fillers in the PPS matrix.

[0012] The twin-screw extruder features the following screw configuration: Zones 1 to 4 are the conveying section, employing right-hand threaded elements; Zones 5 to 7 are the melt mixing section, equipped with kneading discs with a staggered angle of 45° and a thickness of 10 mm; Zones 8 to 10 are the homogenization section, employing left-hand threaded elements to establish back pressure; and Zone 11 is the metering section, employing shallow-groove threaded elements to stabilize output. This screw configuration ensures that the filler undergoes sufficient shear dispersion and distribution mixing in the melt, while avoiding graphene sheet breakage or secondary agglomeration of nano-silica due to excessive shearing.

[0013] In another preferred embodiment of the present invention, the mass ratio of modified graphene to nano-silica in the multi-scale filler premix is ​​1:1. At this ratio, the two-dimensional sheet structure of graphene effectively blocks the thermal movement of polymer chain segments in the planar direction, while the spherical particles of nano-silica fill the gaps between graphene sheets and the amorphous regions of PPS, restricting the expansion of chain segments in the vertical direction. The two work synergistically to form an isotropic thermal expansion suppression effect.

[0014] The PPS-based composite material prepared by the method of this invention has the following microstructural characteristics: modified graphene is uniformly dispersed in the PPS matrix in the form of monolayers or few layers, without obvious stacking or wrinkles; nano-silica particles are attached to the edges and surface of the graphene sheets and partially embedded in the amorphous phase of PPS, forming a graphene-silica-PPS three-phase interface region; transmission electron microscopy reveals a continuous transition layer in this interface region with a thickness of approximately 5-10 nm, confirming the existence of chemical bonding. This microstructure effectively eliminates the local stress concentration caused by interfacial slippage or debonding in traditional composite systems, thus macroscopically exhibiting a simultaneous improvement in high dimensional stability and mechanical properties.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. Graphene and nano-silica produce a positive synergistic effect in inhibiting thermal expansion, significantly reducing the coefficient of linear expansion and eliminating anisotropy; 2. Through the amino-maleic anhydride-epoxy ternary reaction system, multiple chemical bonds are constructed between the filler and the matrix, which greatly improves the interfacial bonding strength, effectively transfers load and inhibits the initiation of microcracks; 3. Optimized screw configuration and processing parameters ensure that the filler is uniformly dispersed in the melt, avoids agglomeration defects, and ensures the uniformity of the microstructure of the product; 4. The resulting composite material has high rigidity, high heat resistance and excellent humid heat stability, and can be directly used to manufacture key components such as high-precision electronic connector housings, vehicle sensor brackets and micro motor end caps, meeting the integrated requirements of high-end manufacturing fields for the comprehensive performance of materials. 5. A method for the large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials with reasonable structural design, strong process controllability, excellent performance indicators and suitability for industrial production is provided. This method fundamentally solves the technical bottleneck of the difficulty in simultaneously suppressing thermal expansion and strengthening the interface in the existing technology, and provides a reliable technical path for the in-depth application of high-performance engineering plastics in the field of precision structural parts. Detailed Implementation

[0016] This invention provides a method for the large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials. The core of this method lies in constructing a multi-scale synergistic reinforcement system of graphene and nano-silica, and introducing an interfacial chemical anchoring mechanism during melt blending. This effectively solves the mismatch between thermal expansion suppression efficiency and interfacial synergistic reinforcement mechanism in existing technologies. This method significantly reduces the coefficient of linear expansion, improves dimensional stability and mechanical property consistency while ensuring good processing flowability, meeting the stringent requirements for long-term reliability in high-precision applications such as electronics, electrical appliances, and automotive parts.

[0017] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0018] Example 1: Modified graphene: nano-silica = 1:1 (total filler content 25wt%); maleic anhydride grafted PPS compatibilizer 1.2wt%; twin-screw extrusion temperature 300℃; injection molding temperature 315℃, mold temperature 150℃; Preparation process: PPS resin drying → multi-scale filler premixing → dry mix preparation → twin-screw melt blending (side-feed compatibilizer) → extrusion pelletizing → masterbatch drying → injection molding.

[0019] Example 2: Total filler content 15wt% (modified graphene: nano silica = 1:1), other formulations and processes are the same as in Example 1; Preparation process: Same as in Example 1.

[0020] Example 3: Total filler content 30wt% (modified graphene: nano silica = 1:1), other formulations and processes are the same as in Example 1; Preparation process: Same as in Example 1.

[0021] Example 4: Modified graphene: nano-silica = 3:7 (total content 25wt%), the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1.

[0022] Example 5: Modified graphene: nano-silica = 7:3 (total content 25wt%), the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1.

[0023] Example 6: Maleic anhydride grafted with PPS compatibilizer 0.5wt%, the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1.

[0024] Example 7: Maleic anhydride grafted with PPS compatibilizer 2.0 wt%, the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1.

[0025] Example 8: Injection mold temperature 140℃, other formulations and processes are the same as in Example 1; Preparation process: Same as in Example 1.

[0026] Comparative Example 1: Unmodified graphene, only nano-silica (total content 25wt%); the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1 (unmodified graphene premixing step).

[0027] Comparative Example 2: No maleic anhydride-grafted PPS compatibilizer; the rest of the formulation and process are the same as in Example 1; Preparation process: Same as in Example 1 (without the side-feed compatibilizer step).

[0028] Test method: Thermal expansion and dimensional testing: The coefficient of linear expansion between 23℃ and 150℃ was determined using a thermomechanical analyzer; the difference in expansion in the X and Y directions was detected; and the dimensional change rate was determined after 1000 hours of damp heat aging at 85℃ / 85%RH.

[0029] Mechanical property testing: tensile strength and flexural modulus are determined by a universal testing machine; notched impact strength is determined by an impact testing machine.

[0030] Microstructure testing: Observe the uniformity of filler dispersion; verify the interfacial transition layer and chemical bonding.

[0031] The test data comparisons are shown in Table 1 and Table 2.

[0032]

[0033]

[0034] Examples 1-8 have a linear expansion coefficient ≤12.5ppm / K and a size change rate ≤0.04%, which are far superior to the comparative examples. Comparative example 1 lacks graphene synergy, resulting in insufficient thermal expansion suppression, while comparative example 2 lacks compatibilizer, leading to weak interfacial bonding. This demonstrates that the core process is the key to low expansion and high stability.

[0035] The total filler content increased (Examples 2→1→3), the coefficient of linear expansion decreased, and the mechanical properties improved; the proportion of modified graphene increased (Examples 4→1→5), and the tensile strength and flexural modulus were optimized; the amount of compatibilizer increased (Examples 6→1→7), and the dimensional stability and interface consistency were enhanced.

[0036] The embodiments are compatible with existing twin-screw extrusion and injection molding production lines without additional modifications; the products exhibit low anisotropy and excellent damp heat stability, meeting the requirements of high-precision electronic and automotive components; and the performance fluctuations between batches are small, making them suitable for large-scale production.

[0037] Compared to a single filler system (Comparative Example 1), the linear expansion coefficient of the example was reduced by 55%, and the tensile strength was increased by 21%; compared to a system without compatibilizer (Comparative Example 2), the dimensional stability was improved by 57%, solving the industry problem of high thermal expansion and large dimensional fluctuation of traditional PPS composite materials.

[0038] The process described in this invention achieves low expansion, high dimensional stability, and excellent mechanical properties through multi-scale filler synergy and interfacial chemical anchoring. Different parameter combinations can achieve this synergy, making it suitable for the mass production of high-end precision structural components.

[0039] The above are merely preferred embodiments of the present invention and are 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 within the protection scope of the present invention.

Claims

1. A method for the large-scale preparation of a low-expansion, high-dimensionally stable PPS-based composite material, characterized in that, Includes the following steps: PPS resin particles were vacuum dried at 120℃ for 8 hours to reduce their moisture content to below 0.05%. Modified graphene that has undergone surface functionalization with 3-aminopropyltriethoxysilane is mixed with nano-silica coated with γ-glycidoxypropyltrimethoxysilane at a mass ratio of (3:7)-(7:3) to form a multi-scale filler premix. The premix and dried PPS resin are added to a high-speed mixer at a total filler content of 15-30 wt% and mixed to obtain a uniform dry mix. The dry mixture is fed into a twin-screw extruder through the main feed port, and 0.5-2.0 wt% of maleic anhydride-grafted polyphenylene sulfide compatibilizer is injected into zones 5 to 8 through the side feed port for melt blending and reactive extrusion. The extrudate is water-cooled, stretched, and pelletized to obtain composite material masterbatch. After the masterbatch is dried, the product is obtained by injection molding.

2. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The modified graphene is prepared in the following manner: The original graphene powder was dispersed in anhydrous ethanol at a concentration of 2 mg / mL and then ultrasonicated to homogenize it. Add 3-aminopropyltriethoxysilane at 5% of the mass of graphene and stir to react; Centrifuge, wash three times with ethanol, and vacuum dry; The resulting modified graphene has fewer than 5 layers and an average sheet diameter of 1-3 μm.

3. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The nano-silica is a spherical amorphous particle; its surface is coated with epoxy functionalization by reacting γ-glycidoxypropyltrimethoxysilane at a mass ratio of 100:3 at 100°C for 2 hours.

4. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The maleic anhydride-grafted polyphenylene sulfide compatibilizer has a grafting rate of 0.8%-1.5% and a weight-average molecular weight of 40,000-60,000 g / mol. Its maleic anhydride groups undergo an amidation reaction with the amino groups on the surface of modified graphene, while its polar groups undergo a ring-opening addition reaction with the epoxy groups on the surface of nano-silica, forming a three-dimensional cross-linked network structure.

5. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The screw assembly configuration of the twin-screw extruder is as follows: Zones 1 to 4 are conveying sections, using right-hand threaded elements; Zones 5 to 7 are melt mixing sections, equipped with kneading discs; Zones 8 to 10 are homogenization sections, using left-hand threaded elements; and Zone 11 is metering section, using shallow-groove threaded elements.

6. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The mass ratio of the modified graphene to nano-silica is 1:

1.

7. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 6, characterized in that, When the total filler content is 25wt%, the linear expansion coefficient of the resulting composite material is 8.2ppm / K in the temperature range of 23-150℃, and the difference between the linear expansion coefficients in the X and Y directions is less than 0.5ppm / K.

8. The method for large-scale preparation of low-expansion, high-dimensionally stable PPS-based composite materials according to claim 1, characterized in that, The composite material has a tensile strength higher than 140 MPa, a flexural modulus higher than 9 GPa, and a notched impact strength higher than 8 kJ / m. 2 The heat distortion temperature is higher than 260℃.

9. The method for large-scale preparation of the low-expansion, high-dimensionally stable PPS-based composite material according to claim 1, characterized in that, The composite material exhibits a dimensional change rate of less than 0.05% after 1000 hours of humid heat aging at 85℃ / 85%RH.

10. The method for large-scale preparation of the low-expansion, high-dimensionally stable PPS-based composite material according to claim 1, characterized in that, In the multi-scale filler premix, modified graphene is uniformly dispersed in the PPS matrix in the form of monolayers or few layers, and nano-silica is attached to the edges and surface of the graphene sheets and partially embedded in the PPS amorphous phase to form a graphene-silica-PPS three-phase interface region with a continuous transition layer of 5-10 nm thickness.

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