High-temperature-resistant enhanced polyphenylene sulfide composite material and preparation process thereof

Abstract

The invention belongs to the technical field of polymer composite materials, and discloses a high-temperature-resistant enhanced polyphenylene sulfide composite material and a preparation process thereof. The composite material comprises the following components in percentage by mass: 65%-85% of polyphenylene sulfide resin, 10%-25% of functionalized graphene aerogel, 2%-8% of a nucleating aid and 1%-3% of a heat stabilizer, a three-dimensional confinement nano reaction environment is constructed through functionalized graphene aerogel, and a through type shish-kebab crystal structure is formed in situ in combination with ultrasonic or magnetic field external field induction. According to the high-temperature-resistant enhanced polyphenylene sulfide composite material and the preparation process thereof provided by the invention, a novel high-performance composite material system with excellent comprehensive performance is successfully constructed by innovatively fusing three technical elements of nano confinement, surface functionalization and external field induction; the heat resistance, the mechanical strength and the thermal cycle size stability of the material are remarkably improved, and the material is suitable for high-end electronic and aviation parts.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, and relates to a high-temperature-resistant reinforced polyphenylene sulfide composite material and its preparation process. Background Technology

[0002] Polyphenylene sulfide (PPS), a high-performance thermoplastic engineering plastic, has been widely used in high-end fields with stringent requirements for material service stability, such as electronics, automotive manufacturing, and aerospace, due to its excellent chemical corrosion resistance, inherent flame retardancy, and good electrical insulation properties.

[0003] Especially in structural components that operate for extended periods in high-temperature environments, polyphenylene sulfide (PPS) is considered an ideal candidate material to replace traditional metals or ordinary engineering plastics due to its high glass transition temperature (Tg≈90℃) and melting point (Tm≈285℃).

[0004] In existing technologies, the conventional strategy for improving the heat resistance of polyphenylene sulfide (PPS) mainly relies on increasing its crystallinity. Theoretically, higher crystallinity can effectively enhance the packing density between molecular chains, thereby inhibiting the thermal motion of chain segments at high temperatures and delaying the softening and creep behavior of the material.

[0005] The industry commonly employs methods such as adding nucleating agents, heat treatment annealing, or controlling the cooling rate to promote perfect crystallization. These methods did indeed significantly improve the heat distortion temperature and short-term thermal stability of polyphenylene sulfide (PPS) products during certain historical periods. However, while increasing the crystallinity of PPS can enhance its upper temperature resistance, it inevitably exacerbates volume shrinkage and internal stress accumulation during the molding process, leading to significant warping, cracking, or even failure of the products after high-temperature service or thermal cycling.

[0006] Traditional crystallization control methods often induce the formation of a large number of isolated, disordered, and unevenly sized spherulite structures. Such crystals exhibit significant anisotropic expansion effects when heated, making it difficult to achieve macroscopic dimensional stability. Furthermore, under the coupled action of high-temperature loads, the spherulite interface is prone to become a weak area for stress concentration and microcrack initiation, which weakens the overall structural integrity of the material. Summary of the Invention

[0007] To achieve the aforementioned objectives, this invention provides a high-temperature-resistant reinforced polyphenylene sulfide composite material and its preparation process. The composite material constructs a nano-reaction environment with a three-dimensional confinement effect, and, combined with controllable external field intervention, guides the polyphenylene sulfide molecular chains to achieve directional extension and ordered crystallization within the confined space, thereby constructing a through-type shish-kebab crystal structure in situ. This simultaneously achieves synergistic optimization of high temperature resistance, high dimensional stability, and excellent mechanical properties.

[0008] The high-temperature resistant reinforced polyphenylene sulfide composite material of the present invention comprises, by mass percentage: 65%-85% polyphenylene sulfide resin, 10%-25% functionalized graphene aerogel, 2%-8% nucleating agent, and 1%-3% heat stabilizer. The functionalized graphene aerogel is a sulfonated three-dimensional porous network structure with a specific surface area greater than 500 m². 2 The particles, with a pore size distribution concentrated in the 10-100 nm range and a porosity greater than 95%, are grafted with sulfonic acid groups on their surface at a density of 0.8-1.2 sulfonic acid groups per square nanometer. The nucleating agent is a composite of talc and sodium terephthalate in a 3:1 mass ratio, with an average particle size of 0.5-1.5 μm. The heat stabilizer is a mixture of hindered phenols and phosphites in a 1:1 mass ratio, with a melting point range of 120-150 °C.

[0009] The functionalized graphene aerogel, acting as a nanoreactor, forms a continuous, interconnected three-dimensional confined space within the composite material. The geometric scale of this confined space matches the radius of gyration of the polyphenylene sulfide (PPS) molecular chains, forcibly confining the chains within the nanopores in the molten state, suppressing their random coil conformation and promoting their extension along the pore axis. Simultaneously, weak coordination interactions are formed between the sulfonic acid groups on the aerogel framework surface and the sulfur atoms on the PPS backbone, further anchoring the molecular chain orientation and providing a structural template for subsequent externally induced crystal nucleation.

[0010] In a preferred embodiment of the present invention, the through-type shish-kebab crystal structure consists of a centrally extended chain crystal (shish) and laterally folded chain lamellar crystals (kebab). The shish phase extends continuously along the pore axis of the functionalized graphene aerogel, with a length greater than 50 μm and a diameter of 20-50 nm. The kebab phase grows perpendicularly on the surface of the shish phase, with a lamellar thickness of 10-30 nm and an interlayer spacing of 0.54 nm, conforming to the characteristic diffraction values ​​of polyphenylene sulfide crystal planes. This crystal structure is distributed in a three-dimensional network within the composite material, with each shish phase interconnected through an aerogel framework, forming mechanical and thermal conduction pathways throughout the entire material volume.

[0011] The present invention also provides a preparation process for the above-mentioned high-temperature-resistant reinforced polyphenylene sulfide composite material, which includes the following steps:

[0012] Step 1, preparation of functionalized graphene aerogel: Aqueous dispersion of graphene oxide (concentration of 2 mg / mL) was placed in a sealed reactor, p-aminobenzenesulfonic acid was added, and the mixture was reacted at 80°C for 6 hours to covalently graft sulfonic acid groups onto the edges of graphene sheets via amide bonds; then freeze-drying was performed to obtain a sulfonated graphene aerogel precursor; then thermal reduction was performed at 200°C under a nitrogen atmosphere for 2 hours to obtain functionalized graphene aerogel.

[0013] Step 2, Premixing: Add polyphenylene sulfide resin particles, functionalized graphene aerogel, nucleating agent and heat stabilizer to a high-speed mixer in proportion, and mix at 80°C for 15 minutes to make the components uniformly dispersed.

[0014] Step 3, melt blending and external field-induced crystallization: The premixed material is added to a twin-screw extruder, and the temperature zones are set as follows: feeding section 260℃, compression section 280℃, metering section 290℃, and die 285℃; the screw speed is 200 rpm; an ultrasonic probe is installed at the end of the metering section, applying an ultrasonic frequency of 40 kHz and a power density of 5 W / cm³. 2 The ultrasonic field was applied for more than 30 seconds. The ultrasonic field caused the polyphenylene sulfide melt to generate microscale shear flow in the confined channels of the functionalized graphene aerogel, driving the molecular chains to be highly oriented along the flow direction and forming shish crystal nuclei. Subsequently, during the cooling process, kebab grew epitaxially with shish as the core, completing the in-situ construction of the shish-kebab structure.

[0015] Step 4, Granulation and Molding: The extruded material is water-cooled and pelletized to obtain composite material particles; then, the final product is made by injection molding or compression molding. The injection temperature is 295℃, the mold temperature is 140℃, and the holding time is 30 seconds.

[0016] In another preferred embodiment of the present invention, a magnetic field is used instead of an ultrasonic field in the external field induction step. An electromagnetic coil is wound around the outer periphery of the metering section of a twin-screw extruder, and a pulsed direct current is applied to generate an alternating magnetic field with an intensity of 0.8-1.2T and a pulse frequency of 10Hz. The functionalized graphene aerogel is doped with iron oxide nanoparticles (doping amount of 3% of the aerogel mass) during the preparation process, giving it magnetic responsiveness. Under the action of the external magnetic field, the aerogel skeleton undergoes microscale vibration and orientation, driving the polyphenylene sulfide molecular chains confined within its channels to orient synchronously, thus achieving the directional formation of shish crystal nuclei.

[0017] In the aforementioned preparation process, the amount of functionalized graphene aerogel added directly affects the strength of the confinement effect and the continuity of the crystal structure. When its content is below 10%, the three-dimensional network is discontinuous, and a through-type crystal structure cannot be formed; when it is above 25%, the melt viscosity increases sharply, leading to processing difficulties and easy generation of bubble defects. Talc in the nucleating agent provides heterogeneous nucleation sites, while sodium terephthalate promotes the orderly stacking of lamellar crystals through π-π interactions with polyphenylene sulfide segments. The synergistic effect of the two significantly shortens the crystallization induction period and increases the crystallization rate.

[0018] The formation mechanism of the through-type shish-kebab crystal structure is as follows: During the melt blending stage, polyphenylene sulfide molecular chains enter the nanopores of the functionalized graphene aerogel. Constrained by the spatial limitations of the pore walls, their conformational entropy decreases, forcing them to extend along the pore axis. Simultaneously, the weak coordination between the sulfonic acid groups on the pore walls and the sulfur atoms of the main chain further fixes the orientation of the chain segments. Under the action of an external ultrasonic or magnetic field, the melt generates directional flow or skeletal vibration within the pores, applying shear stress to the oriented molecular chains, causing them to locally untangle and form straightened chain bundles, i.e., shish crystal nuclei. When the temperature drops below the melting point, the unoriented chain segments fold and stack around the shish as the core, forming kebab lamellar crystals. Due to the three-dimensional continuity of the aerogel skeleton, each shish crystal nucleus is spatially interconnected, ultimately forming a crystal network that runs through the entire material.

[0019] This crystal network has a dual function: firstly, the shish phase acts as a high-strength, high-modulus molecular reinforcing bar, effectively transferring loads and significantly improving the material's rigidity and creep resistance; secondly, the regular stacking of kebab lamellar crystals and the axial constraint of the shish phase together suppress thermally induced anisotropic expansion, enabling the material to exhibit near-isotropic thermal expansion behavior on a macroscopic scale, thereby achieving high dimensional stability.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention utilizes functionalized graphene aerogel as a nanoreactor, combined with external field induction technology, to successfully achieve the directional crystallization of polyphenylene sulfide (PPS) molecular chains in a three-dimensional confined space, constructing a through-hole shish-kebab crystal structure in situ. This structure fundamentally resolves the inherent contradiction between high crystallinity and high dimensional stability, enabling the composite material to maintain the inherent chemical resistance and flame retardancy of PPS while significantly improving high-temperature mechanical retention, heat distortion temperature, and thermal cycling dimensional stability. It is suitable for manufacturing precision structural components that require long-term operation above 200°C, such as housings for electronic control units in new energy vehicles, sensor brackets for aero-engines, and high-frequency connectors for 5G base stations—high-end applications. Detailed Implementation

[0022] This invention provides a high-temperature-resistant reinforced polyphenylene sulfide composite material and its preparation process. This composite material constructs a nano-reaction environment with a three-dimensional confinement effect, combined with controllable external field intervention, to guide the polyphenylene sulfide molecular chains to achieve directional extension and ordered crystallization within the confined space, thereby constructing a through-type shish-kebab crystal structure in situ. This simultaneously achieves synergistic optimization of high temperature resistance, high dimensional stability, and excellent mechanical properties.

[0023] 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.

[0024] Example 1: 75% polyphenylene sulfide resin, 18% functionalized graphene aerogel, 5% nucleating agent, 2% heat stabilizer; ultrasonic field 40kHz, power density 5W / cm² 2 Injection mold temperature: 140℃;

[0025] Preparation process: Functionalized graphene aerogel preparation → raw material premixing → twin-screw melt blending (ultrasonic external field induction) → granulation → injection molding → finished product.

[0026] Example 2: 10% functionalized graphene aerogel, with the remaining formulation and process the same as in Example 1;

[0027] Preparation process: Same as in Example 1.

[0028] Example 3: 25% functionalized graphene aerogel, with the remaining formulation and process the same as in Example 1;

[0029] Preparation process: Same as in Example 1.

[0030] Example 4: Magnetic field external field 1.0T, pulse frequency 10Hz (aerogel doped with 3% iron oxide), other formulations and processes are the same as in Example 1;

[0031] Preparation process: Same as in Example 1 (Fe3O4 is doped during aerogel preparation, and the external field is replaced by a magnetic field).

[0032] Example 5: 2% nucleating agent, the rest of the formulation and process are the same as in Example 1;

[0033] Preparation process: Same as in Example 1.

[0034] Example 6: 8% nucleating agent, the rest of the formulation and process are the same as in Example 1;

[0035] Preparation process: Same as in Example 1.

[0036] Example 7: Ultrasonic power density 3W / cm² 2 The remaining formulas and processes are the same as in Example 1;

[0037] Preparation process: Same as in Example 1.

[0038] Example 8: Ultrasonic power density 7W / cm² 2 The remaining formulas and processes are the same as in Example 1;

[0039] Preparation process: Same as in Example 1.

[0040] Comparative Example 1: Non-functional graphene aerogel, 93% polyphenylene sulfide resin, 5% nucleating agent, 2% heat stabilizer; no external field induction; the rest of the formulation and process are the same as in Example 1;

[0041] Preparation process: raw material premixing → twin-screw melt blending → granulation → injection molding → finished product.

[0042] Comparative Example 2: Aerogel without sulfonation treatment (without sulfonic acid group grafting), the rest of the formulation and process are the same as in Example 1;

[0043] Preparation process: Same as in Example 1 (aerogel preparation without sulfonation step).

[0044] Test method:

[0045] Temperature resistance test: Heat distortion temperature is measured at 260℃ using a heat distortion temperature measuring instrument; tensile strength retention rate is tested after 1000 hours of heat aging at 200℃.

[0046] Mechanical and dimensional testing: tensile strength and flexural modulus are determined by a universal testing machine; linear thermal expansion coefficient is determined by a thermomechanical analyzer; and warpage is determined by a thermal cycling test (-40-220℃, 50 cycles).

[0047] Structural testing: wide-angle X-ray diffraction analysis of crystal orientation; transmission electron microscopy observation of the integrity of the shish-kebab crystal structure.

[0048] The test data comparisons are shown in Table 1 and Table 2.

[0049] Table 1. Comparison of Heat Deflection Temperature, Heat Aging Strength Retention Rate, and Linear Thermal Expansion Coefficient

[0050] Test Project Heat distortion temperature (°C) Heat aging strength retention rate (%) <![CDATA[Linear thermal expansion coefficient (×10 -6 / °C)]]> Example 1 258 87 18 Example 2 250 82 22 Example 3 262 90 15 Example 4 256 86 19 Example 5 253 83 21 Example 6 260 88 17 Example 7 254 84 20 Example 8 259 89 16 Comparative Example 1 215 68 36 Comparative Example 2 235 75 28

[0051] Table 2 Comparison of Tensile Strength, Flexural Modulus, and Thermal Cycle Warpage

[0052] Test Project Tensile strength (MPa) Flexural modulus (GPa) Thermal cycling warpage (mm / 100mm) Example 1 185 12.5 0.12 Example 2 170 11.2 0.14 Example 3 192 13.8 0.1 Example 4 178 11.8 0.13 Example 5 175 11.5 0.15 Example 6 188 13.2 0.11 Example 7 176 11.6 0.14 Example 8 189 13.5 0.11 Comparative Example 1 145 9 0.45 Comparative Example 2 160 10.2 0.28

[0053] Examples 1-8 have a heat distortion temperature ≥250℃ and a heat aging strength retention rate ≥82%, which is far superior to the comparative examples. Comparative example 1, due to the lack of aerogel and external field induction, cannot form a shish-kebab structure and has extremely poor performance. Comparative example 2 has no sulfonated aerogel, weak interfacial interaction, and poor crystal orientation, which confirms that the core process is the key to high performance.

[0054] Increased aerogel content (Examples 2→1→3) simultaneously improves temperature resistance and mechanical properties; optimized external field power (Examples 7→1→8) results in a more regular crystal structure; increased nucleating agent ratio (Examples 5→1→6) enhances crystallization rate and perfection.

[0055] The embodiments are compatible with existing twin-screw extrusion and injection molding equipment, with process compatibility; they have excellent temperature resistance and dimensional stability, and are suitable for high-temperature scenarios above 200°C; they have strong mechanical properties and can replace high-end engineering plastics and metal parts.

[0056] Compared to the aerogel-free system (Comparative Example 1), the heat distortion temperature of the example is increased by 20% and the coefficient of thermal expansion is reduced by 50%; compared to the unsulfonated aerogel (Comparative Example 2), the temperature resistance is improved by 9% and the warpage is reduced by 61%, solving the industry problem of high-temperature dimensional instability and rapid mechanical decay of traditional polyphenylene sulfide.

[0057] In summary, the composite material described in this invention achieves a synergistic effect of high temperature resistance, high rigidity, and high dimensional stability through functionalized aerogel confinement and external field induction, with different parameter combinations, making it suitable for demanding applications such as high-end electronics and aerospace.

[0058] 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 high-temperature-resistant reinforced polyphenylene sulfide composite material, characterized in that, The components of the composite material, by mass percentage, include: Polyphenylene sulfide resin 65%-85%; Functionalized graphene aerogels: 10%-25%; Nucleating agent 2%-8%; And 1%-3% heat stabilizer; The composite material contains an in-situ constructed through-type shish-kebab crystal structure, which consists of a straight-chain shish phase that extends continuously along the axial direction of the functionalized graphene aerogel channels and a folded chain kebab phase that grows vertically on its surface. The shish phases are interconnected through the aerogel skeleton to form a three-dimensional network distribution.

2. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The functionalized graphene aerogel is a three-dimensional porous network structure that has undergone sulfonation treatment. The pore size distribution is concentrated in the range of 10-100 nm, the porosity is greater than 95%, and the surface is grafted with sulfonic acid groups with a grafting density of 0.8-1.2 sulfonic acid groups per square nanometer.

3. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The nucleating agent is a complex composed of talc and sodium terephthalate in a mass ratio of 3:

1.

4. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The heat stabilizer is a mixture of hindered phenols and phosphites in a mass ratio of 1:1, with a melting point range of 120-150℃.

5. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The functionalized graphene aerogel has a shish phase with a length greater than 50 μm and a diameter of 20-50 nm; the kebab phase has a lamellar thickness of 10-30 nm and an interlayer spacing of 0.54 nm.

6. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The polyphenylene sulfide resin has an intrinsic viscosity of 0.45-0.65 dL / g, a melting point of 280-290℃, and a moisture content of less than 0.05%.

7. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The functionalized graphene aerogel has a weak coordination relationship between the sulfonic acid groups on the backbone surface and the sulfur atoms on the polyphenylene sulfide backbone, with a coordination bond energy of 15-25 kJ / mol.

8. The high-temperature-resistant reinforced polyphenylene sulfide composite material according to claim 1, characterized in that, The functionalized graphene aerogel is doped with iron oxide nanoparticles at a doping amount of 3% of its mass, and the iron oxide nanoparticles are surface modified with oleic acid.

9. A preparation process for the high-temperature-resistant reinforced polyphenylene sulfide composite material as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Preparation of functionalized graphene aerogel: A 2 mg / mL aqueous dispersion of graphene oxide was reacted with p-aminobenzenesulfonic acid, freeze-dried, and then thermally reduced in a nitrogen atmosphere. S2. Premixing: Polyphenylene sulfide resin, functionalized graphene aerogel, nucleating agent and heat stabilizer are mixed evenly at high speed. S3. Melt blending and external field-induced crystallization: The premixed material is added to a twin-screw extruder and melt-extruded under the conditions of 260°C in the feeding section, 280°C in the compression section, 290°C in the metering section, and 285°C in the die. An external field is applied at the end of the metering section to induce the in-situ formation of the shish-kebab crystal structure. S4. Granulation and molding: After water cooling and pelletizing the extruded material, it is made into products by injection molding or compression molding.

10. The preparation process according to claim 9, characterized in that, The external field in step S3 is an ultrasonic field with a frequency of 40kHz and a power density of 3-7W / cm². 2 The duration of action is greater than 30 seconds.