High-temperature-resistant polypropylene composite material for rapid thermal cycle injection molding

Abstract

The invention belongs to the technical field of high polymer material modification engineering, polymer rheological design and modern advanced plastic processing and forming, and particularly relates to a high-temperature-resistant polypropylene composite material for rapid thermal cycle injection molding. The invention aims to solve the problems of mechanical property degradation, contradiction between material heat resistance and processing fluidity, surface floating fiber, roughness and the like of the polypropylene composite material. According to the composite material disclosed by the invention, high-crystallinity co-polypropylene is taken as a continuous phase matrix, modified wollastonite whiskers and microfibrillated elastomers are introduced, and a hybrid enhanced network is constructed in the matrix. The preparation method comprises the following steps: by taking tetraethoxysilane as a precursor, uniformly coating a silicon dioxide buffer shell layer on the surface of a micro-nano aluminum oxide particle to prepare an aluminum oxide-silicon dioxide core-shell structure heat-conducting particle; hydrogenated petroleum resin is introduced, and the extremely low viscosity lubricating effect of the hydrogenated petroleum resin in a molten state and the high modulus steric hindrance effect of the hydrogenated petroleum resin in a glassy state are utilized, so that the processing fluidity and the macroscopic heat distortion temperature of the material are synergistically improved.

Description

Technical Field

[0001] This invention belongs to the fields of polymer material modification engineering, polymer rheological design and modern advanced plastic processing and molding technology, and specifically relates to a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding. Background Technology

[0002] Rapid thermal cycling injection molding is an advanced injection molding technology that rapidly heats the mold to above the resin's heat distortion temperature before filling and then rapidly cools it after filling. This effectively eliminates weld lines, flow marks, and loose fibers on the surface of the product, achieving high-gloss, seamless injection molding. This technology is widely used in the production of plastic products with extremely high surface quality requirements, such as automotive interior parts, household appliance housings, and 3C electronic products.

[0003] Polypropylene, one of the five major general-purpose plastics, boasts advantages such as low density, low price, and good processability, making it widely used in the automotive and home appliance industries. However, ordinary polypropylene has a relatively low heat resistance temperature, with a heat distortion temperature typically between 80 and 100°C, which is insufficient to meet the heat resistance requirements of the RHCM process. Simultaneously, the RHCM process requires materials with a certain degree of thermal conductivity to facilitate rapid heat transfer from the mold and shorten the molding cycle. Furthermore, in high-temperature molds, the viscosity of the polypropylene melt decreases, causing reinforcing fibers to easily float to the surface, resulting in fiber floating defects that severely affect the appearance quality of the finished product.

[0004] To improve the heat resistance of polypropylene, existing technologies typically employ the addition of reinforcing fillers such as glass fiber, talc, or whiskers. For example, existing patent CN104945741A discloses a high heat-resistant polypropylene composite material that improves heat resistance by adding talc and glass fiber; however, this system has poor thermal conductivity and exhibits severe surface fiber floating.

[0005] Therefore, there is an urgent need to develop a polypropylene composite material that combines high heat resistance, high thermal conductivity, excellent rigidity-toughness balance, and high surface quality to meet the requirements of rapid thermal cycling injection molding processes, which has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the complex technical challenges in existing technologies, such as the difficulty in balancing processing fluidity and macroscopic heat resistance, the drastic deterioration of the system's mechanical toughness caused by inorganic thermally conductive fillers, and the inevitable surface fiber formation in traditional reinforcing materials during injection molding, this invention constructs a hybrid reinforced three-dimensional network with high energy dissipation. It designs alumina-silica core-shell structure buffer thermally conductive particles with a gradient modulus transition layer and introduces in-situ microfiberization technology, dynamic vulcanization fixation technology, and an intelligent rheological control mechanism for hydrogenated petroleum resin. This results in a composite material with high thermal conductivity, high heat resistance, and high toughness.

[0007] A high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding, the technical solution of which is as follows: S1: Take 8-10 parts by weight of alumina powder as a reference, disperse it in 30-35 parts of ethanol / water mixture, with a volume ratio of ethanol to water of 4:1, ultrasonically disperse for 30 minutes, adjust the pH of the suspension to 9 with ammonia, heat to 50℃ and stir, slowly add 2-3 parts of tetraethyl orthosilicate, react for 6 hours, filter after the reaction is completed, dry with anhydrous ethanol under vacuum, and finally calcine it. After natural cooling, alumina-silica core-shell thermally conductive particles are obtained. S2: Using needle-shaped wollastonite as raw material and drying it, then diluting it with γ-aminopropyltriethoxysilane and anhydrous ethanol at a ratio of 1:1, and uniformly spraying the diluted γ-aminopropyltriethoxysilane solution onto the wollastonite powder under stirring, and then treating it at 100℃~120℃ for 20~30 minutes to prepare modified wollastonite whiskers; S3: Take 100 parts of highly crystalline copolymer polypropylene, 20-30 parts of alumina-silica core-shell thermally conductive particles prepared in step S1, 15-25 parts of modified wollastonite whiskers prepared in step S2, 8-10 parts of EPDM rubber, 0.2-0.4 parts of octylphenol resin vulcanizing agent, 0.5-1 parts of stannous chloride catalyst, 4-6 parts of hydrogenated C9 petroleum resin, 3-5 parts of MAH-g-PP, 0.4-0.6 parts of composite antioxidant B215, antioxidant 1010 and antioxidant 168 are mixed at a mass ratio of 1:2, and 0.7-0.9 parts of pentaerythritol stearate are added to a high-speed mixer with a temperature control jacket for dispersion, and then placed in a twin-screw extruder for extrusion, water cooling, strip drawing, and pelletizing to obtain composite masterbatch; S4: The composite masterbatch is dried in an 80°C forced-air drying oven for 4 hours, then placed on a rapid thermal cycle injection molding machine for molding. The mold is then rapidly cooled to 40°C to obtain the high-temperature resistant polypropylene composite material of the present invention.

[0008] Furthermore, the vacuum drying described in step S1 specifically involves vacuum drying at 80°C for 12 hours.

[0009] Furthermore, the calcination described in step S1 specifically involves heating to 600°C at a heating rate of 5°C / min and calcining for 2 hours.

[0010] Furthermore, the drying described in step S2 specifically involves drying at 100°C to 120°C for 2 to 3 hours.

[0011] Furthermore, the amount of γ-aminopropyltriethoxysilane used in step S2 is 0.5% to 1.0% of the mass of wollastonite.

[0012] Furthermore, the dispersion described in step S3 specifically involves a rotation speed of 800 rpm and dispersion for 5 minutes.

[0013] Furthermore, the extruder described in step S3 has the following parameters: first section 180°C, second section 210°C, third section 230°C, fourth section 220°C, and fifth extruder head section 210°C.

[0014] Furthermore, the specific parameters of the rapid thermal cycle injection molding machine described in step S4 are set as follows: barrel temperature 220℃~240℃, initial mold temperature 40℃, mold rapidly heated to 130℃ before injection, injection speed 80mm / s, holding pressure 60MPa, and holding time 10 seconds.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention solves the problems of high filling inevitably becoming brittle and added plastics inevitably becoming heat-insensitive by combining core-shell stress buffer design with in-situ dynamic microfibrillation technology; while ensuring high thermal conductivity of the material, it significantly reduces interfacial thermal resistance and eliminates stress concentration points.

[0016] (2) By introducing hydrogenated petroleum resin, the present invention utilizes its extremely low viscosity lubrication effect in the molten state and its high modulus steric hindrance effect in the glassy state to achieve a synergistic improvement in material processing fluidity and macroscopic heat distortion temperature.

[0017] (3) In the synthesis of alumina-silica core-shell thermally conductive particles, the present invention eliminates toxic coupling agents and expensive surfactants, and adopts a clean and green water-alcohol microemulsion system, which is easy to scale up for industrial production; the dynamic in-situ microfibrillation technology does not require multi-step processing, the production process is highly integrated and automated, and the process control is precise and extremely stable and reliable. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to the present invention.

[0019] Figure 2 The infrared spectrum is from Experiment Example 1.

[0020] Figure 3 The image shown is a SEM image from Experiment Example 2. Detailed Implementation

[0021] The following embodiments further explain and illustrate the technical solutions of the present invention. It is particularly noted that each specific embodiment is a specific interpretation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention. (See attached...) Figure 1 The diagram shows a process flow for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding. The detailed preparation steps are as follows: 1. Preparation of alumina-silica core-shell thermally conductive particles High-purity α-alumina inorganic powder was dispersed in an ethanol / water mixture and ultrasonically dispersed for 30 minutes. The pH of the suspension was adjusted to 9 with ammonia, and the mixture was heated to 50°C and stirred at a constant temperature. Tetraethyl orthosilicate was slowly added dropwise. Ammonia, acting as a morphological catalyst for the subsequent hydrolysis of tetraethyl orthosilicate, provided a suitable weakly alkaline pH environment to the dispersion system, resulting in a moderately negative charge on the surface of the alumina particles. This maintained the long-term thermodynamic suspension stability of the dispersion through electrostatic repulsion. The large number of suspended alumina particles in the reaction system provided a huge specific surface area. According to the principle of nucleation thermodynamics, the Gibbs free energy barrier for heterogeneous nucleation is much lower than that for homogeneous nucleation in solution. The orthosilicic acid molecules generated by in-situ slow hydrolysis exhibited a strong adhesion tendency, preferentially adsorbing at the solid-liquid interface of the alumina particles and rapidly forming a dense cross-linked Si-O-Si silicon-oxygen bond network through dehydration condensation between silanol groups. To further enhance the density of the silica coating, close the micropores, and remove excess silanol groups and any trace organic volatiles remaining on the surface, it is finally calcined and naturally cooled to obtain alumina-silica core-shell thermally conductive particles with a physical core-shell structure.

[0022] 2. Modified wollastonite whiskers Using acicular wollastonite as raw material, silane coupling agent γ-aminopropyltriethoxysilane was mixed and diluted with anhydrous ethanol. Under stirring, the diluted γ-aminopropyltriethoxysilane solution was uniformly sprayed into wollastonite powder to prepare modified wollastonite whiskers. γ-aminopropyltriethoxysilane is an amino-functionalized silane. One end of its molecular structure can react with the hydroxyl groups on the surface of inorganic wollastonite, firmly adhering to the filler surface. The amino group at the other end can be compatible with or react with organic polymers, thus acting as a molecular bridge to tightly connect polar wollastonite and non-polar polypropylene. The modified acicular wollastonite whiskers serve as a rigid physical framework providing high modulus support. 3. Composite Masterbatch The matrix resin is selected as a nucleation-modified highly crystalline copolymer polypropylene as the continuous phase supporting the system; needle-like wollastonite whiskers, deeply modified with KH-550 aminosilane coupling agent, are selected as the rigid physical framework providing high modulus support; the elastomer phase is selected as EPDM rubber with a small amount of diene third monomer in the molecular chain side groups as the precursor for in-situ microfibrilation, whose long chain flexibility helps to absorb fracture energy, while the diene provides active sites for crosslinking; in order to lock the microfibrilation morphology, octylphenol resin combined with a trace amount of Lewis acid catalyst stannous chloride dihydrate is selected as a non-sulfur dynamic vulcanization crosslinking agent with a suitable initiation temperature; modification Hydrogenated C9 petroleum resin with a softening point precisely calibrated at 125℃ and a hydrogenation saturation of 99% was selected as the intelligent rheology modifier. The compatibilizer was maleic anhydride-grafted polypropylene (MAH-g-PP) with a high grafting rate. The antioxidant system used a compound hindered phenol / phosphite antioxidant B215, and the lubrication and demolding system employed high-temperature resistant pentaerythritol stearate. All the above solid and liquid raw materials were fed into a high-speed mixer with a temperature-controlled jacket for high-intensity physical dispersion and mixing. The frictional micro-heat between particles caused some low-melting-point additives to initially melt and coat the powder surface, resulting in a uniformly dispersed multiphase premix. Subsequently, the premix was extruded to obtain masterbatch.

[0023] In the aforementioned preparation process, when the multiphase viscous fluid is conveyed to the melt kneading section with a large number of staggered kneading blocks, the rotor generates extremely high shear rates and intense tensile deformation micro-flow fields at a certain rotational speed. At this time, the macroscopic continuous phase has high melt strength and apparent viscosity, while the microscopic dispersed phase exhibits low viscosity. This negative viscosity deviation, coupled with an extremely high number of capillaries, causes the originally micron-sized spherical free-dispersed elastomer phase to be unable to maintain its spherical shape due to surface tension. Under the intense tensile flow field peeling action, it undergoes extreme uniaxial tensile distortion and is highly stretched into continuous slender fibers with diameters of only tens to hundreds of nanometers and lengths of tens of micrometers or even longer. Simultaneously, with the localized viscous dissipation and temperature rise caused by extrusion work, the hydroxymethyl active groups of the phenolic resin vulcanizing agent pre-embedded in the system are rapidly thermally activated and dissociated. Under the catalysis of stannous chloride, they rapidly attack and attach to the diene unsaturated double bonds next to the main chain of the EPDM rubber molecular chain, which is under extreme stretching, initiating an extremely rapid chemical crosslinking reaction. This dynamic crosslinking increases the melt network crosslinking density, apparent viscosity, and elastic recovery relaxation time of the elastomer microfibers. The formation of chemical bonds completely locks and freezes the topological morphology of this part of the microfiber phase in the flow field, preventing the microfiber spheroidization regression or Rayleigh instability breakage that would normally occur due to interfacial tension contraction from a thermodynamic perspective. After the crosslinking is completed, these chemically shaped high aspect ratio elastic microfiber networks and the simultaneously existing rigid needle-like wollastonite whiskers with extremely high elastic modulus undergo three-dimensional geometric interlocking, physical crossing, and chain segment entanglement in the polypropylene substrate macromolecule, constructing the core microscopic physical structure of this invention—a rigid-flexible three-dimensional interpenetrating mechanical network.

[0024] 4. Post-processing The masterbatch is dried to remove moisture and then placed on a high-speed thermal circulation injection molding machine for molding. The barrel temperature is controlled at 220℃~240℃, the initial mold temperature is 40℃, the mold is rapidly heated to 130℃ before injection, the injection speed is 80mm / s, and then pressure is maintained and cooled to obtain the high-temperature resistant polypropylene composite material of the present invention.

[0025] Example 1 Table 1 Raw Material Information Table A high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding, the preparation steps of which are as follows: S1: Take 9 parts by weight of alumina powder as a reference, disperse it in 32 parts of ethanol / water mixture with a volume ratio of ethanol to water of 4:1, ultrasonically disperse for 30 minutes, adjust the pH of the suspension to 9 with ammonia, heat to 50℃ and stir, slowly add 2.5 parts of tetraethyl orthosilicate, react for 6 hours, filter after the reaction, wash 3 times with anhydrous ethanol, vacuum dry at 80℃ for 12 hours, and finally calcine it, heating to 600℃ at a heating rate of 5℃ / min, calcining for 2 hours, and naturally cooling to obtain alumina-silica core-shell thermally conductive particles; S2: Using needle-shaped wollastonite with an aspect ratio of 20:1 as raw material, it was dried at 110℃ for 2.5 hours. Then, the silane coupling agent γ-aminopropyltriethoxysilane was mixed and diluted with anhydrous ethanol at a ratio of 1:1. The amount of γ-aminopropyltriethoxysilane was 0.8% of the mass of wollastonite. Under stirring, the diluted γ-aminopropyltriethoxysilane solution was uniformly sprayed into the wollastonite powder. Then, it was treated at 110℃ for 25 minutes to prepare modified wollastonite whiskers. S3: Take 95 parts of high-crystallinity copolymer polypropylene, 25 parts of alumina-silica core-shell thermally conductive particles prepared in step S1, 20 parts of modified wollastonite whiskers prepared in step S2, 9 parts of EPDM rubber, 0.3 parts of octylphenol resin vulcanizing agent, 0.8 parts of stannous chloride catalyst, 5 parts of hydrogenated C9 petroleum resin, 4 parts of MAH-g-PP, 0.5 parts of composite antioxidant B215, with a mass ratio of 1010:168 of 1:2, and 0.8 parts of pentaerythritol stearate. Put them into a high-speed mixer with a temperature control jacket, rotate at 800 rpm, disperse for 5 minutes, and then put them into a twin-screw extruder. The first section is 180℃, the second section is 210℃, the third section is 230℃, the fourth section is 220℃, and the fifth extruder head section is 210℃. The molten material is extruded through the die head, water-cooled into strips, and pelletized to obtain composite masterbatch. S4: The composite masterbatch is dried in an 80°C forced-air drying oven for 4 hours, and then placed on a rapid thermal circulation injection molding machine for molding. The barrel temperature is 230°C, the initial mold temperature is 40°C, the mold is rapidly heated to 130°C before injection, the injection speed is 80mm / s, the holding pressure is 60MPa, the holding time is 10 seconds, and then the mold is rapidly cooled to 40°C to obtain the high-temperature resistant polypropylene composite material of the present invention.

[0026] Example 2 The preparation method is the same as in Example 1, but with the following differences: In step S1: 10 parts by weight of alumina powder, 35 parts by weight of ethanol / water mixture, and 3 parts by weight of tetraethyl orthosilicate; In step S2: Dry at 120°C for 2 hours; the amount of γ-aminopropyltriethoxysilane used is 1.0% of the mass of wollastonite; treat at 120°C for 30 minutes; In step S3: 30 parts of alumina-silica core-shell thermally conductive particles prepared in step S1, 25 parts of modified wollastonite whiskers prepared in step S2, 10 parts of EPDM rubber, 0.4 parts of octylphenol resin vulcanizing agent, 1 part of stannous chloride catalyst, 6 parts of hydrogenated C9 petroleum resin, 5 parts of MAH-g-PP, 0.6 parts of composite antioxidant B215, with a mass ratio of 1010:168 of 1:2, and 0.9 parts of pentaerythritol stearate; In step S4: the barrel temperature is 240℃.

[0027] Example 3 The preparation method is the same as in Example 1, but with the following differences: In step S1: 80 parts by weight of alumina powder, 30 parts by weight of ethanol / water mixture, and 2 parts by weight of tetraethyl orthosilicate; In step S2: Dry at 100°C for 3 hours; the amount of γ-aminopropyltriethoxysilane used is 0.5% of the mass of wollastonite; treat at 100°C for 30 minutes; In step S3: 20 parts of alumina-silica core-shell thermally conductive particles prepared in step S1, 15 parts of modified wollastonite whiskers prepared in step S2, 8 parts of EPDM rubber, 0.2 parts of octylphenol resin vulcanizing agent, 0.5 parts of stannous chloride catalyst, 4 parts of hydrogenated C9 petroleum resin, 3 parts of MAH-g-PP, 0.4 parts of composite antioxidant B215 (1010:168 mass ratio 1:2), and 0.7 parts of pentaerythritol stearate; In step S4: the barrel temperature is 220℃.

[0028] Comparative Example 1 The preparation method of Example 1 is followed, but the alumina-silica core-shell thermally conductive particles are replaced with an equal amount of uncoated ordinary alumina. All other steps are the same.

[0029] Comparative Example 2 The preparation method of Example 1 is followed, but without the addition of modified wollastonite whiskers. All other steps are the same.

[0030] Comparative Example 3 The preparation method of Example 1 is followed, but the EPDM rubber is replaced with an equal amount of ordinary polyolefin toughening agent. All other steps are the same.

[0031] Comparative Example 4 The preparation method of Example 1 is followed, but the hydrogenated C9 petroleum resin is replaced with an equal amount of ordinary naphthenic mineral oil. All other steps are the same.

[0032] Experimental Example 1 Infrared spectroscopy was performed on the alumina-silica core-shell thermally conductive particles prepared in Example 1. 2 mg of the thermally conductive particle sample was mixed with dry, spectroscopically pure potassium bromide powder at a mass ratio of 1:100. The mixture was then thoroughly and meticulously ground in the same direction in a clean agate mortar until it became an extremely fine powder. The ground powder was then compressed into tablets. The test mode was transmission mode, and the spectral scanning range was 4000 cm⁻¹. -1 -400cm -1 Spectral resolution: 4cm -1 Number of scans: 64; test results as follows: Figure 2 As shown; 1105cm -1 The strong and broad absorption band at 904 cm⁻¹ is attributed to the antisymmetric stretching vibration of the Si-O-Si bonds in the three-dimensional network structure. This extremely strong and broad peak is due to the extensive cross-linking of silicon-oxygen bonds to form a network, confirming that the precursor tetraethyl orthosilicate hydrolysis products successfully underwent condensation polymerization on the alumina surface, forming a three-dimensional amorphous silicon-oxygen network shell. -1 The characteristic absorption peak at 796 cm⁻¹ is attributed to the stretching vibration of the Si-O bond; -1 The characteristic absorption peak at 468 cm⁻¹ is attributed to the symmetric stretching vibration of Si-O-Si; -1 The characteristic absorption peaks at this location are attributed to the bending vibrations of Si-O-Si; these three sets of characteristic peaks, along with the peak at 1105 cm⁻¹, are related to the bending vibrations of Si-O-Si. -1 The strong peaks, as multiple fingerprint peaks, jointly confirm the integrity and structural stability of the dense silica layer coating; the low-frequency region 500-800 cm⁻¹ -1 The frequency band itself covers the unique broadband vibrational absorption of Al-O bonds in pure phase alumina; due to the dense silica shell covering the surface, some Al-O absorption signals may overlap with or be masked by the low-frequency peaks of Si-O-Si.

[0033] Experimental Example 2 Standard specimens were prepared from the high-temperature resistant polypropylene composite material prepared in Example 1 and characterized using FE-SEM. The inner core layer sample was cut using a precision cutter in a liquid nitrogen environment to obtain thin slices with flat cross-sections. The sliced ​​samples were then subjected to prolonged reflux extraction in boiling hot xylene, followed by multiple ultrasonic cleanings, vacuum drying, and surface gold sputtering. The accelerating voltage was set to 3.0kV-5.0kV; the working distance was between 5.0mm and 8.0mm; a secondary electron detector was used; and the magnification was 5000x-10000x. The test results are as follows: Figure 3 As shown; The vast network of interwoven, elongated fibers in the diagram, ranging from tens to hundreds of nanometers in diameter and tens of micrometers in length, represents EPDM rubber microfibers undergoing deep three-dimensional chemical cross-linking. In the high-shear tensile flow field of a twin-screw extruder, EPDM rubber undergoes uniaxial tensile distortion. Due to the instantaneous dynamic vulcanization of the octylphenol resin vulcanizing agent under stannous chloride catalysis, the diene side groups are chemically cross-linked, "freezing" and locking the microfiber topology, preventing spheroidization regression or Rayleigh instability breakage. The prominently displayed, relatively smooth, and robust cylinders are added needle-like wollastonite whiskers. As a high-modulus, hard physical framework, wollastonite whiskers provide robust support against macroscopic high-temperature deformation when the material is under stress. The regularly spherical micron-sized particles scattered throughout the microfiber network are alumina-silica core-shell thermally conductive particles. The figure shows that flexible cross-linked microfibers are wrapped around and attached to the wollastonite whiskers, forming strong and flexible bridges between multiple whiskers; confirming the successful construction of the three-dimensional geometric interlocking configuration of "rigid skeleton-flexible tendon".

[0034] Experimental Example 3 The comprehensive properties of the high-temperature resistant polypropylene composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were determined. Tensile strength test: Refer to standard ISO 527-2:2025 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", and use a universal testing machine. The specimen specification is a type 1A dumbbell-shaped strip. An extensometer is set up. The tensile speed is 50 mm / min and the test environment is 23℃. Flexural modulus test: The test was conducted in accordance with the standard ISO 178:2019 "Determination of flexural properties of plastics". A three-point bending fixture was used, the span was adjusted to 64 mm, the test speed was 2 mm / min, and the test environment was 23℃. Notched impact strength test: The test was conducted in accordance with the standard ISO 180:2023 "Determination of impact strength of plastic cantilever beams". A V-notch was machined and a high-energy pendulum impact test was carried out under the test environment of 23°C. Heat distortion temperature test: The test was conducted in accordance with the standard ISO 75-2:2013 "Determination of deflection temperature under load of plastics - Part 2: Plastics and hard rubber". A thermomechanical analyzer was used, the load pressure was set to the high stress level of 1.80 MPa, and the heating rate was 120℃ / h. The specific test comparison results are shown in Table 2: Table 2. Comparison of overall performance between Examples 1-3 and Comparative Examples 1-4 The comparison results show that: Comparative Example 1, using ordinary alumina to replace the core-shell structure, suffers from poor interfacial bonding, leading to reduced stress transfer efficiency. Uncoated particles act as stress concentration points, causing brittle fracture and resulting in reduced tensile and impact strength. Comparative Example 2, without the addition of modified wollastonite whiskers, loses its rigid framework support, resulting in a significant decrease in rigidity. The lack of a high-modulus framework to resist high-temperature creep affects various properties. Comparative Example 3, using ordinary toughening agents, cannot form a microfiber network, resulting in low toughening efficiency and no cross-linking lock, thus reducing the material's heat resistance. Comparative Example 4, using mineral oil to replace hydrogenated petroleum resin, lacks steric support in the glassy state. Mineral oil migration weakens the interface, making it impossible to achieve glassy rigid support and heat resistance.

Claims

1. A high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding, characterized in that, By weight, it consists of the following components: 100 parts of highly crystalline copolymer polypropylene, 20-30 parts of alumina-silica core-shell thermally conductive particles, 15-25 parts of modified wollastonite whiskers, 8-10 parts of EPDM rubber, 0.2-0.4 parts of octylphenolic resin vulcanizing agent, 0.5-1 part of stannous chloride catalyst, 4-6 parts of hydrogenated C9 petroleum resin, 3-5 parts of MAH-g-PP, 0.4-0.6 parts of composite antioxidant B215, and 0.7-0.9 parts of pentaerythritol stearate lubricant.

2. The high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 1, characterized in that, The alumina-silica core-shell thermally conductive particles consist of an alumina core and a nano-silica shell coating the alumina surface; the modified wollastonite whiskers are needle-shaped wollastonite whiskers surface-treated with an aminosilane coupling agent; the composite antioxidant B215 is obtained by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

2.

3. A method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding as described in any one of claims 1-2, characterized in that, Includes the following steps: S1: Take 8-10 parts by weight of alumina powder as a reference, disperse it in 30-35 parts of ethanol / water mixture, with a volume ratio of ethanol to water of 4:1, ultrasonically disperse for 30 minutes, adjust the pH of the suspension to 9 with ammonia, heat to 50℃ and stir, add 2-3 parts of tetraethyl orthosilicate, react for 6 hours, filter after the reaction, dry with anhydrous ethanol under vacuum, and finally calcine and cool naturally to obtain alumina-silica core-shell thermally conductive particles. S2: Using needle-shaped wollastonite as raw material and drying it, then diluting it with γ-aminopropyltriethoxysilane and anhydrous ethanol at a ratio of 1:1, and uniformly spraying the diluted γ-aminopropyltriethoxysilane solution onto the wollastonite powder under stirring, and then treating it at 100℃~120℃ for 20~30 minutes to prepare modified wollastonite whiskers; S3: Take 100 parts of highly crystalline copolymer polypropylene, 20-30 parts of alumina-silica core-shell thermally conductive particles prepared in step S1, 15-25 parts of modified wollastonite whiskers prepared in step S2, 8-10 parts of EPDM rubber, 0.2-0.4 parts of octylphenol resin vulcanizing agent, 0.5-1 parts of stannous chloride catalyst, 4-6 parts of hydrogenated C9 petroleum resin, 3-5 parts of MAH-g-PP, 0.4-0.6 parts of composite antioxidant B215, and 0.7-0.9 parts of pentaerythritol stearate and disperse them in a high-speed mixer with a temperature control jacket. Then, put them into a twin-screw extruder for extrusion, water cooling, and pelletizing to obtain composite masterbatch. S4: The composite masterbatch is dried in an 80°C forced-air drying oven for 4 hours, then placed on a rapid thermal cycle injection molding machine for molding. The mold is then rapidly cooled to 40°C to obtain the high-temperature resistant polypropylene composite material of the present invention.

4. The method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The vacuum drying described in step S1 specifically involves vacuum drying at 80°C for 12 hours.

5. The method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The calcination described in step S1 specifically involves heating to 600°C at a heating rate of 5°C / min and calcining for 2 hours.

6. The method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The drying process described in step S2 specifically involves drying at 100℃~120℃ for 2~3 hours.

7. The method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The amount of γ-aminopropyltriethoxysilane used in step S2 is 0.5% to 1.0% of the mass of wollastonite.

8. The method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The dispersion described in step S3 specifically involves a rotation speed of 800 rpm and a dispersion time of 5 minutes.

9. A method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The extruder described in step S3 has the following parameters: first section 180°C, second section 210°C, third section 230°C, fourth section 220°C, and fifth extruder head section 210°C.

10. A method for preparing a high-temperature resistant polypropylene composite material for rapid thermal cycling injection molding according to claim 3, characterized in that, The rapid thermal cycling injection molding machine described in step S4 has the following specific parameters: barrel temperature 220℃~240℃, initial mold temperature 40℃, mold rapidly heated to 130℃ before injection, injection speed 80mm / s, holding pressure 60MPa, and holding time 10 seconds.

Images