An integrated embedding and encapsulation injection molding process for multi-material composite parts

Abstract

The present application relates to the technical field of polymer material forming and processing, and discloses an embedding and sealing glue integrated injection molding process for multi-material composite parts, which comprises the following steps: placing a metal insert in a mold cavity; injecting a phase separation type sealing composite material containing a thermoplastic base, a low-melting-point sealing resin, a rheological modifier and a chemical bonding agent; applying a periodic oscillating pressure in the pressure maintaining stage, and driving the sealing component to migrate to the interface by using the shear thinning characteristics of the rheological modifier; controlling the pressure maintaining temperature to be between the base crystallization temperature and the sealing resin freezing point, and maintaining a liquid feeding channel; and finally cooling and setting. The present application induces phase separation by oscillating shear, so that the low-melting-point resin and the bonding agent are enriched on the metal interface, fill the micro shrinkage gaps and form a chemically bonded flexible buffer layer, without the need for an additional dispensing process, effectively solving the interface sealing failure problem caused by the difference in thermal expansion coefficient, and significantly improving the air tightness and cold and hot impact resistance of the composite part.

Description

Technical Field

[0001] This invention relates to the field of polymer material molding and processing technology, specifically to an integrated injection molding process for embedding and sealing multi-material composite components. Background Technology

[0002] Metal-polymer composite components, combining the high strength and conductivity of metals with the lightweight, insulating, and easily processed properties of polymers, have found widespread application in automotive electronics, new energy batteries, and communication equipment. In applications such as controller housings, sensor assemblies, or battery module endplates, the interface between the metal insert and the polymer matrix not only needs sufficient mechanical strength but also typically requires strict requirements for airtightness or watertightness to prevent external moisture or corrosive gases from penetrating the component.

[0003] Existing manufacturing processes typically employ metal insert injection molding technology. To improve the bonding quality at the metal-polymer interface, common industrial methods include physical or chemical pretreatment of the metal insert surface, such as sandblasting, laser etching, or nanomaterial molding (NMT), to increase surface roughness and achieve mechanical interlocking; or post-processing steps such as dispensing, potting, or assembling rubber seals after injection molding to compensate for interfacial gaps. Some technical solutions also attempt to pre-coat the metal surface with heat-activated adhesives, utilizing the heat of the melt during injection molding to activate the adhesive layer.

[0004] There is a significant difference in the coefficient of thermal expansion between metallic materials and general-purpose thermoplastic engineering plastics. During injection molding and cooling, the volume shrinkage rate of the polymer matrix is ​​much greater than that of the metal insert. This shrinkage mismatch causes the polymer to tend to peel off from the metal surface, resulting in unavoidable microscopic gaps at the interface. While mechanical interlocking created by a physically rough structure can provide some tensile strength, it is difficult to completely block the permeation path of gas or liquid at the microscale. Furthermore, the rigid physical interface lacks a stress buffering mechanism. Under long-term thermal shock cycles, the alternating shear stress generated at the interface due to the difference in thermal expansion and contraction can easily lead to cracking of the polymer layer or failure of the mechanical interlocking. Post-processing methods relying on dispensing or sealing rings not only increase the process flow and manufacturing costs, but the adhesives themselves also have problems such as poor temperature resistance and easy aging, making it difficult to meet the long-term service requirements of high-performance components in complex environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an integrated injection molding process for embedding and sealing multi-material composite components, which solves the problems of micro-gaps at the interface, sealing failure, and significant attenuation of bonding strength caused by the large difference in thermal expansion coefficients between the polymer matrix and the metal insert and the shrinkage of the polymer during curing under drastic temperature alternation.

[0006] To achieve the above objectives, the present invention provides an integrated injection molding process for embedding and sealing multi-material composite components, employing the following technical solution:

[0007] An integrated injection molding process for embedding and sealing multi-material composite components includes the following steps:

[0008] S1. Place the metal insert into the cavity of the injection mold and close the mold;

[0009] S2. Inject molten phase-separated sealing composite material into the mold cavity until the cavity is filled; the phase-separated sealing composite material includes a thermoplastic resin matrix, a low-melting-point sealing resin, a rheology modifier, and a chemical bonding agent.

[0010] S3. Oscillating and holding pressure treatment: During the holding pressure stage, the oscillating pressure is applied to the melt in the mold cavity by the screw or piston of the injection molding machine. Under the action of the shear field formed by the oscillating pressure, the rheology modifier reduces the shear viscosity of the melt, causing the low melting point sealing resin and chemical bonding agent to migrate to the interface of the metal insert.

[0011] S4. Cool and solidify, open the mold and remove the multi-material composite part.

[0012] In the step of oscillation and pressure holding, the mold temperature is controlled to be lower than the crystallization temperature of the thermoplastic resin matrix and higher than the solidification point of the low melting point sealing resin.

[0013] By employing the above technical solution, utilizing the melting point differences and rheological response characteristics among the components of the phase-separated sealing composite material, and combining this with a dynamic oscillation and pressure-holding process, the filling of interfacial micro-defects and the enhancement of chemical bonding are achieved. Its mechanism and process are as follows:

[0014] First, shear-induced phase separation and migration occur. Rheology modifiers, due to their highly branched molecular structure, have low molecular chain entanglement. In the periodic shear field introduced by oscillating pressure holding, the rheology modifier preferentially responds and undergoes shear thinning, leading to a local decrease in melt viscosity. Based on the shear fractionation effect in hydrodynamics, low-viscosity components (including low-melting-point sealing resins, chemical bonding agents, and rheology modifiers) tend to migrate towards the mold walls and metal insert interfaces with higher shear rates, thereby accumulating on the metal surface to form a highly fluid sealing precursor layer.

[0015] Secondly, liquid-phase shrinkage is achieved by utilizing the difference in thermodynamic phase transitions. The process is designed with a temperature window between the crystallization temperature of the matrix resin and the solidification point of the sealing resin. When the high-melting-point thermoplastic resin matrix begins to crystallize and undergo volume shrinkage, the low-melting-point sealing resin at the interface remains in a molten liquid state. At this time, the oscillating pressure field continues to act, forcing the liquid sealing resin into the micro-voids generated by the shrinkage of the matrix and the micro-grooves on the metal surface, blocking gas leakage channels and eliminating interface shrinkage cavities.

[0016] Finally, a chemical anchoring and stress buffer layer is formed. The chemical bonding agents enriched at the interface expand their active groups at high temperatures, reacting with the oxide layer on the metal surface to form covalent bonds. Simultaneously, the polymer layer formed after the low-melting-point sealing resin cures has a lower modulus than the matrix resin. This low-modulus layer constitutes a stress buffer zone between the metal insert and the rigid matrix, absorbing interfacial shear stress caused by the mismatch in thermal expansion coefficients under thermal shock conditions, thus inhibiting crack initiation.

[0017] Preferably, the phase-separated sealing composite material is made from raw materials comprising the following parts by weight: 40-60 parts of thermoplastic resin matrix; 30-50 parts of reinforcing fiber; 10-20 parts of low-melting-point sealing resin; 0.5-3 parts of rheology modifier; 1-5 parts of chemical bonding agent masterbatch; 0.1-0.5 parts of antioxidant; and 0.2-1.0 parts of lubricant. The chemical bonding agent is present as the active component of the chemical bonding agent masterbatch.

[0018] By adopting the above technical solution, the proportions of each component are limited to balance structural strength and sealing performance. The matrix resin and reinforcing fibers form the mechanical framework, while the low-melting-point resin provides the sealing medium. The introduction of a chemical bonding agent in masterbatch form prevents premature evaporation of liquid small-molecule silanes at the high-temperature injection molding stage, thus preventing the formation of bubble defects at the interface and ensuring interface compactness.

[0019] Preferably, the low-melting-point sealing resin is a ternary copolyamide; the melting point of the ternary copolyamide is 20°C to 40°C lower than that of the thermoplastic resin matrix; the thermoplastic resin matrix is ​​selected from polyamide 66 or polyamide 6; the ternary copolyamide is copolymerized from caprolactam, hexamethylene adipate, and dodecanoic acid.

[0020] By employing the above technical solution, a process window with solid-liquid coexistence is constructed using the melting point difference of 20℃ to 40℃, ensuring that the sealing resin still possesses shrinkage compensation capability during the pressure holding stage after the matrix loses its fluidity. The long-chain dodecalactam structural unit introduced into the ternary copolyamide reduces the material's moisture absorption rate and elastic modulus, and improves the stability of the interface in humid environments and its ability to dissipate stresses.

[0021] Preferably, the rheology modifier is a hydroxyl-terminated hyperbranched polyester; the hydroxyl-terminated hyperbranched polyester is a second- to fourth-generation hyperbranched polymer with trimethylolpropane as the core and 2,2-dimethylolpropionic acid as the monomer; the hydroxyl value of the hydroxyl-terminated hyperbranched polyester ranges from 200 mg KOH / g to 500 mg KOH / g.

[0022] By employing the above technical solution, the near-spherical molecular topology of the hydroxyl-terminated hyperbranched polyester reduces intermolecular entanglement, providing internal lubrication and effectively lowering melt viscosity. Simultaneously, the high-density hydroxyl groups on its periphery improve the wettability of the polymer melt on polar metal surfaces and provide auxiliary active sites for the grafting reaction of silane coupling agents.

[0023] Preferably, the chemical bonding agent masterbatch is made from components comprising the following weight percentages: 80 to 90 wt% carrier resin; 8 to 15 wt% silane coupling agent; and 0.5 to 2 wt% initiator; wherein the silane coupling agent is at least one of epoxy silane or amino silane. More preferably, the chemical bonding agent masterbatch is prepared by a reactive extrusion process, which includes the following steps: uniformly mixing the carrier resin, silane coupling agent, and initiator, and then adding the mixture to a twin-screw extruder; controlling the temperature of the reaction section of the twin-screw extruder to be 180°C to 220°C, and controlling the screw speed to be 300 rpm to 500 rpm, so that the silane coupling agent is grafted onto the molecular chain of the carrier resin; extruding, granulating, and drying to obtain a chemical bonding agent masterbatch with a grafting rate greater than 1.5%.

[0024] By employing the above technical solution, a highly active silane coupling agent is grafted and fixed onto the carrier resin chain segments through reactive extrusion, improving the thermal stability of the silane during high-temperature injection molding and preventing its decomposition or volatilization failure due to high temperatures. Under the shear and thermal effects of injection molding, the grafted chain segments unwrap and expose the active groups, achieving effective bonding to the metal interface.

[0025] Preferably, in the step of oscillation pressure holding treatment, the process parameters of oscillation pressure holding treatment include: oscillation frequency of 1.5Hz to 4.0Hz; pressure amplitude of 10% to 20% of the pressure holding reference pressure; and oscillation duration covering the entire gate freezing time.

[0026] By adopting the above technical solution, the frequency setting of 1.5Hz to 4.0Hz is matched with the relaxation characteristics of the rheology modifier to maximize the shear thinning effect while avoiding material degradation caused by high-frequency shear heating. The pressure amplitude is set to 10% to 20% of the reference pressure, which provides the power required to drive the low-viscosity component to fill the micro-gaps while avoiding excessive pressure fluctuations that could lead to residual internal stress inside the component.

[0027] Preferably, in the step of placing the metal insert into the mold cavity of the injection mold and closing the mold, the metal insert is pretreated; the pretreatment includes: plasma cleaning or sandblasting the surface of the metal insert, and preheating the metal insert to 100°C to 120°C.

[0028] By employing the above technical solutions, plasma or sandblasting treatments remove contaminants from the metal surface and increase the specific surface area. Preheating the metal insert aims to reduce the temperature difference when the molten metal contacts the interface, preventing premature freezing of the molten metal at the interface due to quenching, thereby ensuring that the low-melting-point sealing resin has sufficient time to wet the metal surface and complete the chemical reaction.

[0029] Preferably, in the step of injecting the molten phase-separated sealing composite material into the mold cavity, the melt temperature of the molten phase-separated sealing composite material is 260°C to 290°C, and the mold temperature is controlled between 80°C and 100°C.

[0030] By adopting the above technical solution, the temperature range ensures that the matrix resin is fully melted and plasticized. At the same time, the mold temperature of 80℃ to 100℃ controls the crystallization rate of the matrix, maintains a suitable phase separation thermodynamic environment, and ensures the implementation effect of the oscillation and pressure holding process.

[0031] Preferably, the low-melting-point sealing resin is thermodynamically incompatible with the thermoplastic resin matrix; after cooling and setting, the low-melting-point sealing resin forms a flexible sealing layer rich in silane bonding points on the surface of the metal insert.

[0032] By adopting the above technical solution, based on the thermodynamic incompatibility between components, phase separation is induced in the system during the molding process, and a functional gradient structure is finally formed on the cross-section of the component: the interior is a fiber-reinforced rigid support layer, and the interface is a high-density, low-modulus flexible sealing layer, thus taking into account both the overall mechanical strength and the sealing durability of the interface.

[0033] This invention provides an integrated injection molding process for embedding and sealing multi-material composite components. It offers the following advantages:

[0034] 1. This invention utilizes the synergistic effect of an oscillating pressure-holding process and a rheology modifier. By leveraging the shear-thinning properties of the rheology modifier under a dynamic shear field, the local melt viscosity is reduced, driving the low-melting-point sealing resin and chemical bonding agent to migrate and accumulate directionally at the metal insert interface. This mechanism allows the liquid sealing component to actively fill the micro-gaps and micro-grooves on the metal surface caused by the cooling and shrinkage of the matrix resin. Without adding additional sealing processes, it significantly reduces the porosity of the interface, achieving an airtight seal at the multi-material interface.

[0035] 2. This invention solves the problem of poor weather resistance at the interface of heterogeneous materials by constructing a dual stabilization mechanism of "chemical bonding + flexible buffering" at the interface. The silane bonding agent enriched at the interface reacts with the metal surface to form covalent bonds for anchoring, providing high-strength chemical bonding force; at the same time, the low-modulus flexible layer formed after the low-melting-point ternary copolyamide is cured can effectively absorb and dissipate the shear stress generated in thermal shock cycles due to the mismatch of thermal expansion coefficients between the metal and the polymer matrix, inhibiting the initiation and propagation of interface fatigue cracks, and significantly improving the long-term reliability of composite components in complex service environments.

[0036] 3. This invention improves process stability and production efficiency by using reaction-grafted solid-phase silane masterbatch instead of liquid silane and combining it with one-step injection molding. The solid-phase masterbatch effectively avoids bubble defects caused by the volatilization of small liquid molecules during high-temperature injection molding, ensuring the density of the interface; at the same time, the integrated molding process eliminates the separate dispensing, curing, or mechanical assembly steps in traditional technologies, simplifying the production process, reducing manufacturing costs, and making it suitable for the large-scale manufacturing of complex composite components. Attached Figure Description

[0037] Figure 1 The figures are comparative differential scanning calorimetry (DSC) temperature rise curves of composite material particles in the embodiments and comparative examples of the present invention. Figure (a) is the DSC temperature rise curve of sample A in Example 1, Figure (b) is the DSC temperature rise curve of Example 2, and Figure (c) is the DSC temperature rise curve of Comparative Example 5.

[0038] Figure 2 Figure 1 shows the test results of the rheological thixotropy and oscillation response of the composite material melt of the present invention. Figure 2(a) is a double logarithmic curve of the complex viscosity of each group in the angular frequency range of 0.1-100 rad / s as a function of frequency. Figure 3(b) is a bar chart comparing the complex viscosity of each group in three key process nodes: low frequency static region, oscillation pressure holding region and high shear injection region.

[0039] Figure 3 Figure 1 shows the test results of the metal-polymer interface air tightness and sealing performance of the present invention. Figure 2(a) is a comparison of the average helium leakage rate of each group, and Figure 3(b) is a statistical chart of the number of samples with large leaks or failures in each group.

[0040] Figure 4 Figure 1 shows the axial pull-out force test results of the metal inserts of the present invention. Figure 2(a) is a bar chart comparing the average pull-out force of the metal inserts in each group. The error bars in the figure represent the standard deviation. Figure 3(b) is a comparison of the pull-out force of Example 1 and Comparative Example 6 and a quantitative analysis of the interface enhancement mechanism.

[0041] Figure 5The following are the test results of the thermal shock resistance of the present invention. Figure (a) is a comparison of the interfacial pull-out force of each group before and after 500 thermal shock cycles, and Figure (b) is a statistical chart of the interfacial bonding force retention rate of each group after the thermal shock test. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0044] Polyamide 66, CAS No. 32131-17-2, relative viscosity 2.7 (measured in 96% sulfuric acid), melting point 262℃.

[0045] Short-cut glass fibers, alkali-free E glass, monofilament diameter 11μm, initial cut length 3mm, surface treated with silane coupling agent.

[0046] Ternary copolyamide 6 / 66 / 12, CAS No. 63428-84-2, melting point 130℃, melt flow rate 30g / 10min (190℃, 2.16kg).

[0047] Maleic anhydride-grafted ethylene-octene copolymer, maleic anhydride grafting rate 1.0 wt%, density 0.87 g / cm³ 3 The base resin has CAS number 26221-73-8.

[0048] Polyamide 6, CAS No. 25038-54-4, relative viscosity 2.45, melting point 220℃.

[0049] Trimethylolpropane, CAS No. 77-99-6, purity ≥99%.

[0050] 2,2-Dimethylolpropionic acid, CAS No. 4767-03-7, purity ≥99%.

[0051] Vinyltrimethoxysilane, CAS No. 2768-02-7, purity ≥98%.

[0052] Dicumyl peroxide, CAS No. 80-43-3, purity ≥99%.

[0053] p-Toluenesulfonic acid monohydrate, CAS No. 6192-52-5, purity ≥98.5%.

[0054] Antioxidant 1098, CAS No. 23128-74-7.

[0055] Antioxidant 168, CAS No. 31570-04-4.

[0056] Preparation Example 1:

[0057] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester (HBPE-OH-1), comprising the following steps:

[0058] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 268.2 g (2.0 mol) of 2,2-dimethylolpropionic acid to a four-necked flask equipped with a mechanical stirrer, a nitrogen inlet tube and a water separator. Purge with nitrogen for protection and heat to 145 °C to melt the trimethylolpropane and mix it with the 2,2-dimethylolpropionic acid to form a uniform slurry reaction mixture.

[0059] (2) Add 0.85g of p-toluenesulfonic acid monohydrate as a catalyst, adjust the stirring speed to 300rpm, slowly raise the temperature to 155℃, and react at atmospheric pressure for 3.5 hours. During this period, the generated water is continuously removed, and the system gradually becomes clear as the reaction proceeds.

[0060] (3) Connect the vacuum pump and gradually increase the vacuum to -0.09MPa, while raising the temperature to 165℃ and continuing the reaction for 1.5 hours to remove residual small molecules and increase the degree of polymerization;

[0061] (4) Stop heating, release the vacuum, pour out the product and cool it in a dryer. After crushing, hydroxyl-terminated hyperbranched polyester HBPE-OH-1 is obtained, and its hydroxyl value is measured to be 380 mg KOH / g.

[0062] Preparation Example 2:

[0063] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester (HBPE-OH-2), comprising the following steps:

[0064] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 201.2 g (1.5 mol) of 2,2-dimethylolpropionic acid to the reaction vessel (molar ratio 1:15), and the other conditions are the same as in step (1) of Preparation Example 1.

[0065] (2) Add 0.64 g of p-toluenesulfonic acid monohydrate and react at 150 °C and atmospheric pressure for 3.0 hours;

[0066] (3) Continue the reaction for 1.0 hour at a vacuum of -0.08 MPa and a temperature of 160°C;

[0067] (4) The post-treatment was the same as in Preparation Example 1, and the terminal hydroxyl hyperbranched polyester HBPE-OH-2 with lower molecular weight and higher fluidity was obtained. Its hydroxyl value was measured to be 425 mg KOH / g.

[0068] Preparation Example 3:

[0069] This preparation example provides a method for preparing a hydroxyl-terminated hyperbranched polyester (HBPE-OH-3), comprising the following steps:

[0070] (1) Add 13.4 g (0.1 mol) of trimethylolpropane and 335.3 g (2.5 mol) of 2,2-dimethylolpropionic acid to the reaction vessel (molar ratio 1:25), and the other conditions are the same as in step (1) of Preparation Example 1.

[0071] (2) Add 1.05g of p-toluenesulfonic acid monohydrate and react at 160℃ and atmospheric pressure for 4.0 hours;

[0072] (3) Continue the reaction for 2.0 hours at a vacuum of -0.09 MPa and a temperature of 170°C;

[0073] (4) The post-treatment was the same as in Preparation Example 1, and a terminal hydroxyl hyperbranched polyester HBPE-OH-3 with a higher molecular weight and denser branching was obtained. Its hydroxyl value was measured to be 320 mg KOH / g.

[0074] Preparation Example 4:

[0075] This preparation example provides a method for preparing silane-grafted polyamide masterbatch (PA6-g-VTMS-1), including the following steps:

[0076] (1) Dry 100 kg of polyamide 6 chips in a vacuum oven at 80°C for 4 hours until the moisture content is less than 0.05%;

[0077] (2) Mix 2.5 kg of vinyltrimethoxysilane with 0.08 kg of dicumyl peroxide and spray it evenly onto the surface of the dried polyamide 6 chips. Stir at low speed for 15 minutes in a high-speed mixer, then seal and let stand for 2 hours to ensure uniform impregnation.

[0078] (3) Add the mixture to a twin-screw extruder with a length-to-diameter ratio of 44:1. Set the screw speed to 300 rpm. The barrel temperature distribution is as follows: Zone 1 110℃-120℃ (to prevent silane from evaporating too early at the feed port), Zones 2 to 6 (reaction section) 225℃-230℃, Zone 7 to the die head 230℃.

[0079] (4) In the eighth and ninth zones of the extruder, a strong vacuum devolatilization is activated, and the vacuum level is maintained below -0.09 MPa to remove unreacted monomers;

[0080] (5) After the extruded strip is cooled by water and granulated, it is immediately vacuum sealed in an aluminum-plastic composite bag to obtain grafted masterbatch PA6-g-VTMS-1.

[0081] Preparation Example 5:

[0082] This preparation example provides a method for preparing silane-grafted polyamide masterbatch (PA6-g-VTMS-2), including the following steps:

[0083] (1) The raw material ratio is adjusted to: 100 kg of polyamide 6 chips, 3.0 kg of vinyltrimethoxysilane, and 0.10 kg of dicumyl peroxide;

[0084] (2) The screw speed of the extruder is increased to 350 rpm, and the reaction temperature in zones two to six is ​​increased to 235°C to match the reaction rate of high-concentration monomers;

[0085] (3) The remaining steps and process parameters are the same as in Preparation Example 4, and high grafting rate masterbatch PA6-g-VTMS-2 is obtained.

[0086] Preparation Example 6:

[0087] This preparation example provides a method for preparing silane-grafted polyamide masterbatch (PA6-g-VTMS-3), including the following steps:

[0088] (1) The raw material ratio is adjusted to: 100 kg of polyamide 6 chips, 1.5 kg of vinyltrimethoxysilane, and 0.05 kg of dicumyl peroxide;

[0089] (2) The extruder temperature setting is slightly reduced, and the temperature in zones two to six is ​​maintained at 220℃-225℃ to reduce side reactions and protect the matrix color;

[0090] (3) The remaining steps and process parameters are the same as in Preparation Example 4 (Note: the temperature setting in Zone 1 is also kept at 110℃-120℃) to obtain low grafting rate masterbatch PA6-g-VTMS-3.

[0091] Preparation Example 7:

[0092] This preparation example provides a general method for preparing composite material granules for subsequent injection molding, including the following steps:

[0093] (1) According to the formulation amount of the examples or comparative examples, the remaining raw materials (including polyamide 66, ternary copolyamide, maleic anhydride grafted ethylene-octene copolymer, antioxidant, and the hydroxyl-terminated hyperbranched polyester and silane grafted polyamide masterbatch prepared in the above preparation examples) except for the short glass fiber are premixed.

[0094] (2) Add the mixture to the main feed port of the twin-screw extruder, and add the chopped glass fiber through the side feed port;

[0095] (3) Set the extruder process parameters: screw speed 400 rpm, barrel temperature from feed port to die head is 265℃, 270℃, 275℃, 275℃, 275℃, 270℃, vacuum degree of vacuum exhaust section -0.08MPa;

[0096] (4) After the extruded strip is cooled by water, granulated and dried (110℃, 5 hours), composite material granules are obtained and sealed for storage.

[0097] Example 1:

[0098] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components, specifically including the following steps:

[0099] (1) Weigh the raw materials by weight: 70.0 parts of polyamide 66, 30.0 parts of chopped glass fiber, 12.0 parts of ternary copolyamide, 2.0 parts of hydroxyl-terminated hyperbranched polyester (HBPE-OH-1) prepared in Preparation Example 1, 2.0 parts of silane-grafted polyamide masterbatch (PA6-g-VTMS-1) prepared in Preparation Example 4, 3.0 parts of maleic anhydride-grafted ethylene-octene copolymer, 0.2 parts of antioxidant 1098, and 0.2 parts of antioxidant 168.

[0100] (2) According to the method described in Preparation Example 7, the above raw materials were melt-extruded and granulated to obtain composite material granules, and the granules were dried in a vacuum oven at 120°C for 4 hours until the moisture content was less than 0.02%.

[0101] (3) Install the mold with aluminum alloy inserts on an injection molding machine equipped with a dynamic pressure control system. Preheat the aluminum alloy inserts to 95°C and place them into the mold cavity. Set the mold temperature to 90°C and the barrel temperature to: 260°C for the rear section, 275°C for the middle section, 280°C for the front section, and 280°C for the nozzle.

[0102] (4) High shear phase separation injection: The melt is injected into the mold cavity at an injection speed of 120 mm / s and the injection pressure is set to 110 MPa until 98% of the cavity is filled.

[0103] (5) Static skeleton shaping: Hold at a constant holding pressure of 100MPa for 3.0 seconds to allow the matrix polyamide 66 to initially crystallize and form a rigid skeleton.

[0104] (6) Oscillating shear penetration and anchoring: Start the dynamic pressure holding program, set the reference pressure to 50MPa, superimpose a sine wave pressure oscillation, with an oscillation frequency of 2.0Hz, an amplitude of ±8.0MPa (i.e., the pressure fluctuates between 42-58MPa), and a duration of 8.0 seconds.

[0105] (7) Gradient cooling: Stop oscillation, reduce the pressure linearly to 20MPa within 2.0 seconds, then cool for 15 seconds, open the mold and take out the part.

[0106] Example 2:

[0107] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components, specifically including the following steps:

[0108] (1) Weigh the raw materials by weight: 65.0 parts of polyamide 66, 25.0 parts of chopped glass fiber, 15.0 parts of ternary copolyamide, 2.5 parts of hydroxyl-terminated hyperbranched polyester (HBPE-OH-1) prepared in Preparation Example 1, 3.0 parts of high grafting rate masterbatch (PA6-g-VTMS-2) prepared in Preparation Example 5, 4.0 parts of maleic anhydride grafted ethylene-octene copolymer, 0.25 parts of antioxidant 1098, and 0.25 parts of antioxidant 168.

[0109] (2) The granulation and drying steps are the same as in Example 1.

[0110] (3) The injection molding basic parameters are set in the same way as in Example 1.

[0111] (4) High shear phase separation injection: the injection speed is increased to 140 mm / s and the injection pressure is 120 MPa.

[0112] (5) Static skeleton shaping: holding pressure 90MPa, holding time 2.5 seconds.

[0113] (6) Oscillating shear penetration and anchoring: reference pressure 60MPa, oscillation frequency 1.5Hz, amplitude ±10.0MPa, duration 10.0 seconds.

[0114] (7) Gradient cooling: Same as in Example 1.

[0115] Example 3:

[0116] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components, specifically including the following steps:

[0117] (1) Weigh the raw materials by weight: 75.0 parts of polyamide 66, 35.0 parts of chopped glass fiber, 10.0 parts of ternary copolyamide, 1.0 parts of hydroxyl-terminated hyperbranched polyester (HBPE-OH-1) prepared in Preparation Example 1, 1.5 parts of low grafting rate masterbatch (PA6-g-VTMS-3) prepared in Preparation Example 6, 2.0 parts of maleic anhydride grafted ethylene-octene copolymer, 0.15 parts of antioxidant 1098, and 0.15 parts of antioxidant 168.

[0118] (2) The granulation and drying steps are the same as in Example 1.

[0119] (3) The injection molding basic parameters are set in the same way as in Example 1.

[0120] (4) High shear phase separation injection: injection speed 100 mm / s, injection pressure 130 MPa.

[0121] (5) Static skeleton shaping: holding pressure 100MPa, holding time 4.0 seconds.

[0122] (6) Oscillating shear penetration and anchoring: reference pressure 45MPa, oscillation frequency 2.5Hz, amplitude ±5.0MPa, duration 6.0 seconds.

[0123] (7) Gradient cooling: Same as in Example 1.

[0124] Example 4:

[0125] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components, mainly examining low-frequency, large-amplitude process parameters, and specifically includes the following steps:

[0126] (1) The raw material formula is the same as in Example 1.

[0127] (2) The granulation and drying steps are the same as in Example 1.

[0128] (3) The injection molding basic parameters are set in the same way as in Example 1.

[0129] (4) High shear phase separation injection: injection speed 120 mm / s, injection pressure 110 MPa.

[0130] (5) Static frame shaping: holding pressure 95MPa, holding time 3.0 seconds.

[0131] (6) Oscillating shear penetration and anchoring: reference pressure 55MPa, oscillation frequency set to 0.5Hz (low frequency), amplitude set to ±10.0MPa (large amplitude), duration 10.0 seconds.

[0132] (7) Gradient cooling: Same as in Example 1.

[0133] Example 5:

[0134] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components, mainly examining high-frequency, low-amplitude process parameters, and specifically includes the following steps:

[0135] (1) The raw material formula is the same as in Example 1.

[0136] (2) The granulation and drying steps are the same as in Example 1.

[0137] (3) The injection molding basic parameters are set in the same way as in Example 1.

[0138] (4) High shear phase separation injection: injection speed 120 mm / s, injection pressure 110 MPa.

[0139] (5) Static frame shaping: holding pressure 95MPa, holding time 3.0 seconds.

[0140] (6) Oscillating shear penetration and anchoring: reference pressure 50MPa, oscillation frequency set to 3.0Hz (high frequency), amplitude set to ±5.0MPa (small amplitude), duration 7.0 seconds.

[0141] (7) Gradient cooling: Same as in Example 1.

[0142] Example 6:

[0143] This embodiment provides an integrated injection molding process for embedding and sealing multi-material composite components. It mainly examines the impact of different specifications of hyperbranched polyester on the process, specifically including the following steps:

[0144] 1. Weigh the raw materials according to the following parts by weight: 70.0 parts of polyamide 66, 30.0 parts of chopped glass fiber, 12.0 parts of ternary copolyamide, 2.0 parts of low molecular weight hydroxyl-terminated hyperbranched polyester (HBPE-OH-2) obtained in Preparation Example 2, 2.0 parts of silane-grafted polyamide masterbatch (PA6-g-VTMS-1) obtained in Preparation Example 4, 3.0 parts of maleic anhydride-grafted ethylene-octene copolymer, 0.2 parts of antioxidant 1098, and 0.2 parts of antioxidant 168.

[0145] (2) The granulation and drying steps are the same as in Example 1.

[0146] (3) The injection molding basic parameters are set in the same way as in Example 1.

[0147] (4) High shear phase separation injection: injection speed 120 mm / s, injection pressure 110 MPa.

[0148] (5) Static skeleton shaping: holding pressure 100MPa, holding time 3.0 seconds.

[0149] (6) Oscillating shear penetration and anchoring: reference pressure 50MPa, oscillation frequency 2.0Hz, amplitude ±8.0MPa, duration 8.0 seconds.

[0150] (7) Gradient cooling: Same as in Example 1.

[0151] Comparative Example 1:

[0152] Compared with Example 1, the only difference is that: the hydroxyl-terminated hyperbranched polyester (HBPE-OH-1) was not added to the raw material components, and the missing 2.0 parts by weight were made up by the matrix polyamide 66. The other raw materials and injection molding process parameters are the same.

[0153] Comparative Example 2:

[0154] Compared with Example 1, the only difference is that in the injection molding process step (6), the oscillating shear penetration process is not used, but the traditional constant pressure holding process is used, with the holding pressure set at 50MPa and the holding time at 8.0 seconds. The other raw materials and processes are the same.

[0155] Comparative Example 3:

[0156] Compared with Example 1, the only difference is that: instead of adding silane-grafted polyamide masterbatch (PA6-g-VTMS-1) to the raw material components, an equal amount of ungrafted liquid vinyltrimethoxysilane (0.05 parts, equivalent to silane content) is directly added, and the remaining polymer carrier is made up by polyamide 6. All other processes are the same.

[0157] Comparative Example 4:

[0158] Compared with Example 1, the only difference is that an equal amount of conventional lubricant ethylene bis-stearamide (EBS) is used to replace the hydroxyl-terminated hyperbranched polyester (HBPE-OH-1), while the other raw materials and injection molding process parameters are the same.

[0159] Comparative Example 5:

[0160] Compared with Example 1, the only difference is that: low-melting-point ternary copolyamide (Co-PA) was not added to the raw material components, and the missing 12.0 parts by weight were made up by the matrix polyamide 66. All other raw materials and injection molding process parameters are the same.

[0161] Comparative Example 6:

[0162] Compared with Example 1, the only difference is that silane-grafted polyamide masterbatch (PA6-g-VTMS-1) was not added to the raw material components, and the missing parts were made up by polyamide 6. All other raw materials and processes are the same.

[0163] Test Example 1: Validation of the thermodynamic phase separation window (Differential Scanning Calorimetry)

[0164] Experimental Description: This experiment aims to determine the thermal transformation behavior of the composite material system using differential scanning calorimetry (DSC) to confirm whether the matrix phase (polyamide 66) and the dispersed sealing phase (terpolymer copolyamide) maintain independent thermodynamic properties in the compound system. The experiment focuses on capturing the distribution of endothermic peaks during the heating process and quantifying the difference in melting points between the two phases (ΔTm) to verify the material basis for achieving "solid-liquid coexistence" within a specific injection molding holding temperature range.

[0165] Experimental steps:

[0166] Dry composite material granules prepared in Examples 1, 2 and Comparative Example 5 (without low-melting-point copolyamide) were selected as test samples. Slices of 5 mg to 8 mg were cut from the cross-section of the granules and placed in aluminum crucibles, which were then covered and compacted.

[0167] The prepared sample was placed in the furnace of the differential scanning calorimeter (model: DSC 214 Polyma), with a blank aluminum crucible as the reference sample. High-purity nitrogen was introduced as a protective gas, and the gas flow rate was set to 50 mL / min.

[0168] Perform the heat history elimination procedure: First, heat from 25°C to 290°C at a rate of 20°C / min, hold at 290°C for 3 minutes to ensure complete melting and homogenization of the components, and then cool down to 25°C at a rate of 20°C / min.

[0169] Execute the test procedure: Increase the temperature again from 25℃ to 290℃ at a rate of 10℃ / min, and record the heat flow curve data of the sample as a function of temperature in real time.

[0170] The second heating curve was integrated using analysis software to identify and label the peak temperature (Tm) of the endothermic peak and the initial melting temperature (Tonset) on the curve, and the temperature difference between different melting peaks was calculated.

[0171] Experimental data:

[0172] Table 1: DSC thermal transformation characteristics test data of composite material systems

[0173] Sample number Peak melting point of the sealed phase Tm1 (°C) Sealing phase melting range width (°C) Matrix phase melting peak Tm2 (°C) The difference in melting points between the two phases, ΔTm (°C). Example 1 - Sample A 129.8 11.4 262.3 132.5 Example 1 - Sample B 130.2 12.1 261.8 131.6 Example 1 - Sample C 128.9 10.8 262.5 133.6 Example 2 131.5 13.2 261.2 129.7 Comparative Example 5 — — 262.1 —

[0174] in conclusion:

[0175] according to Figure 1 As shown in Table 1, the DSC test results of Examples 1 and 2 both exhibit significant dual melting point characteristics. The endothermic peak in the low-temperature region is concentrated in the range of 129℃-131℃, corresponding to the melt transition of the ternary copolyamide (Co-PA); the endothermic peak in the high-temperature region is stable between 261℃-262℃, corresponding to the melt transition of the polyamide 66 (PA66) matrix.

[0176] The data shows that the melting point difference (ΔTm) between the two phases remained stable at around 130℃, and the melting peaks of the two phases were completely separated on the temperature axis with no overlapping regions. This confirms that during the blending modification and extrusion granulation process, the low-melting-point sealing phase and the high-melting-point matrix phase did not undergo complete molecular-level compatibility or transesterification reactions, but rather maintained their independent thermodynamic phase states. In contrast, Comparative Example 5 only detected a single high-temperature melting peak, corroborating that the low-temperature peak did indeed originate from the added ternary copolyamide.

[0177] This thermodynamic property directly supports the process mechanism of this scheme: when the melt temperature in the injection mold is between 150℃ and 220℃ (i.e., the holding pressure stage), the matrix PA66 has already fallen below its melting point (Tm2) and has undergone crystallization and solidification, constructing a rigid physical support skeleton; while at this time the ambient temperature is still much higher than the melting point of the sealing phase (Tm1), causing the Co-PA component and its carried chemical anchoring agent to remain in a low-viscosity liquid fluid state. This difference in physical state provides an absolute thermodynamic operating window for achieving "skeleton fixation and fluid penetration" under an oscillating pressure field, ensuring that the sealing material can independently compensate for the microscopic interface without compromising the overall dimensional accuracy of the part.

[0178] Test Example 2: Rheological Thixotropy and Oscillation Response Test

[0179] Experimental description:

[0180] This experiment utilizes a rotational rheometer to perform dynamic frequency scanning on composite materials in the molten state, aiming to analyze the complex viscosity of the material at different shear frequencies. Response Behavior. The experiment mainly investigated whether the system exhibited significant non-Newtonian fluid characteristics (shear thinning) and sensitivity to specific frequency oscillation fields after the introduction of terminal hydroxyl hyperbranched polyester (HBPE). By comparing the viscosity differences of different formulations at low frequencies (simulating static or low-speed flow) and high frequencies (simulating injection or high-frequency oscillation), the mechanism of HBPE as a rheology modifier in the "high-shear phase separation" and "oscillatory shear penetration" processes was demonstrated.

[0181] Experimental steps:

[0182] Composite material granules prepared in Example 1, Comparative Example 1 (without HBPE) and Comparative Example 4 (with EBS lubricant) were selected and dried in a vacuum oven at 100°C for 6 hours to remove moisture and prevent hydrolysis from interfering with viscosity measurement.

[0183] Using a rotational rheometer (model: ARES-G2) equipped with a 25mm parallel plate clamp, the test temperature was set to 270℃, and a nitrogen protective atmosphere was introduced with the gas flow rate controlled at 50mL / min to prevent oxidative cross-linking of the sample at high temperature.

[0184] Place the dried sample in the center of the heating plate. After the sample has completely melted, lower the upper plate to a test gap of 1.0 mm, scrape off the excess melt overflowing from the edge of the plate, and let it stand at a constant temperature for 3 minutes to eliminate the heat history of the load.

[0185] Within the linear viscoelastic region, the strain is set to 1%, and a dynamic frequency sweep program is executed to determine the angular frequency. The scan range was set from 0.1 rad / s to 100 rad / s, and samples were taken at logarithmic intervals.

[0186] Complex viscosity data were collected and calculated at each frequency point. The viscosity values ​​in the low-frequency region (0.1 rad / s), the process-related frequency band (10-20 rad / s, corresponding to 1.5-3.0 Hz in the actual process), and the high-frequency region (100 rad / s) were extracted and compared for analysis.

[0187] Experimental data:

[0188] Table 2: Dynamic rheological frequency scanning data of composite material melt (270℃)

[0189] Angular frequency ω (rad / s) Example 1: Complex Viscosity (Pa·s) Comparative Example 1: Complex viscosity (Pa·s) Comparative Example 4: Complex viscosity (Pa·s) 0.10 8542.3 9105.6 7654.2 0.25 8120.5 9088.1 7598.4 0.63 7433.8 8950.4 7502.1 1.58 6105.2 8642.7 7320.6 3.98 4215.6 8105.3 6985.5 10.00 2548.9 7254.8 6412.3 15.85 1876.4 6540.2 6054.7 25.12 1254.1 5420.6 5421.9 63.10 685.3 3850.5 4102.8 100.00 412.7 2654.1 2985.4

[0190] in conclusion:

[0191] according to Figure 2 According to the data in Table 2, the initial viscosity of each component in the low-frequency region (0.1 rad / s) is not significantly different. The viscosity of Example 1 (8542.3 Pa·s) is even higher than that of Comparative Example 4, which has added conventional lubricant. This indicates that under static or extremely low shear conditions, the hyperbranched polymer does not excessively reduce the melt strength of the matrix, which is beneficial to maintaining the strip stability during extrusion granulation.

[0192] However, with increasing angular frequency, Example 1 exhibited extremely sensitive shear-thinning behavior. Particularly in the frequency range of 10.00 rad / s to 25.12 rad / s (this range covers the 1.5 Hz–4.0 Hz oscillation holding frequency in the injection molding process of this invention), the complex viscosity of Example 1 decreased sharply. At high shear rates (100 rad / s), its viscosity (412.7 Pa·s) dropped to an extremely low level, less than 20% of that of Comparative Example 1 and Comparative Example 4. In contrast, although Comparative Example 4 added the small-molecule lubricant EBS, resulting in a slightly lower overall viscosity than Comparative Example 1, its viscosity showed a more gradual trend with frequency, exhibiting typical rheological characteristics of a linear polymer and lacking a nonlinear response to shear rate.

[0193] This rheological evidence demonstrates that HBPE's unique spherical, unentangled topology endows the system with significant thixotropy. During the injection stage, at high shear rates (>100 rad / s), the extremely low viscosity (412.7 Pa·s) drives the sealing components to migrate (phase separation) towards the mold wall and insert interface, where resistance is minimal. During the holding pressure stage, applying pressure oscillations at a specific frequency effectively activates the system's low-viscosity state, allowing it to maintain excellent flowability at the microscopic level even after the matrix framework has been established, thereby achieving deep penetration and filling of minute gaps.

[0194] Test Example 3: Air tightness and sealing performance test (helium leak detection method)

[0195] Experimental description:

[0196] This experiment uses helium mass spectrometry leak detection technology to quantitatively assess the sealing integrity of the metal-polymer interface in injection molded parts. Based on the extremely small atomic radius and high penetrability of helium molecules, the experiment establishes a pressure gradient across the interface and detects the flow rate of helium leaking through microscopic gaps in the interface. This determines the final interfacial density of the composite material under the synergistic effects of thermodynamic phase separation, rheology, and chemical anchoring, particularly the filling effect on microscopic shrinkage cavities and bubble defects.

[0197] Experimental steps:

[0198] Ten samples were randomly selected from each group of injection-molded samples prepared in Examples 1 to 6 and Comparative Examples 1 to 6 as test samples. The samples were conditioned for 48 hours in a standard environment of 23°C and 50% relative humidity to eliminate the initial fluctuations in shrinkage and moisture absorption after injection molding.

[0199] The injection-molded sample is secured using a custom-designed sealing fixture. The fixture uses double O-rings to seal the polymer outer wall of the sample, ensuring that the only potential gas pathway during testing is the interface between the metal insert and the polymer.

[0200] Connect the fixture to the inlet of the helium mass spectrometer (model: Pfeiffer ASM 340), and start the vacuum pump to evacuate the test chamber (one side of the sample interface) until the background vacuum level is below 1.0 × 10⁻⁶. -3 mbar.

[0201] Apply 99.999% pure helium gas to the other side of the sample interface (metal insert end), set the inflation pressure to 0.2 MPa (relative pressure), and maintain the pressure for 30 seconds.

[0202] After the leak detector reading stabilizes, record the helium leak rate in mbar·L / s. For leaks exceeding the range (leak rate > 1.0 × 10⁻⁶), record the leak rate. -2 The sample of mbar·L / s is denoted as "Gross Leak". The arithmetic mean of 10 samples in each group is taken as the final evaluation data (the calculation is performed after removing the Gross Leak samples; if all samples are Gross Leaks, they are recorded as failures).

[0203] Experimental data:

[0204] Table 3: Test Results of Helium Leakage Rate at Metal-Polymer Interfaces

[0205] Group Average helium leakage rate (mbar·L / s) Number of large leaks / failure samples (per 10) Remark Example 1 <![CDATA[3.2×10 -8 ]]> 0 Excellent airtightness Example 2 <![CDATA[5.4×10 -8 ]]> 0 Excellent airtightness Example 3 <![CDATA[1.8×10 -8 ]]> 0 Excellent airtightness Example 4 <![CDATA[4.1×10 -8 ]]> 0 Good low-frequency large amplitude effect Example 5 <![CDATA[2.9×10 -8 ]]> 0 High-frequency, small-amplitude vibrations perform well Example 6 <![CDATA[7.6×10 -8 ]]> 0 Different HBPEs vary slightly Comparative Example 1 <![CDATA[2.1×10 -4 ]]> 3 HBPE rheological guidance Comparative Example 2 <![CDATA[6.5×10 -5 ]]> 1 Oscillation-free pressure holding Comparative Example 3 <![CDATA[8.9×10 -4 ]]> 5 Liquid silane foaming Comparative Example 4 <![CDATA[1.5×10 -4 ]]> 2 Lubricant without thixotropy Comparative Example 5 <![CDATA[>1.0×10 -2 ]]> 10 (All Invalid) No liquid phase window Comparative Example 6 <![CDATA[3.3×10 -5 ]]> 0 No chemical bonding, physical bonding

[0206] in conclusion:

[0207] according to Figure 3 As shown in Table 3, the example group and the comparative example group exhibited a significant difference in sealing performance, indicating a difference of orders of magnitude. The average helium leakage rate of Examples 1 to 6 remained stable at 10%. -8 It reaches the mbar·L / s level, meeting stringent electronic hermeticity standards (typically requiring <1×10⁻⁶). -7 (mbar·L / s), and no samples showed large leakage failure. This indicates that the process of the present invention successfully constructed a dense interface structure.

[0208] The complete failure data of Comparative Example 5 (without low-melting-point Co-PA) confirms the necessity of the "thermodynamic window". When there is a lack of a mobile phase that remains molten during the holding pressure stage, the crystallization shrinkage of the PA66 matrix directly leads to interfacial debonding, forming macroscopic through channels.

[0209] The high leakage rate (8.9 × 10⁻⁶) of Comparative Example 3 (direct addition of liquid silane) -4 The high failure rate (mbar·L / s) and high failure rate validate the importance of "bubble-free chemical anchoring." Microbubbles generated by the volatilization of free small-molecule silane at high temperatures form a porous structure at the interface, disrupting the sealing layer. The example, however, introduces silane through grafted masterbatch, effectively avoiding the volatilization problem.

[0210] The leakage rates of Comparative Example 2 (no oscillation) and Comparative Example 1 (no HBPE) remained at 10. -5 Up to 10 -4 While the performance in the mbar·L / s range was better than that of Comparative Examples 3 and 5, it still did not meet the high airtightness standard. This indicates that material formulation alone or static pressure holding alone is insufficient to completely eliminate micro-shrinkage cavities. The data from the examples demonstrate that only by combining the thixotropic properties of HBPE with the "micro-pumping effect" of the oscillating pressure field can the melt be forcibly pressed into the micron-level shrinkage gaps, achieving true "micro-shrinkage compensation".

[0211] Test Example 4: Metal-Polymer Interfacial Bond Strength Test (Pull-off Force Test)

[0212] Experimental description:

[0213] This experiment utilizes a universal testing machine to perform axial pull-out tests on injection-molded samples, aiming to quantitatively characterize the interfacial bonding strength between the metal insert and the polymer matrix. By recording the maximum load at the interface failure point, the experiment analyzes the contribution ratio of mechanical interlocking force and chemical bonding force to the total bonding strength, thereby verifying the interfacial strengthening effect of the synergistic effect of grafted masterbatch and hyperbranched polyester.

[0214] Experimental steps:

[0215] Five samples without appearance defects were randomly selected from the injection molded samples prepared in each group and conditioned for 48 hours in a standard environment of 23℃ and 50% relative humidity to eliminate the interference of internal stress relaxation on the test results.

[0216] The sample was mounted on the testing platform of a universal testing machine (model: Instron 5966). The polymer outer coating of the sample was fixed using a custom self-centering clamp to ensure uniform stress on the polymer and prevent lateral slippage. At the same time, the exposed end of the metal insert was held using a wedge tension clamp, and the position of the crossbeam was adjusted so that the tension axis was strictly aligned with the center axis of the insert to eliminate bending moment.

[0217] Set the beam movement speed to 5 mm / min, zero the sensor, and then start the stretching program.

[0218] The loading continues until the metal insert is completely removed from the polymer matrix or the polymer matrix fractures. The system automatically records the load-displacement curve during the loading process and extracts the maximum load value (Peak Load) on the curve as the interface pull-out force data.

[0219] Observe and record the morphology of the fracture surface to distinguish between interfacial adhesion failure (smooth insert surface) and cohesive failure (residual polymer on insert surface).

[0220] Experimental data:

[0221] Table 4: Test results of axial pull-out force of metal inserts

[0222] Group Sample 1 (N) Sample 2 (N) Sample 3 (N) Sample 4 (N) Sample 5 (N) Average pull-out force (N) Example 1 4256 4310 4188 4295 4230 4255.8 Example 2 4450 4380 4512 4425 4405 4434.4 Example 3 4105 4088 4150 4092 4125 4112.0 Example 4 4320 4365 4290 4345 4310 4326.0 Example 5 4180 4210 4155 4195 4175 4183.0 Example 6 4050 4015 4090 4065 4030 4050.0 Comparative Example 1 2450 2510 2420 2485 2460 2465.0 Comparative Example 2 2890 2915 2850 2880 2930 2893.0 Comparative Example 3 1420 1380 1450 1410 1435 1419.0 Comparative Example 4 2580 2610 2555 2590 2625 2592.0 Comparative Example 5 650 720 580 690 610 650.0 Comparative Example 6 3120 3150 3080 3135 3100 3117.0

[0223] in conclusion:

[0224] according to Figure 4 As shown in Table 4, the example groups exhibited excellent interfacial bonding performance, with an average pull-out force consistently above 4000 N, with Example 2 reaching the highest value of 4434.4 N. The comparison with Comparative Example 6 (average pull-out force 3117.0 N) provides important mechanistic indications: although Comparative Example 6 contained a low-melting-point sealing phase (Co-PA) and underwent oscillatory pressure holding, providing some holding force through physical coating and friction, it lacked silane grafted masterbatch, thus failing to form chemical bonds. Example 1 improved the bonding force by approximately 1100 N compared to Comparative Example 6; this increase is directly attributed to the anchoring effect of the "polymer-Si-O-metal" covalent bonds formed at the interface.

[0225] The data from Comparative Example 1 (2465.0N) and Comparative Example 4 (2592.0N) show that in the absence of hydroxyl-terminated hyperbranched polyester (HBPE) to guide the process, even if the system contains silane masterbatch, the probability of chemical bonding is greatly reduced because the high-viscosity melt cannot effectively transport the active groups to the metal interface, and the bonding force mainly depends on the physical shrinkage clamping force of the matrix.

[0226] The low strength of Comparative Example 3 (1419.0 N) confirms the harmful effects of directly adding small-molecule silanes; the volatilized gases formed a defect layer at the interface, significantly reducing the contact area. The extremely low strength of Comparative Example 5 (650.0 N) further confirms the prerequisite status of "thermodynamic phase separation." The lack of a low-melting-point phase for compensation means that matrix shrinkage directly leads to interfacial delamination, essentially resulting in a loss of load-bearing capacity. In summary, high bonding strength is the result of the synergistic effect of three mechanisms: rheological transport, micro-filling, and chemical bonding.

[0227] Test Example 5: Test on the retention rate of interfacial adhesion to thermal shock

[0228] Experimental description:

[0229] This experiment aims to evaluate the interfacial durability of multi-material composite components under severe alternating temperature stress. Due to the significant difference in the coefficients of thermal expansion (CTE) between the polymer matrix and the metal insert, repeated volume expansion and contraction will generate periodic shear stress at the interface. By comparing the changes in interfacial pull-out force before and after thermal shock aging, the strength retention rate is calculated, thereby distinguishing the reliability differences between simple physical coating and the synergistic mechanism of "chemical bonding + flexible buffering" under long-term service conditions.

[0230] Experimental steps:

[0231] Five untested new samples were taken from each of the injection-molded samples prepared in Examples 1 to 6 and Comparative Examples 1 to 6 as aging test groups.

[0232] Place all test samples on the sample rack of the two-chamber thermal shock test chamber (model: Espec TSA-101L) and set the impact program: the low temperature zone temperature is -40℃ and the high temperature zone temperature is 120℃.

[0233] Initiate the cyclic test, with the sample staying in the high-temperature zone and the low-temperature zone for 30 minutes each, and the transition time between the two zones set to be less than 10 seconds, for a total of 500 high and low temperature shock cycles.

[0234] After the cycle is completed, the sample is removed and left to stand in a standard laboratory environment at 23°C for 24 hours to complete the conditioning.

[0235] The axial pull-out force of the aged sample was tested using the same equipment and parameters as in Test Example 4 (universal testing machine, tensile speed 5 mm / min), and the maximum destructive load was recorded.

[0236] The initial average pull-out force (denoted as) was measured according to Test Example 4. The average pull-out force after aging measured in this experiment (denoted as ) ), Calculate the binding force retention rate of each group: .

[0237] Experimental data:

[0238] Table 5: Interfacial pull-out force and retention rate after 500 thermal shocks

[0239] Group Initial average pull-out force (N) Sample 1 (N) after aging Sample 2 (N) after aging Sample 3 (N) after aging Sample 4 (N) after aging Sample 5 (N) after aging Average pull-out force Faged (N) after aging Strength retention rate R (%) Example 1 4255.8 3980 3855 3920 3890 3945 3918.0 92.1 Example 2 4434.4 4120 4080 4150 4095 4105 4110.0 92.7 Example 3 4112.0 3750 3680 3720 3710 3690 3710.0 90.2 Example 4 4326.0 4010 3985 4050 3990 4025 4012.0 92.7 Example 5 4183.0 3820 3790 3850 3810 3830 3820.0 91.3 Example 6 4050.0 3680 3620 3650 3640 3660 3650.0 90.1 Comparative Example 1 2465.0 1520 1480 1550 1510 1490 1510.0 61.3 Comparative Example 2 2893.0 1850 1790 1820 1880 1810 1830.0 63.3 Comparative Example 3 1419.0 450 520 480 410 580 488.0 34.4 Comparative Example 4 2592.0 1650 1720 1680 1620 1690 1672.0 64.5 Comparative Example 5 650.0 0 (shedding) 50 0 (shedding) 80 0 (shedding) 26.0 4.0 Comparative Example 6 3117.0 1680 1750 1710 1690 1720 1710.0 54.9

[0240] in conclusion:

[0241] according to Figure 5 According to the data in Table 5, after 500 thermal shock cycles, the interfacial bonding performance of each group showed a distinctly different degradation trend, which strongly confirms the decisive role of the chemical bond anchoring mechanism in long-term reliability.

[0242] The strength retention rates of Examples 1 to 6 all exceeded 90%, with minimal attenuation. This indicates that the "polymer-silane-metal" covalent bonds formed at the interface possess extremely high bond energies, effectively resisting cyclic shear stress caused by the mismatch in thermal expansion coefficients. Simultaneously, the low-modulus ternary copolyamide (Co-PA) introduced into the system acts as a flexible buffer layer, dissipating some thermal stress at the microscale and protecting the chemical bonds from tearing.

[0243] The most crucial comparison occurs between Example 1 and Comparative Example 6. Comparative Example 6 (silane-free grafted masterbatch) initially exhibited a high pull-out force of approximately 3100 N due to the physical coating of Co-PA, but after aging, its strength dropped significantly to 1710 N, with a retention rate of only 54.9%. This is because the physical coating primarily relies on the frictional force and mechanical interlocking generated by the polymer's cooling and shrinkage. During repeated thermal expansion and contraction, the polymer undergoes stress relaxation and creep, leading to the gradual failure of the physical locking force.

[0244] Furthermore, Comparative Example 1 (without HBPE) showed a retention rate of only 61.3%, indicating that without the rheological transport effect of hyperbranched polymers, even with the presence of chemical bonding agents, a high density of effective bonding points cannot be formed at the interface, resulting in an "island-like" distribution of the interfacial layer, which cannot inhibit the propagation of thermal fatigue cracks. The complete failure of Comparative Example 5 (retention rate of 4.0%) further demonstrates that "thermodynamic phase separation" is the physical basis for the existence of interfaces; once a liquid phase component adapting to deformation is lacking, the rigid matrix undergoes interfacial delamination upon initial cooling contraction.

[0245] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An insert and encapsulation integrated injection molding process of a multi-material composite part, characterized in that, Includes the following steps: S1. Place the metal insert into the cavity of the injection mold and close the mold; S2. Inject molten phase-separated sealing composite material into the mold cavity until the mold cavity is filled; the phase-separated sealing composite material comprises a thermoplastic resin matrix, a low-melting-point sealing resin, a rheology modifier, and a chemical bonding agent; S3. Oscillating and holding pressure treatment: During the holding pressure stage, the oscillating pressure is applied to the melt in the mold cavity by the screw or piston of the injection molding machine. Under the action of the shear field formed by the oscillating pressure, the rheology modifier reduces the shear viscosity of the melt, causing the low melting point sealing resin and the chemical bonding agent to migrate to the interface of the metal insert. S4. Cool and solidify, then open the mold and remove the multi-material composite component; In the step of the oscillation and pressure holding process, the mold temperature is controlled to always be lower than the crystallization temperature of the thermoplastic resin matrix and higher than the solidification point of the low melting point sealing resin.

2. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, The phase-separation type sealing composite material is made from raw materials comprising the following parts by weight: The thermoplastic resin matrix is ​​40-60 parts; 30-50 parts of reinforcing fiber; 10-20 parts of the low-melting-point sealing resin; The rheology modifier is 0.5-3 parts; 1-5 parts of chemical bonding agent masterbatch; Antioxidant 0.1-0.5 parts; Lubricant 0.2-1.0 parts; The chemical bonding agent exists as the active ingredient in the chemical bonding agent masterbatch.

3. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, The low-melting-point sealing resin is a ternary copolyamide; The melting point of the ternary copolyamide is 20°C to 40°C lower than that of the thermoplastic resin matrix; The thermoplastic resin matrix is ​​selected from polyamide 66 or polyamide 6; the ternary copolyamide is copolymerized from caprolactam, hexamethylenediamine adipic acid and dodecyl lactam.

4. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, The rheology modifier is a hydroxyl-terminated hyperbranched polyester; The hydroxyl-terminated hyperbranched polyester is a second- to fourth-generation hyperbranched polymer with trimethylolpropane as the core and 2,2-dimethylolpropionic acid as the monomer. The hydroxyl-terminated hyperbranched polyester has a hydroxyl value ranging from 200 mg KOH / g to 500 mg KOH / g.

5. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, The chemical bonding agent masterbatch is made from components comprising the following weight percentages: Carrier resin 80-90 wt% Silane coupling agent 8-15 wt%; Initiator 0.5-2wt%; The silane coupling agent is at least one of epoxy silane or amino silane.

6. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 5, characterized in that, The chemical bonding agent masterbatch is prepared by a reactive extrusion process, which includes the following steps: After the carrier resin, the silane coupling agent and the initiator are mixed evenly, they are added to a twin-screw extruder; The temperature of the reaction section of the twin-screw extruder is controlled at 180°C to 220°C, and the screw speed is controlled at 300 rpm to 500 rpm, so that the silane coupling agent is grafted onto the molecular chain of the carrier resin. The chemical bonding agent masterbatch is obtained by extrusion granulation and drying, with a grafting rate greater than 1.5%.

7. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, In step S3, the process parameters for the oscillation and pressure holding process include: The oscillation frequency is from 1.5 Hz to 4.0 Hz; The pressure amplitude is 10% to 20% of the holding pressure reference pressure; The duration of the oscillation covers the entire gate freezing time.

8. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, In step S1, the metal insert is pretreated; The pretreatment includes: plasma cleaning or sandblasting the surface of the metal insert, and preheating the metal insert to 100°C to 120°C.

9. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, In step S2, the melt temperature of the molten phase-separated sealing composite material is between 260°C and 290°C, and the mold temperature is controlled between 80°C and 100°C.

10. The integrated injection molding process for embedding and sealing multi-material composite components according to claim 1, characterized in that, The low-melting-point sealing resin is thermodynamically incompatible with the thermoplastic resin matrix; After cooling and setting in step S4, the low-melting-point sealing resin forms a flexible sealing layer rich in silane bonding points on the surface of the metal insert.

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