A high-toughness, high-light-shielding polycarbonate composite material and its preparation method

Abstract

This invention relates to the field of polymer composite materials, and discloses a high-toughness, high-light-shielding polycarbonate composite material and its preparation method, solving the technical problem that existing polycarbonate materials cannot simultaneously achieve high light-shielding properties and high impact toughness. By constructing a polyurethane elastic composite coating containing nano-carbon black in situ on the surface of continuous glass fibers, the coating acts as a microscopic light-shielding network and an interfacial stress buffer layer. This not only effectively blocks light transmission and imparts high optical density to the material, but also passivates crack tips and absorbs impact energy. As a result, the composite material maintains high rigidity while possessing excellent notched impact toughness and a high-gloss black appearance without loose fibers.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials, and more specifically, to a high-toughness, high-light-shielding polycarbonate composite material and its preparation method. Background Technology

[0002] In the fields of high-end consumer electronics (such as smartphones and VR / AR devices) and automotive smart cockpits, precision components such as camera module brackets, display black matrix bezels, and LiDAR housings bear extremely critical optical and structural functions. From an optical perspective, in order to ensure the clarity of sensor imaging, prevent stray light interference, and avoid display backlight leakage, these components must have extremely high light-blocking performance, achieving complete light blocking with extremely thin walls.

[0003] As products become increasingly thinner and more integrated, these light-shielding components often need to function as internal structural frames or external protective shells. In actual use, they inevitably face high mechanical stress scenarios such as drop impacts, vibration collisions, and large deformations of clips during assembly. If the material lacks sufficient toughness, it is highly susceptible to brittle fracture under stress, leading to equipment structural failure or misalignment of precision optical paths. Therefore, there is an urgent need for a composite material that can simultaneously meet the requirements of extreme optical shielding and high impact resistance safety standards to ensure the performance stability and lifespan of precision optoelectronic products. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a high-toughness, high-light-shielding polycarbonate composite material and its preparation method, solving the technical problem that existing polycarbonate materials cannot simultaneously achieve high light-shielding performance and high impact toughness.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for preparing a high-toughness, high-light-shielding polycarbonate composite material, comprising the following steps: S1. By weight, take 5-15 parts of waterborne polyurethane emulsion, 1-5 parts of nano carbon black and 0.1-0.5 parts of silane coupling agent, mix and disperse them to prepare a black functionalized impregnation liquid. S2. Introduce continuous glass fibers into the black functionalized impregnation liquid for coating, and control the coating load to be 1.0%~2.0% of the fiber mass; then perform gradient heat setting at 80~160℃ for 3~5 minutes to obtain functionalized continuous fibers with a black elastic coating on the surface. S3. Polycarbonate resin and processing aids are melt-plasticized and then melt-impregnated with the functionalized continuous fibers in an impregnation mold. The mass fraction of the continuous glass fibers in the composite material is controlled to be 20% to 50%. The composite material is then cooled and pelletized to obtain long fiber reinforced masterbatch. S4. The long fiber reinforced masterbatch is injection molded under low shear conditions to obtain the high toughness and light-shielding polycarbonate composite material.

[0007] As a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, wherein: in the black functionalized impregnation liquid, the aqueous polyurethane emulsion is 10 parts, the nano carbon black is 3 parts, and the silane coupling agent is 0.3 parts.

[0008] As a preferred embodiment of the method for preparing high-toughness, high-light-shielding polycarbonate composite material according to the present invention, the coating loading is 1.5% of the fiber mass; the gradient heat setting includes a dehydration and drying stage, a preheating and activation stage, and a high-temperature grafting reaction stage performed sequentially.

[0009] In a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, the continuous glass fiber has a mass fraction of 35% in the composite material.

[0010] As a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, the process conditions for the dehydration and drying stage are: temperature 100℃~120℃ and time 110s~130s; the process conditions for the preheating and activation stage are: temperature 110℃~130℃ and time 20s~50s; and the process conditions for the high-temperature grafting reaction stage are: temperature 130℃~150℃ and time 50s~70s.

[0011] As a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, wherein: the aqueous polyurethane emulsion is an anionic polyester polyurethane dispersion with a solid content of 35%~45%; the nano carbon black is ordinary pigment carbon black or acetylene black with a native particle size of 10nm~30nm; and the silane coupling agent is γ-glycidoxypropyltrimethoxysilane. In the specific steps of the dispersion treatment, the mixture is first added dropwise at a speed of 300~800 rpm. After the addition is completed, the speed is increased to 1200~1800 rpm and ultrasonic dispersion treatment is carried out for 20~40 minutes.

[0012] In a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, the continuous glass fiber is an alkali-free glass fiber roving with a single filament diameter of 11 μm to 13 μm; the process conditions for the dehydration and drying stage are a temperature of 110°C and a time of 120 s; the process conditions for the preheating and activation stage are a temperature of 120°C and a time of 35 s; and the process conditions for the high-temperature grafting reaction stage are a temperature of 135°C and a time of 60 s.

[0013] As a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, wherein: the polycarbonate resin is a bisphenol A type polycarbonate with a melt flow rate of 20~25g / 10min; the melt plasticizing temperature is 240℃~270℃; and the pellet length is 10mm~12mm.

[0014] In a preferred embodiment of the method for preparing the high-toughness, high-light-shielding polycarbonate composite material of the present invention, the temperature of the injection molding barrel is 260℃~280℃ and the temperature of the mold is 80℃~100℃.

[0015] The present invention also provides a high-toughness, high-light-shielding polycarbonate composite material, which is prepared by the above-mentioned preparation process, wherein: the composite material has a micro-layered structure, the inner layer is a continuous glass fiber skeleton, the middle layer is a nano carbon black and polyurethane elastic composite coating covering the surface of each glass fiber, and the outer layer is a polycarbonate resin matrix. The elastic composite coating forms a chemical bond network with the inner glass fiber and the outer resin matrix through a silane coupling agent, and the nano carbon black is dispersed in the interior of the elastic composite coating without directly contacting the polycarbonate resin matrix.

[0016] The beneficial effects of this invention are as follows: By constructing a polyurethane elastic composite coating containing nano-carbon black on the surface of continuous glass fibers, the light-shielding and toughening functional components are integrated at the microscopic interface. This elastic coating forms a dense light-shielding network, effectively blocking light transmission within the transparent fibers and imparting high optical density to the material. Furthermore, as an interfacial stress buffer layer, it absorbs external impact energy and blunts crack tips, avoiding the matrix stress concentration and embrittlement caused by the direct high-filling of rigid light-shielding particles in traditional blending processes.

[0017] Furthermore, by combining the chemical bonding network formed between the fibers, coating, and matrix using silane coupling agents and the long fiber retention process during melt impregnation, this composite material significantly improves notched impact strength while maintaining high rigidity. Simultaneously, the pre-applied black organic coating improves the compatibility between the glass fibers and the polycarbonate matrix, effectively suppressing fiber floating during injection molding and allowing the manufactured parts to exhibit a high-gloss black appearance without the need for spraying. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The figure shows the experimental results of optimizing the ratio of carbon black to polyurethane emulsion.

[0020] Figure 2 The figure shows the experimental results of optimizing the ratio of coupling agent to glass fiber.

[0021] Figure 3 The figure shows the experimental results of optimizing the ratio of glass fiber to polycarbonate matrix.

[0022] Figure 4 The figure shows the experimental results of optimizing the loading of the modified carbon black coating.

[0023] Figure 5 The figure shows the results of the screening experiment for coating dehydration process parameters.

[0024] Figure 6 The figure shows the experimental results for screening preheating activation reaction conditions.

[0025] Figure 7 The figure shows the experimental results of screening reaction conditions for the high-temperature bonding stage.

[0026] Figure 8 This is a flowchart of a method for preparing a high-toughness, high-light-shielding polycarbonate composite material. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "example" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The appearance of an embodiment in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments. Example 1

[0030] This embodiment aims to develop a polycarbonate composite material that combines ultimate optical shielding with high impact resistance and toughness. The target material needs to achieve full-band light blocking while ensuring extremely thin wall thickness, and completely overcome the matrix embrittlement problem caused by traditional high filler.

[0031] 1.1 Screening experiment for matrix resin types To construct a composite material system that simultaneously meets the requirements of optical shielding and mechanical safety, it is first necessary to determine the polymer matrix as the continuous phase. The stability of the microstructure and the retention of macroscopic properties of different types of polymer resins when rigid fillers are introduced are then evaluated.

[0032] Test groups: polyamide 66 (PA66), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer (ABS), polypropylene (PP), polymethyl methacrylate (PMMA), and bisphenol A type polycarbonate (PC).

[0033] According to ISO 180 standard, the cantilever beam notched impact strength was tested at 23°C using a type A notch to assess the material's resistance to fracture under stress concentration and determine the matrix's toughness. According to ISO 294-4 standard, the dimensional change rate of the injection-molded sample after cooling and setting was measured to evaluate whether the matrix material meets the dimensional stability requirements of precision optical components. According to ISO 1133 standard, the melt flow rate was determined at the standard test temperature and load for each resin to evaluate the matrix resin's tolerance to high filler content and the ease of subsequent injection molding processing.

[0034] The test results are as follows:

[0035] Among them, ABS has excellent notched impact strength, demonstrating its advantage in toughness, but its low melt flow rate limits the feasibility of high-filling processes; PMMA has the best dimensional stability (shrinkage rate), but its extremely low notched impact strength indicates its extreme brittleness, completely failing to meet impact resistance requirements; PA66 and PP have good processing fluidity, but both have excessively high molding shrinkage rates. Considering toughness, precision, and processability, bisphenol A polycarbonate exhibits balanced characteristics without obvious weaknesses, thus establishing it as the matrix resin.

[0036] 1.2 Reinforcing Fiber Screening To further enhance the mechanical strength and dimensional stability of polycarbonate matrices, fibrous reinforcing materials need to be introduced to construct a microscopic skeletal network. Ideally, the reinforcing fibers should significantly improve the rigidity and strength of the material while achieving a strong and tough gain effect through crack bridging and pull-out mechanisms, and to some extent, assist in improving the optical blocking properties of the material, thereby achieving a synergistic improvement in structural strength and functional characteristics.

[0037] Experimental groups: A1 carbon fiber; A2 basalt fiber; A3 aramid fiber (para-aramid); A4 ultra-high molecular weight polyethylene fiber; A5 ceramic fiber; A6 alkali-free glass fiber. All groups uniformly employed the continuous fiber reinforced thermoplastic process (CFRTP), introducing 30% by mass of continuous fiber into a bisphenol A type polycarbonate matrix to prepare standard samples.

[0038] In addition to testing the notched impact strength and optical density of the cantilever beam, the flexural modulus, which reflects the material's resistance to bending deformation, is tested according to ISO 178 standard to assess the level of rigid support provided by the reinforcing skeleton. Interlaminar shear strength is tested according to ISO 14130 standard (short beam shear method) to determine the strength of the interfacial bond between the fiber surface and the resin matrix, and to evaluate the stability of the microstructure.

[0039] The test results are as follows:

[0040] Among them, carbon fiber performs best in flexural modulus (rigidity) and optical density (light-shielding properties), but its notched impact strength is low, showing obvious brittleness and failing to meet the requirements of high toughness; aramid fiber has the best notched impact strength, indicating that it has good toughness, but its flexural modulus is too low, resulting in the material being too soft overall, and its extremely low interlaminar shear strength indicates that its interfacial bonding with the PC matrix is ​​extremely poor, making it prone to delamination failure; ceramic fiber has extremely high rigidity, but its extreme brittleness results in low impact strength.

[0041] Although glass fiber is naturally transparent, resulting in a lower optical density, its remaining parameters are all at a high level. As long as its light-shielding shortcomings are addressed, an ideal composite material can be obtained. Therefore, continuous glass fiber was selected as the reinforcing skeleton.

[0042] 1.3 Construction and Optimization of Parameter Optimization System After establishing the basic formulation with bisphenol A type polycarbonate as the matrix and continuous glass fiber as the reinforcing skeleton, it is still necessary to solve the optical leakage problem caused by the natural transparency of glass fiber, and at the same time, it is necessary to solve the matrix embrittlement problem caused by high filling rigid particles in the traditional blending light-blocking process.

[0043] 1.3.1 Screening of light-blocking additives Experimental groups: B1 with 0.5% solvent black; B2 with 4.0% flake aluminum silver paste; B3 with 5.0% rutile titanium dioxide; B4 with 3.0% synthetic mica powder; B5 with 2.5% nano zinc oxide; B6 with 2.0% nano carbon black. Further comprehensive evaluation of the cantilever beam notched impact strength, flexural modulus, interlaminar shear strength, and optical density was conducted to analyze the impact of the light-shielding modifier on material properties.

[0044] The test results are as follows:

[0045] Among them, aluminum silver paste achieves the best optical density due to the total internal reflection mechanism of metal, but its sheet-like structure severely damages the interfacial bonding, resulting in extremely low notched impact strength; solvent black, being molecularly dispersed and without the introduction of foreign matter, retains high notched impact strength and interlaminar shear strength, but its optical density is low and it appears transparent black, making it unable to achieve complete masking; mica powder, while increasing stiffness, is accompanied by severe embrittlement.

[0046] Nano-carbon black provides high opacity without significantly impacting the material's mechanical properties. Therefore, carbon black was ultimately selected as the base opacifier, and future work will focus on addressing its relatively low toughness.

[0047] 1.3.2 Screening of toughening agent systems Experimental groups: C1 with 6.0% methyl methacrylate-butadiene-styrene copolymer (MBS); C2 with 5.0% ethylene-acrylate copolymer (EMA); C3 with 8.0% thermoplastic polyester elastomer (TPEE); C4 with 6.0% styrene-ethylene-butadiene-styrene block copolymer (SEBS); C5 with 6.0% polyolefin elastomer (POE); C6 with 4.5% waterborne polyurethane (WPU).

[0048] After the finished product is prepared, the notched impact strength of the cantilever beam, the interlaminar shear strength (interfacial bonding), and the optical density (for the dispersion state of carbon black) are tested to evaluate its effectiveness.

[0049] The test results are as follows:

[0050] Among them, MBS, with its perfect core-shell structure, gives the material the best notched impact strength, but its optical density is relatively low; TPEE, due to the good transesterification reaction between its polyester segments and the PC matrix, achieves the highest interlaminar shear strength and the best interfacial bonding, but its high hardness limits its toughening effect. Waterborne polyurethane exhibits the best optical density, and its modified material simultaneously achieves high toughness, strong interfacial bonding, and high opacity, thus establishing it as the preferred toughening component.

[0051] 1.5 Screening of interfacial crosslinking agents There is a natural chemical barrier between the inorganic glass fiber surface and the organic polyurethane or carbon black coating, as well as between the coating and the PC matrix. If this chemical barrier cannot be overcome, the coating will only be physically adsorbed onto the fiber surface, and will easily debond and peel off under stress.

[0052] KH-550 (γ-aminopropyltriethoxysilane), KH-570 (γ-methacryloyloxypropyltrimethoxysilane, double bond type), KH-792 (diamino silane), NDZ-201 (isopropyltris(dioctylpyrophosphate)titanate), DL-411 (aluminate coupling agent), and KH-560 (γ-glycidoxypropyltrimethoxysilane) with a solid content of 2% were added to the coating respectively.

[0053] The performance of the modifier is evaluated by testing interlayer shear strength, cantilever beam notched impact strength, melt mass flow rate, and optical density.

[0054] The test results are as follows:

[0055] Among them, KH-550 and KH-792 in group C achieved extremely high interlaminar shear strength due to their highly active amino groups. However, their MFR data showed an abnormal surge, and their notched impact strength dropped precipitously. This confirmed that the strongly basic amino groups catalyzed the hydrolysis and chain scission of polycarbonate ester bonds during high-temperature processing, leading to severe matrix degradation. Titanate coupling agents had excellent optical density data, indicating excellent wetting and dispersing effects on carbon black, but their reactivity with the glass fiber surface was weak, resulting in poor interlaminar shear strength and an inability to provide sufficient interfacial support. KH-560 had excellent overall performance and was therefore the final selected crosslinking agent. Example 2

[0056] Reference Figures 1-4 This is the second embodiment of the present invention. This embodiment aims to optimize the quantitative proportions of the selected preferred components through a systematic orthogonal experimental design. Although the functionality of each individual component has been confirmed, the final performance of the composite material is not a simple summation of the properties of each component, but depends on the competition and synergy between the components at the microscopic interfaces.

[0057] 2.1 Optimization of the ratio of carbon black to polyurethane emulsion As the core material for constructing the elastic buffer layer and light-shielding layer between the fiber and the matrix, the ratio of nano-carbon black to waterborne polyurethane emulsion directly determines the microstructure and macroscopic performance of the composite coating. If the carbon black content is too low, the light-shielding network of the coating will be sparse and unable to effectively block the light path; if the carbon black content is too high, exceeding the coating limit of polyurethane (critical pigment-to-binder ratio), the excess carbon black particles will be exposed on the coating surface, causing powdering, and the coating itself will harden and crack rapidly due to excessive rigid particle filling, losing its toughening and buffering function.

[0058] Using 10 parts by weight (dry weight) of waterborne polyurethane as a baseline, 10 gradients (from 1 to 10 parts by weight) of nano-carbon black addition were set. The nano-carbon black was uniformly dispersed in the polyurethane emulsion to prepare a series of coating slurries with consistent solid content, and then dried into standard films for testing.

[0059] According to ISO 527-3 standard, tensile testing of the dried free film to determine its elongation at break and the coating's flexibility limit are key indicators of its ability to effectively buffer stress on the composite material. The slurry is applied to a transparent substrate at a fixed wet film thickness, and its optical density is tested after drying to determine the light-blocking efficiency per unit thickness of the coating.

[0060] According to the ISO105-X12 standard, the coating surface is rubbed 50 times under a fixed pressure using a standard white cloth to assess the staining grade of the white cloth (grades 1-5, with grade 5 being the best). This is used to determine whether the carbon black is completely encapsulated and fixed by the resin and whether there is a risk of surface powdering and peeling.

[0061] Test results are as follows Figure 1 As shown, through data fitting, the critical carbon black content for the marginal benefit threshold of optical density is 3.42 parts; to maintain an elongation at break above 200%, the amount of nano-carbon black added should be less than 3.56 parts; the rubbing fastness data exhibits a step function characteristic, with the maximum carbon black tolerance to maintain a level above 4 being 3.28 parts. Considering that both elongation at break and rubbing fastness are indicators that significantly affect material properties, the final mass ratio of nano-carbon black to polyurethane was chosen to be 3:10.

[0062] 2.2 Optimization of the ratio of coupling agent to glass fiber As a chemical bridge connecting inorganic glass fibers and organic matrices / coatings, the silane coupling agent KH-560's coverage density on the fiber surface directly determines the microstructure and macroscopic transfer efficiency of the interface. If the amount of coupling agent is too small, the active hydroxyl groups on the fiber surface will not be fully covered, and a continuous chemical bonding network cannot be formed, resulting in interface defects and easy debonding under stress. If the amount is too large, the excess silane molecules will undergo self-condensation reaction on the fiber surface, forming a loosely structured physical adsorption layer (weak boundary layer), which will reduce the interfacial shear strength. Furthermore, unreacted small molecules may act as plasticizers, leading to a decrease in local rigidity.

[0063] Based on 100 parts by weight of continuous glass fiber, 10 gradients of KH-560 addition were set from 0.2 to 2. KH-560 was dissolved in an appropriate amount of solvent to prepare a treatment solution, and the fiber was subjected to standardized impregnation treatment, followed by composite with a sufficient amount of PC matrix.

[0064] In addition to testing interlaminar shear strength and cantilever beam notched impact strength, it is also necessary to immerse the standard sample in distilled water at 23°C for 24 hours according to ISO 62 standard, and measure the mass change before and after water absorption to evaluate the hydrophobic modification effect of the coupling agent on the hydrophilic glass fiber surface and the density of the interface.

[0065] Test results are as follows Figure 2 As shown, the interlaminar shear strength exhibits a typical unimodal parabolic distribution. With increasing KH-560 dosage, the interfacial bonding force rises rapidly. The stationary point where the first derivative of the curve is zero is calculated, and the theoretical peak strength corresponds to a coupling agent dosage of 1.05 parts. At this point, the monomolecular chemical bond layer coverage reaches saturation, and the interfacial transfer efficiency is highest. The notched impact strength shows a highly positive correlation with the shear strength, with its fitted peak located near 1.08 parts, indicating that good interfacial bonding facilitates effective stress transfer and dissipation. Water absorption exhibits an exponential decay, plateauing after the dosage exceeds 0.95 parts, indicating that the hydrophilic groups on the fiber surface have been effectively sealed.

[0066] Based on the above three fitting extreme points, and considering the need to reserve a trace amount of reaction consumption in industrial production, the optimal addition amount of KH-560 was finally determined to be 1.1% (i.e., 1.1 parts) of the glass fiber mass. This ratio ensures the formation of a dense interface structure without weak boundary layers.

[0067] 2.3 Optimization of the ratio of glass fiber to polycarbonate matrix As the load-bearing skeleton of composite materials, the volume fraction (Vf) of continuous glass fiber directly determines the upper and lower limits of the material's macroscopic mechanical properties. If the fiber content is too low, the skeleton network is sparse and cannot effectively share the load borne by the matrix, resulting in an insignificant reinforcement effect. If the fiber content is too high, exceeding the wetting and coating capacity of the resin matrix, it will lead to fiber accumulation, dry spots, and increased porosity, which will become sources of stress concentration. Furthermore, the sharp increase in melt viscosity will severely deteriorate the processability.

[0068] The product uses a PC matrix and incorporates optimized glass fibers (loaded with 1.1% KH-560). The glass fiber content ranges from 10% to 50% in increments of 5%, with a total weight of 100 parts, and the remainder being the PC matrix.

[0069] The effectiveness was evaluated using the cantilever beam notch impact strength, flexural modulus, and melt mass flow rate.

[0070] The test results are as follows Figure 3 As shown, the first derivative of the notched impact strength fitting curve was calculated, and the coordinates of the extreme point of the strength were (34.2%, 48.35 kJ / m²). At this point, the fiber skeleton network was most complete and no significant accumulation defects had been generated. The MFR followed an exponential decay model. The minimum flow threshold that can meet the requirements of precision thin-wall injection molding was set to 8 g / 10 min. The upper limit coordinates of the fiber content obtained by solving the inverse equation were (36.5%, 8.04 g / 10 min). Although the flexural modulus showed a linear increase, a clear slope inflection point appeared at (41.2%, 18.23 GPa), indicating that the fiber wetting efficiency began to decrease.

[0071] Based on the above key coordinate points, to maximize toughness benefits and ensure processing safety, the weighted average of the impact strength extreme point x-axis (34.2%) and the MFR safety threshold x-axis (36.5%) was taken (with weights set at toughness 0.7 and processing 0.3), resulting in a theoretically optimal fiber content of 34.89%. For the sake of standardization in industrial formulations, the optimal addition amount of continuous glass fiber was ultimately selected as 35%.

[0072] 2.4 Optimization of the loading rate of modified carbon black coating After establishing the optimal fiber-to-matrix skeleton ratio (GF=35%), a modified carbon black coating with an optimized ratio (carbon black:WPU=3:10) needs to be introduced to impart the final optical shielding function to the material. If the coating load is too low, the fiber surface will not be fully covered, which can easily lead to white core light leakage; if the load is too high, the excessively thick flexible organic layer will become a weak point in mechanical structure, resulting in a decrease in interlaminar shear strength, and excessive coating may undergo thermal degradation or migration during processing.

[0073] The coating load ranged from 0.5% to 5% in 0.5% increments. The finished product performance was evaluated by measuring optical density, interlaminar shear strength, and cantilever beam notched impact strength.

[0074] Test results are as follows Figure 4 As shown, the optical density exhibits a logarithmic growth trend. Taking the first derivative of the curve, the coordinates of the inflection point where the marginal benefit of shading efficiency decreases most significantly are (1.68%, 3.98). After this point, the cost-effectiveness of increasing the amount of shading increases sharply. The ILSS decreases linearly with increasing loading, but the slope increases sharply after the loading exceeds 2.8%, indicating that the interface has changed from being dominated by chemical bonding to being dominated by a weak boundary layer, and the risk of interface failure increases dramatically. The notched impact strength shows a slight trend of first increasing and then decreasing, with the peak appearing at (1.56%, 50.35 kJ / m²). At this point, an appropriate amount of flexible coating plays the best role in toughening and buffering.

[0075] Taking into account both the inflection point of shading efficiency (1.68%) and the peak mechanical efficiency (1.56%), and introducing a comprehensive benefit evaluation function based on the unit coating increment, the theoretically optimal loading was calculated to be 1.62%. For ease of industrial production control and to ensure sufficient shading margin, the optimal loading for the modified carbon black coating was ultimately selected as 1.5%. At this point, the material achieves high shading while maintaining optimal interfacial bonding and impact toughness. Example 3

[0076] Reference Figures 5-7 This is the third embodiment of the present invention. This embodiment aims to verify the optimal formulation determined in the laboratory pilot test of Example 2 through pilot-scale production and systematically optimize the industrial-scale process parameters. Considering the shear heat effect, residence time distribution, and non-ideal flow state during industrial-grade high-speed stirring and continuous extrusion processes, the actual reaction kinetics and dispersion behavior often differ significantly from the static pilot test. Dynamic experiments are needed to correct the process window to ensure the reproducibility of the final product's performance.

[0077] 3.1 Industrial preparation of black high-toughness functionalized impregnation liquid Deionized water (approximately 60% of total mass) was added to a 200L stainless steel high-speed dispersion vessel as the dispersion medium. The agitator was turned on at 400-600 rpm for pre-dispersion. Then, a waterborne polyurethane emulsion with a total solids content of 40% (equivalent to 25 wet parts per 10 dry parts) and pre-dispersed nano-carbon black slurry (equivalent to 15 wet parts per 3 dry parts) were added sequentially. To prevent carbon black agglomeration from affecting the light-blocking effect and mechanical properties, the stirring speed was linearly increased to 1000-2000 rpm after the addition was completed, and an inline high-shear emulsifier was turned on to assist dispersion for 20-40 minutes. The temperature of the material inside the vessel was controlled to not exceed 50°C to prevent polyurethane demulsification.

[0078] Once the mixture becomes a uniform, dark black fluid with a metallic luster, reduce the rotation speed to 200-500 rpm, add the silane coupling agent KH-560 (approximately 0.2 wet weight parts based on 0.2 dry weight parts), and continue stirring at low speed for 15-25 minutes to allow for the curing reaction. The final product is a black functionalized impregnating liquid with a solid content of approximately 15%-20%. This ensures that the light-shielding particles are stably encapsulated within elastic polyurethane microcapsules, rather than being directly exposed in the PC matrix and becoming stress concentration points.

[0079] 3.2 Online Coating and Drying of Continuous Fibers Multiple bundles of continuous alkali-free glass fiber rovings are drawn from an unwinding frame and kept at a constant tension by a closed-loop tension controller. They are then introduced into an impregnation tank containing a prepared functionalized impregnation solution at a traction speed of 3–8 m / min. Inside the tank, the fibers are squeezed by three staggered impregnation rollers. The squeezing, pressing, and suction effects force the impregnation solution to fully penetrate the individual filaments within the fiber bundle, rather than merely remaining on the surface of the roving. Subsequently, the wet fiber bundles enter an infrared drying tunnel for segmented heat treatment, undergoing dehydration and grafting reactions to prevent coating blistering or incomplete cross-linking.

[0080] 3.2.1 Screening Experiment for Coating Dehydration Process Parameters The dehydration stage mainly removes water and solvent from the coating. If the temperature is too low or the time is too short, residual water will cause blistering during subsequent extrusion. If the temperature is too high or the temperature rises too quickly, the water will vaporize rapidly, which will damage the integrity of the coating and form pinhole defects.

[0081] A full-factor experiment was conducted with temperature gradients (80~140℃, step size 10℃) and time gradients (30~180s, step size 30s). Residual moisture content (to determine the degree of drying) and coating adhesion (to determine the film quality) were measured.

[0082] Test results are as follows Figure 5 As shown. Microscopic morphology observation reveals that when the temperature exceeds 120℃ and the time exceeds 60s, a large number of micropore defects appear in the coating due to the boiling of water; data from this area were excluded during analysis. The residual moisture content shows a monotonically decreasing trend with increasing temperature and time. Setting the industrial standard threshold to <0.1%, the process window must be within the range of (T>100℃, t>120s). The adhesion exhibits a typical peak-shaped distribution, with the peak value at (108℃, 115s). The experimental parameters of 110℃ and 120s, closest to this theoretical point, were selected as the final dehydration process parameters.

[0083] 3.2.2 Screening Experiments for Interface Grafting Reaction Process Parameters The grafting process is essentially a chemical reaction between a solid and a semi-solid phase, consisting of two kinetic stages: preheating activation and high-temperature bonding. The preheating activation stage aims to allow the silanol groups on the glass fiber surface and the alkoxy groups of the coupling agent molecules in the coating to overcome the diffusion barrier through a medium-temperature environment, resulting in initial physical adsorption and orientation alignment. It also slowly evaporates residual water molecules and small molecule byproducts, creating a defect-free microscopic contact surface for subsequent reactions. If the temperature rises too quickly in this stage, the intense molecular thermal motion will lead to desorption of the adsorption layer, affecting the effective utilization rate of the bonding sites.

[0084] Set the preheating temperature to 100~140℃ in 5℃ increments. Start the preheating time at 10s, and for every 5s increase, remove a portion of the sample for rapid cooling until the temperature reaches 60s.

[0085] The water contact angle was measured using a contact angle meter. A larger contact angle indicates a more regular outward orientation of the hydrophobic ends of the coupling agent. The characteristic peak area of ​​the epoxy group (910 cm⁻¹) was measured using attenuated total reflectance infrared spectroscopy (ATR-FTIR). A larger area indicates a higher retention rate of effective active groups on the surface.

[0086] Test results are as follows Figure 6 As shown, the water contact angle exhibits a typical single-peak distribution, reaching its theoretical peak at (123.5℃, 31.5s), at which point the coupling agent molecules have completed their optimal orientation alignment under thermal drive. The extreme point of the characteristic peak area fitting is located at (114.8℃, 40.2s), indicating that the effective epoxy group density adsorbed on the surface is the highest at this point, and desorption and self-polymerization have not yet occurred. Combining the two extreme points, taking their geometric center, and considering the temperature control accuracy of the equipment, the optimal preheating activation parameters were finally determined to be 120℃, 35s.

[0087] The high-temperature bonding stage further increases the temperature to cross the reaction activation energy threshold, triggering the ring-opening addition and condensation reaction between the epoxy groups of the coupling agent and the polyurethane molecular chains and fiber surface hydroxyl groups, forming a dense three-dimensional cross-linked network. This stage requires strict control of temperature and time to ensure that the degree of reaction (cross-linking degree) reaches saturation, while preventing the polyurethane coating from undergoing thermal oxidation degradation or discoloration and embrittlement due to prolonged exposure to high temperatures.

[0088] Set the temperature to 120~160℃ in 5℃ increments. Start the cooling time at 30s, and every 5s increment, extract a portion of the sample for rapid cooling until 90s.

[0089] The gel content was determined by Soxhlet extraction with acetone for 24 hours to assess the degree of chemical crosslinking between KH-560 and the matrix / fiber in the coating. The yellowing index (YI) was measured using a colorimeter to evaluate the degree of thermal oxidative degradation of the coating at high temperature. The tensile strength of the peeled cured coating film was tested to detect the cohesive strength of the coating after curing; too low a value indicates incomplete curing, while too high a value indicates embrittlement.

[0090] Test results are as follows Figure 7 As shown, the gel content increases in an S-shape with temperature and time, exceeding the 90% threshold at (133.5℃, 56.5s); the yellowing index deteriorates exponentially with temperature and time, and the process window is limited to (136.2℃, 68.4s) with YI < 2.0 as the boundary; the tensile strength shows a single-peak distribution, with the peak value located near (141.2℃, 58.5s), and the strength decreases due to thermal aging and over-crosslinking embrittlement after exceeding this temperature / time.

[0091] Taking into account the gel saturation point, aging threshold and mechanical peak, the optimal grafting reaction process parameters were finally selected as 135℃, 60s.

[0092] 3.3 Melt Impregnation and Preparation of Long Fiber Granules Polycarbonate resin is premixed with processing aids (including 0.3 parts hindered phenolic antioxidants and 0.2 parts pentaerythritol stearate) and then fed into the main feed port of a twin-screw extruder. The temperature of each zone of the extruder is set between 240°C and 270°C to ensure that the PC resin is fully melted and plasticized to form a stable melt flow. The melt enters a specially designed T-shaped impregnation die, and simultaneously, the resulting black functionalized continuous fibers are introduced into the center of the melt flow channel of the die.

[0093] Under the pressure of the melt inside the mold, high-temperature PC resin coats the pretreated black fiber bundles. By controlling the size of the mold orifice, the fiber-to-resin ratio in the composite is adjusted to the optimal value (GF=35%). The extruded strip is cooled and shaped in a water bath before entering a pelletizer. The pelletizer's cutter speed and traction speed are controlled in a linkage mechanism to cut the strip into long cylindrical particles with a length of 10mm~12mm. This ensures that the length of the internal glass fiber is consistent with the particle length, and the black elastic layer on the fiber surface prevents rigid collision between the glass fiber and the PC resin, resulting in a significant toughening effect.

[0094] 3.4 Injection Molding and the Formation of the Final Part An injection molding machine employing a low-shear screw is used to prevent excessive damage to fiber length during plasticization. The injection molding machine barrel temperature is set at 260℃~280℃, and the mold temperature is controlled at 80℃~100℃. During the screw advance, the long fiber bundles disperse into a monofilament network. Because each fiber surface is pre-securely coated with a polyurethane layer containing carbon black, even if the fibers are randomly distributed in the matrix, they can effectively block light penetration, achieving excellent light-blocking properties (high OD value). Simultaneously, when the material is subjected to external impact, the flexible polyurethane layer on the fiber surface can absorb impact energy and blunt crack tips, preventing rapid crack propagation in the brittle PC matrix. After injection molding and holding pressure, the material is cooled and ejected, resulting in a polycarbonate composite part with a glossy black surface, no internal loose fibers, and both high toughness and complete light-blocking properties. Example 4

[0095] Reference Figure 8 This is the fourth embodiment of the present invention. This embodiment provides a method for preparing a high-toughness, high-light-shielding polycarbonate composite material, the specific steps of which are as follows: S1. Preparation of functionalized wetting solution Ten parts (dry weight) of anionic polyester polyurethane dispersion (40% solid content) were placed in a high-speed dispersion vessel. Three parts (dry weight) of nano-carbon black slurry and 0.3 parts of silane coupling agent KH-560 were slowly added dropwise at 500 rpm. After the addition was complete, the speed was increased to 1500 rpm and an ultrasonic disperser was turned on to assist dispersion for 30 minutes. The system temperature was controlled below 50℃ to obtain a black functionalized impregnating liquid with uniform solid content and a metallic luster.

[0096] S2, Preparation of Functionalized Continuous Fibers Continuous alkali-free glass fiber roving with a monofilament diameter of 13 μm was selected and introduced into a prepared black functionalized impregnation solution for online coating. The coating load after drying was controlled to be 1.5% of the fiber mass by adjusting the pressure of the extrusion rollers. Subsequently, the wet fiber bundle was introduced into a gradient drying tunnel for three stages of heat setting treatment. First stage (dehydration and drying): temperature 110℃, residence time 120s, to remove solvent moisture and initially form a film; Second stage (preheating activation): temperature 120℃, residence time 35s, to induce the coupling agent molecules to align. The third stage (graft curing): temperature 135℃, residence time 60s, to initiate interfacial chemical bonding and coating crosslinking.

[0097] After the above treatment, functionalized continuous fibers with a black elastic coating firmly coated on the surface are obtained.

[0098] S3. Preparation of long fiber reinforced masterbatch Bisphenol A type polycarbonate resin with a melt flow rate of 22 g / 10 min was premixed with 0.5 parts of processing aids (antioxidant 1010 and lubricant PETS) and fed into a twin-screw extruder. At a melt temperature of 260°C, the melt entered a T-die for melt impregnation and composite with functionalized continuous fibers introduced into the die center. The mass fraction of continuous glass fiber in the composite material was controlled to be 35% by the die orifice. After water cooling and setting, the extruded strip was cut into 11 mm long fiber-reinforced masterbatches by a pelletizer.

[0099] S4, Injection Molding The above-mentioned long fiber reinforced masterbatch was added to an injection molding machine and injection molded under conditions of barrel temperature 270℃, mold temperature 90℃, and low shear screw speed to obtain the standard sample of the high toughness and light-shielding polycarbonate composite material.

[0100] The prepared sample was tested, and the results are as follows:

[0101] The resulting composite material, while maintaining high rigidity due to high glass fiber reinforcement, achieves high notched impact strength, successfully overcoming the brittleness of traditional glass fiber reinforced materials. Furthermore, without adding a high concentration of matrix carbon black, high gloss density is achieved solely through a black elastic coating on the fiber surface, resulting in a glossy black surface without any fiber loosening. This demonstrates that the interfacial elastic coating technology successfully resolves the conflict between light-blocking, toughening, and appearance at the microscopic level, achieving the design goals.

[0102] In summary, by constructing a polyurethane elastic composite coating containing nano-carbon black on the surface of continuous glass fibers, the integration of light-shielding and toughening functional components at the microscopic interface is achieved. This elastic coating forms a dense light-shielding network, effectively blocking light transmission within the transparent fibers and imparting high optical density to the material. Furthermore, as an interfacial stress buffer layer, it absorbs external impact energy and blunts crack tips, avoiding the matrix stress concentration and embrittlement caused by the direct high-filling of rigid light-shielding particles in traditional blending processes.

[0103] Furthermore, by combining the chemical bonding network formed between the fibers, coating, and matrix using silane coupling agents and the long fiber retention process during melt impregnation, this composite material significantly improves notched impact strength while maintaining high rigidity. Simultaneously, the pre-applied black organic coating improves the compatibility between the glass fibers and the polycarbonate matrix, effectively suppressing fiber floating during injection molding and allowing the manufactured parts to exhibit a high-gloss black appearance without the need for spraying.

[0104] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-toughness, high-light-shielding polycarbonate composite material, characterized in that, Includes the following steps: S1. By weight, take 5-15 parts of waterborne polyurethane emulsion, 1-5 parts of nano carbon black and 0.1-0.5 parts of silane coupling agent, mix and disperse them to prepare a black functionalized impregnation liquid. S2. Introduce continuous glass fibers into the black functionalized impregnation liquid for coating, and control the coating load to be 1.0%~2.0% of the fiber mass; then perform gradient heat setting at 80~160℃ for 3~5 minutes to obtain functionalized continuous fibers with a black elastic coating on the surface. S3. Polycarbonate resin and processing aids are melt-plasticized and then melt-impregnated with the functionalized continuous fibers in an impregnation mold. The mass fraction of the continuous glass fibers in the composite material is controlled to be 20% to 50%. The composite material is then cooled and pelletized to obtain long fiber reinforced masterbatch. S4. The long fiber reinforced masterbatch is injection molded under low shear conditions to obtain the high toughness and light-shielding polycarbonate composite material.

2. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, In the black functionalized impregnation liquid, the aqueous polyurethane emulsion is 10 parts, the nano carbon black is 3 parts, and the silane coupling agent is 0.3 parts.

3. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, The coating loading is 1.5% of the fiber mass; the gradient heat setting includes a dehydration and drying stage, a preheating and activation stage, and a high-temperature grafting reaction stage performed sequentially.

4. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, The continuous glass fiber has a mass fraction of 35% in the composite material.

5. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 3, characterized in that, The process conditions for the dehydration and drying stage are: temperature 100℃~120℃, time 110s~130s; the process conditions for the preheating and activation stage are: temperature 110℃~130℃, time 20s~50s; and the process conditions for the high-temperature grafting reaction stage are: temperature 130℃~150℃, time 50s~70s.

6. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, The aqueous polyurethane emulsion is an anionic polyester polyurethane dispersion with a solid content of 35% to 45%; the nano carbon black is ordinary pigment carbon black or acetylene black with a primary particle size of 10nm to 30nm; and the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. In the specific steps of the dispersion treatment, the mixture is first added dropwise at a speed of 300~800 rpm. After the addition is completed, the speed is increased to 1200~1800 rpm and ultrasonic dispersion treatment is carried out for 20~40 minutes.

7. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 5, characterized in that, The continuous glass fiber is an alkali-free glass fiber roving with a single filament diameter of 11μm~13μm; the process conditions for the dehydration and drying stage are a temperature of 110℃ and a time of 120s; the process conditions for the preheating and activation stage are a temperature of 120℃ and a time of 35s. The process conditions for the high-temperature grafting reaction stage are a temperature of 135°C and a time of 60 seconds.

8. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, The polycarbonate resin is a bisphenol A type polycarbonate with a melt flow rate of 20~25g / 10min; the melt plasticizing temperature is 240℃~270℃; and the pellet length is 10mm~12mm.

9. The method for preparing high-toughness, high-light-shielding polycarbonate composite material according to claim 1, characterized in that, The temperature of the injection molding barrel is 260℃~280℃, and the temperature of the mold is 80℃~100℃.

10. A high-toughness, high-light-shielding polycarbonate composite material, characterized in that, The composite material has a micro-layered structure, with an inner layer of continuous glass fiber skeleton, a middle layer of nano carbon black and polyurethane elastic composite coating covering the surface of each glass fiber, and an outer layer of polycarbonate resin matrix. The elastic composite coating forms a chemical bond network with the inner glass fiber and the outer resin matrix through a silane coupling agent, and the nano carbon black is dispersed in the interior of the elastic composite coating without directly contacting the polycarbonate resin matrix.

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