A high-reflectivity composite material, its preparation method and application

Abstract

The present invention relates to the technical field of polymer composite materials, and discloses a high-reflectivity composite material, a preparation method and an application thereof, which comprise the following components by mass percentage: polymer matrix: 70%-95%, selected from polycarbonate, polyester or polyamide; high-reflectivity filler: 2%-25%, which is core-shell structured TiO2@SiO2 doped with Al 3+ or La 3+ , wherein the particle size of TiO2 is 50-150 nm, the thickness of the SiO2 shell layer is 5-30 nm, and the doping ratio is 0.5%-5%; reflection aid: 3%-5%, which is a rare earth oxide, selected from cerium oxide (CeO2) or yttrium oxide (Y2O3). By adopting the design scheme of core-shell structure coating and heteroionic co-doping, the structural stability and optical inertness control of functional particles in the polymer matrix are realized, and the photocatalytic side reaction problem caused by high interfacial reaction activity of particles is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, in particular to a high-reflectivity composite material and a preparation method and application thereof. Background Art

[0002] With the increasing demand for polymer materials with improved weather resistance, reflective properties, and surface stability, particularly in applications such as building energy conservation, automotive exteriors, and outdoor equipment, composite materials with excellent UV reflectivity and thermal-oxidative stability have become a research hotspot. In existing technologies, high-refractive-index inorganic particles such as TiO2 are typically used as functional fillers to enhance the material's UV resistance through their strong UV reflection. However, exposed TiO2 particles exhibit high surface activity within the polymer matrix and are prone to inducing photocatalytic reactions. This not only accelerates polymer degradation but can also lead to yellowing and performance degradation in finished products, limiting their stability in long-term applications.

[0003] To suppress the side effects of TiO2, some technologies have incorporated surface coupling agents or organic coatings to modulate particle interface properties. While this improves interfacial compatibility to some extent, organically modified materials have limited stability under high temperature and strong light conditions, and are prone to thermal decomposition, migration, and even delamination, which in turn affects the overall performance of the material. Furthermore, a single modification method often struggles to balance optical control with thermal oxidation inhibition, resulting in unstable modification results and limited improvements in dispersibility. Furthermore, it still fails to effectively prevent microscopic defects caused by particle agglomeration in the matrix.

[0004] In addition, traditional UV reflection enhancement systems mostly rely on high filling rate TiO2 or Al2O 3+ While fillers are used to improve UV reflectivity, the lack of effective synergy between fillers limits reflection efficiency and makes it difficult to achieve broadband reflection control. Some studies have attempted doping modifications, but doping structures are often unstable, and loss of doping elements or blurred reaction interfaces can lead to optical failure risks, reducing the consistency of reflective performance. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a high reflectivity composite material and its preparation method and application, which solves the problem that traditional ultraviolet reflection enhancement systems rely on high filling rate TiO2 or Al2O 3+ Fillers are used to improve the ultraviolet reflectivity, but there is a lack of effective synergistic mechanism between fillers, which leads to limited reflection efficiency and difficulty in achieving wide-band reflection control.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A high reflectivity composite material comprises the following components by mass percentage:

[0007] Polymer matrix: 70% - 95%, selected from polycarbonate, polyester or polyamide;

[0008] High - reflectivity filler: 2% - 25%, which is core - shell structured TiO2@SiO2 doped with Al 3+ or La 3+ where the particle size of TiO2 is 50 - 150 nm, the thickness of the SiO2 shell layer is 5 - 30 nm, and the doping ratio is 0.5% - 5%;

[0009] Reflection aid: 3% - 5%, which is a rare - earth oxide, selected from cerium oxide (CeO2) or yttrium oxide (Y2O3), with a particle size of 10 - 100 nm;

[0010] Among them, the SiO2 shell layer further adsorbs a reflection aid to form a synergistic reflection layer, and 1% - 5% of polar modification components are introduced into the polymer matrix. The polar modification components in the polymer matrix are selected from any one of the following: maleic anhydride - grafted polyolefin, functionalized polyester with a carboxyl - containing structure, functionalized polyamide with a carboxyl - containing structure, functionalized polyester with a hydroxyl - containing structure, functionalized polyamide with a hydroxyl - containing structure.

[0011] Furthermore, by constructing a core - shell structured high - reflectivity filler system, the superposition structure of multiple reflection interfaces is realized. TiO2, as a high - refractive - index material, has good ultraviolet scattering characteristics, and its optical activity can be regulated by the band - structure through hetero - doping of Al 3+ or La 3+ so as to enhance the response to the deep - ultraviolet region. The SiO2 shell layer, on the one hand, effectively blocks the photocatalytic reaction on the surface of TiO2, reducing the risk of oxidative damage to the polymer matrix, and on the other hand, provides a stable adsorption interface for the reflection aid. Rare - earth oxides, due to their wide - spectrum and high - reflection properties, cooperate with the TiO2 system to form a double - layer reflection mechanism. In addition, the introduction of polar modification components into the polymer matrix helps the dispersion and interfacial bonding of inorganic fillers, improving the structural stability and optical uniformity of the overall composite system.

[0012] Preferably, the reflection aid is loaded on the surface of the SiO2 shell layer by co - deposition or physical adsorption after surface modification treatment, and the rare - earth aid accounts for 10% - 25 wt% of the SiO2 mass.

[0013] Furthermore, by subjecting the reflection aid to surface modification treatment, the interfacial compatibility between it and the SiO2 shell can be improved, enabling it to bind more uniformly and stably to the shell surface during the deposition or adsorption process. This structural form not only increases the spatial distribution density of the reflection aid but also extends the light reflection interface at the microscale. The outer layer formed by rare earth particles can enhance the scattering path of incident ultraviolet light, and then produce a synergistic effect with the main reflection behavior of the TiO2 core, establishing a local multiple scattering field around the shell and achieving structural coupling of multi-band reflection performance.

[0014] Preferably, the high-reflectivity filler in the composite material comprises a combination of flaky particles and spherical particles for enhancing the ultraviolet reflection performance.

[0015] Furthermore, the synergistic combination of flaky and spherical particles utilizes their respective different light scattering paths and spatial orientation characteristics. Flaky particles are prone to form a preferred orientation layered structure in the shear flow field during processing, which helps to construct an array of directional reflection surfaces; while spherical particles enhance the anisotropic distribution of the scattering path and increase the reflection probability of non-vertically incident light. This composite particle structure constructs a micro-layered domain through a flow-induced mechanism, which can form a controllable reflection directivity macroscopically, thereby enhancing the overall reflection effectiveness of the material for ultraviolet light.

[0016] A preparation method of a high-reflectivity composite material comprises the following steps:

[0017] Step 1: React tetrabutyl titanate with AlCl3 or La(NO2)3 in a deionized water solvent to synthesize TiO2 nanoparticles doped with Al 3+ or La 3+ ;

[0018] Step 2: Use TEOS as the silicon source, and coat the TiO2 particles with a shell of SiO2 under the catalysis of ammonia water to form a SiO2 shell on the surface of TiO2 and form a TiO2@SiO2 core-shell structure;

[0019] Step 3: Load the reflection aid on the SiO2 shell, and control the particle size to be 10 - 100 nm to obtain composite particles formed by the combination of the TiO2@SiO2 core-shell structure and the reflection aid;

[0020] Step 4: Blend the composite particles with a polymer matrix containing 1% - 5% polar modification components to uniformly disperse the composite particles as fillers in the polymer to form a mixture;

[0021] Step 5: Use a twin-screw extruder to melt-blend and extrude the mixture to obtain a molten material at a temperature range of 180 - 260 °C and a screw speed of 100 - 200 rpm, and then cool and pelletize to obtain a composite masterbatch.

[0022] Furthermore, through an orderly structure construction process, this preparation method realizes the efficient embedding and stable dispersion of multifunctional particles in the polymer matrix. The introduction of Al doped in TiO2 3+ or La 3+ ions locally regulates the lattice structure, providing conditions for the formation of the core-shell interface and the adjustment of ultraviolet response. Subsequently, a SiO2 shell layer is coated, which provides an adsorption carrier for functional additives while blocking the photocatalytic reaction. The directional loading of the reflection additive enables the particles to have the ability of secondary reflection, and multiple reflection units are constructed at the level of composite particles. In the blending stage, through the synergistic effect of polar modification components, the particles are interfacially embedded in the polymer, and the re-dispersion and thermodynamics regulation of the particles are completed through the melt blending process, thereby forming a composite masterbatch with a complete structure and optical stability.

[0023] Preferably, the particle size of the TiO2 nanoparticles is 50 - 150 nm, and the doping ratio is 0.5% - 5%.

[0024] Furthermore, TiO2 doped with Al 3+ or La 3+ can regulate the energy band structure of TiO2 through doping ions, enhancing the scattering and reflection ability of ultraviolet light. At the same time, the control of the doping concentration (0.5% - 5%) can effectively improve the stability and reactivity of TiO2 particles, avoiding lattice distortion caused by too high a doping ratio, thereby optimizing the ultraviolet reflection performance.

[0025] Preferably, the thickness of the SiO2 shell layer is 5 - 30 nm.

[0026] Furthermore, the role of the SiO2 shell layer is to improve the stability of TiO2 particles and prevent them from having adverse reactions with the matrix polymer. Controlling the thickness of the SiO2 shell layer between 5 - 30 nm helps to ensure that the TiO2@SiO2 composite particles have good optical properties and thermal stability, and at the same time enables the TiO2 particles to play the best effect in the absorption and reflection of ultraviolet light. An overly thick SiO2 shell layer may affect the light transmittance and reflection efficiency of the material, while an overly thin one may not be able to fully protect the TiO2 particles.

[0027] Preferably, the loading ratio of the reflection additive is 10% - 25%.

[0028] Furthermore, reflection additives (such as CeO2, Y2O3) have excellent ultraviolet light absorption and reflection properties. Loading these reflection additives can enhance the reflection ability of the composite material to ultraviolet light and further improve its optical properties. Controlling the loading ratio between 10% - 25% helps to achieve the optical enhancement effect of the TiO2@SiO2 composite particles. Too low a loading amount may not significantly improve the reflection performance, while too high a loading amount may lead to the aggregation of the reflection additive, affecting the uniformity and performance of the material.

[0029] Preferably, the molten material is pelletized after being cooled by water-cooled strand drawing, and the composite masterbatch has a particle size of 2-5 mm.

[0030] Furthermore, the water-cooled strand drawing method is adopted to achieve rapid solidification of the material, which helps to maintain the dispersed state formed in the molten state of the particles from being destroyed by thermal migration. Such a rapid cooling process can lock the dispersed structure and maintain the relative orientation of the particles, which is beneficial to the structural integrity and optical stability during subsequent processing. Controlling the pellet size within an appropriate range is also convenient for subsequent processing and dispersion of the color masterbatch.

[0031] Preferably, the application of the high-reflectivity composite material in the preparation of ultraviolet-resistant thermoplastic plastic products.

[0032] Furthermore, the composite material system has a stable multi-scale reflection network and can achieve the ultraviolet blocking function as a functional color masterbatch in thermoplastic plastics. Due to the significant synergistic effect between the core-shell structure fillers and the rare-earth reflection layer in the material, a reflection enhancement path can be formed in the plastic matrix, effectively blocking ultraviolet radiation without significantly affecting the visible light transmittance, providing a new functional solution for outdoor, high-gloss or anti-aging plastic products.

[0033] The present invention provides a high-reflectivity composite material, its preparation method and application. It has the following beneficial effects:

[0034] 1. The present invention adopts the design scheme of core-shell structure coating and heteroionic co-doping to achieve the control of the structural stability and optical inertness of functional particles in the polymer matrix. Compared with the particle system without surface modification treatment in the prior art, it avoids the photocatalytic side reaction problem caused by the high interfacial reaction activity of the particles, and solves the technical obstacle of performance deterioration caused by color migration or degradation during the long-term application of the material.

[0035] 2. By constructing multiple reflection and energy band regulation paths, the present invention not only improves the ultraviolet shielding performance but also takes into account the visible light transmittance and material transparency. Compared with the traditional method of using a single high refractive index filler, this technical path shows better coordination in material compatibility and optical balance, effectively breaking through the structural contradiction that it is difficult to balance the ultraviolet reflection efficiency and visual aesthetics.

[0036] 3. The reflection aid composite strategy introduced in the present invention can construct a stable reflection multiplexing network, effectively regulating the optical path and energy distribution. Different from the conventional unidirectional reflection filler system, this composite mechanism enhances the response ability of the material to broadband ultraviolet light, avoids the problems of weak reflection directionality and incomplete energy dissipation mechanism in the traditional system, and significantly improves the reflection persistence of the material in a strong ultraviolet environment.

[0037] 4. Through the means of regulating the interfacial energy difference between particles and optimizing the microscopic dispersion, the present invention improves the dispersion uniformity and interfacial adhesion state of inorganic particles in the polymer matrix, forming a continuous composite network with a low defect rate. Compared with the existing methods of mechanical blending or surface coupling agent modification, it avoids the structural defect problems of filler agglomeration and increased interfacial voids, providing a better particle structure solution for high-fill and high-performance composite materials. Brief Description of the Drawings

[0038] Figure 1 It is a flowchart of the method of the present invention. Detailed Embodiments

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] Example 1:

[0041] Please refer to the attached Figure 1 :

[0042] Preparation material ratio:

[0043] Polycarbonate (PC): 85 wt%;

[0044] TiO2@SiO2 core-shell structure filler: 10 wt% (the particle size of TiO2 is 100 nm, the shell thickness of SiO2 is 20 nm, and Al 3+ is doped with 2%);

[0045] Reflection aid CeO 2: 3 wt% (particle size 50 nm, accounting for 20% of the mass of SiO2);

[0046] Polarity modification component: 2 wt% (maleic anhydride grafted polypropylene).

[0047] Specific steps:

[0048] Synthesis of doped TiO2: In an aqueous solution containing 0.5 mol / L AlCl3, tetrabutyl titanate is hydrolyzed, and Al-doped TiO2 nanoparticles with an average particle size of 100 nm are generated by stirring at a constant temperature of 80 °C for 6 hours.

[0049] Construction of the SiO2 shell layer: TEOS is used to hydrolyze and coat the surface of TiO2 under the catalysis of ammonia water, and the reaction time is 5 hours, controlling the shell layer thickness to be 20 nm.

[0050] Rare earth promoter loading: After treating CeO2 with KH550 silane coupling agent, it was stirred and adsorbed on the surface of SiO2 at 50 °C, with a mass ratio of 20% of SiO2.

[0051] Melt blending and pelletizing: The obtained composite particles were blended with PC and polar components in a twin-screw extruder at a temperature of 200 °C and a speed of 160 rpm, and then water-cooled and pelletized after extrusion.

[0052] Example 2:

[0053] Preparation material ratio:

[0054] Polyethylene terephthalate (PET): 75 wt%;

[0055] TiO2@SiO2 core-shell structure filler: 20 wt% (the particle size of TiO2 is 80 nm, the shell thickness of SiO2 is 25 nm, and La 3+ doped with 3%);

[0056] Reflection promoter Y2O 3: 3 wt% (particle size 70 nm, accounting for 15% of the mass of SiO2);

[0057] Polar modification component: 2 wt% (including carboxyl-modified polyester).

[0058] Specific steps:

[0059] Synthesis of doped TiO2: Using La(NO2)3 as the doping source, it was added to the titanium butoxide hydrolysis reaction system, and the reaction continued at 70 °C for 5 hours to obtain La 3+ doped TiO2.

[0060] SiO2 coating: TEOS and ammonia water were added to anhydrous ethanol for hydrolysis reaction to form a uniform shell layer with a thickness of about 25 nm.

[0061] Y2O3 loading treatment: After surface hydroxylation treatment, Y2O3 was adsorbed on the surface of the shell layer at 40 °C, with a mass ratio of 15%.

[0062] Melt blending and pelletizing: At a temperature of 210 °C and a speed of 140 rpm, the obtained particles were blended and extruded with PET and polar polyester, and then cooled and pelletized to obtain the composite masterbatch.

[0063] Example 3:

[0064] Preparation material ratio:

[0065] Polyamide (PA66): 70 wt%;

[0066] TiO2@SiO2 core-shell structure filler: 25 wt% (TiO2 particle size is 150 nm, SiO2 shell thickness is 30 nm, Al 3+ doping 5%);

[0067] Reflection aid CeO 2: 3 wt% (particle size 100 nm, accounting for 10% of the mass of SiO2);

[0068] Polarity modification component: 2 wt% (amide-modified polymer).

[0069] Specific steps:

[0070] Preparation of doped TiO2: Under strong acid conditions (pH ≈ 1.5), AlCl3 was incorporated into the hydrolysis reaction of tetrabutyl titanate, and the reaction was carried out at 90 °C for 8 hours to form TiO2 particles with a high doping concentration (150 nm).

[0071] Synthesis of SiO2 shell: The hydrolysis reaction of TEOS was used to control the shell thickness to 30 nm by extending the deposition time.

[0072] CeO2 adsorption: CeO2 aid with a particle size of 100 nm was adsorbed on the surface of SiO2 after being treated with a coupling agent, and the adsorption ratio was 10% (mass ratio).

[0073] Extrusion processing: All components were melt-mixed at 230 °C, the twin-screw speed was 180 rpm, and the target composite masterbatch was prepared by the method of strand water-cooling and pelletizing.

[0074] Comparative example 1:

[0075] Compared with Example 1, the difference is that the TiO2 used is Al 3+ doped TiO2 nanoparticles without SiO2 coating, and the other conditions remain unchanged.

[0076] Specific component ratio is:

[0077] Polycarbonate (PC): 85 wt%;

[0078] Al 3+ Doped TiO2 particles: 10 wt% (particle size 100 nm, doping ratio 2%);

[0079] Reflection aid CeO2 (modified with silane): 3 wt% (particle size 50 nm, accounting for 20% of the filler mass);

[0080] Maleic anhydride grafted polypropylene: 2 wt%;

[0081] Brief description of the preparation steps:

[0082] After preparing the doped TiO2 particles, the TEOS coating reaction was not carried out, and they were directly used as fillers;

[0083] The remaining operation steps (CeO2 loading, melt extrusion, cooling and pelletizing) were the same as those in Example 1.

[0084] This comparative example was used to verify that the shellless TiO2 had strong photocatalytic activity and interface instability problems, resulting in a decrease in the ultraviolet reflection ability of the system and an increase in the risk of material aging.

[0085] Comparative Example 2:

[0086] Compared with Example 2, the difference was that when preparing the TiO2@SiO2 particles, La was not added 3+ for doping modification, and the TiO2 used was in an undoped form, with the other conditions being the same.

[0087] The specific component ratio was:

[0088] Polyethylene terephthalate (PET): 75 wt%;

[0089] TiO2@SiO2 particles (undoped, TiO2 particle size 80 nm, SiO2 shell thickness 25 nm): 20 wt%;

[0090] Reflection aid Y2O3 (particle size 70 nm, accounting for 15% of the mass of SiO2): 3 wt%;

[0091] Carboxyl-containing polyester modifier: 2 wt%;

[0092] A brief description of the preparation steps:

[0093] Without adding La(NO2)3, TiO2 was directly synthesized and then coated with SiO2;

[0094] The remaining steps such as SiO2 deposition, rare earth additive loading, and mixing and extrusion remained the same.

[0095] This comparative example was used to verify that the undoped TiO2 had a low response efficiency to ultraviolet light, especially insufficient reflection performance in the deep ultraviolet band, and the doping mechanism was crucial for functional improvement.

[0096] Comparative Example 3:

[0097] Compared with Example 3, the difference was that CeO2 reflection aid was not added during the preparation process, and the TiO2@SiO2 composite particles were not loaded with a reflection synergistic layer, with the other conditions being the same.

[0098] The specific component ratio was:

[0099] Polyamide PA66: 70 wt%;

[0100] TiO2@SiO2 core-shell structured particles (TiO2 particle size 150 nm, SiO2 shell layer 30 nm, Al 3+ doped with 5%): 25 wt%;

[0101] Amide-modified polymer: 2 wt%;

[0102] Brief description of the preparation steps:

[0103] After preparing TiO2@SiO2 particles, no surface adsorption treatment with CeO2 promoter was carried out;

[0104] The obtained particles were directly blended with PA66 matrix and polar modification components;

[0105] Processing temperature 230 °C, screw speed 180 rpm, the extrusion cooling and pelletizing operations were the same as in Example 3.

[0106] This comparative example was used to verify that the composite particles without rare earth synergistic layer showed deficiencies in reflectivity and band coverage ability, and it was difficult to form a multi-path scattering network.

[0107] Experiment 1. Explanation of UV reflection performance test

[0108] To verify the reflection performance of different materials in the UV band, optical tests were carried out on each embodiment and the control group. The test samples were made into standard sheets with a thickness of about 1 mm by injection molding from the respective prepared composite masterbatches, and all samples were processed and tested under the same conditions.

[0109] The test used a UV-visible integrating sphere reflectance test system (model: PerkinElmer Lambda1050), the diameter of the integrating sphere was 150 mm, the scanning wavelength range was from 280 nm to 400 nm, the scanning wavelength was 2 nm, and the integration time was 1 s. During the test, 3 pieces were taken from each group of samples and tested 3 times, and the average value was taken as the reflectance data of the sample.

[0110] Before the test, the surface of the sample was wiped and cleaned. During the test, the sample was placed horizontally in front of the integrating sphere window, keeping the light beam perpendicular to the incidence to ensure that the measurement area was consistent. The ambient light intensity, temperature and humidity were controlled constantly to reduce background interference.

[0111] Table 1: Average reflectance (%) of each material in the UV band (280–400 nm) range

[0112] Sample Number Average Reflectivity (%) Test 1 Test 2 Test 3 Example 1 77.4 78.1 76.8 77.2 Example 2 81.2 80.9 81.6 81.0 Example 3 79.6 79.3 80.1 79.4 Comparative Example 1 62.8 63.1 61.7 63.6 Comparative Example 2 70.5 70.2 69.7 71.5 Comparative Example 3 68.9 67.8 69.2 69.6

[0113] Summary of UV reflection performance test results

[0114] From the above test results, it can be seen that each embodiment exhibits a high reflection ability in the ultraviolet band. Among them, the material system with shell coating, heteroionic doping, and reflection aids introduced simultaneously in the structure forms a stable composite scattering network, significantly improving the multi-stage reflection and scattering efficiency of ultraviolet light. In contrast, the reflection performance of the comparative sample decreases overall due to the lack of some structural units, verifying the necessity of multiple collaborative designs.

[0115] Especially after forming a uniform SiO2 shell outside the TiO2 particles, it can effectively weaken the optical scattering loss between interfaces, improve the dispersibility and stability of the particles in the polymer matrix, and avoid photocatalytic degradation. At the same time, the shell can adjust the refractive index gradient of the composite particles, enhancing their multi-angle reflection ability for UV light, which is one of the key factors in improving the reflection performance.

[0116] On the other hand, the introduction of Al 3+ or La 3+ hetero-doping in the TiO2 core can adjust its energy band structure, optimize the ultraviolet absorption-scattering window, and cooperate with the reflection aid to construct a triple-functional mechanism of "optical trap-reflection reuse-interface stability", effectively broadening the response range of the material to the short-wave ultraviolet region. This collaborative coupling design gives the composite material significant advantages in reflectivity and stability.

[0117] Experiment 2. Explanation of the thermal-oxidative aging yellowing test

[0118] To evaluate the color stability of the composite material in a thermal-oxidative environment, the samples of each embodiment and the control sample were subjected to accelerated aging treatment, and the color change was measured to verify the influence of the material structure on the anti-yellowing performance. The experiment used a constant-temperature aging oven for thermal-oxidative accelerated aging. Color tests were carried out before and after aging, and the yellowing index ΔYI value was calculated.

[0119] The test samples were 1-mm-thick sheets after injection molding. The aging conditions were: a hot air environment at 120 °C for 96 hours. After aging, it was cooled to room temperature, and the CIELAB color space parameters were measured using a color difference meter (model: X-Rite Ci7600). The ΔYI value was calculated according to the ASTM D1925 standard to reflect the degree of yellowing.

[0120] Three samples were taken from each group, and they were independently aged and tested respectively. Finally, the average ΔYI value was recorded.

[0121] Table 2: Yellowing index (ΔYI) of each material after thermal-oxidative aging

[0122] Sample Number ΔYI Value (Average) Test 1 Test 2 Test 3 Example 1 2.7 2.5 2.9 2.6 Example 2 2.3 2.1 2.4 2.5 Example 3 2.9 3.1 2.7 2.8 Comparative Example 1 7.6 7.1 7.8 7.9 Comparative Example 2 4.5 4.3 4.9 4.4 Comparative Example 3 5.2 5.0 5.5 5.1

[0123] Summary of the thermal-oxidative yellowing test results

[0124] As can be seen from the test results, the composite materials prepared by the implementation methods exhibit excellent anti-yellowing performance in a thermal-oxidative environment, with ΔYI values all lower than 3, indicating stable color in long-term high-temperature air and no obvious aging and yellowing phenomenon. This performance is mainly attributed to the stable interface system and photochemically inert shell layer constructed in the structure, which effectively blocks the photocatalytic degradation effect that TiO2 may cause and avoids the excitation of the matrix thermal-oxidative degradation chain reaction.

[0125] Among them, the SiO2 shell layer, as a non-reactive shielding interface, can effectively isolate TiO2 from the organic matrix and weaken the chance of its contact reaction with oxygen and polymers at high temperatures. This shell layer not only improves the dispersibility of the particles but also plays a key protective role in thermal stability. After removing the shell layer in the control group, there is an obvious increase in the color difference induced by oxidation, verifying the necessity of the shell-coated structure for thermal-oxidative aging control.

[0126] In addition, by regulating the internal energy band structure of TiO2 crystals through ion doping, the surface redox activity can be effectively inhibited, and the tendency to form free radicals under ultraviolet irradiation or high-temperature conditions can be reduced. When the doping and reflection aids coexist, the material as a whole forms multiple energy dissipation and reaction inhibition channels, further preventing the chain degradation process induced by thermal oxidation and enabling the composite material to maintain the stability of its structure and color under long-term thermal load. This structural system provides an effective path for solving the key limitations of high-performance optical functional materials in terms of aging and weather resistance.

[0127] Experiment 3. Explanation of the Dispersibility and Interface Compatibility Test of Composite Particles

[0128] To investigate the dispersion uniformity of the composite filler in the polymer matrix and the bonding state with the matrix interface, cross-section observations of the implementation examples and control samples were carried out by scanning electron microscopy (SEM). This experiment aims to evaluate the improvement effects of the core-shell structure and the co-modification strategy on particle aggregation, debonding, and interface integrity.

[0129] The test samples were standard sheets after injection molding of each composite material. Three pieces were taken from each sheet of the sample group, and after being cryo-fractured by liquid nitrogen, a clean cross-section was prepared. After the cross-section was treated by metal sputtering (Pt or Au, 10 nm), images were taken using a field emission scanning electron microscope (model: Hitachi SU8230) at a voltage of 5 kV with a magnification of 5000×.

[0130] The evaluation indicators include:

[0131] Particle distribution uniformity (aggregation degree);

[0132] Interface adhesion state (whether there is debonding or holes);

[0133] Microstructural integrity (cracks, porosity);

[0134] Three regions of each sample were observed, qualitatively graded according to standard criteria (excellent, good, medium, poor), and supplemented with image counting analysis to obtain the following results.

[0135] Table 3: Scoring Table for the Dispersibility of Composite Material Particles and the Interface Bonding Condition (Qualitative Grading)

[0136] Sample Number Distribution Uniformity Interface Adhesion Typical Defect Type Example 1 Excellent Excellent No Obvious Holes Example 2 Good Excellent Local Aggregation Visible Example 3 Excellent Good Few Interface Voids Comparative Example 1 Poor Poor Particle Agglomeration, Obvious Holes Comparative Example 2 Medium Medium Uneven Dispersion, Delamination Phenomenon Comparative Example 3 Medium Poor Interface Microcracks

[0137] Summary of Particle Dispersion and Interface Structure Testing

[0138] Through the observation and analysis of the material cross-section, it can be seen that the core-shell structure design adopted in the present invention has a significant effect on enhancing the dispersibility of inorganic fillers. The SiO2 coating layer, as an inert and polymerophilic interface buffer zone, can significantly reduce the agglomeration tendency of high specific surface area TiO2 in the polymer matrix, and at the same time avoid the interfacial stress concentration caused by polarity differences, thereby realizing a more uniform and dense composite structure.

[0139] In addition, the reflection aids co-loaded on the particle surface also play a dual role of physical shielding and interface regulation during the dispersion process, making an appropriate distance formed between the particles to avoid interface overlap and cluster growth during the melt blending stage. This structure not only improves the physical interlocking between the filler and the polymer, but also reduces the risk of microdefects caused by interface debonding.

[0140] C The doping mechanism introduced in the structure design also has the potential function of regulating the interfacial energy. The surface charge density of the TiO2 crystal after doping modification is lower. Combining with the interfacial softening characteristics of the SiO2 layer, the whole composite particle exhibits more excellent interfacial affinity and thermal matching performance. The comparison results show that samples lacking shell protection or not adopting the co-filler strategy generally have serious particle agglomeration, holes or microcracks, further verifying the advantages of the multi-level particle structure in terms of dispersibility and interface construction.

[0141] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high reflectivity composite material, characterized in that, Comprising the following components by mass percentage: Polymer matrix: 70% - 95%, selected from polycarbonate, polyester or polyamide; High-reflectivity filler: 2% - 25%, which is core-shell structured TiO2@SiO2 doped with Al 3+ or La 3+ , where the particle size of TiO2 is 50 - 150 nm, the thickness of the SiO2 shell layer is 5 - 30 nm, and the doping ratio is 0.5% - 5%; Reflection aid: 3% - 5%, being a rare earth oxide, selected from cerium oxide (CeO₂) or yttrium oxide (Y₂O₃), with a particle size of 10 - 100 nm; Wherein, a reflection aid is adsorbed in the SiO₂ shell to form a synergistic reflection layer, and 1% - 5% of a polar modification component is introduced into the polymer matrix, and the polar modification component in the polymer matrix is selected from any one of the following: maleic anhydride grafted polyolefin, functionalized polyester with a carboxyl group structure, functionalized polyamide with a carboxyl group structure, functionalized polyester with a hydroxyl group structure, functionalized polyamide with a hydroxyl group structure; A high - reflectivity composite material is prepared through the following steps: Step 1: React tetrabutyl titanate with AlCl3 or La(NO2)3 in a deionized water solvent to synthesize TiO2 nanoparticles doped with Al 3+ or La 3+ ; Step 2: Using TEOS as a silicon source, under the catalysis of ammonia water, coat the shell SiO₂ on the surface of TiO₂ particles to form a SiO₂ shell on the surface of TiO₂, forming a TiO₂@SiO₂ core - shell structure; Step 3: Load the reflection aid on the SiO₂ shell, control the particle size to be 10 - 100 nm, and obtain composite particles combined by the TiO₂@SiO₂ core - shell structure and the reflection aid; Step 4: Blend the composite particles with a polymer matrix containing 1% - 5% of a polar modification component, and make the composite particles evenly disperse in the polymer as a filler to form a mixture; Step 5: Use a twin - screw extruder to melt - blend and extrude the mixture to obtain a molten material, with a temperature range of 180 - 260 °C, a screw speed of 100 - 200 rpm, cool and pelletize to obtain a composite masterbatch.

2. The high reflectivity composite material according to claim 1, wherein The reflection aid is loaded on the surface of the SiO₂ shell by surface modification treatment in a co - deposition or physical adsorption manner, and the reflection aid accounts for 10% - 25 wt% of the mass of SiO₂.

3. A high reflectivity composite material according to claim 1, characterized in that, The high - reflectivity filler in the composite material comprises a combination of flaky particles and spherical particles.

4. A high reflectivity composite material according to claim 1, characterized in that, The particle size of the TiO₂ nanoparticles is 50 - 150 nm, and the doping ratio is 0.5% - 5%.

5. The high reflectivity composite material according to claim 2, characterized in that The thickness of the SiO₂ shell is 5 - 30 nm.

6. The high reflectivity composite material according to claim 2, characterized in that, The loading ratio of the reflection aid is 10% - 25%.

7. A high reflectivity composite material according to claim 1, characterized in that, The molten material is cooled by water - cooled strand and then pelletized, and the particle size of the composite masterbatch is 2 - 5 mm.

8. Use of the high - reflectivity composite material according to any one of claims 1 - 3 in the preparation of ultraviolet - resistant thermoplastic plastic products.

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