A functional composite material based on an inorganic compound system and a preparation method thereof

Abstract

The present invention discloses a functional composite material based on an inorganic compound system and a preparation method, which belongs to the field of functional material technology and includes the following steps: processing and drying of raw materials; modification of Salix psammophila fibers; step-by-step mixing and paving assembly; the inorganic compound system is montmorillonite, zinc oxide and nano-conductive carbon black; hot pressing: hot pressing the obtained slab to obtain the functional composite material based on the inorganic compound system. The present invention adopts silane coupling agent KH550 as an interfacial activator between wood powder and polylactic acid matrix to improve the interface compatibility of the composite material and enhance the mechanical strength, while constructing an "inorganic compound system" to provide the composite material with excellent mechanical, aging resistance, electromagnetic shielding and flame retardant properties. The test results show that the mechanical strength, surface resistivity, electromagnetic shielding effectiveness and flame retardant properties of the composite material meet the requirements of the corresponding national / industry standards, and the aging resistance and thermal stability are significantly improved.

Description

Technical Field

[0001] The present application relates to the technical field of functional materials, and more specifically, to a functional composite material based on an inorganic compound system and a preparation method thereof. Background Art

[0002] In recent years, with increasing attention to ecological conservation and deepening research in the field of materials, natural plant fiber / biodegradable plastic composites have gradually attracted widespread attention due to their low cost, environmental friendliness, excellent mechanical properties, strong plasticity, and good chemical stability. They show promising application prospects in building materials, landscaping, vehicle and shipbuilding, home improvement, and other fields.

[0003] As natural and environmentally friendly materials, inorganic substances have flame retardant, aging-resistant, antibacterial, conductive and mechanical functions, which can improve the performance of composite materials. Therefore, the introduction of inorganic substances as fillers to improve the functionality of natural plant fiber / biodegradable plastic composite materials plays an important role in the development of composite materials, provides a scientific basis and theoretical guidance for the development of plant fiber reinforced polymer composite materials, and to a certain extent can solve the urgent need for the single performance of functional plant fiber polymer composite materials. In addition, the development of inorganic functional fillers with excellent performance and green environmental protection is an urgent problem to be solved in the field of functional composite materials, which is of great significance to the promotion of research on multifunctional composite materials. Solving the problem of single function of plant fiber reinforced polymer composite materials is of great significance for the development of multi-performance, safe and non-toxic materials and the establishment of an environmentally friendly society.

[0004] The development of functional composite materials represents the advancement of multi-faceted performance control. The functional reconstruction of traditional plant fiber polymer material systems allows for the expansion of applications and has synergistic effects in the field of sustainable manufacturing. Although composite system research has achieved phased breakthroughs, it still faces the following challenges: (1) The functionalization of composite materials is mainly achieved through organic additives. Commonly used functional organic additives are relatively traditional and have a single function, making it difficult to simultaneously meet multiple performance requirements; (2) With an eye on the broader application prospects of functional plant fiber-reinforced PLA composites, the research and development of antistatic, conductive, and electromagnetic shielding composite materials deserves greater attention; (3) Some organic additives contain toxic ingredients (such as flame retardants), which pose a threat to human health or the environment.

[0005] Therefore, how to develop a functional composite material based on an inorganic compound system and a preparation method is a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0006] In view of this, the present invention provides a functional composite material based on an inorganic compound system and a preparation method thereof.

[0007] A method for preparing a functional composite material based on an inorganic compound system comprises the following steps:

[0008] (1) Processing and drying of raw materials: After peeling the Salix psammophila wood strips, crushing, sieving, and drying to obtain Salix psammophila fiber;

[0009] (2) Modification of Salix psammophila fiber: dissolving a coupling agent in an ethanol aqueous solution with a volume fraction of 95% to obtain a coupling agent solution, spraying the coupling agent solution evenly on the Salix psammophila fiber obtained in step (1), and drying to obtain modified Salix psammophila fiber;

[0010] (3) Stepwise mixing and paving of the blank: the modified Salix psammophila fiber, polylactic acid and inorganic compound system obtained in step (2) are divided into the first part and the second part of the material according to their mass, the modified Salix psammophila fiber, polylactic acid and inorganic compound system of the first part are stirred and mixed, and then the remaining modified Salix psammophila fiber, polylactic acid and inorganic compound system of the second part are added and stirred and mixed, the mixed material is placed in a mold for paving, the material is pressed, and it is allowed to stand for a period of time. After the material shape is fixed, a blank is obtained;

[0011] The inorganic compound system is montmorillonite, zinc oxide and nano-conductive carbon black;

[0012] (4) Hot pressing: The slab obtained in step (3) is hot pressed to obtain the functional composite material based on the inorganic compound system.

[0013] Furthermore, in step (1), the safflower wood powder with a particle size of 40-60 mesh is screened and dried at a temperature of 70±2° C. until the moisture content of the safflower fiber is below 2%.

[0014] The beneficial effects of adopting the above-mentioned further technical solution: Research has shown that 40-60 mesh Salix psammophila wood flour can form a well-interwoven state within the composite material, which is conducive to the uniform distribution of the matrix and the effective transfer of stress, further improving the mechanical properties. A drying temperature of 70±2°C ensures that the modified wood flour achieves a high drying efficiency while preventing the wood flour from becoming brittle due to excessive temperatures. Drying to a moisture content below 2% ensures that the wood flour has a certain plasticity, which facilitates hot pressing, while preventing excessive water vapor generated during hot pressing due to excessive moisture content, which may affect product quality.

[0015] Furthermore, in step (2), the coupling agent is silane coupling agent KH550.

[0016] The beneficial effects of adopting the above-mentioned further technical solution are as follows: the silane coupling agent KH550 forms Si-OC bonds with the hydroxyl groups on the surface of the tamarisk wood powder through a hydrolysis condensation mechanism, and its organic functional groups (such as vinyl, amino, etc.) are further covalently bonded to the polylactic acid matrix to achieve two-phase interface strengthening, which is beneficial to the improvement of mechanical strength.

[0017] Furthermore, in step (2), the concentration of the coupling agent solution is 20 wt%, and the amount of coupling agent used is 2% of the mass of the Salix psammophila fiber.

[0018] The beneficial effects of adopting the above-mentioned further technical solution are as follows: adding the coupling agent in the form of a solution is conducive to the dispersion of the coupling agent between the matrices, thereby achieving a better interface modification effect; studies have shown that when the coupling agent addition amount is 2%, the interface modification effect is optimal.

[0019] Furthermore, in step (2), the drying temperature is 70±2° C., and the modified Salix psammophila fiber is dried until the moisture content is below 2%.

[0020] The beneficial effects of adopting this further technical solution include: a drying temperature of 70±2°C ensures efficient drying of the modified wood flour while preventing the wood flour from becoming brittle due to excessive temperatures. Drying to a moisture content below 2% ensures that the wood flour retains a certain plasticity for hot pressing, while preventing excessive moisture content from generating excessive water vapor during hot pressing, which could affect product quality.

[0021] Furthermore, in step (3), the mass ratio of the modified salix fiber to the polylactic acid is 3:7, the amount of the inorganic compound system added is 3-9% of the total mass of the modified salix fiber and the polylactic acid material, and the mass ratio of montmorillonite, zinc oxide and nano-conductive carbon black is (1-3): (1-3): (1-3).

[0022] Beneficial effects of the aforementioned further technical solutions: Research has shown that a 3:7 mass ratio of salix fiber to polylactic acid ensures good mechanical toughness in the composite material, fully utilizing the reinforcing effect of the salix fiber. An inorganic compounding system with an addition level of 3-9% of the total mass of the modified salix fiber and polylactic acid ensures good functional properties in the composite material. A synergistic mechanism among montmorillonite, zinc oxide, and nano-conductive carbon black is fully realized when the mass ratio is (1-3):(1-3):(1-3).

[0023] Furthermore, in step (3), the mass ratio of the first part and the second part of the material is 3:7, and the modified tsavorite fiber, polylactic acid and inorganic compound system of the first part are stirred and mixed for 5-10 minutes at a stirring speed of 20-30 rpm, and then the remaining modified tsavorite fiber, polylactic acid and inorganic compound system of the second part are added and stirred and mixed for 5-10 minutes at a stirring speed of 20-30 rpm.

[0024] The beneficial effect of adopting the above-mentioned further technical solution is that the "two-step" adding process can ensure more thorough mixing of the materials and further improve the uniformity of the dispersion of the material system.

[0025] Furthermore, in step (3), the pressure of the pressed material is 1 MPa and the standing time is 10 min.

[0026] The beneficial effects of adopting the above-mentioned further technical solution are as follows: the process can achieve the initial shaping of the slab material, the slab has sufficient initial strength, can ensure that the slab does not collapse, and meet the convenience of subsequent slab transportation, loading and other processes.

[0027] Furthermore, in step (4), the slab obtained in step (3) is hot-pressed at a temperature of 190° C., a hot-pressing pressure of 7 MPa, and a hot-pressing time of 7 min.

[0028] The beneficial effects of adopting the above further technical solution are as follows: the above process can achieve full forming of the material, and achieve the dual effects of good board quality and high production efficiency.

[0029] The present invention also provides a functional composite material based on an inorganic compound system prepared by the above method with a density of 0.80-1.20 g / cm 3 .

[0030] The beneficial effects of this invention include addressing the limitations of existing organic functional additives, which often have limited functionality and are sometimes toxic, by employing the silane coupling agent KH550 as an interfacial activator between wood flour and the polylactic acid matrix. This improves the composite's interfacial compatibility and mechanical strength, while also creating an "inorganic compound system" that provides the composite with excellent mechanical, aging resistance, electromagnetic shielding, and flame retardancy. Test results demonstrate that the composite's mechanical strength, surface resistivity, electromagnetic shielding effectiveness, and flame retardancy meet the requirements of relevant national and industry standards, with significantly enhanced aging resistance and thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1The bar graphs show the effect of the Na-MMT / ZnO / CCB compound ratio on the mechanical properties of SPP / PLA composite materials, where (a) is a bar graph of static bending strength, (b) is a bar graph of static bending strength retention rate, (c) is a bar graph of elastic modulus, and (d) is a bar graph of elastic modulus retention rate.

[0032] Figure 2 The bar graphs show the effect of Na-MMT / ZnO / CCB composite on the impact strength of SPP / PLA composites, where (a) is the impact strength bar graph and (b) is the impact strength retention rate bar graph.

[0033] Figure 3 Figure 3 is a physical diagram of the effect of Na-MMT / ZnO / CCB composite on the vertical combustion of SPP / PLA composites, where (a) shows the initial combustion state of the SPP / PLA composite of the control group at 15 s, (a1) shows the residual carbon state of the SPP / PLA composite of the control group, (b) shows the initial combustion state of the composite of Na-MMT / ZnO / CCB with a composite ratio of 3:1:1 at 15 s, (b1) shows the residual carbon state of the composite of Na-MMT / ZnO / CCB with a composite ratio of 3:1:1, (c) shows the initial combustion state of the composite of Na-MMT / ZnO / CCB with a composite ratio of 1:3:1 at 15 s, (c1) shows the residual carbon state of the composite of Na-MMT / ZnO / CCB with a composite ratio of 1:3:1, and (d) shows the residual carbon state of the composite of Na-MMT / ZnO / CCB with a composite ratio of 1:1:3 at 15 s. s initial combustion state, (d1) shows the residual carbon state of the Na-MMT / ZnO / CCB composite material with a compound ratio of 1:1:3.

[0034] Figure 4 These are curves showing the effects of Na-MMT / ZnO / CCB composites on the heat release rate and total amount of the composite material, where (a) is the heat release rate curve and (b) is the total heat release curve.

[0035] Figure 5 The graphs are of the effects of Na-MMT / ZnO / CCB composites on the smoke release rate and total amount of the composite materials, wherein (a) is the smoke release rate graph, and (b) is the total smoke release graph.

[0036] Figure 6 The figure (a) is a bar graph showing the effect of the Na-MMT / ZnO / CCB compound ratio on the mass loss of the composite material, where (b) is a mass histogram and (a) is a mass loss rate curve.

[0037] Figure 7 This is a bar graph showing the effect of the Na-MMT / ZnO / CCB compounding ratio on the contact angle of the composite material.

[0038] Figure 8 The graphs show the effect of the Na-MMT / ZnO / CCB compound ratio on the thermal stability of the composite material, where (a) is the weight loss rate graph and (b) is the weight loss velocity graph.

[0039] Figure 9 This is a bar chart showing the effect of the Na-MMT / ZnO / CCB compound ratio on the surface resistivity of the composite material.

[0040] Figure 10 This is a bar chart showing the effect of the Na-MMT / ZnO / CCB compounding ratio on the electromagnetic shielding effectiveness of the composite material.

[0041] Figure 11 Schematic diagram of the synergistic enhancement mechanism of Na-MMT / ZnO / CCB inorganic compound. DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0043] The silane coupling agent KH550 of the present invention was purchased from Nanjing Chuangshi Chemical Additives Co., Ltd.

[0044] The polylactic acid used in the present invention is powder, 100 mesh, molecular weight 5×10 4 , density 1.24g / cm 3 .

[0045] The nano conductive carbon black of the present invention has a diameter of 30-40 nm.

[0046] Example 1

[0047] The preparation method of the functional composite material based on the inorganic compound system comprises the following steps:

[0048] (1) Processing and drying of raw materials: After peeling the Salix psammophila wood strips, crush them, sieve them to obtain Salix psammophila wood powder with a particle size of 40-60 mesh, and dry them at a temperature of 70±2℃ until the moisture content of the Salix psammophila fiber is below 2%;

[0049] (2) Modification of Salix psammophila fiber: dissolving a coupling agent silane coupling agent KH550 in a 95% by volume ethanol aqueous solution to obtain a coupling agent solution with a concentration of 20 wt%, and spraying the coupling agent solution evenly on the Salix psammophila fiber obtained in step (1). The amount of the coupling agent is 2% of the mass of the Salix psammophila fiber. Drying the modified Salix psammophila fiber at a temperature of 70±2°C until the moisture content of the modified Salix psammophila fiber is below 2% to obtain the modified Salix psammophila fiber.

[0050] (3) Step-by-step mixing and laying of the blank: the modified Salix psammophila fiber (SPP), polylactic acid (PLA) and inorganic compound system obtained in step (2) are divided into the first part and the second part of the material according to the mass, and the mass ratio of the first part and the second part of the material is 3:7. The modified Salix psammophila fiber, polylactic acid and inorganic compound system of the first part are stirred and mixed for 8 minutes at a stirring speed of 25 rpm, and then the remaining modified Salix psammophila fiber, polylactic acid and inorganic compound system of the second part are added and stirred and mixed for 8 minutes at a stirring speed of 25 rpm. The mass ratio of Salix psammophila fiber to polylactic acid is 3:7, the addition amount of the inorganic compound system is 5% of the total mass of the Salix psammophila fiber and polylactic acid materials, the inorganic compound system is montmorillonite (Na-MMT), zinc oxide (ZnO) and nano-conductive carbon black (CBB), and the mass ratio of montmorillonite, zinc oxide and nano-conductive carbon black is 3:1:1. The mixed material is placed in a 200mm×200mm mold for paving, and the material is pressed to a thickness of 15mm. The pressing pressure of the material is 1MPa, and the material is allowed to stand for 10 minutes. After the material shape is fixed, a slab is obtained;

[0051] (4) Hot pressing: The slab obtained in step (3) was hot pressed at a temperature of 190°C, a hot pressing pressure of 7 MPa, and a hot pressing time of 7 min. The sample was trimmed to form a slab with a density of 1.0 g / cm 3 , a functional composite material with a thickness of 4mm based on an inorganic compound system.

[0052] According to the above steps, the composite material performance test results are as follows:

[0053] The composite material's static bending strength and elastic modulus are 34.49MPa and 3662MPa, respectively, meeting the secondary index requirements (≥30MPa, ≥2500MPa) for static bending strength and elastic modulus of plain, unfoamed indoor wood-plastic composite materials in LY / T 3274-2021 "Grading of Wood-Plastic Composite Materials," and also meeting GB / T24137-2009 "Requirements for Wood-Plastic Decorative Panels" (≥20MPa, ≥1880MPa). The composite material's impact strength is 4.03 kJ / m 2, meeting the third-level index (≥4) requirement for unnotched impact strength of plain, unfoamed outdoor wood-plastic composite materials in LY / T 3274-2021 "Grading of Wood-Plastic Composite Materials". The limiting oxygen index (LOI) of the composite material is 27.6%, reaching the flame retardant level, and the vertical burning level is V-1. Thermal stability has been improved, the initial degradation temperature has been increased by 200°C, and the heat release has been reduced by 9MJ / m 2 The initial smoke release was significantly reduced. The ignition time was 20s, which was 9s longer than the blank sample, and the mass loss was reduced by 366.6g / m 2 .

[0054] Example 2

[0055] Compared with Example 1, except that the mass ratio of montmorillonite, zinc oxide and nano-conductive carbon black is 1:3:1, other steps and parameters are the same as those in Example 1.

[0056] Composite material performance test results:

[0057] After thermo-oxidative aging treatment at 80°C for 128 h, the static flexural strength and elastic modulus of the composite material were 27.64 MPa and 2986 MPa, respectively, meeting the three-level index requirements (≥23 MPa, ≥1800 MPa) for static flexural strength and elastic modulus of plain unfoamed outdoor wood-plastic composite materials in LY / T 3274-2021 "Grading of Wood-Plastic Composite Materials", and at the same time meeting the requirements of GB / T24137-2009 "Wood-Plastic Decorative Panels" (≥20 MPa, ≥1880 MPa); the mechanical strength retention rates were 92% and 91% respectively, the mass loss rate was only 0.3%, and the surface water contact angle was 115.5°, showing excellent hydrophobicity and thermo-oxidative aging resistance.

[0058] Example 3

[0059] Compared with Example 1, except that the mass ratio of montmorillonite, zinc oxide and nano-conductive carbon black is 1:1:3, other steps and parameters are the same as those in Example 1.

[0060] Composite material performance test results:

[0061] After thermo-oxidative aging treatment at 80°C for 128 h, the static flexural strength and elastic modulus of the composite material were 32.64 MPa and 3465 MPa, respectively, meeting the secondary index requirements (≥30 MPa, ≥2500 MPa) for static flexural strength and elastic modulus of plain unfoamed indoor wood-plastic composite materials in LY / T 3274-2021 "Classification of Wood-Plastic Composite Materials", and also meeting GB / T24137-2009 "Requirements for Wood-Plastic Decorative Panels" (≥20 MPa, ≥1880 MPa).

[0062] The surface resistivity of the composite material is 0.24KΩ·cm, which is a superconducting material; the logarithm of the surface resistivity is 2, which meets the EP-2 level (logarithm of the surface resistivity ≤ 3) in the electrical performance requirements of GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics".

[0063] The composite material's electromagnetic shielding effectiveness is 27.43dB, meeting the SE-3 level (20dB) requirement of GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics".

[0064] Comparative Example 1

[0065] Compared with Example 1, except that the inorganic composite system of montmorillonite, zinc oxide and nano-conductive carbon black was not added, other steps and parameters were the same as those of Example 1.

[0066] The following experiments were conducted using Examples 1-3 of the present invention and Comparative Example 1.

[0067] 1. Effect of Na-MMT / ZnO / CBB system on the properties of SPP / PLA composites

[0068] 1.1 Mechanical properties analysis

[0069] The mechanical properties of Na-MMT / ZnO / CCB reinforced SPP / PLA composites before and after 80℃, 128h thermal oxidative aging are shown in the figure. Figure 1 Figures (a)-(d) show that before aging, the static flexural strength and elastic modulus of the composites decreased and then increased when the Na-MMT / ZnO / CCB ratios were 3:1:1, 1:3:1, and 1:1:3, respectively. When the Na-MMT / ZnO / CCB ratio was 3:1:1, the optimal static flexural strength and elastic modulus reached 34.49 MPa and 3662 MPa, respectively, representing increases of 68% and 50% compared to the blank.

[0070] As the Na-MMT addition level increases, its unique lamellar structure interacts with the matrix through chemical bonding and physical adsorption, evenly distributing ZnO and CCB within the SPP / PLA matrix and preventing filler agglomeration. Furthermore, Na-MMT fills some of the voids, guiding the distribution of ZnO and CCB, resulting in a relatively regular internal structure. When subjected to external forces, stress within the material is evenly distributed, reducing localized stress concentrations and improving the composite's static flexural strength and elastic modulus. When the Na-MMT addition level decreases, CCB maintains its synergistic effect with Na-MMT. The Na-MMT lamellar structure interweaves with the CCB to form a network, effectively filling the voids within the material. This synergistic dispersion restores a relatively uniform distribution of fillers within the matrix, enhancing the material's internal structural integrity. When subjected to external forces, it transfers and disperses stress, increasing static flexural strength and elastic modulus. However, since the structure was already relatively stable at the 3:1:1 ratio, performance is slightly lower at this point.

[0071] After aging, the static flexural strength retention and elastic modulus of the composite material gradually decreased as the Na-MMT / ZnO / CCB ratios were 3:1:1, 1:3:1, and 1:1:3, respectively, and the ZnO addition first increased and then decreased. The retention rate first increased and then decreased. When the Na-MMT / ZnO / CCB ratio was 1:3:1, the static flexural strength and elastic modulus of the composite material after aging were 27.64 MPa and 2986 MPa, respectively. The optimal mechanical retention values ​​were 92% and 91%, respectively, indicating excellent resistance to thermal oxidative aging.

[0072] As the ZnO content increases, ZnO can fully exert its antioxidant properties, absorbing and consuming free radicals generated during thermal oxidative aging. At the same time, Na-MMT, CCB, and ZnO work synergistically. The layered structure of Na-MMT acts as a barrier to the diffusion of oxygen and free radicals, making it difficult for them to reach the matrix components within the material. During this process, CCB, through its physical or chemical properties, assists ZnO in its antioxidant reactions, stabilizing the composite's internal structure. This synergistic effect enables the material to maintain internal structural integrity and interfacial stability, effectively transferring stress and resisting oxidation-induced damage to the interface. This maximizes the retention of the material's static flexural strength and elastic modulus. When the ZnO content decreases, the lamellar structure of Na-MMT provides a protective effect on the composite's internal microstructure, filling some voids and guiding filler distribution. During the thermo-oxidative aging process, although Na-MMT and CCB play a certain role, ZnO, as an effective antioxidant, has a low content that limits the overall antioxidant capacity of the composite material. Its ability to scavenge free radicals and its antioxidant protection of the internal microstructure are relatively insufficient, resulting in an increase in voids inside the material, breakage of molecular chains and structural damage. It is unable to resist deformation when subjected to external forces, and reduces the static bending strength and elastic modulus retention rate of the material.

[0073] The impact strength change trend of Na-MMT / ZnO / CCB reinforced SPP / PLA composites before and after 80℃, 128h thermal oxidative aging is shown in the figure. Figure 2 As shown in Figures (a) and (b). Before aging, when the Na-MMT / ZnO / CCB ratios were 3:1:1, 1:3:1, and 1:1:3, the impact strength of the composite material first decreased and then increased. When the Na-MMT / ZnO / CCB ratio was 3:1:1, the optimal impact strength of the composite material was 4.03 kJ / m 2 , an increase of 57% compared with the blank sample.

[0074] When the amount of Na-MMT added increases, Na-MMT can fill the voids inside the material, guide the distribution of ZnO and CCB, and make the internal structure of the material relatively regular. This regular microstructure gives the material good toughness. When the material is impacted, the regular microstructure can absorb and dissipate energy through deformation instead of brittle fracture, thereby improving the impact strength of the composite material. When the amount of Na-MMT added decreases, the composite material agglomerates, resulting in voids and uneven areas inside the material, reducing the toughness of the material, and making the material more susceptible to brittle fracture when impacted. At the same time, Na-MMT and CCB are relatively small, and they cannot effectively fill these voids and repair the microstructure, resulting in a decrease in impact strength.

[0075] After aging, when the Na-MMT / ZnO / CCB ratios were 3:1:1, 1:3:1, and 1:1:3, the amount of ZnO added first increased and then decreased, and the impact strength retention rate of the composite material showed a trend of first increasing and then decreasing. When the Na-MMT / ZnO / CCB ratio was 1:3:1, the impact strength of the composite material after aging was 3.21 kJ / m 2 The optimal impact strength retention rate is 94%, and the heat and oxygen aging resistance is better.

[0076] When the amount of ZnO added increases, the interface bonding is enhanced through chemical bonds or physical adsorption. At the same time, Na-MMT and CCB can also cooperate with ZnO to further improve the stability of the interface. During the thermo-oxidative aging process, stress and energy can be effectively transferred, so that when the material is impacted, the filler can better share the energy, reduce the degree of damage to the material, and increase the impact strength retention rate of the material. When the amount of ZnO added is low, there is a certain basis for the interface stability between it and the matrix and other fillers. However, during the thermo-oxidative aging process, due to limited antioxidant capacity, peeling will gradually occur at the interface due to oxidation and stress. As aging proceeds, the stress transfer capacity at the interface decreases. When the material is impacted, energy cannot be effectively transferred between the filler and the matrix, reducing the impact strength retention rate of the material.

[0077] 1.2 Limiting oxygen analysis

[0078] Table 1 shows the effect of the Na-MMT / ZnO / CBB ratio on the LOI of the SPP / PLA composite. When the Na-MMT / ZnO / CBB ratios were 3:1:1, 1:3:1, and 1:1:3, the LOI of the composites initially decreased and then increased. When the Na-MMT / ZnO / CBB ratio was 3:1:1, the optimal LOI of the composite reached 27.6, a 6.3% increase compared to the blank, reaching a flame-retardant grade. This upgrade from a flammable material to a flame-retardant material improves the composite's resistance to combustion. When exposed to flame, the composite requires a longer ignition time, significantly enhancing its flame retardancy. As the ratios varied, the composite's LOI continued to increase compared to the blank, but the increase was less pronounced than when the ratio was 3:1:1.

[0079] Table 1 Effect of Na-MMT / ZnO / CBB on LOI of SPP / PLA composites

[0080]

[0081] When the Na-MMT addition level is highest, Na-MMT, ZnO, and CCB exhibit a synergistic flame-retardant effect. Na-MMT's physical barrier and char stabilization effects dominate, while ZnO inhibits the free radical chain reaction that triggers combustion. CCB synergizes with Na-MMT to improve the material's physical structure and enhance flame retardancy. This combined synergistic flame-retardant effect results in the highest LOI. When the Na-MMT addition level is reduced, the synergistic flame-retardant effect becomes unbalanced. Due to the relatively low amount of Na-MMT, its dominant role is weakened. Furthermore, the flame-retardant mechanism of ZnO does not synergize well with the physical barrier and char stabilization mechanisms of Na-MMT. While CCB can synergize with Na-MMT to restore some of the physical barrier and char stabilization effects, and also cooperates with ZnO to inhibit combustion, the LOI remains lower than at a 3:1:1 ratio, as the synergistic flame retardancy is already relatively optimized.

[0082] 1.3 Vertical combustion analysis

[0083] The effect of the Na-MMT / ZnO / CCB ratio on the vertical combustion of the composite material is shown in Table 2. The t1 time of the blank sample was 157 seconds. When the Na-MMT / ZnO / CCB ratio was 3:1:1, 1:3:1, and 1:1:3, the t1 times of the composite material were 25 seconds, 96 seconds, and 82 seconds, respectively. When the Na-MMT / ZnO / CCB ratio was 3:1:1, the composite material reached a V-1 vertical combustion level, with no dripping and self-extinguishing. Compared with the blank sample, the first combustion time (t1) was significantly reduced, shortening the burning time of the composite material after ignition and enhancing the flame retardant effect of the composite material.

[0084] The initial combustion and carbon residue state of the composite material vertical combustion test at 15s are as follows Figure 3 Figures (a) to (d1) show the results. The blank sample (a) exhibited the most intense initial combustion, with the highest flame height. The blank sample (a1) also exhibited the least carbon residue, indicating that the composite material was easily ignited and the combustion process was complete. The greater the amount of Na-MMT added, the better the flame retardant effect. The composite materials with Na-MMT / ZnO / CCB added exhibited slower initial combustion than the blank sample, with significantly lower flame heights and a significantly reduced intensity of initial combustion. Compared to the blank sample, the composite materials exhibited significantly more carbon residue, indicating less complete combustion, shortening the combustion time in the event of a fire. The carbon residue provided support for the material. When the Na-MMT / ZnO / CCB ratio was 3:1:1, the composite material (b1) exhibited the highest carbon residue, was less likely to ignite, and had the shortest combustion time, significantly enhancing the flame retardant effect.

[0085] Table 2 Effect of Na-MMT / ZnO / CCB ratio on vertical combustion of composite materials

[0086]

[0087] Note: t1 is the afterflame time of a single sample; t2 is the afterflame time of a single sample after the second application of flame

[0088] The synergistic effect of Na-MMT / ZnO / CCB facilitates the rapid and stable formation of a char layer on the material surface. CCB promotes the carbonization process on the material surface, ZnO catalyzes the carbonization reaction of the SPP / PLA components, and the layered structure of Na-MMT provides an excellent template for the growth of the char layer. The char layer acts as a thermal and oxygen-isolating barrier, preventing the heat of the flame from directly transferring to the underlying material and preventing oxygen from contacting the combustible components. This improves vertical combustion performance, reduces combustion velocity, and can even cause the material to self-extinguish.

[0089] 1.4 Cone calorimeter analysis

[0090] The effect of the NaMMT / ZnO / CCB ratio on the composite CONE is shown below. The combustion performance of the composite material, including ignition time (TTI), peak heat release rate (peak-HRR), average heat release rate (average HRR), total heat release (THR), total smoke production (TSP) and mass loss (Mass Lost), is shown in Table 3. The heat release rate and total heat release curves are shown in Figure 4 As shown in Figures (a) and (b), the smoke release rate and the total amount of smoke released are as follows Figure 5 As shown in Figures (a) and (b), Table 3 shows that when the Na-MMT / ZnO / CCB compounding ratio is 3:1:1, the ignition time of the SPP / PLA composite material is 20s, which is 9s longer than that of the blank sample, and the mass loss is reduced by 366.6g / m 2 .

[0091] Table 3 Cone calorimetry test parameters of SPP / PLA composites

[0092]

[0093] When the Na-MMT / ZnO / CCB ratio is 3:1:1, the inorganic components in the composite material dilute the concentration of the combustible components during the thermal decomposition process. From the perspective of the combustion triangle (combustible materials, combustion-supporting materials, and ignition source), the reduced concentration of combustible materials makes the combustion reaction more difficult and prolongs the ignition time. Na-MMT, as a layered silicate mineral, improves the thermal stability of the composite material. Its layered structure forms a barrier that slows heat transfer and reduces the decomposition rate of the material at high temperatures. ZnO catalyzes certain chemical reactions, promoting the stability of the material during decomposition. CCB, as a filler, improves the structural strength and rigidity of the composite material, reduces the porosity of the material, reduces the diffusion of gas and heat, and improves the overall thermal stability. Therefore, the synergistic effect of the inorganic substances enhances the compatibility between SPP / PLA, improves the uniformity and dispersion of the composite material, and reduces mass loss during heat treatment.

[0094] Heat release represents the amount of heat released by the composite material during combustion. Figure 4 It can be seen that when the Na-MMT / ZnO / CCB compound ratio is 3:1:1, the average-HRR and HRR of the composite material are reduced. The peak-HRR of the blank sample is 377.8kW / m 2 After adding inorganic materials, the peak-HRR of the composite material is 353.5kW / m 2 .

[0095] ZnO, CCB, and Na-MMT exhibit a synergistic flame-retardant effect. ZnO undergoes physical and chemical changes during heating, absorbing heat or catalyzing certain reactions, inhibiting efficient combustion. CCB also acts as a physical barrier or participates in certain combustion-inhibiting reactions. When these interact with Na-MMT, they further reduce combustion efficiency and, consequently, the heat release rate.

[0096] TSP represents the total amount of smoke generated by the composite material during combustion. Figure 5 It can be seen that before 210s, when the Na-MMT / ZnO / CCB compound ratio is 3:1:1, the SPR of the composite material is lower than that of the blank sample at the beginning, and after 210s, the SPR gradually increases. Before 500s, the TSP of the composite material is lower than that of the blank sample, and gradually increases after 500s, with a TSP of 3.9m 2 , the total amount of smoke increased.

[0097] This is due to the synergistic effect between ZnO, Na-MMT, and CCB during the initial combustion phase, forming a network structure that inhibits combustion and smoke generation. At elevated temperatures, this network structure is disrupted, and Na-MMT, ZnO, and CCB produce volatile substances during thermal degradation, which increase smoke production, speed up flame propagation, or alter the composition of smoke generated during combustion, leading to an increase in the total amount of smoke. This suggests that the combination of these three inorganic substances can improve the flame retardancy and thermal stability of the composite material, but it can also produce the side effect of smoke suppression later on.

[0098] 1.5 Analysis of aging resistance

[0099] (1) Mass loss test analysis

[0100] The mass change and mass loss rate of Na-MMT / ZnO / CBB composite reinforced composites before and after thermal oxidation aging at 80℃ for 128h are as follows: Figure 6 Figures (a) and (b) show that when the Na-MMT / ZnO / CBB ratios are 3:1:1, 1:3:1, and 1:1:3, the mass loss rate of the composite material first decreases and then increases. When the Na-MMT / ZnO / CBB ratio is 1:3:1, the composite mass before and after aging is 9.65g and 9.62g, respectively. The optimal mass loss rate is 0.3%, indicating excellent resistance to thermal oxidative aging.

[0101] When the ZnO addition level is low, the interfacial stability between the SPP / PLA matrix and filler is relatively stable. The lamellar structure of Na-MMT enhances interfacial bonding. However, due to the limited ZnO content, the improvement in the interface's antioxidant capacity and stress transfer capacity is limited during thermal oxidative aging. As aging progresses, delamination gradually occurs at the interface, disrupting the material's internal structure and increasing mass loss during thermal oxidative aging. Increasing the ZnO addition level strengthens the interfacial bonding with the matrix and filler through chemical bonding or physical adsorption. Furthermore, Na-MMT and CCB synergize with ZnO to further enhance interfacial stability. CCB fills the interfacial voids, working together with ZnO and Na-MMT to resist oxidation damage to the interface. Even if some degree of oxidation occurs within the material, the stable interface ensures the relative integrity of the overall structure, thereby minimizing mass loss and maintaining a minimal mass loss rate.

[0102] (2) Contact angle test analysis

[0103] The contact angles of Na-MMT / ZnO / CBB reinforced SPP / PLA composites were tested and photographed before and after 128h of thermal oxidative aging at 80℃ (stabilized for 30s). The contact angle change trend and state are shown in the figure. Figure 7As shown in the figure. When the Na-MMT / ZnO / CBB ratios were 3:1:1, 1:3:1, and 1:1:3, respectively, the contact angles of the composites before and after aging showed a trend of first increasing and then decreasing. When the Na-MMT / ZnO / CBB ratio was 1:3:1, the contact angles of the composites before and after aging were 127.4° and 115.5°, respectively. The contact angle before aging increased by 55% compared to the blank sample, and the difference in contact angle change after aging was the lowest in this group of experiments, indicating excellent hydrophobicity and resistance to thermal oxygen aging.

[0104] When the ZnO addition level is low, the interfacial stability between Na-MMT, ZnO, and CCB and the SPP / PLA matrix is ​​relatively stable. However, due to the low ZnO content, during the thermo-oxidative aging process, minor interface damage causes internal components to migrate to the surface, changing the surface chemical composition, increasing surface hydrophilicity, decreasing the contact angle, and resulting in a significant difference in contact angles before and after aging. When the ZnO addition level increases, Na-MMT, CCB, and ZnO work synergistically to improve interfacial stability, prevent internal component migration, and resist the effects of oxidation on the surface during thermo-oxidative aging. This stable interface ensures the relative stability of the material's surface physical and chemical properties, minimizing the difference in contact angles before and after aging.

[0105] 1.6 Thermogravimetric analysis

[0106] The TGA-DTG curves of Na-MMT / ZnO / CBB reinforced SPP / PLA composites are shown in Figure 2. Figure 8 The TGA-DTG curves show that the thermal weight loss process of the composite material can be divided into three stages. The specific temperature range, weight loss rate, maximum decomposition rate, and residual carbon content are shown in Table 4.

[0107] Table 4 Weight loss rate and temperature of SPP / PLA composites at each stage

[0108]

[0109] Note: Tmax / ℃ is the maximum weight loss temperature

[0110] The first stage of thermal decomposition of the composite material ranged from 50°C to 249°C, primarily due to water evaporation. When the Na-MMT / ZnO / CBB ratio was 3:1:1, the composite material experienced 0% mass loss, and the initial degradation temperature was 200°C higher than that of the blank sample. This is because the interlayer ions of Na-MMT interact with the active sites on the ZnO surface and the functional groups of CCB, forming new active centers that adsorb active groups on the PLA molecular chain. This increases the energy required to initiate the ester bond cleavage reaction in the PLA, raising the initial degradation temperature.

[0111] The temperature range of the second stage of thermal decomposition of the composite material is 249~425℃. When the Na-MMT / ZnO / CBB compound ratio is 3:1:1, the degradation temperature of the composite material increases by 348℃ compared with the blank sample, the mass loss rate is 74.9%, and the Tmax increases by 204℃. Because Na-MMT / ZnO / CCB cooperate with each other in the composite material, a more powerful physical barrier system is constructed. Na-MMT forms a layered stack, ZnO fills the interlayers or adheres to its surface, and CCB further fills the gaps and distributes around. The heat transfer path within the material is severely hindered by the structure.

[0112] The third stage of thermal decomposition of the composite material occurs at temperatures ranging from 425°C to 800°C. When the Na-MMT / ZnO / CBB ratio is 3:1:1, the residual carbon content in the composite material is 23.1%. This is due to the synergistic effect of the three elements, which alters the thermal decomposition reaction path and favors carbon formation.

[0113] 1.7 Resistivity test analysis

[0114] Effect of Na-MMT / ZnO / CBB ratio on the surface resistivity of SPP / PLA composites Figure 9 As shown in Figure 2, the resistivity of the composite material gradually decreased when the Na-MMT / ZnO / CCB ratios were 3:1:1, 1:3:1, and 1:1:3, respectively. When the MMT / ZnO / CBB ratio was 1:1:3, the resistivity of the composite material reached 0.24 kΩ·cm, becoming a superconducting material and representing a 99% decrease compared to the blank sample.

[0115] When the amount of CCB added increases, the interfacial conductivity is optimized. The groups in the CCB chemical structure form stable chemical bonds or physical adsorption structures with the matrix, ZnO, and Na-MMT. The synergistically optimized interface can transfer electrons more effectively, reduce the scattering and loss of electrons at the interface, improve the connection points in the circuit, enable the current to pass more smoothly, and reduce the resistivity of the composite material. When the amount of CCB added decreases, the interfacial interaction between Na-MMT, ZnO and CCB and the matrix has limited effect on improving the conductivity. Due to the relatively low content of ZnO and CCB, the interface bonding with the matrix is ​​not tight enough. During the electron transfer process, areas with higher resistance are prone to appear at the interface because electrons are hindered when passing through the interface, resulting in a higher resistivity of the composite material.

[0116] 1.8 Electromagnetic Shielding Test Analysis

[0117] Effect of Na-MMT / ZnO / CBB ratio on electromagnetic shielding of SPP / PLA composites Figure 10As shown in Figure 2, the electromagnetic shielding performance of the composite material gradually increased when the compounding ratios changed from 3:1:1 to 1:3:1 and then to 1:1:3. When the Na-MMT / ZnO / CBB compounding ratio reached 1:1:3, the composite material achieved an electromagnetic shielding effectiveness of 27.43 dB, an 862% improvement over the blank sample. The radiation attenuation rate reached 99%, meeting the SE-3 rating specified in GB / T 32511-2016, "General Technical Requirements for Electromagnetic Shielding Plastics."

[0118] When the amount of CCB added increases, CBB forms chemical bonds or physical adsorption structures with the matrix, ZnO and Na-MMT. The synergistically optimized interface can guide electromagnetic waves into the conductive network, reduce energy loss at the interface, and enhance the material's shielding effect on electromagnetic waves. When the amount of CCB added decreases, the electromagnetic properties at the interface between Na-MMT, ZnO and CBB and the SPP / PLA matrix are relatively weak. Due to the low content of ZnO and CBB, the interface between the matrix is ​​not tightly bonded, and there is a mismatch in electromagnetic properties. The transition of dielectric constant and magnetic permeability at the interface is not smooth, which will cause electromagnetic waves to be reflected and scattered at the interface, reducing the overall effectiveness of electromagnetic shielding.

[0119] 2. Analysis of the synergistic effect principle of Na-MMT / ZnO / CCB

[0120] By constructing a Na-MMT / ZnO / CCB composite system and optimizing the blending ratio, a synergistic effect can be achieved on the mechanical, flame retardant, aging resistance, and electromagnetic shielding properties of the SPP / PLA composite material. The specific mechanism of this synergistic effect is analyzed as follows: First, Na-MMT interacts with the SPP / PLA matrix through chemical bonding and physical adsorption. Its lamellar structure uniformly distributes ZnO and CCB throughout the matrix, preventing filler agglomeration and enhancing the mechanical properties of the composite material.

[0121] Secondly, Na-MMT, ZnO, and CCB exhibit a synergistic flame-retardant effect. Na-MMT's physical barrier and carbon layer stabilization are dominant, and its endothermic reaction generates substances such as water (H2O), carbon dioxide (CO2), and carbon monoxide (CO), reducing the surface temperature of the material. At the same time, Na-MMT migrates to the surface of the material to form a silicon-containing porous carbon layer, hindering heat exchange between the inside and outside of the material; ZnO inhibits the free radical chain reaction of the combustion reaction; and CCB and Na-MMT synergistically improve the physical structure of the material, thereby enhancing flame retardancy.

[0122] Furthermore, Na-MMT, CCB, and ZnO synergistically enhance the composite's aging resistance. ZnO's antioxidant and thermal stabilization properties are dominant. At high temperatures, it can withstand a certain amount of heat load, absorbing heat and slowing the thermal degradation of SPP and PLA. It also forms a dense oxide film with oxygen, preventing oxygen penetration and acting as an antioxidant. CCB fills the gaps at the interface, working together with ZnO and the thermally stable Na-MMT to resist oxidation damage to the interface, ensuring the relative integrity of the material's overall structure and the relative stability of its surface physical and chemical properties, thereby slowing aging.

[0123] Finally, the synergistic effect of Na-MMT, CCB and ZnO enhances the electromagnetic shielding effectiveness of the composite material. The good electrical conductivity of CCB is dominant, and the groups in its chemical structure can form more stable chemical bonds or physical adsorption structures with the matrix, ZnO, and Na-MMT, optimizing the interfacial conductivity, more effectively transferring electrons, improving the connection points in the circuit, allowing current to pass more smoothly, and reducing the resistivity of the composite material. Better guiding electromagnetic waves into the conductive network, reducing energy loss at the interface, and further enhancing the shielding effect of the material against electromagnetic waves. In summary, the mechanism of Na-MMT / ZnO / CCB compounding to enhance the mechanical, flame retardant, heat-oxidative aging resistance, and electromagnetic shielding properties of SPP / PLA composites is as follows: Figure 11 shown.

[0124] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a functional composite material based on an inorganic compound system, characterized in that: The following steps are involved: (1) Processing and drying of raw materials: peeling the Salix psammophila wood strips, crushing, sieving, and drying to obtain Salix psammophila fiber; (2) Modification of Salix psammophila fiber: dissolving a coupling agent in a 95% by volume ethanol aqueous solution to obtain a coupling agent solution, spraying the coupling agent solution evenly on the Salix psammophila fiber obtained in step (1), and drying to obtain modified Salix psammophila fiber; (3) Stepwise mixing and paving of the blank: the modified Salix psammophila fiber, polylactic acid and inorganic compound system obtained in step (2) are divided into the first part and the second part of the material according to their mass, the modified Salix psammophila fiber, polylactic acid and inorganic compound system of the first part are stirred and mixed, and then the remaining modified Salix psammophila fiber, polylactic acid and inorganic compound system of the second part are added and stirred and mixed, the mixed material is placed in a mold for paving, the material is pressed, and it is allowed to stand for a period of time. After the material shape is fixed, a blank is obtained; The inorganic compound system comprises montmorillonite, zinc oxide and nano-conductive carbon black, and the mass ratio of montmorillonite, zinc oxide and nano-conductive carbon black is (1-3):(1-3):(1-3); (4) Hot pressing: hot pressing the slab obtained in step (3) to obtain the functional composite material based on the inorganic compound system.

2. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (1), the safflower wood powder with a particle size of 40-60 mesh is screened and dried at a temperature of 70±2° C. until the moisture content of the safflower fiber is below 2%.

3. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (2), the coupling agent is silane coupling agent KH550.

4. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (2), the concentration of the coupling agent solution is 20 wt%, and the amount of the coupling agent used is 2% of the mass of the Salix psammophila fiber.

5. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (2), the drying temperature is 70±2° C., and the modified Salix psammophila fiber is dried until the moisture content is below 2%.

6. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (3), the mass ratio of the modified Salix psammophila fiber to the polylactic acid is 3:7, and the added amount of the inorganic compounding system is 3-9% of the total mass of the modified Salix psammophila fiber and the polylactic acid material.

7. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (3), the mass ratio of the first part and the second part of the material is 3:

7. The modified tsavorite fiber, polylactic acid and inorganic compound system of the first part are stirred and mixed for 5-10 minutes at a stirring speed of 20-30 rpm, and then the remaining second part of the modified tsavorite fiber, polylactic acid and inorganic compound system is added and stirred and mixed for 5-10 minutes at a stirring speed of 20-30 rpm.

8. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (3), the pressure of the pressed material is 1 MPa and the standing time is 10 min.

9. The method for preparing a functional composite material based on an inorganic compound system according to claim 1, characterized in that: In step (4), the slab obtained in step (3) is hot-pressed at a temperature of 190° C., a hot-pressing pressure of 7 MPa, and a hot-pressing time of 7 minutes.

10. A functional composite material based on an inorganic compound system prepared by the method according to any one of claims 1 to 9, characterized in that: Density is 0.80-1.20g / cm 3 .

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