A method for preparing a fly ash reinforced polypropylene material for injection molded building form

Abstract

The application discloses a preparation method of fly ash reinforced polypropylene material for injection molding building templates and belongs to the technical field of polymer material processing, which comprises the following raw materials in parts by weight: 45-60 parts of polypropylene resin; 15-25 parts of activated coated fly ash; 10-20 parts of alkali-free glass fiber powder; 4-6 parts of a compatilizer; 3-5 parts of a toughening agent; 0.4-0.5 parts of a light stabilizer; 0.2-0.5 parts of an antioxidant; and 0.5-1 parts of a lubricant. The activated coated fly ash is prepared by using fly ash as raw material, reacting with an amino silane coupling agent first, and then adding EAA wax, an initiator and maleic anhydride to react and graft and coat, so as to form a core-shell coating structure. A double modified structure with a flexible interface layer and chemical bonding is formed. The interface bonding strength of the activated coated fly ash and the polypropylene matrix is obviously improved, the tensile strength and the bending modulus are effectively improved, and the heat distortion temperature is correspondingly increased.

Description

Technical Field

[0001] This invention belongs to the field of polymer material processing technology, specifically relating to a method for preparing fly ash reinforced polypropylene material for injection-molded building templates. Background Technology

[0002] Formwork is an essential tool in construction, traditionally made of materials such as wood and steel. Wood formwork suffers from short lifespan, susceptibility to moisture absorption and deformation, and low reusability; while steel formwork boasts high strength, it is heavy, prone to corrosion, inefficient in construction, and expensive. In recent years, polypropylene (PP)-based plastic formwork has gained attention due to its lightweight, recyclability, and water and corrosion resistance. However, its insufficient rigidity, poor heat resistance, and dimensional instability limit its application in high-rise buildings or high-load-bearing conditions. To improve the mechanical properties of PP formwork, existing technologies incorporate glass fiber (GF) reinforcement, achieving higher modulus and strength. However, GF is expensive, causes significant wear on processing equipment, and can reduce material flowability, hindering stable injection molding processes. Therefore, its widespread application in the construction formwork field is constrained.

[0003] Fly ash, a major industrial solid waste generated by coal-fired power plants, has become a crucial issue in environmental protection due to its resource utilization. Fly ash particles are spherical, primarily composed of silica and alumina, which theoretically can improve polymer rigidity, reduce the coefficient of thermal expansion, and offer significant cost advantages. However, current technologies that directly fill fly ash into a polypropylene matrix often result in increased internal defects and weak interfacial bonding in the composite material due to the strong surface polarity of fly ash and its poor compatibility with polypropylene. This leads to decreased mechanical properties and even brittle fracture. Furthermore, unmodified fly ash exhibits poor dispersion in the matrix, easily agglomerating and affecting the overall processing flowability and mechanical uniformity of the material, making it difficult to meet the high rigidity and dimensional stability requirements of building formwork. Some technologies have attempted to treat fly ash with simple silane coupling agents, but these still cannot simultaneously achieve a balance between good dispersion, strong interfacial bonding, and processing flowability, hindering the industrial application of fly ash-reinforced polypropylene composites in the building formwork field.

[0004] Therefore, how to effectively modify fly ash to enhance its compatibility with the polypropylene matrix, and on this basis, synergize with other reinforcing components to obtain composite materials with high rigidity, good dimensional stability and cost advantages while ensuring processing performance, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing fly ash reinforced polypropylene material for injection molding building templates, so as to solve the problem that fly ash has a poor reinforcing effect on polypropylene and easily leads to a decline in the mechanical properties of the material.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a fly ash-reinforced polypropylene material for injection-molded building templates, comprising the following raw materials in parts by weight: 45-60 parts polypropylene resin; 15-25 parts activated coated fly ash; 10-20 parts alkali-free glass fiber powder; 4-6 parts compatibilizer; 3-5 parts toughening agent; 0.4-0.5 parts light stabilizer; 0.2-0.5 parts antioxidant; and 0.5-1 part lubricant. The activated coated fly ash is produced by reacting fly ash with an aminosilane coupling agent, followed by grafting and coating with EAA wax, an initiator, and maleic anhydride to form a core-shell coated structure. This invention significantly improves the mechanical properties and thermal stability of polypropylene-based composites by optimizing the grafting process of activated coated fly ash. Specifically, the fly ash surface is sequentially treated with a silane coupling agent, physically coated with ethylene-acrylic acid copolymer wax (EAA wax), and grafted with maleic anhydride, forming a dual-modified structure with a flexible interface layer and chemical bonding. In this invention, the interfacial bonding strength between the activated coated fly ash and the polypropylene matrix is ​​significantly improved, with effective increases in tensile strength and flexural modulus, and a corresponding increase in heat distortion temperature. Simultaneously, thanks to the constraint effect of the tight interfacial bonding on the thermal motion of the polymer molecular chains, the linear expansion coefficient of the material decreases while maintaining high mechanical properties, thus improving dimensional thermal stability.

[0007] In some possible implementations, the alkali-free glass fiber powder has a length D50 ≤ 50 μm and has been surface-treated with a silane coupling agent.

[0008] In some possible implementations, the silane coupling agent used for the surface treatment of the alkali-free glass fiber powder is an aminosilane coupling agent. The amount of aminosilane coupling agent is 1.5%-2% of the mass of the alkali-free glass fiber powder, preferably N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. Its amino functional group can undergo a rapid ring-opening / condensation reaction with the carboxyl groups and anhydride groups in the EAA / maleic anhydride coating layer on the fly ash surface to form a strong chemical bond, thereby establishing an efficient stress transfer bridge between the glass fiber and the fly ash.

[0009] In some possible implementations, the alkali-free glass fiber powder undergoes in-situ sol deposition of silica during silane treatment.

[0010] Anhydrous ethanol, deionized water, and ammonia (25%) were mixed in a volume ratio of 100:10:1. TEOS (tetraethyl orthosilicate) was slowly added while stirring to make the TEOS concentration 0.1-0.2 mol / L. Stirring was continued for 30 min to obtain the hydrolysate.

[0011] Add alkali-free glass fiber powder to the above hydrolysate (solid-liquid ratio 1:10), add KH-792 (1.5%-2% of the alkali-free glass fiber powder mass), and stir at room temperature for 1.5-2 hours. During this time, nano-SiO2 (particle size 20-40 nm) generated by TEOS hydrolysis gradually deposits on the glass fiber surface. Filter, wash twice with anhydrous ethanol, and vacuum dry at 120℃ for 2 hours.

[0012] In some possible implementations, the activated coated fly ash is prepared by the following steps: Fly ash is dried at 110-120℃ for 2-4 hours and then pulverized by an air jet mill to D90≤5μm. The dried and pulverized fly ash is then heated and stirred at 110-130℃ for 15-30 minutes. A 1:1 dilution of silane coupling agent (KH-792) in anhydrous ethanol is sprayed onto the fly ash, and the mixture is stirred at a constant temperature for 15-20 minutes. Ethylene-acrylic acid copolymer wax (EAA wax) is then added and mixed for 10-15 minutes. Finally, initiator DCP and maleic anhydride are added and reacted for 10-15 minutes to perform grafting and coating, resulting in activated and coated fly ash. In some possible implementations, the amount of KH-792 used is 1.5%–2% of the fly ash mass; the amount of EAA wax used is 3%–4% of the fly ash mass. The amount of initiator DCP (dicumyl peroxide) is 0.3%–0.4% of the mass of EAA wax; The amount of maleic anhydride used is 3%–4% of the mass of EAA wax.

[0013] In some possible implementations, the polypropylene resin includes homopolymer polypropylene and copolymer polypropylene; The compatibilizer is polypropylene grafted with maleic anhydride; The toughening agent is an elastomer, POE or EPDM; The light stabilizer is a histamine-based light stabilizer, such as light stabilizer 944; Antioxidants include primary antioxidant 1010 and secondary antioxidant 168; The lubricant is ethylene bis-stearamide or silicone powder.

[0014] In some possible implementations, the mass ratio of homopolymer polypropylene to copolymer polypropylene is 1-2:1; The mass ratio of primary antioxidant 1010 to secondary antioxidant 168 is 1:1.

[0015] A second aspect of this invention provides a method for preparing fly ash-reinforced polypropylene material for injection-molded building formwork, comprising the following steps: Premixing: Weigh the polypropylene resin, activated fly ash, alkali-free glass fiber powder, toughening agent, compatibilizer, light stabilizer, antioxidant, and lubricant, and mix them in a high-speed mixer for 5-10 minutes. Melt blending: Add the premixed material to a twin-screw extruder, set the temperature range to 160-200℃ (increasing from the feeding zone to the die head), and the screw speed to 200-300 rpm, and extrude and granulate.

[0016] In some possible implementations, the materials are mixed in a high-speed mixer for 5-10 minutes, and then fed into a twin-screw extruder (L / D=40) for extrusion granulation. The temperature of each zone is set as follows: Zone 1 to 3: 160-170℃, Zone 4: 170-180℃, Zone 5: 180-190℃, Zone 6: 190-195℃, Zones 7 to 10: 195-200℃, Zone 11: 190℃, Screen changer and die: 180-190℃, and screw speed: 200-300 rpm.

[0017] The beneficial effects of this invention are: (1) The fly ash pretreatment uses an air jet mill to pulverize the fly ash to D90≤5μm, which increases the specific surface area and is more conducive to subsequent surface treatment; (2) When treating fly ash surface, use KH-792 with diamino groups, and then use EAA wax, initiator, and maleic anhydride to react and graft coating to form a core-shell coating structure, which can better achieve the dispersion effect of fly ash particles. (3) By adding about 10%-20% alkali-free glass fiber powder, and in conjunction with fly ash reinforcement, the overall strength of the composite material is significantly improved, with tensile strength ≥35MPa and flexural modulus ≥2500MPa, meeting the requirements of high load-bearing building formwork. (4) The treated fly ash effectively reduces the shrinkage rate and warping tendency of the composite material: the low coefficient of thermal expansion of fly ash particles and the interfacial bonding force after surface modification reduce internal stress, and the linear coefficient of thermal expansion (CLTE) is ≤60×10 -6 / K exhibits superior dimensional stability compared to traditional PP / GF materials; (5) Compatibilizers and toughening agents are used in combination in the formulation to balance toughness while maintaining rigidity and avoid increasing brittleness; (6) The material has excellent processing fluidity, is suitable for injection molding, and has high production efficiency. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The following is a detailed description with reference to specific examples.

[0020] Example 1 This embodiment provides a fly ash reinforced polypropylene material for injection molding construction templates, comprising the following raw materials in parts by weight: 55 parts polypropylene resin; 20 parts activated coated fly ash; 15 parts alkali-free glass fiber powder; 6 parts compatibilizer; 4 parts toughening agent; 0.4 parts light stabilizer; 0.2 parts antioxidant; and 0.5 parts lubricant. The polypropylene resin includes homopolymer polypropylene and copolymer polypropylene, with a mass ratio of 1:1; the compatibilizer is polypropylene grafted with maleic anhydride; the toughening agent is elastomer POE; the light stabilizer is light stabilizer 944; the antioxidants include primary antioxidant 1010 and secondary antioxidant 168, with a mass ratio of 1:1; and the lubricant is ethylene bis-stearamide.

[0021] Alkali-free glass fiber powder with a length D50 ≤ 50μm, and surface treated with a silane coupling agent: Anhydrous ethanol, deionized water, and ammonia (25%) were mixed in a volume ratio of 100:10:1. Alkali-free glass fiber powder (solid-liquid ratio 1:10) was added, along with KH-792 (1.5% of the mass of the alkali-free glass fiber powder). The mixture was stirred at room temperature for 1.5 hours. The mixture was then filtered, washed twice with anhydrous ethanol, and dried under vacuum at 120°C for 2 hours.

[0022] The activated coated fly ash is prepared through the following steps: Fly ash was dried at 110℃ for 4 hours and then pulverized by an air jet mill to a D90≤5μm. The dried and pulverized fly ash was placed at 110℃ and stirred for 15 minutes. A 1:1 dilution of silane coupling agent (KH-792) in anhydrous ethanol was sprayed on the fly ash and stirred at a constant temperature for 20 minutes. Ethylene-acrylic acid copolymer wax (EAA wax) was then added and mixed for 15 minutes. Initiator DCP and maleic anhydride were then added and reacted for 15 minutes to perform grafting and coating, resulting in activated and coated fly ash. The dosage of KH-792 is 1.5% of the fly ash mass; the dosage of EAA wax is 3% of the fly ash mass; the dosage of initiator DCP (dicumyl peroxide) is 0.3% of the EAA wax mass; and the dosage of maleic anhydride is 3% of the EAA wax mass.

[0023] The preparation method of fly ash reinforced polypropylene material for injection molded building formwork includes the following steps: Premixing: Weigh the polypropylene resin, activated fly ash, alkali-free glass fiber powder, toughening agent, compatibilizer, light stabilizer, antioxidant, and lubricant, and mix them in a high-speed mixer for 10 minutes. Melt blending: Add the premixed material to a twin-screw extruder, set the temperature range to 160-200℃ (increasing from the feeding zone to the die head), and the screw speed to 200-300 rpm, and extrude and granulate.

[0024] Example 2 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 lies in the proportions of the raw materials. Specifically, it includes the following raw materials by weight: 50 parts polypropylene resin; 22 parts activated coated fly ash; 18 parts alkali-free glass fiber powder; 6 parts compatibilizer; 4 parts toughening agent; 0.4 parts light stabilizer; 0.2 parts antioxidant; and 0.5 parts lubricant. The remaining raw materials and preparation process are the same as in Embodiment 1.

[0025] Example 3 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 lies in the proportions of the raw materials. Specifically, it includes the following raw materials by weight: 45 parts polypropylene resin; 25 parts activated coated fly ash; 20 parts alkali-free glass fiber powder; 6 parts compatibilizer; 4 parts toughening agent; 0.4 parts light stabilizer; 0.2 parts antioxidant; and 0.5 parts lubricant. The remaining raw materials and preparation process are the same as in Embodiment 1.

[0026] Example 4 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 lies in the proportions of the raw materials. Specifically, it includes the following raw materials by weight: 60 parts polypropylene resin; 15 parts activated coated fly ash; 10 parts alkali-free glass fiber powder; 4 parts compatibilizer; 5 parts toughening agent; 0.4 parts light stabilizer; 0.2 parts antioxidant; and 0.5 parts lubricant. The remaining raw materials and preparation process are the same as in Embodiment 1.

[0027] Example 5 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 lies in the proportions of the raw materials. Specifically, it includes the following raw materials by weight: 52 parts polypropylene resin; 18 parts activated coated fly ash; 15 parts alkali-free glass fiber powder; 5 parts compatibilizer; 3 parts toughening agent; 0.4 parts light stabilizer; 0.2 parts antioxidant; and 0.5 parts lubricant. The remaining raw materials and preparation process are the same as in Embodiment 1.

[0028] Example 6 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 is that the activated and coated fly ash is prepared through the following steps: Fly ash was dried at 110℃ for 4 hours and then pulverized by an air jet mill to a density of D90≤5μm. The dried and pulverized fly ash was then heated and stirred at 110℃ for 30 minutes. A 1:1 dilution of silane coupling agent (KH-792) in anhydrous ethanol was sprayed onto the fly ash and stirred at a constant temperature for 15 minutes. Ethylene-acrylic acid copolymer wax (EAA wax) was then added and mixed for 10 minutes. Finally, initiator DCP and maleic anhydride were added and reacted for 10 minutes to perform grafting and coating, resulting in activated and coated fly ash. The dosage of KH-792 is 2% of the fly ash mass; the dosage of EAA wax is 4% of the fly ash mass; the dosage of initiator DCP (dicumyl peroxide) is 0.4% of the EAA wax mass; and the dosage of maleic anhydride is 4% of the EAA wax mass.

[0029] The remaining raw materials and preparation process are the same as in Example 1.

[0030] Example 7 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 is that the alkali-free glass fiber powder is prepared through the following steps: Anhydrous ethanol, deionized water, and ammonia (25%) were mixed in a volume ratio of 100:10:1. TEOS (tetraethyl orthosilicate) was slowly added while stirring to make the TEOS concentration 0.1 mol / L. Stirring was continued for 30 min to obtain the hydrolysate.

[0031] Add alkali-free glass fiber powder to the above hydrolysate (solid-liquid ratio 1:10), add KH-792 (1.5% of the alkali-free glass fiber powder mass), and stir at room temperature for 1.5 h. During this time, nano-SiO2 (particle size 20-40 nm) generated by TEOS hydrolysis gradually deposits on the glass fiber surface. Filter, wash twice with anhydrous ethanol, and vacuum dry at 120℃ for 2 h.

[0032] The remaining raw materials and preparation process are the same as in Example 1.

[0033] Example 8 This embodiment provides a fly ash-reinforced polypropylene material for injection-molded building formwork. The difference between this embodiment and Embodiment 1 is that the alkali-free glass fiber powder is prepared through the following steps: Anhydrous ethanol, deionized water, and ammonia (25%) were mixed in a volume ratio of 100:10:1. TEOS (tetraethyl orthosilicate) was slowly added while stirring to make the TEOS concentration 0.1 mol / L. Stirring was continued for 30 min to obtain the hydrolysate.

[0034] Add alkali-free glass fiber powder to the above hydrolysate (solid-liquid ratio 1:10), add KH-792 (2% of the alkali-free glass fiber powder mass), and stir at room temperature for 2 hours. During this time, nano-SiO2 (particle size 20-40 nm) generated by TEOS hydrolysis gradually deposits on the glass fiber surface. Filter, wash twice with anhydrous ethanol, and vacuum dry at 120℃ for 2 hours.

[0035] The remaining raw materials and preparation process are the same as in Example 1.

[0036] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that the activated coated fly ash was prepared by the following steps: the fly ash was dried at 110°C for 4 hours and pulverized by an air jet mill to D90≤5μm; the dried and pulverized fly ash was placed at 110°C and stirred and heated for 15 minutes, and a 1:1 diluted solution of silane coupling agent (KH-792) and anhydrous ethanol was sprayed on it, and the mixture was stirred at a constant temperature for 20 minutes; the alkali-free glass fiber powder was obtained by separation and drying.

[0037] The remaining raw materials and preparation process are the same as in Example 1.

[0038] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that the activated coated fly ash was prepared by the following steps: the fly ash was dried at 110°C for 4 hours and then pulverized by an air jet mill to D90≤5μm; the dried and pulverized fly ash was placed at 110°C and stirred and heated for 15 minutes, and a 1:1 diluted solution of silane coupling agent (KH-570) and anhydrous ethanol was sprayed on it, and the mixture was stirred at a constant temperature for 20 minutes; the alkali-free glass fiber powder was obtained by separation and drying.

[0039] The remaining raw materials and preparation process are the same as in Example 1.

[0040] Comparative Example 3 The activated coated fly ash is prepared through the following steps: Fly ash was dried at 110℃ for 4 hours and then pulverized by an air jet mill to a D90≤5μm. The dried and pulverized fly ash was placed at 110℃ and stirred for 15 minutes. A 1:1 diluted solution of silane coupling agent (KH-570) and anhydrous ethanol was sprayed on it and stirred at a constant temperature for 20 minutes. Ethylene-acrylic acid copolymer wax (EAA wax) was then added and mixed for 15 minutes. Initiator DCP and maleic anhydride were then added and reacted for 15 minutes to perform grafting and coating, resulting in activated and coated fly ash. The dosage of KH570 is 1.5% of the fly ash mass; the dosage of EAA wax is 3% of the fly ash mass; the dosage of initiator DCP (dicumyl peroxide) is 0.3% of the EAA wax mass; and the dosage of maleic anhydride is 3% of the EAA wax mass.

[0041] The remaining raw materials and preparation process are the same as in Example 1.

[0042] Test example: Performance tests were conducted on Examples 1-8 and Comparative Examples 1-3, according to GB / T 1040, ISO 75, and ISO 1135. The results are shown in Table 1. Table 1

[0043] According to Table 1, combined with Examples 1-8 and Comparative Examples 1-3, the tensile strength and flexural modulus were as follows: Comparative Example 2 had the lowest tensile strength, while Comparative Examples 1 and 3 showed slight improvements but remained at a low level. In Examples 1 to 5, both indicators gradually increased with optimization of the amounts of fly ash, glass fiber, and compatibilizer, with Example 3 reaching the highest in this group. Example 6 was comparable to the moderate levels of Examples 1-5. Examples 7 and 8 showed further significant improvements, reaching the highest values ​​among all samples, indicating that the increased amount of nano-SiO2 deposition and coupling agent had the most significant reinforcing effect.

[0044] Heat distortion temperature: Comparative Example 2 had the lowest, while Comparative Examples 1 and 3 showed a slight increase. In Examples 1-5, the heat distortion temperature increased with the improvement of mechanical properties, with Example 3 having the highest. Example 6 was close to Example 2. Examples 7 and 8 reached the highest, showing better heat resistance.

[0045] Linear expansion coefficient: Comparative Example 2 has the lowest coefficient, followed by Comparative Example 1, but both also exhibit the worst mechanical properties and heat resistance, indicating that the excessively low expansion coefficient may originate from interface defects rather than effective constraints. Comparative Example 3 is similar to Examples 7 and 8, at a relatively low level. In Examples 1 to 5, the linear expansion coefficient shows a trend of first decreasing and then increasing with the increase of filler ratio and interface optimization, with Examples 3 and 4 being lower and Example 5 slightly higher. Examples 7 and 8 maintain the highest mechanical properties while exhibiting significantly lower linear expansion coefficients than Examples 1 to 5, demonstrating a synergistic optimization of good dimensional thermal stability and reinforcement efficiency.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fly ash-reinforced polypropylene material for injection-molded building formwork, characterized in that, The raw materials include the following parts by weight: 45-60 parts polypropylene resin; 15-25 parts activated coated fly ash; 10-20 parts alkali-free glass fiber powder; 4-6 parts compatibilizer; 3-5 parts toughening agent; 0.4-0.5 parts light stabilizer; 0.2-0.5 parts antioxidant; and 0.5-1 parts lubricant. The activated coated fly ash is made by reacting fly ash with an aminosilane coupling agent, and then adding EAA wax, an initiator, and maleic anhydride to react and graft the coating, forming a core-shell coated structure.

2. The fly ash reinforced polypropylene material for injection-molded building formwork according to claim 1, characterized in that, The alkali-free glass fiber powder has a length D50≤50μm and has been surface-treated with a silane coupling agent.

3. The fly ash-reinforced polypropylene material for injection-molded building formwork according to claim 1, characterized in that, The silane coupling agent used in the surface treatment of the alkali-free glass fiber powder is an aminosilane coupling agent.

4. The fly ash reinforced polypropylene material for injection-molded building formwork according to claim 1, characterized in that, The alkali-free glass fiber powder undergoes in-situ sol deposition of silica during silane agent treatment.

5. The fly ash reinforced polypropylene material for injection-molded building formwork according to claim 1, characterized in that, The activated coated fly ash is prepared through the following steps: Fly ash is pulverized to D90≤5μm, placed at 110-130℃ and stirred and heated for 15-30min, then sprayed with KH-792 anhydrous ethanol 1:1 diluted solution, and stirred at constant temperature for 15-20min; then EAA wax is added and mixed for 10-15min, then initiator DCP and maleic anhydride are added and reacted for 10-15min, and grafting is performed to obtain activated coated fly ash.

6. The fly ash-reinforced polypropylene material for injection-molded building formwork according to claim 5, characterized in that, The dosage of KH-792 is 1.5%–2% of the fly ash mass; The amount of EAA wax used is 3%–4% of the mass of fly ash; The initiator dosage is 0.3%–0.4% of the mass of EAA wax; The amount of maleic anhydride used is 3%–4% of the mass of EAA wax.

7. The fly ash reinforced polypropylene material for injection-molded building formwork according to claim 1, characterized in that, Polypropylene resins include homopolymer polypropylene and copolymer polypropylene; The compatibilizer is polypropylene grafted with maleic anhydride; The toughening agent is an elastomer, POE or EPDM; The light stabilizer is a histamine-based light stabilizer; Antioxidants include primary antioxidant 1010 and secondary antioxidant 168; The lubricant is ethylene bis-stearamide or silicone powder.

8. The fly ash reinforced polypropylene material for injection-molded building formwork according to claim 7, characterized in that, The mass ratio of homopolymer polypropylene to copolymer polypropylene is 1-2:1; The mass ratio of primary antioxidant 1010 to secondary antioxidant 168 is 1:

1.

9. A method for preparing fly ash-reinforced polypropylene material for injection-molded building formwork, used to prepare the fly ash-reinforced polypropylene material for injection-molded building formwork as described in any one of claims 1-8, characterized in that, Includes the following steps: After weighing the polypropylene resin, activated fly ash, alkali-free glass fiber powder, toughening agent, compatibilizer, light stabilizer, antioxidant, and lubricant, they are mixed in a high-speed mixer. Add the premixed material to a twin-screw extruder, set the temperature range to 160-200℃, and extrude and granulate.

10. The method for preparing fly ash reinforced polypropylene material for injection-molded building formwork according to claim 9, characterized in that, Mix all materials in a high-speed mixer for 5-10 minutes, then add them to a twin-screw extruder for granulation. The temperature settings for each zone are as follows: Zone 1 to 3: 160-170℃; Zone 4: 170-180℃; Zone 5: 180-190℃; Zone 6: 190-195℃; Zones 7 to 10: 195-200℃; Zone 11: 190℃; Screen changer and die: 180-190℃; Screw speed: 200-300 rpm.

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