Inorganic microcapsule phase change synergistic a-class flame-retardant pultrusion composite material and preparation method thereof

Abstract

This invention relates to the field of flame-retardant pultruded composite materials, and particularly to an inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material and its preparation method, comprising the following components by mass percentage: 75%~85% reinforcement, 15%~25% resin matrix; wherein the resin matrix comprises the following components by mass percentage: 60~65 parts flame-retardant resin, 8~12 parts inorganic microcapsule phase change material, 18~22 parts inorganic flame-retardant filler, 3~5 parts nanoscale synergist, 8~12 parts reactive diluent, and 85~12 parts curing agent. The inorganic microcapsule phase change material comprises 95 parts of an accelerator, 0.4-0.9 parts of a coupling agent, 0.4-0.7 parts of an internal release agent, and 0.2-0.4 parts of an internal release agent. The inorganic microcapsule phase change material is inorganically coated, with a phase change temperature of 80-120℃, a latent heat ≥150J / g, a microcapsule particle size of 10-60μm, and a coating layer thickness of 100-250nm. The total calorific value of the inorganic microcapsule phase change material is ≤5MJ / kg. This invention has the following beneficial effects: it meets A2 fire resistance standards and possesses excellent mechanical properties and good pultrusion processability.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant pultruded composite materials, and particularly to an inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material and its preparation method. Background Technology

[0002] Fiber-reinforced pultruded composites are widely used in rail transit, building curtain walls, and power utility tunnels. However, traditional thermosetting resin matrices are flammable and cannot meet the A2 flame retardant requirements of GB8624-2012. Existing technologies mainly achieve flame retardancy by using high-filling inorganic flame-retardant fillers such as aluminum hydroxide and magnesium hydroxide, or by using phosphorus-nitrogen-based flame-retardant resins. The former typically requires fillers of 40% to 60% or more of the resin mass, leading to increased resin viscosity, decreased fiber wettability, poorer pultrusion processability, and significantly deteriorated mechanical properties. The latter, while maintaining better mechanical properties, is difficult to achieve A2 grade when used alone and still requires a large amount of filler, similarly facing a contradiction between processability and performance.

[0003] Inorganic phase change materials (PCMs) such as hydrated salts and minerals with water of crystallization possess advantages such as non-flammability, high phase change enthalpy, and low cost. Their total calorific value can be as low as below 5 MJ / kg, and during thermal decomposition, they undergo heat absorption through the release of water of crystallization and phase change, forming a synergistic flame-retardant mechanism with phosphorus-nitrogen flame-retardant systems and inorganic fillers. However, their direct application in structural composite materials faces three major obstacles: the volume change during phase change can easily lead to leakage and cracking; they are corrosive to organic resin matrices; and supercooling and phase separation phenomena affect stability. Currently, there is a lack of technical solutions for successfully applying inorganic PCM microcapsules to continuous fiber-reinforced pultruded composite materials while simultaneously meeting the requirements of A2 fire resistance, excellent mechanical properties, and good pultrusion processability.

[0004] Therefore, developing a Class A flame-retardant composite material that can utilize inorganic phase change materials for synergistic flame retardancy and is well-matched with the pultrusion process is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material and its preparation method, which has the characteristics of meeting Class A2 fire resistance, excellent mechanical properties and good pultrusion processability.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] An inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material comprises the following components, by mass percentage: 75%~85% reinforcement and 15%~25% resin matrix; wherein the resin matrix comprises the following components by mass percentage: 60~65 parts flame-retardant resin, 8~12 parts inorganic microcapsule phase change material, 18~22 parts inorganic flame-retardant filler, 3~5 parts nano-scale synergist, 8~12 parts reactive diluent, 85~95 parts curing agent, 0.4~0.9 parts accelerator, 0.4~0.7 parts coupling agent, and 0.2~0.4 parts internal release agent;

[0008] The inorganic microcapsule phase change material is inorganically coated, with a phase change temperature of 80~120℃, latent heat ≥150J / g, microcapsule particle size of 10~60μm, and coating layer thickness of 100~250nm; the total calorific value of the inorganic microcapsule phase change material is ≤5MJ / kg.

[0009] The combustion performance of the composite material meets the GB8624-2012 A2-s1-d0-t0 standard, with a total heat release per unit area ≤7.5 MJ / m². 2 Tensile strength ≥680MPa, flexural strength ≥720MPa, profile density 2100~2200kg / m³ 3 .

[0010] Preferably, the reinforcement is a continuous fiber reinforcement, selected from one or more of alkali-free glass fiber, carbon fiber, and basalt fiber, with a fiber volume fraction of 70% to 80%, and is laid up using a continuous yarn and felt composite layer or a single continuous yarn layer.

[0011] Preferably, the flame-retardant resin is a halogen-free flame-retardant thermosetting resin adapted to the pultrusion process, selected from one or more of epoxy resin, phenolic epoxy resin, o-cresol resin, and vinyl ester resin, with a total calorific value of 30.0~38.0 MJ / kg; the reactive diluent is selected from glycidyl ether reactive diluents; the curing agent is selected from one of acid anhydride or amine curing agents; the accelerator is selected from quaternary phosphate salt or tertiary amine accelerators; and the coupling agent is selected from silane coupling agents or titanate coupling agents, used to improve the interfacial compatibility between the inorganic microcapsules and the resin matrix.

[0012] Preferably, the coating layer of the inorganic microcapsule phase change material is selected from one of silicon dioxide, ceramics, and metal oxides; the core material of the inorganic phase change material is selected from one or more of hydrated salts and water-soluble minerals, wherein the hydrated salts are selected from one or more of magnesium chloride hexahydrate, magnesium sulfate heptahydrate, and disodium hydrogen phosphate dodecahydrate, and the water-soluble minerals are selected from one or more of calcium aluminum hydrotalcite, kaolinite, and vermiculite.

[0013] Preferably, the resin matrix further includes 0.2 to 0.4 parts of smoke suppressant, which is selected from molybdenum-based and tin-based smoke suppressants; the inorganic flame retardant filler is selected from one or more of aluminum hydroxide and magnesium hydroxide, with a particle size of 1 to 10 μm; and the nano-scale synergist is selected from one or more of nano-silica powder and nano-montmorillonite, with a particle size of 50 to 200 nm.

[0014] A method for preparing an inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material includes the following steps:

[0015] (1) Preparation of resin system: Flame retardant resin, inorganic microcapsule phase change material, inorganic flame retardant filler, nano-level synergist, reactive diluent, coupling agent and smoke suppressant are put into a mixing device and mixed for 20-30 min at 20-40℃ and vacuum degree ≤-0.08MPa to obtain component A; curing agent, accelerator and internal release agent are mixed evenly to obtain component B; component A and component B are mixed at a mass ratio of 100:85-95, and the viscosity of the system after mixing is controlled to be 600-1500mPa·s;

[0016] (2) Impregnation and preforming: The continuous fiber reinforcement is impregnated into the resin system prepared in step (1) through an impregnation tank. The impregnation temperature is controlled at 60~70℃ to prevent the inorganic microcapsule phase change material from exuding water and breaking. Then, the fiber layup is sorted and excess resin is removed through a preforming mold.

[0017] (3) Pultrusion curing: The preformed fiber-resin composite is fed into the pultrusion mold and multi-stage gradient temperature control is adopted. The mold temperature is 100~120℃, 130~150℃ and 160~180℃ respectively, and the traction speed is 0.2~0.7m / min to achieve continuous curing.

[0018] (4) Post-processing: Cut, grind and inspect the cured profiles, remove unqualified products and obtain finished products.

[0019] Preferably, in step (1), the stirring speed of the mixing equipment is 200~600 r / min, and intermittent stirring is used during the mixing process to avoid agglomeration of inorganic microcapsule phase change materials; in step (3), the pressure of the pultrusion die is controlled at 8~18 MPa, and the curing time is 2~6 min.

[0020] As a preferred option, in step (2), the impregnation rate of the reinforcement is controlled at 75%~95%; in step (4), the cutting accuracy of the finished product is ±0.5mm, the surface roughness of the profile after grinding is Ra≤1.6μm, and the test items include combustion performance, mechanical properties, density and microcapsule integrity.

[0021] The aforementioned composite materials are used in rail transit, building curtain walls, power utility tunnel structures, and high-end photovoltaic brackets.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. It has good flame retardant properties, and its flammability rating meets the A2 level specified in GB8624-2012. The oxygen index is significantly improved and the smoke density level is further reduced.

[0024] 2. Excellent mechanical properties, with significantly improved tensile and flexural strength compared to ordinary formulations;

[0025] 3. It has good pultrusion processability, controls the resin viscosity within the ideal range, and solves the core problem of poor processability of traditional high-filler Class A flame-retardant pultrusion materials. The encapsulated inorganic phase change microcapsules are the key to achieving long-term durability.

[0026] 4. The composite material has a high overall phase transition enthalpy, which provides a strong temperature buffering effect. Detailed Implementation

[0027] The present invention will now be described in further detail.

[0028] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0029] The inorganic phase change microcapsules used in the examples and comparative examples were all prepared according to the following steps:

[0030] 100 parts of magnesium chloride hexahydrate and 3 parts of nucleating agent were mixed and heated to melt. The mixture was then dispersed in an ethanol-water solution containing a silicon source under the action of an emulsifier. A silica shell was then coated onto the surface of the phase change core material using a sol-gel method, with the shell thickness controlled to be 150–200 nm. The phase change temperature of magnesium chloride hexahydrate is approximately 118 °C. Borax was used as the nucleating agent, and tetraethyl orthosilicate was used as the silicon source in the ethanol-water solution. After the reaction, the mixture was washed, filtered, and vacuum dried to obtain inorganic phase change microcapsules. Testing showed that the microcapsules had a phase change temperature of 115 °C, a latent heat of 162 J / g, a particle size of 15–40 μm, and a total calorific value ≤4.2 MJ / kg.

[0031] Example 1

[0032] formula:

[0033] Reinforcing material: Alkali-free glass fiber continuous yarn, with a fiber volume fraction of 78%, accounting for 80% of the total mass of the composite material.

[0034] The resin matrix, accounting for 20% of the total mass of the composite material, has the following internal composition by mass percentage:

[0035] The flame-retardant resin is a bisphenol A type phosphorus-containing halogen-free epoxy resin: 62 parts

[0036] Inorganic microcapsule phase change materials: 10 parts

[0037] The inorganic flame-retardant filler is aluminum hydroxide, with an average particle size of 5 μm: 20 parts

[0038] The nano-synergist is nano-silicon powder with an average particle size of 80 nm: 4 parts

[0039] The reactive diluent is butyl glycidyl ether: 10 parts

[0040] The curing agent is methyltetrahydrophthalic anhydride: 90 parts

[0041] The accelerator is ethyltriphenylphosphine bromide: 0.6 parts

[0042] The coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane: 0.5 parts

[0043] The internal release agent is a phosphate ester: 0.3 parts.

[0044] The smoke suppressant is ammonium molybdate: 0.3 parts

[0045] Preparation method:

[0046] According to the method described in this invention, flame-retardant resin, inorganic microcapsule phase change material, inorganic flame-retardant filler, nano-scale synergist, reactive diluent, coupling agent, and smoke suppressant are designated as component A. These components are intermittently stirred at 400 rpm for 25 min at 30°C and a vacuum of -0.09 MPa. Curing agent, accelerator, and internal release agent are designated as component B, and the mixtures are homogeneous. A and B are mixed at a mass ratio of 100:90 to obtain a mixed resin with a viscosity of 1200 mPa·s. Fibers are impregnated with the resin at 70°C, and the three-stage mold temperatures are 120°C, 145°C, and 170°C, with a traction speed of 0.5 m / min and a curing pressure of 12 MPa. Pultruded sheets with a cross-section of 20 × 10 mm are obtained.

[0047] Performance test results: see Table 1.

[0048] Example 2

[0049] The difference from Example 1 is that:

[0050] The reinforcement is replaced with carbon fiber, which accounts for 70% of the volume and 75% of the total mass of the composite material. The fiber layup is a combination of continuous yarn and surface mat.

[0051] The amount of inorganic microcapsule phase change material in the resin matrix was increased to 12 parts, while the amount of inorganic flame retardant filler was reduced to 18 parts.

[0052] The core material of the phase change microcapsule was changed to disodium hydrogen phosphate dodecahydrate, with a phase change temperature of about 85°C.

[0053] The rest is the same as in Example 1. The resulting profile has a density of 2150 kg / m³. 3 .

[0054] Example 3

[0055] The difference from Example 1 is that:

[0056] The reinforcement is basalt fiber, which accounts for 80% of the total volume of the composite material.

[0057] The flame retardant resin in the resin matrix was replaced with o-cresol epoxy resin, with a dosage of 65 parts; the nano synergist was replaced with 3 parts nano montmorillonite, 12 parts reactive diluent, and 0.8 parts accelerator.

[0058] The inorganic microcapsule phase change material is used in an amount of 8 parts, and the inorganic flame retardant filler is 22 parts magnesium hydroxide.

[0059] The rest is the same as in Example 1.

[0060] Example 4

[0061] The difference from Example 1 is that:

[0062] The flame retardant resin was replaced with F51 type phenolic epoxy resin, with a dosage of 60 parts.

[0063] The amount of inorganic microcapsule phase change material used was 12 parts.

[0064] The inorganic flame-retardant filler is aluminum hydroxide, with a dosage of 22 parts.

[0065] Three parts of the nano-synergist were used.

[0066] Use 8 parts of reactive diluent.

[0067] The amount of curing agent is 85 parts and the amount of accelerator is 0.4 parts.

[0068] The fiber volume fraction of the reinforcement is 70%, and the reinforcement accounts for 75% of the total mass of the composite material.

[0069] The rest is the same as in Example 1. The resulting profile has a density of 2120 kg / m³. 3 .

[0070] Example 5

[0071] The difference from Example 1 is that:

[0072] The flame-retardant resin was replaced with halogen-free flame-retardant vinyl ester resin, with a dosage of 65 parts.

[0073] Eight parts of inorganic microcapsule phase change material were used.

[0074] The inorganic flame-retardant filler is magnesium hydroxide with an average particle size of 8 μm and a dosage of 18 parts.

[0075] The nano-synergist is nano-montmorillonite with a particle size of 100 nm, and the dosage is 5 parts.

[0076] The active diluent is cashew phenol glycidyl ether, used in 12 parts.

[0077] The curing agent used is 95 parts methylhexahydrophthalic anhydride, and the accelerator used is 0.9 parts 2-ethyl-4-methylimidazole.

[0078] The reinforcement is a mixture of carbon fiber and glass fiber, with a fiber volume fraction of 80%, accounting for 82% of the total mass of the composite material.

[0079] The rest is the same as in Example 1.

[0080] Example 6

[0081] The difference from Example 1 is that:

[0082] The core material of the inorganic microcapsule phase change material is changed to calcium aluminum hydrotalcite, which has a phase change decomposition temperature of about 100-120℃ and a latent heat of 142J / g. It is also coated with silica, and the total calorific value of the microcapsule is ≤3.5MJ / kg.

[0083] The inorganic flame-retardant filler was replaced with 20 parts of magnesium hydroxide.

[0084] The rest is the same as in Example 1.

[0085] Example 7

[0086] The difference from Example 1 is that:

[0087] The coating layer of the inorganic microcapsule phase change material was changed to an alumina ceramic shell, which was prepared by the sol-gel method. The shell thickness was 200 nm, and the core material was still magnesium chloride hexahydrate.

[0088] The rest is the same as in Example 1.

[0089] Example 8

[0090] The difference from Example 1 is that:

[0091] The coupling agent was changed to NDZ-101 titanate coupling agent, with a dosage of 0.7 parts.

[0092] The smoke suppressant was replaced with 0.4 parts of zinc stannate.

[0093] The rest is the same as in Example 1.

[0094] Example 9

[0095] The difference from Example 1 is that:

[0096] It contains no smoke suppressant, but is otherwise identical.

[0097] The smoke density level (SDR) was 58, which still meets the A2-s1 level. The s1 level requires an SDR of ≤50, which is slightly exceeded here. Therefore, without the addition of smoke suppressant, it may be downgraded to the s2 level, indicating that smoke suppressant has an optimization effect but is not necessary.

[0098] Example 10

[0099] The difference from Example 1 is that:

[0100] The reinforcement is a composite layup of continuous basalt fiber yarn and alkali-free glass fiber surface mat, with a fiber volume fraction of 75%, accounting for 78% of the total mass of the composite material.

[0101] The rest is the same as in Example 1.

[0102] Comparative Example 1

[0103] Compared to Example 1, without adding inorganic microcapsule phase change material, the amount of inorganic flame-retardant filler aluminum hydroxide was increased by 10 parts, i.e., the amount of aluminum hydroxide was 30 parts, and the rest remained the same. The viscosity of the resin system increased to 2100 mPa·s, and slight mold clogging occurred during pultrusion, resulting in a decrease in the surface gloss of the product.

[0104] Comparative Example 2

[0105] Compared to Example 1, the inorganic microcapsule phase change material was replaced with an equal amount of uncoated magnesium chloride hexahydrate powder with an average particle size of 30 μm, without silica coating. Everything else remained the same. Water separation and agglomeration occurred during mixing, and salt precipitation and internal microcracks appeared on the surface of the cured profile.

[0106] Comparative Example 3

[0107] Compared to Example 1, no nano-silicon micropowder synergist was added, and the amount of inorganic flame-retardant filler was increased by 4 parts. Everything else remained the same.

[0108] Comparative Example 4

[0109] Compared to Example 1, the amount of inorganic microcapsule phase change material was reduced to 5 parts, and the amount of inorganic flame-retardant filler aluminum hydroxide was increased by 25 parts. All other parameters remained the same.

[0110] Comparative Example 5

[0111] Compared to Example 1, the amount of inorganic microcapsule phase change material was increased to 15 parts, exceeding the upper limit of 12 parts, while the amount of inorganic flame-retardant filler was reduced by 15 parts. Everything else remained the same. After mixing, the viscosity of the resin system was found to be 1800 mPa·s, which was too high, causing mold blockage during pultrusion and resulting in microcapsule agglomeration particles on the profile surface.

[0112] Comparative Example 6

[0113] Compared to Example 1, the amount of inorganic flame-retardant filler aluminum hydroxide was reduced to 15 parts, while the amount of inorganic microcapsule phase change material was increased by an equal amount of 15 parts. All other parameters remained the same.

[0114] Comparative Example 7

[0115] Compared to Example 1, the amount of inorganic flame-retardant filler aluminum hydroxide was increased to 25 parts, exceeding the upper limit of 22 parts, while the amount of inorganic microcapsule phase change material was reduced by 5 parts. All other parameters remained the same.

[0116] Comparative Example 8

[0117] Similar to Comparative Example 3, there was no nano-synergist, but no other compensation.

[0118] Comparative Example 9

[0119] Compared to Example 1, the inorganic microcapsule phase change material was replaced with an equal amount of organic paraffin microcapsules, specifically urea-formaldehyde resin coated with a phase change enthalpy of 180 J / g. All other parameters remained the same. Testing revealed a significant increase in total calorific value and a decrease in flammability rating to B2.

[0120] Table 1. Overall Performance Comparison Table

[0121]

[0122] Results Analysis

[0123] Based on the test data of Examples 1-10 and Comparative Examples 1-9 in Table 1, a systematic analysis was conducted from five aspects: flame retardant performance, mechanical performance, process performance, thermal management performance, and durability performance.

[0124] I. Flame Retardant Performance Analysis

[0125] 1.1 Combustion rating and gross calorific value

[0126] Tested according to the method described in GB / T20284, the combustion performance ratings of Examples 1-10 reached the A2 level specified in GB8624-2012, and the smoke production characteristics, combustion drips / particulate matter, and smoke toxicity ratings reached s1, d0, and t0 levels, respectively. Example 9, due to the absence of a smoke suppressant, was downgraded to s2, but the total calorific value released per unit area was ≤7.5 MJ / m². 2 It still meets the A2 rating. Among them, Example 5 has the lowest total calorific value and the best flame retardancy.

[0127] Comparative Example 1: Total calorific value 12.5 MJ / m 2 The result was only B1 grade, which proves that the phase change endothermic effect and crystal water decomposition of inorganic microcapsule phase change materials significantly reduce the calorific value of combustion.

[0128] Comparative Example 2: Total calorific value 10.8 MJ / m2 The B1 rating, along with leakage and salt precipitation, indicates that the coating is crucial for flame retardant stability and material integrity.

[0129] Comparative Example 4: Total calorific value 14.5 MJ / m 2 The B1 rating indicates insufficient flame retardancy, meaning that 8 parts are the minimum required to guarantee an A2 rating.

[0130] Comparative Example 6: Total calorific value 15.2 MJ / m 2 Only reaching grade B2 proves that 18 parts of inorganic filler are the lower limit necessary to achieve grade A2.

[0131] Comparative Example 9: Total calorific value as high as 18.5 MJ / m³ 2 Grade B2 directly proves the irreplaceable nature of inorganic phase change materials.

[0132] Conclusion: In this invention, 8-12 parts of inorganic microcapsule phase change material and 18-22 parts of inorganic flame retardant filler together constitute the necessary and minimum effective range for achieving A2-level flame retardancy.

[0133] 1.2 Limiting Oxygen Index (LOI)

[0134] The LOI of the examples was 40%~46%, all ≥40%, which is much higher than that of Comparative Example 1 (38%), Comparative Example 4 (36%), and Comparative Example 6 (35%). This indicates that the inorganic phase change microcapsules dilute oxygen by releasing water of crystallization and form an inorganic shell to isolate oxygen, and synergize with the phosphorus and nitrogen flame retardant resin to significantly improve the oxygen index.

[0135] 1.3 Smoke Density Rating (SDR)

[0136] Examples 1-8 and 10 all had a smoke density (SDR) ≤ 45, meeting the requirement of SDR ≤ 50 for S1 level; Example 9 had an SDR of 58, dropping to S2 level; while Comparative Examples 1, 2, 3, 4, 6, and 7 all had an SDR ≥ 55, especially Comparative Example 6 with an SDR of 78. The results indicate that inorganic phase change microcapsules themselves have a certain smoke-suppressing effect, but when combined with nano-synergists and smoke suppressants, the smoke density can be further reduced, achieving S1 level.

[0137] II. Mechanical Property Analysis

[0138] 2.1 Tensile strength and flexural strength

[0139] Examples 1-10: tensile strength 655~725MPa, flexural strength 690~770MPa, with Example 5 exhibiting the highest mechanical properties.

[0140] Comparative Example 1: Tensile strength 510 MPa, flexural strength 545 MPa, a decrease of about 25% compared to Example 1, because the high filler content led to poor resin wetting and increased interface defects.

[0141] Comparative Example 2: The tensile strength was 438 MPa and the bending strength was 462 MPa, which was the lowest. The reason was the precipitation corrosion of the uncoated inorganic phase change material and the propagation of microcracks.

[0142] Comparative Example 4: Tensile strength 545 MPa, bending strength 575 MPa, lower than Example 1, because the matrix became brittle after the filler was added.

[0143] Comparative Example 5: Tensile strength 480MPa, bending strength 510MPa, mechanical properties significantly decreased due to excessive microcapsule aggregation, weakened interfacial bonding, and internal defects caused by die blockage during pultrusion.

[0144] Comparative Example 7: Tensile strength 500MPa, bending strength 530MPa, also due to excessive filler content leading to increased brittleness.

[0145] Comparative Example 8: Tensile strength 590 MPa, bending strength 625 MPa, although higher than Comparative Example 1, but still lower than Example 1, proving that the nano-synergist can improve the interfacial bonding between the filler / microcapsule and the resin and enhance the mechanical properties.

[0146] Conclusion: The optimal window for balancing flame retardancy and mechanical properties is represented by 8-12 parts microcapsules, 18-22 parts filler, and 3-5 parts nano-synergist in this invention. Exceeding or falling below this window will lead to significant deterioration of mechanical properties.

[0147] III. Process Performance Analysis

[0148] 3.1 Resin system viscosity and pultrusion smoothness

[0149] Examples 1-10: Viscosity 1100~1300mPa·s, pultrusion process normal, no mold blockage, smooth surface.

[0150] Comparative Example 1: Viscosity 2100 mPa·s, slight mold clogging, rough surface.

[0151] Comparative Example 5: Viscosity 1800 mPa·s, mold blockage, and microcapsule aggregation.

[0152] Comparative Example 7: Viscosity 2200 mPa·s, severe mold clogging.

[0153] Comparative Examples 3 and 8: Viscosity 1100 mPa·s, although the process was normal, the flame retardancy and mechanical properties decreased.

[0154] Conclusion: By replacing some inorganic fillers with low-viscosity, surface-modified inorganic microcapsule phase change materials, the resin viscosity can be controlled within an ideal range, solving the core problem of poor processability of traditional high-filler Class A flame-retardant pultruded materials.

[0155] 3.2 Microcapsule integrity

[0156] Examples 1-10: The strength retention rate after damp heat aging was 84%~89%, indicating that the silica or alumina ceramic coating effectively protected the inorganic phase change core material and prevented its leakage and corrosion of the matrix.

[0157] Comparative Example 2: The retention rate was only 65%, confirming that uncoated inorganic phase change materials would severely damage the composite material structure under humid and hot conditions.

[0158] Comparative Example 9: Retention rate 70%, because the organic capsule wall is easily degraded under high temperature and high humidity.

[0159] Conclusion: The encapsulated inorganic phase change microcapsules of the present invention are a necessary condition for achieving long-term durability.

[0160] IV. Thermal Management Performance Analysis

[0161] 4.1 Overall Phase Transformation Enthalpy of Composite Materials

[0162] Examples 1-10: Phase change enthalpy 10.2~16.8J / g, all of which have significant phase change heat storage capacity, with Example 2 having the highest.

[0163] Comparative Example 1: Phase transition enthalpy is 0, no thermal management function.

[0164] Comparative Example 2: Although it had 9.2 J / g, it had leaked and could not be used stably.

[0165] Comparative Example 4: Overall phase transition enthalpy 6.8 J / g, lower than the practical level of Examples 1-10.

[0166] Comparative Example 5: Overall phase transition enthalpy 20.1 J / g, but poor processability and decreased mechanical properties, making it practically infeasible.

[0167] Conclusion: Adding 8-12 parts of inorganic microcapsules, while ensuring process and mechanical properties, endows the composite material with practical phase change thermal management capabilities, making it suitable for scenarios requiring passive temperature regulation, such as photovoltaic brackets and power utility tunnels.

[0168] V. Summary of Overall Advantages

[0169] Compared with all comparative examples, the inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite materials provided in Examples 1-10 have the following significant advantages:

[0170] 1. Excellent flame retardant performance: all meet the highest A2-s1, d0, t0 ratings, with a total calorific value per unit area ≤6.5 MJ / m². 2 The limiting oxygen index is ≥40%, far exceeding the control ratio.

[0171] 2. High mechanical properties: tensile strength ≥655MPa, flexural strength ≥690MPa, which is more than 25% higher than the traditional high-filler Class A flame retardant material shown in Comparative Example 1.

[0172] 3. Good processability: The resin viscosity is 1100~1300mPa·s, the pultrusion is smooth and there is no mold blockage, which can realize continuous and stable production.

[0173] 4. Integrated thermal management function: The overall phase change enthalpy of the composite material is ≥10J / g, which has the ability to actively absorb heat and cool down.

[0174] 5. Durable and reliable: Strength retention rate ≥84% after damp heat aging; microcapsules are leak-free and corrosion-free.

[0175] 6. Green and environmentally friendly: The entire system is halogen-free, with low smoke and low toxicity.

Claims

1. An inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material, characterized in that, It comprises the following components, by mass percentage: 75%~85% reinforcing agent, 15%~25% resin matrix; the resin matrix comprises the following components by mass percentage: 60~65 parts flame retardant resin, 8~12 parts inorganic microcapsule phase change material, 18~22 parts inorganic flame retardant filler, 3~5 parts nano-level synergist, 8~12 parts reactive diluent, 85~95 parts curing agent, 0.4~0.9 parts accelerator, 0.4~0.7 parts coupling agent, and 0.2~0.4 parts internal release agent; The inorganic microcapsule phase change material is inorganically coated, with a phase change temperature of 80~120℃, latent heat ≥150J / g, microcapsule particle size of 10~60μm, and coating layer thickness of 100~250nm; the total calorific value of the inorganic microcapsule phase change material is ≤5MJ / kg. The combustion performance of the composite material meets the GB8624-2012 A2-s1-d0-t0 standard, with a total heat release per unit area ≤7.5 MJ / m². 2 Tensile strength ≥680MPa, flexural strength ≥720MPa, profile density 2100~2200kg / m³ 3 .

2. The composite material according to claim 1, characterized in that, The reinforcement is a continuous fiber reinforcement, selected from one or more of alkali-free glass fiber, carbon fiber, and basalt fiber, with a fiber volume fraction of 70% to 80%, and is laid up using a continuous yarn and felt composite layer or a single continuous yarn layer.

3. The composite material according to claim 1, characterized in that, The flame-retardant resin is a halogen-free flame-retardant thermosetting resin adapted to the pultrusion process, selected from one or more of epoxy resin, phenolic epoxy resin, o-cresol resin, and vinyl ester resin, with a total calorific value of 30.0~38.0 MJ / kg; the reactive diluent is selected from glycidyl ether reactive diluents; the curing agent is selected from one of acid anhydride or amine curing agents; the accelerator is selected from quaternary phosphate salt or tertiary amine accelerators; and the coupling agent is selected from silane coupling agents or titanate coupling agents, used to improve the interfacial compatibility between the inorganic microcapsules and the resin matrix.

4. The composite material according to claim 1, characterized in that, The coating layer of the inorganic microcapsule phase change material is selected from one of silicon dioxide, ceramics, and metal oxides; the core material of the inorganic phase change material is selected from one or more of hydrated salts and water-soluble minerals, wherein the hydrated salts are selected from one or more of magnesium chloride hexahydrate, magnesium sulfate heptahydrate, and disodium hydrogen phosphate dodecahydrate, and the water-soluble minerals are selected from one or more of calcium aluminum hydrotalcite, kaolinite, and vermiculite.

5. The composite material according to claim 1, characterized in that, The resin matrix further includes 0.2 to 0.4 parts of smoke suppressant, which is selected from molybdenum-based and tin-based smoke suppressants; the inorganic flame retardant filler is selected from one or more of aluminum hydroxide and magnesium hydroxide, with a particle size of 1 to 10 μm; the nano-level synergist is selected from one or more of nano-silica powder and nano-montmorillonite, with a particle size of 50 to 200 nm.

6. A method for preparing an inorganic microcapsule phase change synergistic Class A flame-retardant pultruded composite material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preparation of resin system: Flame retardant resin, inorganic microcapsule phase change material, inorganic flame retardant filler, nano-level synergist, reactive diluent, coupling agent and smoke suppressant are put into a mixing device and mixed for 20-30 min at 20-40℃ and vacuum degree ≤-0.08MPa to obtain component A; curing agent, accelerator and internal release agent are mixed evenly to obtain component B; component A and component B are mixed at a mass ratio of 100:85-95, and the viscosity of the system after mixing is controlled to be 600-1500mPa·s; (2) Impregnation and preforming: The continuous fiber reinforcement is impregnated into the resin system prepared in step (1) through an impregnation tank. The impregnation temperature is controlled at 60~70℃ to prevent the inorganic microcapsule phase change material from exuding water and breaking. Then, the fiber layup is sorted and excess resin is removed through a preforming mold. (3) Pultrusion curing: The preformed fiber-resin composite is fed into the pultrusion mold and multi-stage gradient temperature control is adopted. The mold temperature is 100~120℃, 130~150℃ and 160~180℃ respectively, and the traction speed is 0.2~0.7m / min to achieve continuous curing. (4) Post-processing: Cut, grind and inspect the cured profiles, remove unqualified products and obtain finished products.

7. The preparation method according to claim 6, characterized in that, In step (1), the stirring speed of the mixing equipment is 200~600r / min, and intermittent stirring is used during the mixing process to avoid agglomeration of inorganic microcapsule phase change materials; in step (3), the pressure of the pultrusion die is controlled at 8~18MPa, and the curing time is 2~6min.

8. The preparation method according to claim 6, characterized in that, In step (2), the impregnation rate of the reinforcement is controlled at 75%~95%; in step (4), the cutting accuracy of the finished product is ±0.5mm, the surface roughness of the profile after grinding is Ra≤1.6μm, and the test items include combustion performance, mechanical properties, density and microcapsule integrity.

9. The application of a composite material as described in any one of claims 1 to 5 in rail transit, building curtain walls, power utility tunnel structural components, and high-end photovoltaic brackets.

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