Dual-mode gradient response microcapsule system self-repairing quartz powder waterproof coating

Abstract

The invention relates to a dual-mode gradient response microcapsule system self-repairing quartz powder waterproof coating, and belongs to the technical field of building waterproof materials. The coating is prepared from the following components in percentage by weight: 60 to 80 percent of quartz powder substrate, 15 to 30 percent of polymer emulsion and 5 to 10 percent of microencapsulated epoxy resin, the method is characterized in that 1, a gradient response microcapsule adopts a double-layer wall material structure, an inner layer is porous urea-formaldehyde resin (containing a nano SiO2 pore-forming agent, and the pore diameter is 50-200nm), an outer layer is stress-sensitive polyurethane (the crosslinking degree is 8-12wt%, and the rupture strength is 2.5 + / -0.3 MPa), and directional rupture and moisture triggered curing when the crack width is less than or equal to 0.3 mm are realized; 2, a bimodal repair mechanism: primary repair: the microcapsules are broken to release epoxy resin, and 80% of the crack depth is filled within 10 min; secondary remediation: aminated nano quartz powder is subjected to secondary remediation in an alkaline environment (pHgt; and the Si-OH group is released under the action of the epoxy resin, and forms a Si-O-C covalent bond with the epoxy resin, and the strength of the restoration body is 105% higher than that of the original coating within 24 hours.

Description

Technical Field

[0001] This invention relates to the field of building waterproofing materials technology, specifically a quartz powder-based waterproof coating with microcrack self-healing function, suitable for waterproofing and protection of concrete structures, underground projects, roofs, and other buildings. This invention relates to a dual-modal gradient response microencapsulation system self-healing quartz powder waterproof coating, belonging to the field of building waterproofing materials technology. The coating is composed of a quartz powder base (60-80 wt%), a polymer emulsion (15-30 wt%), and microencapsulated epoxy resin (5-10 wt%); its characteristic is:

[0002] 1. Gradient-response microcapsules: They adopt a double-layer wall structure, with the inner layer being a porous urea-formaldehyde resin (containing nano-SiO2 pore-forming agent, pore size 50-200nm) and the outer layer being a stress-sensitive polyurethane (crosslinking degree 8-12wt%, breaking strength 2.5±0.3MPa), achieving directional cracking and moisture-triggered curing when the crack width is ≤0.3mm.

[0003] 2. Dual-modal repair mechanism:

[0004] Primary repair: Microcapsules rupture to release epoxy resin, filling 80% of the crack depth within 10 minutes;

[0005] Secondary repair: Aminated nano-quartz powder releases Si-OH groups in an alkaline environment (pH>12), forming Si-OC covalent bonds with epoxy resin. Within 24 hours, the strength of the repaired body exceeds that of the original coating by 105%.

[0006] 3. Industrial control: The distribution uniformity is >92% through electrostatic self-assembly process (microcapsule +35mV / quartz powder -45mV). Combined with the latent curing agent temperature and humidity dual triggering model, the problem of microcapsule dispersion and curing control is solved.

[0007] The coating showed no leakage for 30 minutes under 0.3MPa water pressure, and its repair function retention rate was >85% after 100 freeze-thaw cycles, significantly extending the life of waterproofing projects. Background of the Invention

[0008] Existing technological defects

[0009] 1. Limitations of traditional materials:

[0010] Cement-based rigid coatings are prone to micro-cracks ≤0.3mm, leading to leakage, while polyurethane flexible coatings have poor aging resistance.

[0011] Microbial self-healing coatings are expensive (>¥300 / kg) and require specific temperature and humidity for activation;

[0012] Single-mechanism coatings can only be repaired ≤2 times, with a post-repair strength retention rate of <85%. 2. Industry technical bottlenecks:

[0013] The breakage rate of microcapsules during coating grinding is >25%;

[0014] The self-healing response time is >72 hours, which cannot meet the requirements for rapid waterproofing.

[0015] Solution path of the present invention

[0016] Through triple innovation of gradient microcapsule design, dual-modal repair, and electrostatic self-assembly process:

[0017] Precisely match the stress threshold (2.5±0.3MPa) of a 0.3mm crack with the repair speed (completed in 24 hours);

[0018] By utilizing the alkaline environment of concrete to activate the covalent bonds of nano-quartz powder for repair, the need for external intervention is reduced.

[0019] Industrialized control of microcapsule breakage rate <0.1%, achieving an annual production capacity of 5,000 tons.

[0020] Technological Evolution

[0021] stage Representative technologies limitation First generation Bituminous waterproof membrane Low temperature causes brittleness, high temperature causes flow Second generation Polymer emulsion coatings (such as acrylic) It has good elasticity but low strength and is easily punctured and damaged. Third generation Cement-penetrating crystalline coating Effective only for active cracks This invention Microcapsule + Quartz Powder Composite System Actively repairs microcracks while maintaining strength.

[0022] Purpose of the invention

[0023] 1. Achieve self-repair when the crack width is ≤0.3mm.

[0024] 2. Combining the high wear resistance of quartz powder with the adhesive properties of epoxy resin.

[0025] 3. Simplify construction processes and reduce maintenance costs.

[0026] 4. Improve the durability of the coating in harsh environments such as humidity, heat, freeze-thaw cycles, etc. Summary of the Invention

[0027] Part One: Core Structure

[0028] 1. Basic design of microcapsules for coating system:

[0029] Quartz powder base (60-80 wt%) + polymer emulsion (15-30 wt%) + microencapsulated epoxy resin (5-10 wt%)

[0030] Capsule wall: urea-formaldehyde resin (thickness 1-5μm, tensile strength 2-5MPa).

[0031] Core: Two-component epoxy resin (E-51 epoxy resin + latent curing agent).

[0032] Particle size: 20-100μm (matching crack size).

[0033] 2. Gradient-response microcapsule system (core innovation)

[0034] Inner layer porosification treatment: Nano-SiO2 pore-forming agent (pore size 50-200nm) is added to the wall material to accelerate moisture penetration and trigger the curing reaction.

[0035] Outer stress-sensitive layer: The degree of polyurethane crosslinking is precisely controlled (crosslinking agent dosage 8-12wt%) to match the breaking strength with the 0.3mm crack propagation force (2.5±0.3MPa).

[0036] Part Two: Dual-Modal Repair Mechanism

[0037] I. Implementation Principle of the Dual-Modal Repair Mechanism

[0038] The dual-modal repair mechanism achieves rapid crack closure and long-term reinforcement through a time-series combination of physical filling and chemical bonding. The specific process is as follows:

[0039] (I) Initial Repair Stage: Microcapsule-triggered physical filling

[0040] 1. Mechanical response and release mechanism

[0041] When the coating develops cracks with a width ≤0.3mm, the stress field at the crack tip reaches 2.5–3.2MPa (finite element simulation results), which exceeds the yield strength of the polyurethane wall material of the microcapsule outer layer (2.5±0.3MPa), leading to directional fracture of the wall material.

[0042] The epoxy resin (E-51 type) pre-stored inside the core fills more than 80% of the crack depth within 10 minutes under the drive of capillary effect, forming a temporary physical barrier. This process was confirmed by high-speed microscopy (1000 frames / second) with a flow rate of 0.8 mm / s.

[0043] 2. Moisture-triggered curing start

[0044] When the latent curing agent (microcrystalline encapsulated polyetheramine D230) in the epoxy resin comes into contact with ambient moisture, the nanopores (50–200 nm) of the capsule wall accelerate moisture penetration, initiating a prepolymerization reaction of the epoxy groups, and forming a preliminary cross-linked network within 24 hours. Fourier transform infrared spectroscopy (FTIR) at 915 cm⁻¹... -1 The characteristic peak of epoxy groups was detected at a decay rate of 65%.

[0045] (II) Secondary Repair Stage: Inorganic-Organic Synergistic Chemical Bonding

[0046] 1. Functional activation of nano-quartz powder

[0047] Nano-quartz powder (50–100 nm in size) modified with aminosilane (KH-550) gradually dissolved in an alkaline environment (pH>12) in the cracks, releasing active silanol groups (Si-OH). X-ray photoelectron spectroscopy (XPS) showed that the Si 2p binding energy shifted from 103.2 eV to 102.5 eV, confirming the enrichment of silanol groups.

[0048] 2. Covalent bond enhancement mechanism

[0049] The released Si-OH undergoes a condensation reaction with the ether bonds (COC) in the epoxy prepolymer to form Si-OC covalent bonds (FTIR at 1100 cm⁻¹). -1 (A characteristic broad peak appears at this location). This reaction causes the restoration to form a three-dimensional interpenetrating network:

[0050] Epoxy resin provides a flexible skeleton (120% elongation at break).

[0051] Si-OC bonds improve rigidity (elastic modulus increases to 3.8 GPa).

[0052] Scanning electron microscopy (SEM) shows that nano-quartz powder is embedded in epoxy matrix at the repair interface. Figure 1 Energy dispersive spectroscopy (EDS) confirmed that silicon was enriched at a concentration of 12.7 wt% in the crack region (compared to 5.3 wt% in the matrix).

[0053] II. Dynamic Verification of the Two-Stage Synergistic Effect

[0054] (a) Time scale matching

[0055] 1. Initial repair time: Epoxy resin completes physical filling of cracks within 0.5–2 hours (observed by laser confocal microscope).

[0056] 2. Secondary repair trigger: The dissolution of nano-quartz powder lags behind resin release (30 minutes–4 hours), coinciding with the epoxy prepolymerization time window.

[0057] 3. Complete curing period: Covalent network formation within 24 hours (rheological testing shows storage modulus G' increases from 10). 3 Pa rises to 10 6 Pa).

[0058] (II) Evolution of Repair Intensity

[0059]

[0060]

[0061] Based on the undamaged coating bond strength (4.0 MPa)

[0062] III. Performance Comparison with Single-Stage Repair Systems

[0063] (a) Differences in Repair Integrity

[0064] 1. Pure epoxy remediation system (comparative example):

[0065] Physical filling alone cannot repair the micropores in the interface (SEM shows porosity > 5%).

[0066] After freeze-thaw cycles, the bond strength decreased to 72% of its initial value.

[0067] 2. This bimodal system:

[0068] Si-OC bonds fill resin shrinkage defects (porosity < 0.3%).

[0069] Strength retention after freeze-thaw cycles >95% (ASTM C666 standard).

[0070] (II) Long-term service performance

[0071] 1. Improved chemical stability:

[0072] The Si-OC bond energy (452 ​​kJ / mol) is higher than that of the C-C bond (347 kJ / mol), resulting in a 3-fold increase in hydrolysis resistance (strength loss <8% after immersion in 85℃ hot water for 30 days).

[0073] 2. Ability to repeatedly repair:

[0074] When secondary cracking occurs, the new crack avoids the original repair area (electron backscatter diffraction shows that the grain size in the repair area is reduced by 32%), achieving ≥5 effective repairs.

[0075] IV. Summary of Mechanism Innovation

[0076] The core breakthrough of the dual-modal repair mechanism lies in:

[0077] 1. Timing-based collaborative design: Physical filling (primary) and chemical bonding (secondary) are activated progressively according to the kinetic requirements of crack repair.

[0078] 2. Interface enhancement effect: Inorganic nanoparticles transform from inert fillers into covalent cross-linking points, enabling the strength of the restoration to surpass that of the original coating.

[0079] 3. Environmental Adaptability: The dissolution of nano-quartz is triggered by the alkaline environment of the cracks, requiring no external energy input.

[0080] Supporting data sources:

[0081] Epoxy flow velocity: Particle image velocimetry (PIV)

[0082] Covalent bond formation: In-situ Raman spectroscopy (785nm laser)

[0083] Freeze-thaw test: according to GB / T 50082-2009 standard

[0084] Repair phase Technical solution Innovation effect Primary repair Microcapsule rupture releases epoxy resin Fill 80% of the crack depth within 10 minutes Secondary repair Nano-quartz powder dissolves and releases Si-OH groups Forms Si-OC covalent bonds with epoxy resin

[0085] Nano-quartz powder functionalization: The surface of 800-mesh quartz powder is aminated (KH-550 silane coupling agent) to enable it to participate in the epoxy curing reaction and enhance the strength of the restoration (↑40%).

[0086] 1) Triggering stage: Crack propagation causes the microcapsule to rupture under pressure.

[0087] 2) Release stage: Epoxy resin flows into the crack.

[0088] 3) Curing stage: When the resin comes into contact with moisture in the air, the curing agent triggers a cross-linking reaction.

[0089] 4) Repair complete: A dense polymer network is formed, sealing the cracks (repair time ≤ 72h).

[0090] 4. Key Technical Parameters

[0091]

[0092]

[0093] Part Three: Microscopic Mechanisms of Action

[0094] I. In-situ microscopic observation of the self-healing process:

[0095] 1. Crack formation (0-5 min) →

[0096] 2. Capsule rupture releases resin (5-10 min) →

[0097] 3. Resin capillary penetration (10-30 min) →

[0098] 4. Dissolution and release of Si-OH from nano-quartz powder (30-120 min) →

[0099] 5. Epoxy-Si-OH copolymerization curing (120 min - 24 h)

[0100] Fourier transform infrared evidence: the restoration was at 1100cm -1 The presence of Si-OC characteristic peaks at this location confirms the formation of an organic-inorganic hybrid network.

[0101] SEM evidence: The repaired interface shows an interpenetrating structure in which nano-quartz powder (bright white particles) is embedded in epoxy matrix (gray continuous phase).

[0102] II. Flow Behavior Dominated by Capillary Effect

[0103] The released epoxy resin forms an advancing contact angle θ = 22° within the crack (data from a high-speed contact angle meter), indicating its excellent wettability. The resin flow velocity v satisfies the Washburn equation:

[0104]

[0105] (γ is surface tension, η is viscosity, l is flow distance)

[0106] At 25°C, the average resin flow rate in a 0.3mm wide crack reaches 0.75mm / s, and a crack with a depth of 1.2mm can be filled within 10 minutes.

[0107] III. Experimental Analysis of Microscopic Mechanisms of Action

[0108] 1. Microcapsule rupture and resin release kinetics

[0109] 1.1 Stress-driven directional fracture

[0110] When the coating developed cracks with a width of 0.30±0.02 mm, a stress concentration zone formed at the crack tip (maximum stress of 3.2 MPa in finite element simulation). This stress exceeded the yield strength of the polyurethane wall material of the microcapsule outer layer (2.8 MPa), causing the wall material to fracture preferentially along the crack propagation direction. In-situ observation by scanning electron microscopy (SEM) showed that the crack opening exhibited a radial tearing morphology with a crack width of 8-15 μm, which matched the viscosity of the epoxy resin in the core (3500 mPa·s), ensuring efficient resin outflow.

[0111] Dissolution and interfacial bonding of 2-nanometer quartz powder

[0112] 2.1 Alkali-activated solubility kinetics

[0113] The exposed concrete matrix at the crack releases Ca(OH)₂, causing the local pH to rise to 12.5-13.0. Under these alkaline conditions:

[0114] Aminated nano-quartz powder (≡Si-NH2) hydrolyzes to generate silanol groups (≡Si-OH).

[0115] The Si-O-Si bonds in the quartz lattice break, dissolving and releasing free [SiO4] state. 4- ion.

[0116] Inductively coupled plasma optical emission spectroscopy (ICP-OES) confirmed that the silicon ion concentration in the crack liquid phase increased from 0 ppm to 85 ppm within 30 minutes.

[0117] 2.2 Covalent bond formation mechanism

[0118] The dissolved active silica species undergo an interfacial reaction with the epoxy resin:

[0119] 1) Condensation reaction:

[0120] ≡Si-OH+HO-C≡→≡Si-OC≡+H2O

[0121] 2) Coordinate bond strengthening:

[0122] Released Ca 2+ It forms a Ca-O coordinate bond with the oxygen atom of the ether bond in the epoxy chain segment (bond energy ≈ 210 kJ / mol).

[0123] Fourier transform infrared (FTIR) spectroscopy was performed 24 hours after restoration, showing:

[0124] 1100cm -1 The peak intensity of the antisymmetric stretching vibration of Si-OC increased by 247%.

[0125] 915cm -1 The characteristic peaks of the epoxy groups completely disappeared.

[0126] X-ray photoelectron spectroscopy (XPS) detected a binding energy peak of 102.6 eV in the Si 2p orbital, confirming the formation of the Si-OC bond (the standard Si-O-Si is 103.4 eV).

[0127] 3. Multiscale structural reorganization process

[0128] 3.1 Nanoscale interface structure

[0129] High-resolution transmission electron microscopy (HRTEM) shows:

[0130] There is a 2-5nm thick transition layer at the repair interface.

[0131] The transition layer exhibits a symbiotic structure with a lattice stripe spacing of 0.34 nm (corresponding to the epoxy resin (002) crystal plane) and 0.25 nm (quartz (101) crystal plane).

[0132] Electron energy loss spectroscopy (EELS) surface scanning confirmed the gradient distribution of silicon and carbon elements in the transition layer.

[0133] 3.2 Evolution of Microscopic Mechanical Properties

[0134] Nanoindentation testing (Berkovich probe) shows that:

[0135] area Elastic modulus (GPa) Hardness (GPa) Original epoxy zone 3.1 0.18 Repair transition layer 5.7 0.43 Quartz powder enhancement zone 72.5 8.9

[0136] The 84% increase in transition layer modulus demonstrates the enhancement effect of Si-OC bonds.

[0137] 3.3 Macro-structural integrity

[0138] Synchrotron radiation micro-CT (resolution 0.5μm) 3D reconstruction display:

[0139] The repaired crack volume filling rate reached 98.7±0.5%.

[0140] Only 0.2 vol% of submicron pores (pore size <1 μm) remain in the interface region.

[0141] The bonding area between the restoration and the substrate was increased by 12% compared to the original coating.

[0142] Key experimental evidence chain

[0143]

[0144] The scientific significance of the mechanism

[0145] This microscopic mechanism reveals:

[0146] 1. Directional fracture effect: The precise matching of the crack stress field and the mechanical properties of microcapsules is a prerequisite for achieving efficient repair.

[0147] 2. Chemical-mechanical coupling: The alkaline environment not only activates the dissolution of nano-quartz but also promotes the reaction of Ca... 2+ Participating in coordination bonding.

[0148] 3. Cross-scale synergy: from nanoscale bonding (Si-OC) to micron-scale structural filling (resin flow), macroscopic functional restoration is ultimately achieved.

[0149] IV. Key Points of Industrialization Control and Core Control Elements for Mass Production

[0150] Microcapsule directed distribution technology

[0151] Electrostatic self-assembly process:

[0152] Microcapsule surface modification code logic

[0153] defcapsule_coating():

[0154] if Zeta potential < -30mV: Basic urea-formaldehyde capsules

[0155] Add cationic polymer (chitosan)

[0156] Potential reversed to +35mV

[0157] Anionic groups (-SO3H) are grafted onto the surface of quartz powder.

[0158] Electrostatic adsorption of microcapsules onto the surface of quartz powder

[0159] Results: The microcapsules are distributed uniformly in the coating by more than 92% (compared to only 75% by traditional mechanical mixing), avoiding repair blind spots.

[0160] Curing kinetics control

[0161] Innovation in latent curing agents:

[0162] The modified polyetheramine (D230) encapsulated in microcrystals exhibits the following release characteristics:

[0163]

[0164] (T is temperature in °C. C) h20 Humidity g / m 3 )

[0165] Temperature and humidity dual trigger: complete curing in 72 hours at 25℃ / 60% RH, and can be accelerated to 8 hours at 50℃.

[0166] 4.1 Microcapsule stability control

[0167] 4.1.1 Control of mechanical strength of wall materials

[0168] The degree of crosslinking of the polyurethane wall material of the microcapsule outer layer needs to be strictly controlled within the range of 8.5-11.2% to ensure:

[0169] Fracture strength stability: batch-to-batch fluctuation ≤ ±0.15MPa (tested according to GB / T 1040.2 standard).

[0170] Environmental tolerance: Survival rate > 99% during the coating grinding stage (damage rate as measured by laser particle size analyzer).

[0171] Implementation method: The molar ratio of diisocyanate (HDI) to polyether triol is fixed at 3.2:1. The reaction temperature is 62±1℃ (temperatures >65℃ will lead to a sharp increase in the degree of crosslinking).

[0172] 4.1.2 Improved core-encapsulation efficiency

[0173] When preparing microcapsules using phase separation, the following parameters need to be controlled:

[0174] 1. Oil-to-water ratio: 1:4 to 1:5 (volume ratio). Too low a ratio will lead to deterioration of emulsion particle size dispersibility.

[0175] 2. Emulsification shear rate: 1200±50 rpm, maintained for 30 minutes (a rate deviation of >10% will cause core leakage).

[0176] 3. Curing agent microcrystal size: D50 = 1.8-2.2μm (monitored by Malvern particle size analyzer). If it is too large, it will reduce the encapsulation efficiency.

[0177] Mass production data: A 10-ton reactor can stably achieve an encapsulation rate of 92.3±1.5% (determined by high performance liquid chromatography).

[0178] 4.2 Optimization of electrostatic self-assembly process

[0179] 4.2.1 Precise control of surface potential

[0180] Key parameters for achieving efficient adsorption of quartz powder and microcapsules:

[0181]

[0182] 4.2.2 Self-assembly dynamics control

[0183] The following must be met in the mixing equipment:

[0184] 1) Shear strength: Reynolds number Re = 2500-3000 (transition zone between laminar and turbulent flow).

[0185] 2) Action time: 15±2 minutes (adsorption rate <85% if less than 10 minutes, aggregation will occur if more than 20 minutes).

[0186] 3) Temperature control: 40±2℃ (to promote ion migration but avoid chitosan degradation).

[0187] Verification of effectiveness: X-ray diffraction (XRD) showed that the microcapsules were arranged in a single layer on the surface of the quartz powder (coverage of 93.7%).

[0188] 4.3 Engineering Control of Curing Kinetics

[0189] 4.3.1 Latent Curing Agent Release Model

[0190] The release rate of microcrystalline-encapsulated polyetheramine (D230) follows the following pattern:

[0191]

[0192] (k0=5.3×10 4 s -1 E a =45.2kJ / mol)

[0193] Process control strategies:

[0194] When the ambient humidity is greater than 60%, reduce the amount of microcrystals added by 15% (to prevent surface drying from being too slow).

[0195] When constructing in winter (T < 10℃), add 0.1 wt% zinc acetate to accelerate moisture penetration.

[0196] 4.3.2 Coating Curing Gradient Elimination

[0197] To prevent the microcapsules from rupturing due to pressure caused by excessively rapid curing of the coating surface:

[0198] 1) Film-forming aid compound:

[0199] Dipropylene glycol methyl ether (DPnB) 60%+ 40% (mixed boiling point 186℃).

[0200] 2) Drying curve control:

[0201] Stage 1 (0-2h): 25℃ / RH80% → Surface curing degree <20%

[0202] Stage 2 (2-8h): 35℃ / RH60% → Accelerated bulk curing

[0203] Stage 3 (8-24h): Natural curing at 25℃

[0204] 4.4 Improvement of coating process adaptability

[0205] 4.4.1 Key Points of Production Line Modification

[0206] Process renovation measures Control Target Dispersion grinding Zirconium bead diameter 0.3→0.8mm Microcapsule breakage rate <0.1% Filling Screw pump speed ≤200rpm Shear stress < capsule yield strength Construction spraying Nozzle diameter ≥ 1.2mm Prevent microcapsules from clogging the spray gun

[0207] 4.4.2 On-site construction control

[0208] 1) Surface preparation: Concrete moisture content ≤ 8% (measured with a microwave moisture meter). Surface temperature 5-40℃ (activate temperature control equipment if outside this range).

[0209] 2) Coating parameters: Single wet film thickness 0.3-0.5mm (excessive thickness will cause sagging). Recoating interval 8-12 hours (determined by touch drying method).

[0210] Quality control system

[0211] 4.5 Online monitoring of key indicators

[0212]

[0213] 4.6 Batch Consistency Assurance

[0214] Statistical process control (SPC) is employed.

[0215] Key parameter CpK ≥ 1.33 (e.g., microcapsule particle size CpK = 1.52).

[0216] Samples were retained for every 200 kg of product:

[0217] 1. Accelerated aging test (70℃ / 95%RH, 7 days).

[0218] 2. Freeze-thaw cycle ( 20 times).

[0219] 3. Verification of repair effectiveness (repair rate of ≥90% for 0.3mm cracks).

[0220] Innovation points

[0221] 1. Intelligent response microcapsules: Gradient wall structure realizes a dual triggering mechanism of "pressure-humidity".

[0222] 2. Inorganic-organic synergistic repair: Nano-quartz powder is upgraded from a filler to a functional component, forming a Si-OC covalent network.

[0223] 3. Precise industrial control: Electrostatic self-assembly process solves the problem of microcapsule dispersion, and latent curing agent enables controllable construction window.

[0224] originality

[0225] I. Original Technological Breakthrough

[0226] 1. Gradient-response microcapsules:

[0227] The first-ever "porous urea-formaldehyde / polyurethane" double-layer wall material structure features an inner layer with nanopores that accelerate moisture penetration (permeability ↑ 60%), and an outer layer with precisely controlled cross-linking degree to match crack stress.

[0228] This breakthrough overcomes the contradiction between the fracture strength and curing speed that traditional single-layer microcapsules cannot balance.

[0229] 2. Dual-modal collaborative repair:

[0230] The active solubility characteristics of nano-quartz powder at pH>12 were discovered, and it was converted into covalent cross-linking points;

[0231] For the first time, a time-sequential synergy between physical filling (0.5-2h) and chemical bonding (4-24h) was achieved, with the elastic modulus of the restoration reaching 3.8GPa (84% higher than that of the pure epoxy system).

[0232] 3. Precision industrial control:

[0233] Develop Zeta potential modulation technology (chitosan / sulfonate modification) to solve the problem of microcapsule aggregation;

[0234] Establish a curing agent release kinetic model to achieve intelligent adaptation of the construction window.

[0235] Beneficial effects

[0236] Performance indicators This invention Current standard (JCT2090) Increase Self-repair response time ≤24h 72h 67％ Number of repairs ≥5 times ≤2 times 150％ Repair strength retention rate 105％ 85％ 24％ Microcapsule mass production survival rate ＞99％ 75％ 32％ Salt spray resistance (500h) Repair function remains undiminished Intensity attenuation > 30% ∞

[0237] Testing standards: GB / T 23445-2009 (water resistance), ASTM C666 (freeze-thaw resistance)

[0238] Summary of technical value

[0239] This invention innovates across the entire material-structure-process chain:

[0240] 1. Theoretical Breakthrough: Revealing the covalent bonding mechanism of nano-quartz powder under alkaline conditions (Si-OC bond energy 452kJ / mol);

[0241] 2. Technological barriers: Gradient microcapsule design (double-layer wall material) and electrostatic self-assembly process (precise potential control);

[0242] 3. Engineering value: The repair response time is shortened to 24 hours, and the survival rate of industrial-grade microcapsules is >99%, promoting the application of self-healing coatings in major projects such as nuclear power plant basements and undersea tunnels. Detailed Implementation

[0243] Example 1: Microcapsule Preparation

[0244] 1. Oil phase preparation:

[0245] Dissolve 50g of E-51 epoxy resin and 10g of curing agent (modified amine) in 40g of xylene.

[0246] 2. Aqueous phase preparation:

[0247] Mix 10g urea, 25g formaldehyde solution (37%), and 200g water, and adjust the pH to 3.5.

[0248] 3. Microencapsulation:

[0249] The oil phase was added dropwise to the aqueous phase and emulsified at 1000 rpm for 10 min.

[0250] The reaction was carried out at 60℃ for 4 hours, and the mixture was filtered and dried to obtain white powder microcapsules (average particle size 50 μm).

[0251] Example 2: Coating Preparation and Application

[0252] formula:

[0253] 70 parts of quartz powder (800 mesh)

[0254] 25 parts of styrene-acrylic emulsion (50% solids content)

[0255] 5 parts of microencapsulated epoxy resin

[0256] Dispersant (polycarboxylate) 0.3 parts

[0257] Defoamer (silicone) 0.1 parts

[0258] Process:

[0259] 1. Mix and grind quartz powder, dispersant, and water (20 parts) until the fineness is ≤50μm.

[0260] 2. Add styrene-acrylic emulsion and defoamer, and stir at low speed.

[0261] 3. Finally, add the microcapsules and stir at 600 rpm for 5 minutes (to avoid capsule rupture).

[0262] 4. Apply to concrete substrate (1.0mm thickness) and cure at room temperature for 7 days.

[0263] Example 3: Performance Testing

[0264] Self-healing verification:

[0265] Artificial scratch (0.3mm width) → placed in a 25℃ / 80% RH environment → the crack disappears after 72 hours (microscopic observation). Water resistance:

[0266] The repaired coating withstood 0.3MPa water pressure for 30 minutes without leakage (GB / T 23445-2009).

[0267] Durability:

[0268] After 50 freeze-thaw cycles (-20℃ to +50℃), the repair function retention rate is >85%.

[0269] Example 4: Self-healing efficiency verification (ASTM D1308 standard)

[0270] 1. Prepare a coating (1.5 mm thick) on the concrete slab.

[0271] 2. Generate a 0.3mm wide crack using a precision crack generator.

[0272] 3. Real-time monitoring using laser confocal microscopy:

[0273] 4h: Crack width reduced to 0.1mm (resin filling).

[0274] 24h: The crack is completely closed (hybrid network is formed).

[0275] 4. Post-repair performance:

[0276] The seepage resistance pressure is 0.5 MPa (the national standard requires 0.3 MPa).

[0277] Interfacial bond strength 4.2 MPa (103% over original strength).

[0278] Example 5: Extreme Environment Validation

[0279]

[0280] Summary of innovative points of the implementation examples

[0281] 1. Precise repair threshold: By controlling the microcapsule particle size and wall thickness, it can specifically repair microcracks ≤0.3mm.

[0282] 2. Environmental triggering mechanism: It utilizes environmental moisture to activate solidification without the need for external intervention.

[0283] 3. Synergistic enhancement effect: Quartz powder enhances the mechanical strength of the coating, while microcapsules provide "intelligent repair" function. Attached Figure Description

[0284] Figure 1 Schematic diagram of gradient response microcapsule structure

[0285] Figure 2 Timing Flowchart of Dual-Mode Repair Mechanism

[0286] Figure 3 Schematic diagram of electrostatic self-assembly process

[0287] Figure 4 Repair intensity evolution curve

[0288] Figure 5 Curing kinetic model curves

[0289] Figure 6 : Inner layer porous treatment and outer layer stress-sensitive layer.

Claims

1. A self-healing quartz powder waterproof coating, characterized in that... Include: 60-80 wt% quartz powder, of which 20-30% is aminated nano-quartz powder (KH-550 modified); 15-30wt% styrene-acrylic emulsion; 5-10wt% gradient-responsive microcapsules, with a core of E-51 epoxy resin and microcrystalline encapsulated polyetheramine D230, and a capsule wall consisting of an inner layer of porous urea-formaldehyde resin (containing 5-8wt% nano-SiO2 pore-forming agent) and an outer layer of polyurethane (crosslinking degree 8.5-11.2%).

2. The microcapsule as described in claim 1, characterized in that... The breaking strength is 2.5±0.3MPa, the particle size is 20-100μm, and the wall thickness is 1-5μm.

3. The amination-modified nano-quartz powder as described in claim 1, with a particle size of 50-100 nm and a surface amino density ≥3.2 groups / nm. 2 (XPS measurement) 4. The coating preparation method includes an electrostatic self-assembly process: The microcapsules were treated with 0.5 wt% chitosan to a zeta potential of +35 ± 3 mV; Quartz powder was treated with 1.2 wt% sodium styrene sulfonate to a Zeta potential of -45 ± 3 mV; Mix at Re = 2500-3000 and 40±2℃ for 15±2 min.

5. The coating application method as described in claim 1, characterized in that: The thickness of a single wet film is 0.3-0.5 mm, and the moisture content of the substrate is ≤8%. The curing process is divided into three stages: 0-2h (25℃ / RH80%) → 2-8h (35℃ / RH60%) → 8-24h (natural curing at 25℃).

6. The self-healing method of the coating triggers dual-modal repair when the crack is ≤0.3mm: Primary repair: Microcapsules rupture to release epoxy resin, which fills the crack within 10 minutes; Secondary repair: The pH at the crack is greater than 12, which dissolves the nano-quartz powder and generates Si-OC covalent bonds. The enhanced repair is completed in 24 hours.

7. Application of the coatings described in any of claims 1-6 in the protection of cracks in concrete structures.

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