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Study on Preparation and Snow Melting Properties of UF Resin Phase Change Microcapsules

Road snow and ice accumulation in cold regions causes frequent traffic accidents, heavy highway maintenance costs, and serious pavement corrosion from traditional chloride deicing salts. Salt-based anti-icing agents continuously leach into soil and groundwater, triggering environmental pollution, while direct blending of phase change materials (PCM) into asphalt leads to severe paraffin leakage, reduced pavement strength, and short service life.

Microencapsulation solves core defects of bare PCM materials: encapsulate low-temperature n-tetradecane latent heat core inside rigid urea formaldehyde  resin shell to prevent leakage, isolate asphalt matrix, and release thermal latent heat to delay icing and melt snow automatically. UF resin material features high mechanical strength, good barrier performance, low cost and easy in-situ polymerization.

Raw Materials & Standard In-Situ Polymerization Process

Core Raw Materials List

  • Wall precursors: Urea, melamine, 37% formaldehyde solution (molar ratio U:M:HCHO = 1:3:10)
  • PCM core: n-tetradecane (melting point -10~10℃, latent heat 220 J/g)
  • Modifiers: Nano Al₂O₃ powder, SDS sodium dodecyl sulfate emulsifier
  • Auxiliaries: Ammonia (pH regulator), acetic acid (polycondensation catalyst), emulsified asphalt (coating carrier)

Four-Step Microcapsule Synthesis Workflow

  • Prepare MUF-UF prepolymer: Mix urea, melamine, formaldehyde, adjust pH=8 with ammonia, stir 600 r/min at 65℃ until transparent; separately prepare modified prepolymer with 1%/3% nano-Al₂O₃ added in advance.
  • Emulsify n-tetradecane core: Mix n-tetradecane and water (volume ratio 1:8), add 3%/5%/7%/9 SDS, stir 2000 r/min at 65℃ for 2h to form stable oil-in-water emulsion.
  • In-situ encapsulation: Blend prepolymer and core emulsion at mass ratio 1:1, drop acetic acid to pH 3–4, react 3h at 65℃ under high-speed stirring.
  • Terminate polymerization: Neutralize with ammonia to pH≈8, filter, wash, dry at 70℃ to obtain solid phase change microcapsule powder.

H3 Composite Coating Preparation

  • Mix microcapsule powder and emulsified asphalt at mass ratio 10:1 to form sprayable anti-icing snow melting coating, suitable for highway, urban road and parking lot asphalt surfaces.

Core Modification & Thermal Working Mechanism

Nano-Al₂O₃ Reinforcement Mechanism

Nano alumina nanoparticles disperse uniformly inside UF polymer shell, fill micro-pores and microcracks formed during polycondensation, enhance crosslink density, improve shell toughness and anti-breakage performance during mixing and pavement rolling, preventing n-tetradecane leakage.

Latent Heat Anti-Icing Principle

N-tetradecane core melts and absorbs ambient heat when temperature rises slightly; when pavement temperature drops to near freezing, PCM solidifies and releases stored latent heat, delaying surface temperature decline to block ice crystal nucleation and growth, and melt existing thin snow/ice layers.

UF Resin Shell Barrier Function

Compact urea formaldehyde resin wall isolates PCM paraffin from asphalt binder, avoids paraffin softening asphalt and reducing pavement mechanical strength, compatible with all common emulsified asphalt systems.

Industrial Production & Construction Guidelines

Optimized Full Formulation

  • Prepolymer: Urea:Melamine:Formaldehyde molar ratio =1:3:10, add 3% nano-Al₂O₃ by wall mass
  • Core emulsification: n-tetradecane:water volume ratio 1:1, 7% SDS emulsifier based on core weight
  • Microcapsule-asphalt coating mixing ratio: 10:1 mass ratio
  • Standard construction spread rate: 0.6 kg/m² single spraying

Production Process Key Controls

  • Emulsification stirring speed: 2000 r/min, hold 2h at 65℃ for uniform tiny oil droplets
  • Encapsulation pH strictly controlled 3–4, 3h constant temperature polycondensation to complete shell forming
  • Final drying temperature ≤70℃ to avoid premature PCM melting inside capsules

Pavement Construction Tips

  • Clean road surface dust and gravel before spraying coating to ensure adhesion
  • Apply single layer 0.6kg/m²; thin coating (<0.4kg/m²) insufficient for continuous snow melting
  • Suitable for highways, municipal roads, parking lots, bridge decks in temperate cold zones; not recommended for areas with long-term -10℃ below sustained extreme low temperature
  • Re-spray every 1–2 winter seasons to supplement microcapsule loss from pavement wear

Advantages & Existing Limitations

Core Advantages

  • Environmentally friendly, no chloride salt corrosion, zero soil/water pollution risk
  • Reusable latent heat storage, cut winter road maintenance labor and chemical deicing costs
  • UF microcapsule low production cost, compatible with existing asphalt spraying equipment
  • Dual performance: anti-freezing and automatic snow melting under -5℃ ambient temperature

Current Technical Limitations

  • Cannot sustain snow melting under prolonged extreme low temperature below -10℃
  • Pavement abrasion gradually wears off coating, requiring periodic re-spraying
  • High microcapsule addition slightly reduces coating fluidity, need low-speed stirring during mixing

FAQ

Q1: What’s the optimal nano-Al₂O₃ dosage for UF phase change microcapsules?

A: 3% mass fraction based on urea-formaldehyde wall material delivers the smoothest, crack-free spherical microcapsules with best shell mechanical toughness.

Q2: What SDS emulsifier percentage yields uniform n-tetradecane microcapsules?

A: 7wt% SDS relative to the n-tetradecane core prevents agglomeration and surface resin accumulation for perfect spherical capsule morphology.

Q3: What coating spread rate achieves effective road snow melting at -5℃?

A: 0.6 kg/m² single spray dosage can continuously melt snow for up to 90 minutes under -5℃ environment.

Q4: Can this UF microcapsule coating be reused for multiple snow events?

A: Yes, after temperature rebounds above 0℃ the n-tetradecane core solidifies and restores heat storage capacity, enabling several rounds of cyclic snow melting.

Q5: Why use urea-formaldehyde as PCM microcapsule shell?

A: UF resin features high barrier property, low raw material cost, mild in-situ polymerization conditions, strong adhesion with asphalt coating and no chemical incompatibility with paraffin core.

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