Silicon carbide (SiC), as a high-performance reinforcing material, is used in Teflon (polytetrafluoroethylene, PTFE) non-stick coatings mainly to improve the mechanical strength, wear resistance and service life of the coating, while maintaining the original non-stick and chemical resistance of PTFE. The following are its specific application principles and implementation methods:
Core role: Enhance coating performance
Improved wear resistance:
Pure PTFE coating is soft and easily scratched by metal utensils. After adding silicon carbide (especially nano- or micron-sized particles), its ultra-high hardness (Mohs hardness 9.2, second only to diamond) forms a “skeleton support”, which significantly improves the coating’s scratch resistance.
Effect: The coating life can be extended by 3-5 times, suitable for high-frequency kitchen utensils (such as non-stick pans) or industrial equipment.
Adhesion enhancement:
PTFE has a weak bonding force with the metal substrate. Silicon carbide particles are embedded in the micropores on the surface of the substrate through physical anchoring, enhancing the mechanical bite force between the coating and the substrate.
Process coordination: The substrate needs to be sandblasted or chemically etched first to form a rough surface so that the silicon carbide particles and the substrate form an interlocking structure.
Improved thermal conductivity:
Pure PTFE has poor thermal conductivity (about 0.25 W/m·K), resulting in uneven heating. Silicon carbide has high thermal conductivity (120-490 W/m·K), which can improve the overall thermal conductivity of the coating.
Effect: Avoid coating decomposition caused by local overheating and extend service life (especially suitable for high-temperature cookers).
Key steps in application process
Silicon carbide pretreatment:
The particles need to be surface modified (such as silane coupling agent coating) to enhance compatibility with PTFE and prevent agglomeration.
Particle size control: 1-10 micron particles are commonly used. Too fine (nanoscale) is easy to agglomerate, and too coarse will affect the flatness of the coating.
Dispersion and mixing:
The modified silicon carbide is evenly dispersed in the PTFE emulsion (water-based or solvent-based), and high-speed shearing or ultrasonic treatment is used to ensure no agglomeration.
Typical addition ratio: 5%-15% (weight ratio), excessive amount will reduce non-stick properties.
Spraying and sintering:
After the mixed slurry is sprayed onto the substrate (such as an aluminum pot), it needs to be sintered at high temperature (PTFE melting temperature is about 327°C).
Silicon carbide remains stable during sintering (heat resistance > 1600°C) and is embedded in the PTFE matrix to form a composite structure.
The challenge of performance balance
Features Pure PTFE coating Silicon carbide reinforced PTFE coating Solution
Non-stick performance Excellent Slightly decreased Control the amount of addition ≤15%
Wear resistance Weak Improve 3-5 times Optimize particle size distribution
Coating thickness Thin (20-30μm) Need to be thickened to 40-60μm Multi-layer spraying process
Surface smoothness High May become rough Surface covered with a thin layer of pure PTFE (double coating)
Double coating technology:
Substrate → PTFE bottom layer containing silicon carbide (enhanced adhesion and wear resistance) → Pure PTFE surface layer (guarantee non-stick performance)
Typical application scenarios
High-end kitchenware:
Non-stick pans, baking trays, etc., subject to frequent scraping by metal spatulas.
Industrial parts:
Bearings, valve sealing surfaces, need to be corrosion-resistant and wear-resistant.
Mold release coating:
Rubber/plastic molding molds, reduce adhesion and extend cleaning cycles.
Comparison of other reinforcing fillers
Filler type Advantages Limitations Applicable scenarios
Silicon carbide Ultra-high hardness, high thermal conductivity High cost, easy to settle High temperature and wear-resistant environment
Graphene Super lubricity Difficult to disperse, extremely high cost Laboratory-grade high-end coating
Glass fiber Low cost, toughening Reduced non-stickiness Low-temperature industrial parts
Boron nitride Good lubricity Thermal conductivity is inferior to SiC Medium-temperature lubricating coating
Environmental and safety considerations
Food safety:
Silicon carbide itself is non-toxic (FDA certified), but it is necessary to ensure that the particles are completely coated in PTFE to avoid falling off.
High temperature stability:
Before the decomposition temperature of PTFE (＞400°C), silicon carbide does not react and there is no harmful release.
Summary
Silicon carbide acts as an “invisible armor” in Teflon coatings, compensating for the mechanical defects of PTFE through physical reinforcement mechanisms, while the double coating process balances wear resistance and non-stickiness. Its application embodies the essence of composite material design – achieving the optimal solution between conflicting properties (such as hardness vs. lubricity), ultimately extending the service life of PTFE coatings in harsh environments.