Carbon Fibre Surface Treatment and Sizing
topic
Surface treatment: electrolytic oxidation in aqueous electrolyte (NH₄HCO₃, NaOH) creates oxygen functional groups (carboxyl, hydroxyl, carbonyl) increasing surface energy from 40-50 mN/m to 60-70 mN/m and surface area 10-100×. Sizing (1-2% by weight): epoxy-compatible (DGEBA-based), BMI-compatible, or thermoplastic-compatible (PEEK, PA) containing film formers and coupling agents. Improves interfacial shear strength from 30-40 MPa (unsized) to 70-100 MPa (sized).
Role
Pristine carbon fibre surface is chemically inert and smooth (low adhesion); surface treatment and sizing are essential for composite performance, affecting interlaminar shear strength, impact resistance, and environmental durability.