Thermal Bonding Methods

Thermal bonding via heat and pressure: (1) Calendar bonding—web passed through heated rollers (calendar rolls) under pressure, thermoplastic fibers/binder fibers (low-melt PET, PE/PP bicomponent typically 10-50% of web) melting at bond points creating discrete bonded areas. Roll patterns: point bonding (5-30% bond area creating soft, bulky fabric for hygiene applications—diapers, feminine care), area bonding (30-60% bond area for strength, used in interlinings, technical textiles), and embossing (decorative patterns with bonding). Bonding temperature 110-180°C depending on polymer, pressure 20-100 kN/m, speeds 50-500 m/min. Properties: soft (low bond area) to stiff (high bond area), strength 20-150 N/5cm, controlled air permeability. (2) Through-air bonding—hot air (120-180°C) passed through web, uniformly melting binder fibers creating soft, bulky fabrics with uniform bonding (vs. point-bonded discrete spots). Better softness, bulk retention (porosity 80-95%), used for premium hygiene products (elastic-like feel), slower (30-150 m/min) and energy-intensive limiting adoption. (3) Ultrasonic bonding—high-frequency vibration (20-40 kHz) generating heat at fiber contact points via friction bonding thermoplastic fibers, localized bonding (5-15% area), good hand, used for synthetic nonwovens. Applications: hygiene products (calendar/through-air), interlinings (calendar), medical disposables, filtration.