Viscosity
What is viscosity?
Viscosity describes the flow properties or thickness of adhesives and other liquids. It significantly determines processing behavior, wetting properties, and dosing capability of adhesives. Viscosity is measured in Pascal-seconds (Pa·s) or millipascal-seconds (mPa·s).
Viscosity ranges of adhesives
- Low viscosity: 1-100 mPa·s for deep penetration and impregnation
- Medium viscosity: 100-10,000 mPa·s for standard applications
- High viscosity: 10,000-100,000 mPa·s for vertical applications
- Paste-like: Over 100,000 mPa·s for structural bonding
- Thixotropic: Shear-thinning for controlled application
Factors influencing viscosity
- Temperature: Higher temperatures reduce viscosity
- Shear rate: Shear thinning in many adhesives
- Filler content: Fillers significantly increase viscosity
- Molecular weight: Longer polymer chains = higher viscosity
- Solvent content: Solvents reduce viscosity
Measurement methods
- Rotational viscometer: Standard measurement method for most adhesives
- Capillary viscometer: For low-viscosity systems
- Cone-plate rheometer: For temperature-dependent measurements
- Brookfield viscometer: Industry standard for quality control
Importance for processing
- Dosing: Low viscosity for precise dosing
- Wetting: Optimal viscosity for complete surface wetting
- Flow behavior: Control of adhesive flow after application
- Layer thickness: Higher viscosity for thicker adhesive layers
- Dripping behavior: Prevention of drop formation in vertical applications
Application-specific requirements
- Impregnation: Very low viscosity for penetration into pores
- Gap filling: Medium viscosity for uniform layer thickness
- Structural bonding: Higher viscosity for load-bearing connections
- Sealing applications: Paste-like consistency for dimensional stability
Viscosity modification
- Temperature control: Heating temporarily reduces viscosity
- Dilution: Addition of reactive diluents
- Fillers: Addition of rheological additives for thixotropy
- Polymer modification: Adjustment of molecular weight
DELO Viscosity Solutions
- Adhesive systems in various viscosity ranges
- Application consulting for optimal viscosity selection
- Laboratory service for viscosity measurements
Do you need adhesives with specific viscosity?
