Viscosity

Viscosity is a measure of a fluid's (liquid or gas) resistance to flow, reflecting the magnitude of its internal friction. In foreign trade, viscosity is an important quality indicator for products such as chemicals, lubricants, coatings, inks, and food, directly affecting product performance, processing technology, and applicability. Usage scenarios include: contract specifications, quality inspection reports, product manuals, letter of credit terms, etc. Precautions: 1) Specify test conditions such as temperature and shear rate, because viscosity varies significantly with temperature; 2) Agree on test standards such as ASTM D445, ISO 3104 to avoid disputes arising from different methods; 3) Distinguish between dynamic viscosity (absolute viscosity, unit Pa·s or cP) and kinematic viscosity (unit cSt); the two must not be confused; 4) Differentiate from terms such as density and consistency: viscosity emphasizes flowability, density is the mass-to-volume ratio, and consistency is often a sensory description. Foreign trade practitioners should precisely specify the viscosity range, test method, and tolerance in the contract to prevent disputes over delivery quality.