highviscosity

High viscosity refers to fluids that offer considerable resistance to flow, resulting in slow deformation under applied stress. It is primarily quantified by dynamic viscosity (mu), the ratio of shear stress to shear rate, measured in pascal-seconds (Pa·s). In everyday practice, viscosity is often reported in centipoise (cP) or millipascal-seconds (mPa·s), where 1 cP = 1 mPa·s, and 1 Pa·s = 1000 mPa·s. Kinematic viscosity (nu) is dynamic viscosity divided by density and is expressed in square millimeters per second (mm^2/s) or centistokes (cSt).

Factors influencing high viscosity include temperature, composition, and molecular structure. Temperature typically has a strong inverse effect: higher temperatures lower viscosity as molecular mobility increases. Pressure effects are generally small for liquids under ordinary conditions. More complex formulations with high molecular weight, extensive branching, or polymer content raise viscosity significantly.

Non-Newtonian behavior is common among high-viscosity fluids. Some exhibit shear-thinning, where viscosity decreases with increasing shear rate; others show shear-thickening or thixotropy, where viscosity depends on time and stress history. Such behavior requires rheological testing to characterize viscosity across different conditions.

Measurement methods include capillary viscometers, which determine dynamic viscosity from flow time, and rotational viscometers or rheometers, which apply controlled shear rates and measure response. Applications span lubricants, syrups and food syrups, paints and coatings, resins, and asphalt. Processing high-viscosity materials often requires heating, specialized pumps, and equipment designed to handle substantial resistance to flow, along with safe handling and storage practices.