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A pseudoplastic material is one in which viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
 decreases with increasing rate of shear
Shear stress

File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
 (also termed shear thinning). This property is found in certain complex solutions, such as ketchup
Ketchup

Ketchup, also known as tomato ketchup, tomato sauce, red sauce is a condiment, usually made from tomatoes. The primary ingredients in a typical modern ketchup are tomato concentrate, spirit vinegar, milk, corn syrup, or other sugar, edible salt, spice and herb extracts , spice and garlic powder....
, whipped cream
Whipped cream

Whipped cream is cream, often sweetened, whipped with air. Cream with 30% or more fat can be mixed with air, and the resulting colloid is roughly double the volume of the original cream as air bubbles are captured in a network of fat droplets....
, blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
, paint
Paint

Paint is any liquid, liquifiable, or mastic composition which after application to a Substrate in a thin layer is converted to an opaque solid film....
, and nail polish
Nail polish

Nail polish or nail varnish is a lacquer that is applied to the nail s of both the fingers and toes, usually cosmetically, but also as protection for the nails....
. It is also a common property of polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 solutions and molten polymers. Pseudoplasticity can be demonstrated by the manner in which shaking a bottle of ketchup causes the contents to undergo an unpredictable change in viscosity.






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Encyclopedia


A pseudoplastic material is one in which viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
 decreases with increasing rate of shear
Shear stress

File:Shear stress.JPGA shear stress, denoted , is defined as a stress which is applied parallel or tangent to a face of a material, as opposed to a normal stress which is applied perpendicularly....
 (also termed shear thinning). This property is found in certain complex solutions, such as ketchup
Ketchup

Ketchup, also known as tomato ketchup, tomato sauce, red sauce is a condiment, usually made from tomatoes. The primary ingredients in a typical modern ketchup are tomato concentrate, spirit vinegar, milk, corn syrup, or other sugar, edible salt, spice and herb extracts , spice and garlic powder....
, whipped cream
Whipped cream

Whipped cream is cream, often sweetened, whipped with air. Cream with 30% or more fat can be mixed with air, and the resulting colloid is roughly double the volume of the original cream as air bubbles are captured in a network of fat droplets....
, blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
, paint
Paint

Paint is any liquid, liquifiable, or mastic composition which after application to a Substrate in a thin layer is converted to an opaque solid film....
, and nail polish
Nail polish

Nail polish or nail varnish is a lacquer that is applied to the nail s of both the fingers and toes, usually cosmetically, but also as protection for the nails....
. It is also a common property of polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 solutions and molten polymers. Pseudoplasticity can be demonstrated by the manner in which shaking a bottle of ketchup causes the contents to undergo an unpredictable change in viscosity. The force causes it to go from being thick like honey to flowing like water.

Unlike a thixotropic fluid, shear thinning fluid viscosity decreases with increasing shear rate, while thixotropic fluid viscosity decreases over time at a constant shear rate.

Everyday Examples


Toothpaste
Toothpaste

Toothpaste is a paste or gel dentifrice used to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it can aid in the removal of dental plaque and food from the teeth, aid in the elimination and/or masking of halitosis and deliver active ingredients such as fluoride or xylitol to prevent tooth...
, ketchup, and modern paint
Paint

Paint is any liquid, liquifiable, or mastic composition which after application to a Substrate in a thin layer is converted to an opaque solid film....
s are all pseudoplastic materials, although they are often mis-labeled as being thixotropic. When squeezed out of a tube, toothpaste flows easily but will set-up on the toothbrush. When shaken or squeezed out of a bottle, ketchup will thin and flow readily but will retain its shape on a burger or plate. When modern paints are applied the shear created by the brush or roller will allow them to thin and wet out the surface evenly. Once applied the paints regain their higher viscosity which avoids drips and runs.

External links

  • NASA
    NASA

    The National Aeronautics and Space Administration is an agency of the Federal government of the United States, responsible for the nation's public list of space agencies....
     April 25 2008


See also

  • Non-Newtonian fluid
    Non-Newtonian fluid

    A non-Newtonian fluid is a fluid whose flow properties are not described by a single constant value of viscosity. Many polymer solutions and molten polymers are non-Newtonian fluids, as are many commonly found substances such as ketchup, starch suspensions, paint, blood and shampoo....
  • Power-law fluid
    Power-law fluid

    A Power-law fluid is a type of generalized Newtonian fluid for which the shear stress, τ, is given bywhere:*K is the flow consistency index ,...
  • Dilatant
    Dilatant

    A dilatant material is one in which viscosity increases with the rate of shear stress. Such a shear thickening fluid, also known by the acronym STF, is an example of a non-Newtonian fluid....
  • Rheology
    Rheology

    Rheology is the study of the flow of matter: mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically....
  • Kaye effect
    Kaye Effect

    The Kaye Effect is a property of complex liquids which was first described by the United Kingdom engineer Alan Kaye in 1963.While pouring one viscous mixture of an organic liquid onto a surface, the surface suddenly spouted an upcoming jet of liquid which merged with the downgoing one....
  • Thixotropy
    Thixotropy

    Thixotropy is the property of some Non-Newtonian fluid Power-law fluid fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear stress, the lower is its viscosity....