Apparatus and methods for measuring extensional rheological properties of a material

An apparatus for measuring an extensional rheological property of a fluid, the apparatus comprising

• (a) opposed surfaced defining a sample site disposed therebetween and adapted for axial motion to vary the vertical dimension of the sample site;
• (b) a plunger assembly for varying the vertical dimension of the sample site and for varying the rate of axial movement of at least one of the surfaces;
• (c) a light source for directing a light beam at the sample site;
• and
• (d) a light detector for sensing light passing through the sample site.

An apparatus for measuring an extensional rheological property of a fluid, the apparatus comprising

• (a) opposed surfaces defining a sample site disposed therebetween and adapted for user-defined axial motion to vary the vertical dimension of the sample site.
• (b) a light source for directing a light beam at the sample site;
• (c) a light detector for sensing light passing through the sample site;
• and
• (d) a data analysis unit which converts data from the light detector to an extensional rheological property of the fluid sample.

A method for obtaining an extensional rheological property of a fluid sample comprising the steps of:

• (a) stretching the fluid sample to form a fluid filament at a user-defined rate;
• (b) measuring a time profile of a diameter of the fluid filament;
• and
• (c) analyzing the time profile of the diameter of the fluid filament to obtain an extensional rheological property of the fluid sample, wherein analyzing the time profile comprises converting the time profile to a curve of viscosity versus strain.

A portable apparatus for measuring an extensional rheological property of a fluid, the portable apparatus comprising:

• a body portion comprising:
• opposed surfaces defining a sample site disposed therebetween and adapted for axial motion to vary the vertical dimension of the sample site;
• a housing about the sample site which permits specification of ambient conditions;
• a light source for directing a light beam at the sample site;
• and
• a light detector for sensing light passing through the sample site;
• and
• a handle portion in communication with the body portion, the handle portion having a data processing device.

A method for measuring an extensional rheological property of a fluid, comprising:

• measuring time varying diameter data of a fluid filament;
• displaying effective extensional viscosity;
• and
• further processing the data to determine rheological parameters using a plurality of models, including a model comprising using the diameter data in a non-linear form of an equation having a linear term, an exponential term and an offset term.