SynopsisPolyacrylamide and poly(acrylamide-co-acrylic acid) flocculant solutions were subjected to Shear degradation in a rotating cone instrument. At constant shear rate, shear degradation was minimid (highat limiting intrinsic viscosity) by the use of a lower solution concentration and high ionic strength of the polymer solution. Resistance to shear degradation also increased with increasing anionic character of the polyacrylamide. Sheared polymers showed reduced performance as flocculants of coal preparation plant tailings, their major commercial application in the U.K. Partially anionic polyacrylamide solutions were completely inactivated in the presence of certain multivalent cations. Aluminium, ironlIl, lead, copper, and zinc ions formed complexes with the carboxyl group on the polymer, resulting in zero flocculation activity. Nonionic polyacrylamides were unaffected. Viscosity-aging of polyacrylamide solutions was observed over a period of several months, but was insu5cient to affect the flocculation activity. In the presence of 3% ethanol or methanol, no aging was observed in solutions stored for over a year.

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The Helical Screw Rheometer (HSR) is being evaluated for rheological measurements of fluid food suspensions. the HSR consists of a helical screw enclosed in a tight fitting cylinder. With a closed system the inner screw is rotated creating a linearly increasing pressure differential along the axis of the screw, which is proportional to the viscosity of the fluid. This paper presents theoretical one‐ and two‐dimensional flow analyses for Newtonian fluids using both rectangular and cylindrical coordinates. For non‐Newtonian fluids a one‐dimensional rectangular analysis was developed using the power law model.

To study the strength advantages of pressurized cans used for food packaging, two indicators of can strength, maximum axial load and maximum external pressure, were investigated experimentally. Unbeaded 303 × 406 steel cans having several thicknesses and tempers with various internal pressures were tested. Also tested were beaded steel cans and aluminum cans with 206 × 406 dimensions. Failure of the cans was by both buckling and yielding. the results indicated that steel can thicknesses could be significantly reduced, and beading eliminated, by using internal pressure to supplement can strength.

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