The United States of America As Represented by the United States

Union Carbide Corporation

Montgomery T Shaw

Stuart J Kurtz

Roger L Clough

James H Aubert

Edward M Russick

Carlos A Quintana

Terry A De Rossett

John G Curro

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the resultant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Means for subjecting such a solvent to one-dimensional cooling are also provided. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 .mu.m and a volume such that the foams have a length greater than 1 cm are provided.

Low density microcellular foams

Method and apparatus for testing thermoplastic material comprising: passing as a stream a fractional, continuous, molten and flowable sample of the material to and successively through each of either a controllable pumping zone maintained at constant temperature and pressure or controllable pressure zone maintained at constant flow rate and temperature, and a die zone to form a continuous strand of the material; measuring the viscosity of the material in the pumping and die zones; providing a measurement of elasticity by obtaining a measurement of percentage of cross-section area swell in the strand in passage from the die zone over a constant length distance downstream of a point of strand marking to a point of strand marking to a point of mark sensing; and combining the viscosity measurement with the elasticity measurement to provide fuller rheological characterization data for the material.

Pheological measurement method and apparatus

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Mansfield Center, CT, United States of America

Montgomery T Shaw