ULTRASONIC CHARACTERIZATION OF POLYMERS UNDER SIMULATED PROCESSING CONDITIONS

A method and an apparatus for ultrasonically characterizing polymer materials under simulated processing conditions are disclosed. According to the invention, a sample of a polymer is held in confinement between two axially aligned buffer rods having opposed parallel end surfaces spaced from one another to define a gap filled with the polymer sample, the polymer sample being acoustically coupled to the opposed end surfaces of the buffer rods. Ultrasonic waves are transmitted through one of the buffer rods in a direction toward the polymer sample for interaction therewith, and the polymer sample is subjected to controlled temperature or pressure variations over a predetermined period of time, the variation in temperature or pressure being effected via the buffer rods. Phase and amplitude variations of the ultrasonic waves having interacted with the polymer sample are continuously monitored as well as thickness variations of the polymer sample, over the predetermined period of time, to obtain data comprising phase, amplitude and thickness values measured as a function of temperature or pressure and time, which are then processed to derive characteristic parameters providing both a thermodynamic and viscoelastic characterization of the polymer. The present invention enables one to more adequately control the polymer processing conditions, with a view to optimizing the properties of a given polymer for a given application.