Abstract: A method and apparatus for ultrasonically characterizing a polymer melt flowing in a predetermined direction between two opposed parallel surfaces spaced from one another to define a gap filled with polymer are disclosed. Ultrasonic pulses are propagated through the polymer melt between the two surfaces in a direction normal to the direction of flow for interaction with the polymer, the ultrasonic pulses having a duration such as to prevent successive echoes from overlapping with one another while reverberating between the two surfaces. The time delay between two echoes exiting from the polymer melt and generated from each pulse having interacted with the polymer is continuously monitored while simultaneously monitoring amplitude variations of the two echoes, to provide output signals representative of ultrasonic velocity and attenuation in the polymer melt. These output signals are processed to obtain data comprising ultrasonic velocity and attenuation values measured simultaneously as a function of time.

Abstract: An ultrasonic interferometry technique for composite structures such as metal/polymer/metal structures exhibits high sensitivity to interfacial properties, even at usual ultrasonic wavelengths. A model for the ultrasonic response of multilayered media accounts for viscoelasticity. Results of numerical calculations point out scaling features for interfacial properties in terms of specific stiffness S. A method is provided for characterizing the interfacial adhesion in a multilayer composite in terms of the parameter S. The multilayer composite is ultrasonically irradiated with a pulsed signal to obtain a signal characteristic of the interfacial adhesion between the multilayers. A model is provided of the multilayer composite that includes at least two additional layers which model the behaviour of the interface between the composite layers.

Abstract: 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.

Abstract: The density of polyethylene is determined by measuring the velocity of ultrasound through the material. The determination of density is based on the correlation between the velocity of ultrasound in semi-crystalline materials and their density, and involves the measurement of time delays of a transmitted ultrasonic pulse from each of the front surface of the material the rear surface of the material and a reflector which are immersed in a liquid. Operating within a selected frequency range provides measurements of density while eliminating viscoelastic effects.