ULTRASONIC BEHAVIOR OF POLYMER BLENDS

During the last few years, improvements in control strategies became a necessity, with controls being targeted on material properties. The e ver-increasing demand for polymer blends spells the need for in-line i nstrumentation capable of monitoring blend properties such as morpholo gy. Since ultrasonics have proved to be sensitive to properties of mul tiphase materials, their performance for discriminating blend morpholo gy was explored here. In-line and off-line (static, with no flow) ultr asonic measurements were made on different blends of polystyrene (PS), polyethylene (PE), and polypropylene (PP) for various viscosity ratio s, and over the entire range of composition. Blends were compounded on a ZSK-30 Werner & Pfleiderer intermeshing co-rotating twin-screw extr uder, In-line ultrasonic measurements were performed on both single-sc rew and twin-screw extruders. Ultrasonic properties (velocity and atte nuation) were found to vary approximately linearly with composition. M ixing rules were evaluated for the description of ultrasonic behavior For the attenuation measurements, the positive deviations from these r ules were found significant. The additional attenuation was attributed to scattering generated by the presence of the minor phase inclusions .