Scanning electron microscopy and ultrasonic studies of drawn polypropylenes

Ultrasonic measurements and scanning electron microscope studies are reported on a series of drawn samples of polypropylene. The ultrasonic measurements were performed over the frequency range 15 to 35 MHz and over a temperature range 283 to 343K. The scanning electron microscope observations confirmed the predictions from density data that the ‘void’ content initially increases on drawing and then decreases. The acoustic measurements on the samples with the highest draw ratios indicated that severe restriction of the motion of the polymer occurs when the fibrous structure is formed.