REAL-TIME CRYO-DEFORMATION OF POLYPROPYLENE AND IMPACT-MODIFIED POLYPROPYLENE IN THE TRANSMISSION ELECTRON-MICROSCOPE

Dynamic plane-stress failure has been observed directly in the transmi ssion electron microscope as a function of temperature using a commerc ially available cooling/straining holder in conjunction with a copper deformation cartridge. The low-temperature cooling stage permits studi es of the ductile-brittle transition when the transition is between +2 3 and -170 degrees C. A change in deformation mode was observed on the submicrometre level for polypropylene and impact-modified polypropyle ne. At room temperature, polypropylene and impact-modified polypropyle ne deform by shear yielding. Below the ductile-brittle transition the polymer chain mobility is curtailed and crazing dominates. The stage a llows observation of the deformation at varying temperature, and event s occurring during the deformation can be recorded in real time using a CCD camera.