ISOTACTIC POLYPROPYLENE HYDROGENATED OLIGO(CYCLOPENTADIENE) BLENDS .2. TENSILE-STRESS STRAIN AND MORPHOLOGICAL BEHAVIOR OF ANNEALED SAMPLES

Mechanical tensile tests and morphological analyses were carried out o n samples of isotactic polypropylene/hydrogenated oligo(cyclopentadien e) (iPP/HOCP) blends. The blends were obtained by melt mixing in a Bra bender-like apparatus. Sheets of such blends were prepared by moulding the material under pressure, quenching in iced water and then anneali ng them in an oven at 140-degrees-C under vacuum for 24 h. Stress-stra in tensile tests, previously obtained at room temperature, were perfor med at higher temperatures (80-degrees-C and 100-degrees-C). Morpholog y observations were performed by scanning electron microscopy after tr eatment of the blends with two different etching solvents (n-heptane a nd chloroform) at their boiling temperatures for various times in orde r to dissolve the HOCP component. An acid solution with a strong oxidi zing action was used as well. In all the investigated blends (from pur e iPP to up to 80% HOCP in the blend) the iPP molecules provide the ma terial interconnection, as evidenced by fibre formation. The transitio n from ductile to brittle in the mechanical behaviour depends on tempe rature and composition.