INFLUENCE OF MOLECULAR-MASS, THERMAL-TREATMENT AND NUCLEATING-AGENT ON STRUCTURE AND FRACTURE-TOUGHNESS OF ISOTACTIC POLYPROPYLENE

The influence of processing, crystallization conditions and molecular characteristics on the fracture behaviour of isotactic polypropylene o btained by a new catalyst system was investigated. The sample specimen s were prepared by using two extreme crystallization conditions - quen ching or slow crystallization - in order to obtain crystals and amorph ous phases with different structure. Interesting correlations between fracture parameters and some morphological parameters such as long spa cing and lamellar thickness of the samples were found. The SEM fractog raphic analysis provides useful information on the influence of factor s such as molecular weight, spherulite size and undercooling. Nucleati ng agents were used to tailor the dimensions of spherulites.