Efeito nucleante de cargas minerais na cristalização dinâmica do polipropileno isotático.

Abstract

There is considerable interest on the use of organic as well as inorganic nucleating agents for semi-crystalline thermoplastics. The use of mineral fillers as inorganic nucleating agents has been largely studied, even though these agents are not quite as efficient are the organic ones. The addition of mineral fillers onto polymers often improve mechanical and physical properties, lower costs as well as increase the degree of crystallinity, melt and crystallization temperatures of semi-crystalline polymers. In this work the efficiency of conventional (talc, calcium carbonate) and nonconventional (attapulgite and bentonite) mineral fillers as nucleating agents for isotactic polypropylene were evaluated by differential scanning calorimetry (DSC). The results showed that attapulgite and talc to exhibit the highest nucleating efficiency (61,22 % at 2 % attapulgite content and 41,59 at 5 % talc content) among the fillers under study. The Ozawa method was used to determine the kinetics of non-isothermal crystallization of PP nucleated by attapulgite and talc. Three filler concentrations (1,2 and 5 % w/w) and three cooling rales (2, 5 and 10 °C/min) were used in this study. It was shoron that Ozawa's " n ' 1 expoent increased with Tc, varying from 0,3-3,8 which taken as an indication o f morphological changes from fibrillar to spherulilic structures.