Modification of physical properties of polylactide
Polimery 2005, No 7-8, 562
In the article the results of studies on modification of poly(L-lactide) (PLA) via influencing its thermal history, artificial nucleation of crystallization, plasticization or filling with montmorillonite were summarized. It was found that PLA heated from the glassy state and isothermally cooled from the molten state, crystallized in the form of spherulites (Fig. 1 b and c). Size of spherulites increases with temperature of isothermal crystallization and simultaneously strength at break deteriorates (Fig. 2). Effectiveness of various agents nucleating the crystallization has been compared and effect of the agent content on the size of spherulites has been shown on the example of talc (Fig. 4, 5, Table 1). It was demonstrated that PLA plasticization with poly(oxyethylene glycol) (PEG) lowered glass transition temperature Tg, as well as temperature of non-isothermal crystallization during heating from the glassy state (Fig. 6). Plasticized PLA shows bigger ability to plastic deformation especially in case of amorphous samples (Fig. 7 and 8). Filling of PLA with montmorillonite causes increase in modulus of elasticity (Fig. 11a). Plasticization of both non-filled and filled PLA accelerates crystallization but presence of montmorillonite decreases crystallinity degree (Fig. 9). Investigations by WAXS method allowed to state that nanocomposites with montmorillonite showed intercalated structures (Fig. 10).
Key words: poly(L-lactide), plasticization, nucleation of crystallization, montmorillonite, mechanical properties