Isothermal and Nonisothermal Cold Crystallization Behaviors of Biodegradable Poly(L-lactide)/Octavinyl-Polyhedral Oligomeric Silsesquioxanes Nanocomposites

Isothermal and nonisothermal cold crystallization behaviors of biodegradable poly(L-lactide) (PLLA)/octavinyl-polyhedral oligomeric silsesquioxanes (ovi-POSS) nanocomposites at low ovi-POSS loadings were investigated in this work. For both neat PLLA and its nanocomposites, the overall isothermal cold crystallization rates increase with increasing crystallization temperature, moreover, the overall isothermal cold crystallization rates of PLLA increase With increasing the ovi-POSS loading in the nanocomposites relative to neat PLLA, indicative of the nucleating agent effect of ovi-POSS. Crystallization mechanism and crystal structure of PLLA remain unchanged despite the ovi-POSS loading. For the nonisothermal cold crystallization, the crystallization process of PLLA is accelerated by increasing both heating rate and the ovi-POSS loading. The Ozawa equation failed to fit the crystallization process, while the Tobin equation Could describe it well The activation energies of nonisothermal cold crystallization were calculated by the Kissinger method, which increase with increasing the ovi-POSS loading in the nanocomposites relative to neat PLLA.