Non-isothermal crystallization analysis of isotactic polypropylene filled with titanium dioxide particles modified by a dicarboxylic acid

Used of Chemically Modified Titanium Dioxide Particles to Mediate the Non-isothermal Cold Crystallization of Poly(latic acid)

“…As can be seen in Fig. 9, the composites exhibit higher crystallization rates compared to pure PLA, even at low values, showing the lowest values for PLA/n-TiO2, followed by PLA/s-TiO2 and PLA/c-TiO2; this is attributable to the fact that in composite samples, fillers can act as nucleating agents, improving the efficiency of nucleation activity and leading to a higher crystallization rate than pure PLA [51,75] It is also clear, that a high leads to a shorter crystallization time, since many nucleation centers are formed, which accelerates the crystallization process. Table 2.…”

“…The modelling of non-isothermal crystallization implies a knowledge of the kinetics and morphology developed at each isothermal crystallization temperature ( ). The Avrami equation, which is based on the assumption of a constant crystallization temperature, is given as [51]:…”

“…The complete results of all experiments are given in Table 1 to evaluate the effect of the heating rate on the relative crystallinity as a function of time, ( ); these calculations were obtained by integrating the area under the curve from the data of the crystallization thermograms. Table 1 also shows the crystallization time ( ) for various degrees of crystallinity, as well as the apparent crystallization period (∆ ), which is the difference between the end and the beginning of the cool crystallization process for each [24,51]. As can be seen in Table 1, the required time to reach a 0.99 of relative crystallinity substantial decreases when the cooling rate is higher.…”

“…From the literature [31,75], it is known that ∆ , at which the arrangement of the chain segments within the crystalline lattice occurs, decreases when is greater since the capacity of chain movement decreases at lower temperatures; but at low values of , they have enough time to form large crystals. The addition of fillers in the PLA structure affects the non-isothermal crystallization process [1,27,51] as shown in Figures 6 and 7. For example, at medium heating rates, the addition of external particles (n-TiO2, c-TiO2 and s-TiO2) decreases crystallization times; whereas at high rates, the crystallization time seems to remain the same.…”

“…Due to their inherent characteristics, these compounds have been used in polymer matrices to coat the metal oxide particles with a thin layer around since the bond between the TiO2 particle surface and the organic molecules provides thermal stability. This allows these functionalized particles to be used in an extrusion process at temperatures above the boiling point of the pure substances used to modify the TiO2 [51]. In composites of polymer and nanoparticles, the adhesion between the polymer and particles depends strongly on the crystalline structure at the interface.…”