Authors:S. Reyes-de Vaaben, A. Aguilar, F. Avalos, and L. Ramos-de Valle
The effect of four nucleating agents on the crystallization of isotactic polypropylene (iPP) was studied by differential scanning
calorimetry (DSC) under isothermal and non-isothermal conditions. The nucleating agents are: carbon nanofibers (CNF), carbon
nanotubes (CNT), lithium benzoate and dimethyl-benzylidene sorbitol.
Avramișs model is used to analyze the isothermal crystallization kinetics of iPP.
Based on the increase in crystallization temperature (Tc) and the decrease in half-life time (τ½) for crystallization, the most efficient nucleating agents are the CNF and CNT, at concentrations as low as 0.001 mass%.
Sorbitol and lithium benzoate show to be less efficient, while the sorbitol needs to be present at concentrations above 0.05
mass% to even act as nucleating agent.
Benzoic acid, lithium benzoate, and sodium benzoate were tritiated with virtually 100% regioselectivity in the ortho-positions by the T-for-H exchange reaction with HTO in the presence of RhCl3.3H2O. The labeling of both alkali metal salts was favored by a factor of about 3 over that of benzoic acid. Methyl benzoate was essentially inactive in the present reaction.