Effect of aliphatic chain in dicarboxylic acids on non-isothermal crystallization and mechanical behavior of titanium dioxide/iPP composites

摘要

Non-isothermal crystallization kinetics of isotactic polypropylene (iPP) and its composites prepared with functionalized titanium dioxide (TiO2) were investigated by varying both heating rate and dosage of functionalized particles. Jeziorny's and Mo's methods were used to describe the non-isothermal crystallization process. The behavior of crystallization activation energy as a function of the crystallinity degree was evaluated by applying an isoconversional method. The modification of the TiO2 surface was done by testing three different carboxylic acids: glutaric, pimelic and azelaic acid and these particles were tested at different concentrations in iPP, 0.1, 0.5 and 1 % w/w; which had a high effect on the crystallization process of the polymer matrix. It was demonstrated the efficiency of the dry basis chemical reaction as a method to modify with dicarboxylic acids the surface of TiO2 particles. Such organic coatings chemically bonded to the surface of the TiO2 promoted a better incorporation of the iPP chains during crystallization and there is a clear effect of the length of dicarboxylic acids since the acids with more carbons, pimelic and azelaic, decreased the time to reach the crystalline state. Besides, the values of Young's modulus were modified by functionalized TiO2 particles, being the acid with the longest chain (azelaic acid) the one that more increased this parameter.