Structure and kinetic regulations of PP-R/PPH-g-MAH/Al(OH)3 based nanocomposites crystallization

The article presents the results of studies of the influence of aluminum hydroxide concentration on the crystallization process regularities of nanocomposites based on compatibilized polypropylene random copolymer and aluminum hydroxide (PP-R/PPH-g-MAH/Al(OH)3). The isothermal crystallization kinetics of compatibilized polypropylene random copolymer composites containing 1, 3, 5, 10, 20, 30 and 50 wt. % of aluminum hydroxide was determined by the stepwise dilatometry method using the Kolmogorov-Avrami equation. The crystallization behaviors of composites were investigated on an IIRT-1 device converted into a dilatometer, in the process of stepwise cooling of samples under a load of 5.3 kg. In this study, maleic anhydride functionalized homopolypropylene (PPH-g-MAH) was employed as a compatibilizer to enhance the compatibility between the PP-R and Al(OH)3. Considering the dependence of specific volume and free specific volume on temperature, the first-order phase transition was established and the glass transition temperature values ​​of the composites were determined. The mechanism of formation and development of crystallization centers in the region of the first-order phase transition was investigated. The obtained values ​​of “n” prove that the mechanism or nature of the growth of crystallization centers changes into three-dimensional spherulitic - two-dimensional disc-shaped - one-dimensional rod-shaped with an increase in the amount of aluminum hydroxide in composite. The study of the temperature dependence of the specific volume for the studied samples showed that the first order phase transition occurs at a temperature of 125°C. It was determined that the second order phase transition temperature (the glass transition temperature determined by the dilatometric method) increases with the increase in the amount of filler.