No abstract

Polycaprolactone matrix composites reinforced with natural and chemically treated coir were prepared in a laboratory internal mixer and studied by differential scanning calorimetry (DSC) and tensile tests. The aim of this work was to evaluate the influence of the filler and its surface modification on the rheological, mechanical, and crystallization behaviors of the composites. According to rheological analysis, the higher the filler content, the higher the viscosity of the material and the lower its local pseudoplasticity index. DSC analyses showed that the presence of coir anticipates the crystallization process; however, it does not affect the absolute crystallinity of the matrix. Mechanical tests indicated that an increase in filler content leads to an increase in Young's modulus and a decrease in the elongation at break. Additionally, composites with filler content from 20% can stand higher tensile stress than the neat polymer, and this effect is intensified by the surface modification applied to the filler. POLYM.

No abstract

The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

Polymeric polycaprolactone (PCL) matrix composites reinforced with alumina and niobium pentoxide were prepared in a laboratory internal mixer and studied by differential scanning calorimetry (DSC), tensile and impact tests, in addition to the particle distribution in the matrix. The objective of this study was to evaluate the influence of the oxide content on the rheology, crystallization, and mechanical properties of these composites. According to the rheological analysis, the composites were well mixed and the polymer matrix used in the composites can be considered thermally stable during processing. The effect of the fillers on degradation during processing was minimal. DSC analyses indicate that, in general, the increase in the filler content does not change the crystallization temperature, irrespectively of the oxide added. For the niobium pentoxide composites, crystallinity does not appear to be affected by an increase in filler content or cooling rate. Both tensile strength and elongation at break decreased with filler addition while impact strength decreased and Young's modulus was apparently unaffected. There was good distribution of the oxide particles in the polymer matrix.