Study of Mechanical Responses and Thermal Expansion of CNF-modified Polyester Nanocomposites Processed by Different Mixing Systems

摘要

In this study, different dispersion techniques such as sonication at high frequency, mechanical mixing, and magnetic stirring methods were employed to infuse 0.1 to 0.4 wt.% carbon nanofiber (CNF) into polyester matrix to study the influence of CNF on mechanical and thermal properties of the polyester nanocomposites. Dispersion of CNF studied using scanning electron microscopy (SEM) micrographs revealed excellent dispersion of CNF using sonication when 0.2 wt.% CNF was mixed in polyester resulting in enhanced mechanical response. On the other hand, agglomerations were observed in samples prepared with other mixing methods. Polyester with 0.2 wt.% CNF samples prepared by sonication resulted in 88% and 16% increase in flexural strength and modulus, respectively, over neat samples. Quasi-static compression tests showed similar increasing trend with addition of 0.2 wt.% CNF. Dynamic mechanical analysis (DMA) showed 35% and 5°C improvement in the storage modulus and glass transition temperature (T_g), respectively, in the 0.2 wt.% loaded samples. Thermal mechanical analysis (TMA) performed on neat and samples with 0.2 wt.% CNF showed lower coefficient of thermal expansion (CTE) in nanophased sample compared to neat. Fracture morphology evaluated using SEM revealed relatively rougher surface in CNF-loaded polyester compared to neat as a result of better interaction between fiber and matrix due to the presence of CNF.