Nucleating Effect of Carbon Nanoparticles and Their Influence on the Thermal and Chemical Stability of Polypropylene

The effect of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) on the thermal and chemical stability of polypropylene (PP) when subjected to oxidation in a strong acid medium was studied. The effect of CNFs and CNTs on the crystalline morphology and the melting and crystallization temperatures was also studied. The thermal stability increased markedly; the decomposition temperature, for example, increased from 293 • C for pure PP to 312 and 320 • C for PP with CNFs and CNTs, respectively. The crystallization temperature increased perceptibly with the addition of CNTs or CNFs, from 107 • C for pure PP to 112 and 114 • C for PP with CNFs and CNTs, respectively. The oxidative degradation with nitric acid produced a reduction in molecular weight; however, this negative effect was less pronounced in the PP compositions with carbon nanoparticles. After 8 hours in nitric acid, this reduction was from 141,000 to 68,000 (for pure PP), to 75,000 (for PP-CNFs), and 79,500 (for PP-CNTs). X-ray diffraction showed that the alpha type crystallinity remains, irrespective of the nucleating agent. Finally, the intensity ratio between the (040) (at 16.7 • ) and the (110) (at 13.9 • ) reflections increased, which was taken as an indication of an increasing nucleating efficiency

Nucleating Effect of Carbon Nanoparticles and Their Influence on the Thermal and Chemical Stability of Polypropylene

The effect of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) on the thermal and chemical stability of polypropylene (PP) when subjected to oxidation in a strong acid medium was studied. The effect of CNFs and CNTs on the crystalline morphology and the melting and crystallization temperatures was also studied. The thermal stability increased markedly; the decomposition temperature, for example, increased from 293∘C for pure PP to 312 and 320∘C for PP with CNFs and CNTs, respectively. The crystallization temperature increased perceptibly with the addition of CNTs or CNFs, from 107∘C for pure PP to 112 and 114∘C for PP with CNFs and CNTs, respectively. The oxidative degradation with nitric acid produced a reduction in molecular weight; however, this negative effect was less pronounced in the PP compositions with carbon nanoparticles. After 8 hours in nitric acid, this reduction was from 141,000 to 68,000 (for pure PP), to 75,000 (for PP-CNFs), and 79,500 (for PP-CNTs). X-ray diffraction showed that the alpha type crystallinity remains, irrespective of the nucleating agent. Finally, the intensity ratio between the (040) (at 16.7∘) and the (110) (at 13.9∘) reflections increased, which was taken as an indication of an increasing nucleating efficiency

Morphological Study and Dielectric Behavior of Nonisothermally Crystallized Poly(ethylene naphthalate) Nanocomposites as a Function of Graphene Content

Morphological evolution and dielectric properties of poly(ethylene naphthalate)- (PEN-) graphene nanocomposites nonisothermally crystallized have been investigated. PEN-graphene nanocomposites containing 0.01, 0.025, 0.05, 0.075, and 0.1 wt% of graphene were prepared by melt blending in a mini twin screw extruder. The results showed that graphene exhibited a superior influence on morphological and conformational structure of PEN during nonisothermal crystallization at low graphene contents. Crystallization temperature (Tc) was found to be increased up to 18°C supporting the high nucleating activity of graphene layers. Wide angle X-ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR) indicated that graphene modifies the conformation of PEN chains promoting crystallinity and favoring the evolution from α to β crystalline form with homogeneous lamellar thickness. It may be attributed to the structural similarity between naphthalene rings and graphene structure and to π-π interactions during nucleation. Dielectric behavior was found to be a function of graphene content where the nanocomposites changed from dielectric to low conducting material when passing from 0.075 to 0.1 wt% of graphene content. This phenomenon permits having a wide range of properties to fit a wide variety of applications required to store electrical energy of low voltage