Tailoring the rheology and electrical properties of polyamide 66 nanocomposites with hybrid filler approach: graphene and carbon nanotubes

Thermal Fractionation of Polyolefins: Brief History, New Developments and Future Perspective

Abstract

For semi-crystalline polymer materials, the difference in chain structure often leads to different physical properties; therefore, in-depth analysis of the chain structure is of great significance. With the continuous development of advanced instruments, many research means have emerged to characterize the structure of molecular chains. Among them, fractionation techniques provide effectively structural information on inter- and intra-molecular comonomer distribution, branching degree, and sequence length, etc. This work briefly presents the history of developments of various classical fractionation means such as temperature-rising elution fractionation, stepwise crystallization and successive self-nucleation and annealing, while focusing on the present and future of their applications.

Thermal, electrical and mechanical properties of carbon fiber/copper powder/carbon black reinforced hybrid Polyamide 6,6 composites

The development of low electrical and thermal properties of Polyamide (PA), which is used in place of metals in engineering applications, draws attention to the developments in various industrial disciplines. In this study, the effects of metal and carbon based fillers on the properties of Polyamide 6,6 (PA 6,6) were investigated. Especially, copper powder (Cu), carbon black (CB), carbon fiber (CF) and hybrid fillers (Cu/CB/CF) reinforced composites based on PA 6,6 were prepared by twin-screw extruder followed by injection molding. In the microstructure investigation, it was observed that the dispersion properties of used fillers were different in the PA 6,6 matrix. Both electrical and thermal conductivity of the PA 6,6 composites prepared were higher than pure PA 6,6. The highest electrical and thermal conductivity values were obtained as 7.97x10−2 S/cm and 0.73 W/mK for PA 6,6/CB30 and PA 6,6/CF/CB/Cu 10, respectively. The effects of the fillers on melting and crystallization behaviors and mechanical properties that affect the performance of PA 6,6 composites are also discussed. In general, the results showed that the mechanical properties of PA 6,6 composites were improved with the increase in the amount of hybrid filler. The highest tensile and notched Charpy impact strength were obtained as 252 MPa and 8.84 kJ/m2 in PA 6,6 composite with 30% carbon fiber reinforcement by volume. As a result, the tensile properties of PA 6,6 hybrid composite were found to be superior to PA 6,6/CF composite with the same amount of carbon fiber content.