RESUMEN
In this research work, unfilled and monofilled polytetrafluoroethylene (PTFE) were investigated. The applied fillers were graphene, alumina (Al2O3), boehmite alumina (BA80) and hydrotalcite (MG70). Graphene and Al2O3 are already known in the literature as potential fillers of PTFE, while BA80 and MG70 are novel fillers in PTFE. Materials were produced by room temperature pressing-free sintering method with a maximum sintering temperature of 370 °C. The mass loss and decomposition analyses were carried out by thermogravimetric analysis (TGA) in two different ways. The first was a sensitivity analysis to gain a better view into the sintering process at 370 °C maximal temperature. The second was a heating from 50 °C up to 1000 °C for a full-scale decomposition analysis. BA80 is a suitable filler for PTFE, as most of its functional groups still existed after the sintering process. Both PTFE and Al2O3 had high thermal stability. However, when Al2O3 was incorporated in PTFE, a remarkable mass loss was observed during the sintering process, which indicated that the decomposition of PTFE was catalysed by the Al2O3 filler. The observed mass loss of the Al2O3-filled PTFE was increased, as the Al2O3 content or the applied dwelling time at a 370 °C sintering temperature increased.
RESUMEN
In this research work, unfilled and mono-filled polytetrafluoroethylene (PTFE) materials were developed and characterised by physical, thermal, viscoelastic, mechanical, and wear analysis. The applied fillers were graphene, alumina (Al2O3), boehmite alumina (BA80), and hydrotalcite (MG70) in 0.25/1/4/8 and 16 wt % filler content. All samples were produced by room temperature pressing-free sintering method. All of the fillers were blended with PTFE by intensive dry mechanical stirring; the efficiency of the blending was analysed by Energy-dispersive X-ray spectroscopy (EDS) method. Compared to neat PTFE, graphene in 4/8/16 wt % improved the thermal conductivity by ~29%/~84%/~157%, respectively. All fillers increased the storage, shear and tensile modulus and decreased the ductility. PTFE with 4 wt % Al2O3 content reached the lowest wear rate; the reduction was more than two orders of magnitude compared to the neat PTFE.
RESUMEN
We studied the effect of a multilevel presence of carbon-based reinforcements-a combination of conventional load-bearing unidirectional carbon fiber (CF) with multiwalled carbon nanotubes (CNT) and conductive CNT-containing nonwoven carbon nanofabric (CNF(CNT))-on the fire performance, thermal conductivity, and mechanical properties of reference and flame-retarded epoxy resin (EP) composites. The inclusion of carbon fibers and flame retardant reduced the peak heat release rate (pHRR) of the epoxy resins. The extent to which the nanoreinforcements reduced the pHRR depended on their influence on thermal conductivity. Specifically, high thermal conductivity is advantageous at the early stages of degradation, but after ignition it may lead to more intensive degradation and a higher pHRR; especially in the reference samples without flame retardant. The lowest pHRR (130 kW/m²) and self-extinguishing V-0 UL-94 rating was achieved in the flame-retarded composite containing all three levels of carbon reinforcement (EP + CNF(CNT) + CNT + CF FR). The plasticizing effect of the liquid flame retardant impaired both the tensile and flexural properties; however, it significantly enhanced the impact resistance of the epoxy resin and its composites.