Key Engineering Materials Vols. 334-335

Abstract: In this paper, we have studied the permittivities of E-glass fabric/epoxy composite laminates containing three different types of carbon-based nano conductive fillers such as carbon black (CB), carbon nano fiber (CNF) and multi-wall carbon nano tube (MWNT). The measurements were performed for permittivities at the frequency band of 0.5 GHz ~ 18.0 GHz using a vector network analyzer with a 7 mm coaxial air line. The experimental results show that the complex permittivities of the composites depend strongly on the natures and concentrations of the conductive fillers. The real and imaginary parts of the complex permittivities of the composites were proportional to the filler concentrations. But, depending on the types of fillers and frequency band, the increasing rates of the real and imaginary parts with respect to the filler concentrations were all different. At the frequency of 10 GHz, the rates in the CNF filled composite and the MWNT filled composite were much larger then those of the CB filled composite. Between the CNF filled composite and MWNT filled composite, however, the former showed a little higher increasing rates than the other. These different rates can have great effect on the thickness in designing the single layer microwave absorbers. The effect of the different rates was examined by using Cole-Cole plots; the plot is composed of a single layer absorber solution line and permittivity lines of these three types of composites.

Abstract: Although much research work has been conducted on the production and characterisation of polypropylene/organoclay nanocomposites, the effects of nanoscale fillers with respect to actual morphology through numerical modelling have been rarely addressed. This paper describes a unique development from fabrication and experimental characterisation to the numerical modelling of polypropylene/organoclay nanocomposites based on the real mapping of nano/microstructures. Twin screw extrusion is used with a two-step masterbatch compounding method to prepare such nanocomposites with organoclays (ranging between 1wt% and 10wt%) and maleated polypropylene (1:1 weight ratio). The material characterisation using X-ray diffraction (XRD), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMTA) are conducted and mechanical properties are determined by tensile, flexural and impact tests. Finally, computational models are established by using an innovative object-oriented finite element analysis code (OOF) to predict the overall mechanical properties of nanocomposites.

Abstract: Nano-TiO2 particles or TiO2 whiskers encapsulated by polyaniline/cyanate ester composites were fabricated by solution-mixing method. Then the dispersion of particles in cyanate ester was observed with the aid of TEM. The effect of the content of particles or whiskers on the dielectric properties of cyanate ester composites was investigated. As the content of the particles up to 3% or the whiskers up to 7%, the dielectric loss of the composites achieved its maximum.

Abstract: To improve the flame retardant performance of polypropylene (PP), three composites systems, nano-Al(OH)3/Mg(OH)2/PP, micro-capsulated ammonium polyphosphate (MCAPP)/PP, and nano-Al(OH)3/Mg(OH)2/MCAPP/PP had been developed and studied in this paper. Their flame retardant and mechanical properties were measured and analyzed. The results indicated that there existed synergistic effect of flame retardant among nano-Al(OH)3, nano-Mg(OH)2, and MCAPP. PP composites with the three flame retardants of 3 wt%, 9 wt%, 8 wt% respectively possessed the best integrated properties with OI value of 26.2 and little decrease in mechanical properties.

Abstract: In order to improve the crystallization properties of the polyethylene terephthalate (PET), nano-zinc oxide (nano-ZnO)/PET and nano-ZnO/polyethylene glycol (PEG)/PET composites were successfully synthesized by in-situ polymerization method in this work. The experimental results indicated that nano particles can accelerate the crystallization of the PET which was demonstrated by increase in the intensities of the XRD peaks. PEG and PET form copolymer in composites, leading to the improvement of the flexibility of the molecule chain. Meanwhile, PEG was able to encapsulate the nano particles to make them have both good compatibility to matrix and uniform dispersion in the composites. Therefore, the crystallization rate and crystallization capability of nano-ZnO/PEG/PET composites were reasonably raised.

Abstract: This paper describes the viscoelastic properties of network model. In the first approximation, nanocomposite was modeled as a 3D tetrafunctional network considering entanglements to act as the physical x-links. Nano-sized non-deformable domains of defined shape and size were introduced into the network. The chains in the vicinity of the inclusions were considered immobilized. Hence, the semicrystalline polymer was considered a three-phase system containing flexible matrix bulk phase, immobilized chains near the inclusion surface and rigid crystalline domains. The crystallites were characterized by their Young's modulus and their traction properties were calculated using the Hooke's law. Unlike the model, the real polymer has viscoelastic deformation properties. The components which could cause viscoelastic properties were introduced and their impact on viscoelastic properties of whole network was investigated. The components were for example the reptation motion of chain in entanglements or chain, whose motion was retarded by impact of surroundings. The model enabled to investigate the influence of each component, as well as the influence of distribution of each component. The types of nods, whose influence was investigated in this contribution, were fast knot, free entanglement, one-way entanglement and energy barrier.

Abstract: Slapper detonator is composed of bridge foil, flyer, barrel, tamper and explosive pellet. The function of flyer is insulation, safety and forming flyer in detonator, and it was usually fabricated by thermal-resistant polymer film with cupper coating. In this study, nano-doped polyimide (PI) nanocomposite films have been prepared using in-situ polymerization method through incorporating nano silica fillers, and characterized by SEM and UV-Vis techniques. The possibility used as flyer in slapper detonator of the nanocomposite film was also discussed.