查看更多>>摘要：The DSC measurements of the binary mixtures of nitrocellulose (NC) and dimethyl 4,4'-dinitroheptanedioate (DNHD), of expected fine plasticizing properties, were carried out. It was concluded that depending on the time interval between measurements, in cases of specifically low DNHD content in NC mixtures DNHD did not crystallize. The course of the melting process during the second and subsequent measurements performed on the same sample indicates that the process was taking place in confined spaces, i.e. pores as well as in unconfined space. The occurrence of two i.e. high-temperature and low-temperature glass transitions as well as beta-relaxation was observed, depending on the composition of the samples and time interval between the measurements. The thermochemical properties of the investigated DNHD/NC binary system are complex and allow to conclude that thermal behavior of the samples across a variety of concentration and temperature ranges, reflects limited miscibility of the components used.
查看更多>>摘要：The curing behavior of pure unsaturated polyester resin (Neat UP), resin containing 0.5 wt% graphene oxide (UPGO) and resin containing 0.5 wt% graphene oxide modified by silane agent (UPMGO) was studied. The kinetic parameters of the systems were calculated using the advanced isoconversional method. The cure index was used to evaluate the curing quality of the systems. The results showed that the functional groups on the surfaces of graphene oxide and modified graphene oxide caused significant changes in the activation energies of different regions of resin curing. The formation of radical traps and stabilization of cobalt complexes by the added particles were other factors affecting the activation energy of the systems. The diffusion phenomenon was investigated in all three systems Neat UP, UPGO and UPMGO. The presence of attraction interactions between particles and alkyd resin chains are among the factors affecting the diffusion region of UPGO and UPMGO systems.
查看更多>>摘要：A novel environment-friendly and efficient flame retardant (phytic acid [PA] - layered double hydroxide [LDH]) has been synthesized to enhance the flame retardancy of PVA. PA-LDH possesses better char formation ability with a high char residue of 68.7 wt% at 600 degrees C. Peak release rate (pHRR) and heat release capacity (HRC) values of PVA/PA-LDH15% are 180 W/g and 310 J/g-K, with the descent of 69.4% and 31.7%, respectively. The burning rate of PVA/PA-LDH decreased visibly, presented that higher fire retardancy can be obtained for PVA/PA-LDH. It is worth noting that PA-LDH could restrain the melt-dripping of PVA during the combustion process, which is of great significance in fire-spread control. Furthermore, the synergistic flame-retardant mechanism of phosphorus-contained PA and inorganic LDH is proposed based on microscopic analysis on char residues. In addition, PVA/PA-LDH composites exhibit good mechanical properties, the green flame retardant is of considerable significance to the flame-retardant treatment of polymers.
查看更多>>摘要：The purpose of this work is to add further details to the course of the hydrogen reduction reaction from tungsten-VI-oxide to tungsten powder. The investigations have been carried out under conditions far away from technical processes. The reduction has been studied by thermogravimetry forcing a thermodynamic reaction control by the use of tiny sample amounts and the application of non-isothermal conditions. Thereby the dominance of the kinetics (diffusion control of the reaction pathway) is minimized and the product ratio is determined by the relative stability of the products. The resulting reduction intermediates have been analysed by X-ray diffraction and scanning electron microscopy. It can be demonstrated that the reduction of WO3 to tungsten exhibits a 3-step process in which well crystalline and pure phase intermediate stages are run through.
查看更多>>摘要：To investigate the effect of adding graphene to the thermal properties of fatty acids, an amorphous model of palmitic acid (PA)/graphene composite phase change material (CPCM) was developed. The effects of temperature and mass fraction of graphene on the mean square displacement, self-diffusion coefficient, radial distribution function, radius of gyration, specific heat capacity, and thermal conductivity (k) were calculated by performing molecular dynamics simulations. The phase transition temperature of the CPCMs decreased gradually as the mass fraction of graphene increased. The specific heat capacity and thermal conductivity of PA were significantly enhanced by the addition of graphene. The optimization of the specific heat capacity and thermal conductivity of the CPCMs depended on the system temperature and mass fraction of graphene.
NSTL
Elsevier