The use of laser radiation to initiate the crosslinking process in ultra low‐density polyethylene (ULDPE) and high‐density polyethylene (HDPE) was evaluated. The process was found to be most effective for pulsed laser irradiation when the polymer was traced with a photoinitiator: 4‐chlorobenzophenone (CBP). The gel content measurements proved that crosslinking took place in all the irradiated samples. The degree of crosslinking was measured for different values of irradiation energy, temperature, photoinitiator concentration and the nature and type of crosslinking agents. The effects of all these parameters on the degree of crosslinking and the consequent effects on mechanical properties of the polymers were analyzed. Also found in the present study is the fact that a better efficiency of crosslinking was achieved at longer laser irradiation wavelength. The ultimate tensile stress and elongation at fracture were measured for all cross‐linked samples and compared with those of the controlled ones.
Temperature dependence of the shape and linewidth of the broad-line NMR spectra of commercially available high-density polyethylene (PE/HD), low-density polyethylene (PE/LD with ~3 per cent CH3), block-copolythene (PE/AA with ~3 per cent acrylic acid) and polyethylene single crystal (PE/SC) were investigated to obtain information on the effect of branching and structural changes on the glass-transition temperature (Tg) and activation energy of molecular motion (E). The relatively lower value of Tg ~- ?100° for PE/HD compared to Tg ~- ?85° and ?60° for PE/CH3 and PE/AA, along with the estimated lower value of E ~- 2·1 kcal/mole for PE/HD compared to 2·6 and 5·1 kcal/mole for PE/CH3 and PE/AA, respectively, were interpreted by a molecular reorientational process connected mainly with the sidegroups of the main polymeric chains. 相似文献
A sensitive and selective procedure is presented for the voltammetric determination of copper(II) ion. The procedure involves an adsorptive accumulation of Cu2+-PPKO on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of adsorbed complex at about -0.30 V (vs. SCE). The optimum conditions for the analysis of copper(II) ion include pH (5.8-7.0), 60 microgM PPKO and an accumulation potential of -0.5 V (vs. SCE). The peak current is proportional to the concentration of copper over the range 0.3-76 ng mL(-1) with a detection limit of 0.01ng mL(-1) with an accumulation time of 60 s. The speciation of different forms of complex between copper(II) ion and PPKO, using the Best (Martell program), followed pH measurement were examined. The method was applied to the determination of copper(II) ion content in real samples successfully. 相似文献
In the present work, the pyrolysis of acetylene was studied under steel vacuum carburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from 650 degrees C to 1050 degrees C. The partial pressure of acetylene in the feed mixture was 10 and 20 mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressure of the mixture was 1.6 bar. A kinetic mechanism which consists of seven species and nine reactions has been used in the commercial computational fluid dynamics (CFD) software Fluent. The species transport and reaction model of Fluent was used in the simulations. A comparison of simulated and experimental results is presented in this paper. 相似文献
Lithium bis(oxalato)-borate (LiBOB) is a promising salt for Li-ion batteries owing to its various characteristics such as
non-fluorine, non-toxicity, low cost, and safety. It has the unique merits such as the stability at high temperature and the
film-forming characteristics in propylene carbonate (PC)-based electrolyte. In this work, the utilization of PC as the basal
solvent and dimethyl carbonate, γ-butyrolactone and ethylene carbonate as co-solvents for LiBOB have been investigated. The
results indicate that the co-solvent has conducive effects on the conductivities, viscosities, and battery performance. The
conductivity and viscosity of 0.7 mol L−1 LiBOB in PC+GBL+EC+DMC (1:1:1:1, v/v) are 6.22 mS cm−1 and 3.74 mPa s, respectively, and it is very stable in 0–5 V range. The capacity of Li/LiFePO4 battery is about 160 mAh g−1 at 0.5 °C. Moreover, the battery has exhibited the excellent rate performance. 相似文献