No abstract

Graphite nanoplatelets with an average particle size of 13 μm and an estimated flake thickness of about 76 nm were prepared by microwave exfoliation, followed by ultrasonication-assisted liquid phase delamination, of an expandable graphite. This nano-additive was used to fabricate linear low density polyethylene (LLDPE) and poly(ethylene-co-vinyl acetate) (EVA) based nanocomposite sheets using rotational moulding. The dry blending approach yielded surface resistivities within the static dissipation range at filler loadings as low as 0.25 wt.% (0.1 vol.%). However, even at this low graphite content, impact properties were significantly reduced compared to the neat polymers. Bilayer mouldings via the double dumping method proved to be a feasible approach to achieve both acceptable mechanical properties and antistatic properties. This was achieved by rotomolding nanocomposite sheets with a 1 mm outer layer containing the filler and a 2 mm inner layer of neat LLDPE. Excellent fire resistance, in terms of cone calorimeter testing, was achieved when the outer layer also contained 10 wt.% expandable graphite.

The use of desalination technologies which produce concentrated brines is acutely limited by inadequate waste brine disposal mechanisms such that the brine does not contaminate fresh water resources. The treatment of highly saline brine using freeze desalination technique trade marked as HybridICE TM technology was investigated at pilot scale. The capacity of the HybridICE TM process to generate fresh water by freeze desalination of brine was investigated in this study. Brine samples to feed into the HybridICE process unit were prepared in tanks with volume capacities between 1.0 and 10.0 m 3 by dissolving common salt into tape water. The effects of refrigerant temperature, initial brine concentration, energy consumption were evaluated in relation to product ice quality. Feed brine samples were processed in batches in a closed system where it was continuously re-circulated to generate product ice and more concentrated residual small volume of brine stream. The quality of ice produced could be turned into potable water it terms of its low total dissolved salts and conductivity. The salt removal, based on the average chloride concentration in the ice samples, was 96 %. The energy utilization efficiency amounted to an average of ZAR 10.0/m 3 water assuming energy cost of ZAR 0.39/kWh. The HybridICE TM technology was shown to be a better option than other desalination technologies currently in use, in terms of energy utilization and cleaner byproducts.

Firefighting bunker gear is manufactured from flame-retardant materials, which resist ignition and delay flame spread. However, concerns have been emerging on the potential harmful effects of some flame retardants (FRs) commonly used in flame-retarding materials, particularly the brominated flame retardants. This study investigated the presence of flame retardants in bunker gear, particularly polybrominated diphenyl ethers and their congeners in the garments, and evaluated their impact on thermal performance. X-ray fluorescence spectroscopy was used to ascertain the presence of bromine as a possible indicator for brominated flame retardants. X-ray fluorescence results indicated the presence of Br in all samples, ranging from 444 to 20,367 µg/g. Further analysis via gas chromatography–mass spectrometry was done on samples. Brominated flame retardants, particularly polybrominated diphenyl ethers and hexabromocyclododecane, were detected in all samples with concentrations ranging from 261.61 to 1001.77 µg/g and 0.01 to 0.07 µg/g, respectively. The cone calorimeter was used, with 50 and 75 kW/m2 heat fluxes, to investigate the impact of the brominated flame-retardant concentrations, if any, on thermal performance. New bunker garments, particularly those with lower Br and brominated flame-retardant concentrations, were observed to have higher thermal performance.

No abstract

Combustion measurements, such as heat release rate, critical flux, time-to-ignition, ignition temperature, thermal inertia, and kinematics—activation energy as well as preexponential factor—on epoxy polymer (Prime™20LV) with expandable graphite (EG) inorganic filler of different weight percentage composites, are conducted using the Dual Cone Calorimeter, the thermogravimetric analysis (TGA), and Linseis (Germany) THB100 Transient Hot Bridge thermal conductivity analyser. The results indicate that increasing the amount of EG in polymer composite leads to reduction in the critical flux, the time-to-ignition, the ignition temperature, the thermal inertia, the average thermal conductivity, and the activation energy (from 159.1 ± 2.3 to 145.9 ± 3.1 kJ/mol for neat epoxy to 3 wt.% EG-epoxy) of the composite samples. There is, however, an increase in the heat of gasification with increasing EG content.

No abstract

No abstract