Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Physics

The main object of this work is to investigate and quantify water absorption behavior of hydrophobic carbon black in the 75IIR/25EPDM blend loaded with carbon black and, the water vapour transmission rate (WVTR). We investigate the mechanical properties of four blend samples loaded with of 0, 50, 60, and 70 phr of carbon black, and namely; tensile strength, elongation at break, tear strength, hardness and compression set.The results reveal that such properties are increasing with CB content. Rheometric tests show an increase of the minimum and maximum torques ML and MH, scorch time, and cure rate index of the blends with CB content. Water repellence or surface wettability, and surface energy are investigated by water-rubber and diiodomethane-rubber contact angle experiment.The water absorption is qualitatively and quantitatively studied by keeping 5{u00D7}2.5 {u00D7} 0.2 cm samples in distilled water over three months.The effect of water absorption by unfilled and filled samples is described using two fitting models: the logistic and the twoexponential growth models. The results show the water absorption has non-Fickian behavior for all samples, and water uptake increases continuously.The rate of the uptake is found to be minimum for the sample with CB concentration of 60 phr. The water vapour permeability at a relative humidity of 85% is measured by a differential technique at room temperature The data show that any increase in the CB content markedly reduces the water vapour transmission rate. On the other hand, the waterrubber contact angle values are not proportional to CB content in the samples. The optimum impermeable sample concerned as to be suitable for water insulation in engineering applications is that of 60 phr CB-loading

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