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Untreated sunn hemp hessian cloth and okra hessian cloth reinforced high-density polyethylene (HDPE) composites with 40, 45, 50, 55, 60, and 65 wt% cloth contents were separately prepared by compression molding methods at 190 ℃ and 5-ton pressure. The optimized cloth content for both types of composites was observed to be 55 wt%, as determined by their better mechanical properties. Then, both types of hessian cloths were treated with 5, 10, and 15 wt% concentrations of alkali (NaOH) solutions. With these treated hessian cloths, two series of 55 wt% cloth content reinforced HDPE composites were fabricated. Then, the optimum treatment concentration of alkali was found to be 10 wt%, as evaluated by their superior mechanical properties. 55 wt% cloth content reinforced composite with both untreated and optimum alkali-treated cloths were irradiated under gamma-ray at doses 2.5, 5, and 7.5 kGy at the rate of 6 kGy/h and the optimum dose was found to be 5 kGy. Untreated and alkali-treated sunn hemp and okra cloths reinforced composites as well as their gamma-ray irradiated composites were subsequently characterized by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), X-ray diffractometry (XRD), physical property test, mechanical test, differential scanning calorimetry, and thermo-gravimetric analyses. From the FTIR analyses new bonds of C‒O, C=C, and ‒CH were observed between sunn hemp or okra fibers and HDPE matrix due to gamma-ray irradiation, showing network structure in the irradiated samples. FESEM of their gamma-ray irradiated composites reveals improved fiber-to-matrix adhesion. From the XRD analysis, only the alkali-treated cloth-reinforced composite shows higher crystallinity than all other samples. The water intake properties of 5 kGy dose gamma-ray irradiated sunn hemp hessian cloth composite was obtained as 10.1%, which is 37 and 14% more hydrophobic in nature than that of merely untreated, and alkali-treated cloth-reinforced composites. The tensile strength of the gamma-ray irradiated sunn hemp cloth-reinforced composite is 68 MPa, which is 42% greater than that of untreated cloth reinforced composite. The Young’s modulus of irradiated sunn hemp cloth-reinforced composite is 1.97 GPa, which is 28% higher than that of untreated cloth-reinforced composites, respectively. The melting and degradation temperatures of gamma-ray irradiated sunn hemp composite are 151 ℃ and 331 ℃, respectively. These results are higher than that of other composites of the same kind. Similar tendencies of the results of water intake, mechanical, and thermal properties were observed for untreated, alkali-treated, and gamma-ray irradiated okra hessian cloth-reinforced composites. |
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