Thermomechanical and Thermo-hydro-mechanical Treatments of Luffa Cylindrical Fibers

ABSTRACT The thermomechanical and thermo-hydro-mechanical treatments in Luffa cylindrical fibers were evaluated. The treatments comprised the hot pressing of the fibers in the dry condition (thermomechanical) and in the saturated condition (thermo-hydro-mechanical) with the objectives of porosity reduction and increase of modulus of elasticity of the fibrous material. The thermomechanical treatments were performed at 25, 120, 160 and 200°C. Tensile strength, moisture absorption, scanning electron microscopy (SEM), X-ray diffraction and thermogravimetric analysis were carried out to follow the effect of the proposed treatment. After treatment, the fibers presented a higher modulus of elasticity and lower moisture absorption. The best results were achieved for the saturated fibers pressed at 160ºC, as they presented a 95% increase in the modulus of elasticity and a 22% decrease in the moisture absorption in relation to the compressed fiber at room temperature. When exposed to heat and humidity, the densified sample showed a tendency to return to its original shape. The achieved results show that Luffa cylindrical fiber is suitable and possibly to be used in composites for engineering applications and indicate the high potential of thermomechanical and thermo-hydro-mechanical treatments to improve the properties of this natural fiber.