Mechanical Properties and Equilibrium Swelling Characteristics of Some Polymer Composites Based on Ethylene Propylene Diene Terpolymer (EPDM) Reinforced with Hemp Fibers

EPDM/hemp fiber composites with fiber loading of 0-20 phr were prepared by the blending technique on a laboratory electrically heated roller mill. Test specimens were obtained by vulcanization using a laboratory hydraulic press. The elastomer crosslinking and the chemical modification of the hemp fiber surface were achieved by a radical reaction mechanism initiated by di(tert-butylperoxyisopropyl)benzene. The influence of the fiber loading on the mechanical properties, gel fraction, swelling ratio and crosslink degree was investigated. The gel fraction, crosslink density and rubber-hemp fiber interaction were evaluated based on equilibrium solvent-swelling measurements using the Flory-Rehner relation and Kraus and Lorenz-Park equations. The morphology of the EPDM/hemp fiber composites was analyzed by scanning electron microscopy. The water absorption increases as the hemp fiber loading increases.

Characterization of sodium hydroxide-treated kenaf fibres for biodegradable composite application

Natural fibres have shown immense potential as reinforcement for composites in the place of conventional fibres. Natural fibres are lightweight, cheap and environmentally friendly. However, it is already established that natural fibres have poor interaction with polymers due to its hydrophilic nature, resulting in poor interfacial adhesion, which is detrimental to the properties of the composite. Chemical surface treatment has been done to improve the interfacial adhesion. Various concentrations of sodium hydroxide (NaOH) and soaking times were employed, and the treated fibres were then characterized using thermogravimetric analyser, X-ray powder diffraction and Fourier transform infrared (FTIR) spectrometer. Single-fibre tensile tests were done on selected samples. The surface of the fibre was analysed with field-emission scanning electron microscope to study the surface morphology of the treated and untreated fibres. Generally, the treated fibres have higher thermal stability compared to untreated fibres. However, no significant trend was observed as a result of varying NaOH concentration and soak time. It was also observed that kenaf fibres treated with 4% (w/v) NaOH for 5 h exhibited the highest tensile modulus and tensile strength compared to other treated fibres. Impact properties of composites prepared from untreated and NaOH-treated kenaf were tested to confirm the finding, and it was determined that the treated kenaf composites have superior impact properties to its untreated counterpart.