Mechanical Properties of Kenaf - Unsaturated Polyester Composites: Effect of Fiber Treatment and Fiber Length

Abstract

Kenaf fibre is a natural fibre which is growing in popularity due environmental issues and its properties as filler. Unsaturated polyester was used in this investigation via add 1% MEKP concentration ratio as the catalyst. This matrix was combined with untreated kenaf fiber with various fiber sizes (1-6) mm and (10-30) mm, alkalized with 6% NaOH solution for treated kenaf fiber to form natural fiber for two different fiber lengths composites. Composites were prepared by adding various percentages of kenaf fiber in unsaturated polyester resin. A general trend was observed whereby alkalized fiber composites possessed superior flexural strength and modulus and the maximum strength and modulus was at the 20wt% weight fraction. The length of (10-30) mm gave higher tensile and flexural properties compared to (1-6) mm. The modulus of elasticity showed a regular trend of an increase with fiber weight percent until 30% for both fiber lengths and afterwards a decrease in modulus of elasticity for composites with greater fiber weight fraction. The experimental modulus of elasticity was compared with the theoretical predictions and was found to be in good agreement with Hirsch’s model while the results obtained from Cox – Krenchel underestimating the experimental data.

Studies on the mechanism for the sudden mechanical property drops of graphene/polymer nanocomposites

“…For example, the Halpin‐Tsai model and Cox‐Krenchel model can well describe Young's modulus in many cases, and the Kraus model can describe the Payne effect in many polymer composites. However, in most cases, these models give a linear, semilinear, or monotonic relationship between the mechanical properties of polymer composites and the filler concentration, and hence cannot describe the sudden mechanical property drops . On the other hand, the cutting‐off mechanism can explain the sudden mechanical property drops, especially the low critical concentration.…”

“…However, in most cases, these models give a linear, semilinear, or monotonic relationship between the mechanical properties of polymer composites and the filler concentration, and hence cannot describe the sudden mechanical property drops. 13,15,16,31,32 On the other hand, the cutting-off mechanism can explain the sudden mechanical property drops, especially the low critical concentration. Therefore, if the conventional models and the cutting-off model can be combined together, for instance, using the MPCC equations as a correction term in the conventional models, it is possible to establish a more exact and accurate model for describing the mechanical properties of GPNCs.…”

Insights into the effect of moisture absorption and fiber content on the mechanical behavior of starch–date‐palm fiber composites

“…These interactions lead to more stabilization of the starch matrix when exposed to moisture . It was reported by several authors that water transport in polymer composites occurs through three mechanisms . First, the diffusion of water molecules inside the matrix through microgaps between polymer chains, which depends on molecular and microstructural aspects of the polymer.…”

“…Second, water transport by capillary action at the interface between fiber and matrix where gaps and flaws are present as a result of incomplete adhesion. Third, through the matrix imperfections, such as cracks and pores . In the initial stages of the moisture absorption test, water molecules penetrate and attach to the fiber hydrophilic groups, forming intermolecular hydrogen bond with fibers, and consequently decreasing the matrix/fiber interfacial bond.…”

Mechanical properties of treated Kenaf (Hibiscus cannabinus) polyester composite at different alkaline concentration

“…Based on previous studies by [5], [6] and [7] stated that the increase of the elasticity of treated fibres with an alkali solution caused by the removing of the impurities on the surface of the fibres thus increase the mechanical locking between the fibres and the matrix. Other research also was stated that the changes in hydrophopic properties of the lignocellulosic materials would increase the bonding between fibres [1], [5], [7], and [2]. Further research can be done using alkaline treatment to improve the properties of the fibres.…”