Agro‐Residual Fibers as Potential Reinforcement Elements for Biocomposites

Surface treatments of plant fibers and their effects on mechanical properties of fiber-reinforced composites: A review

“…Their study revealed that increment by alkali treatment in flexural strength of alfa fiber-reinforced composite can be attributed to removal of waxy contents from the surface of alfa fiber which lead to increment in the roughness of fiber surface and compatibility of alfa fibers with matrix phase whereas decrement in flexural strength might be attributed to degradation of cellulosic microfibril. 9,12 Weyenberg et al 85 investigations revealed that 3 wt% of NaOH concentration in mercerization treatment of flax fibers gave highest improvement in longitudinal and transverse bending strength of flax fiber composite which might be attributed to enhancement of interfacial bonding between matrix and fibers.6,17,19, 86 Yan et al 87 conducted a study in which epoxy is reinforced with alkali-treated flax, linen, and bamboo fibers and found that 5 wt% NaOH alkali treatment of flax, linen, and bamboo fibers showed an increment of 16.1, 16.7, 13.6% in flexural strength and 7.2, 9.1, 6.3% increment in modulus respectively which might be attributed to improvement in roughness of fiber surface 88,89 and good interfacial adhesion between matrix and reinforcement.20, 90 Okubo et al 91 found that addition of micro-fibrillated cellulose had significant positive results for flexural strength of banana/PLA composites due to the barrier in crack propagation. Yousif et al 83 found that 6 wt% NaOH-treated kenaf fiber-reinforced composite had higher flexural strength as compared to 5 wt% NaOH-treated kenaf/epoxy composite.…”

“…The density of NFs is a very important physical property because the strength to weight ratio of NFCs is inversely proportional to the density, 8 whereas mechanical properties of NFCs are directly proportional to the aspect ratio and volume fraction of fibers because higher aspect ratio and volume fraction provides large exposure area of fibers to matrix phase. 9…”

“…The density of NFs is a very important physical property because the strength to weight ratio of NFCs is inversely proportional to the density, 8 whereas mechanical properties of NFCs are directly proportional to the aspect ratio and volume fraction of fibers because higher aspect ratio and volume fraction provides large exposure area of fibers to matrix phase. 9 It is necessary to become familiar with mechanical properties of NFs because these properties govern the mechanical properties of NFCs. Table 3 reveals that the mechanical properties of NFs are lesser to synthetic fibers although they possess comparable specific strength.…”

Mechanical Properties of Mortars Reinforced with Amazon Rainforest Natural Fibers

“…According to the graph in Figure 3, the highest crystallinity index of piassava fiber was obtained with the hot water treatment (51.80%), and for tucum fiber by the application of the hybridization treatment (66.73%), where the highest crystalline peak in the plane (002) is observed (Figure 4). This possibly led to the increased packaging of cellulose chains and the transformation of cellulose type I into cellulose type II, the latter being thermodynamically more stable and providing the increased tensile strength of the fiber [37][38][39][40]. The chemical treatments removed dirt and part of the lignin impregnated in the fibrils, causing greater water absorption by the fibers, since it exposed OH groups (hydroxyls) belonging to cellulose.…”

“…According to the graph in Figure 3, the highest crystallinity index of piassava fiber was obtained with the hot water treatment (51.80%), and for tucum fiber by the application of the hybridization treatment (66.73%), where the highest crystalline peak in the plane (002) is observed (Figure 4). This possibly led to the increased packaging of cellulose chains and the transformation of cellulose type I into cellulose type II, the latter being thermodynamically more stable and providing the increased tensile strength of the fiber [37][38][39][40]. On the other hand, for the razor grass fibers, the result of the crystallization indexes of the treated fibers is slightly lower than that of the untreated fiber on average (57.86%), due to the high percentage of holocellulose present in natural (untreated) fiber (95.30%) which did not become type II, even after alkali treatments.…”