Natural fibers are getting attention from researchers and academician to utilize in polymer composites due to their ecofriendly nature and sustainability. The aim of this review article is to provide a comprehensive review of the foremost appropriate as well as widely used natural fiber reinforced polymer composites (NFPCs) and their applications. In addition, it presents summary of various surface treatments applied to natural fibers and their effect on NFPCs properties. The properties of NFPCs vary with fiber type and fiber source as well as fiber structure. The effects of various chemical treatments on the mechanical and thermal properties of natural fibers reinforcements thermosetting and thermoplastics composites were studied. A number of drawbacks of NFPCs like higher water absorption, inferior fire resistance, and lower mechanical properties limited its applications. Impacts of chemical treatment on the water absorption, tribology, viscoelastic behavior, relaxation behavior, energy absorption flames retardancy, and biodegradability properties of NFPCs were also highlighted. The applications of NFPCs in automobile and construction industry and other applications are demonstrated. It concluded that chemical treatment of the natural fiber improved adhesion between the fiber surface and the polymer matrix which ultimately enhanced physicomechanical and thermochemical properties of the NFPCs.

In this work, polylactic acid (PLA) composites filled with microcrystalline cellulose (MCC) from oil palm biomass were successfully prepared through solution casting. Fourier transform infrared (FT-IR) spectroscopy indicates that there are no significant changes in the peak positions, suggesting that incorporation of MCC in PLA did not result in any significant change in chemical structure of PLA. Thermogravimetric analysis was conducted on the samples. The T50 decomposition temperature improved with addition of MCC, showing increase in thermal stability of the composites. The synthesized composites were characterized in terms of tensile properties. The Young's modulus increased by about 30%, while the tensile strength and elongation at break for composites decreased with addition of MCC. Scanning electron microscopy (SEM) of the composites fractured surface shows that the MCC remained as aggregates of crystalline cellulose. Atomic force microscopy (AFM) topographic image of the composite surfaces show clustering of MCC with uneven distribution.

Poly (lactic acid) (PLA)/chitosan (CS) natural polymer/epoxidised natural rubber (ENR) composites were successfully prepared through a solution casting method. The morphological characteristics of fabricated composites were investigated by scanning electron microscopy (SEM) and optical microscopy. The microstructure of PLA/ENR was significantly altered with the addition of CS. SEM analysis of composites fractured surfaces revealed smooth and homogeneous texture and good dispersion of CS. However for 15 wt% CS composites, the phase segregation and poor adhesion between the polymers were observed. Fourier transform infrared spectroscopy revealed some levels of attractive interaction between CS, PLA, and ENR in the composites. The mechanical properties of composites in terms of tensile strength and tensile modulus were significantly improved with the addition of CS into the matrix while the percent elongation at break decreased. The tensile strength increased up to 5 wt% CS loading for both PLA/CS and PLA/ENR/CS and thereafter decreased while Young’s modulus increased up to 10 wt%. However, when the CS content was increased to 15 wt%, the tensile strength and tensile modulus were slightly decreased. These improvements were attributed to good dispersion of CS at the optimum filler levels and attractive interaction between the composites components.

Silica-epoxy nanocomposites are very common among nanocomposites, which makes them very important. Several researchers have studied the effect of nanoparticle’s size, shape, and loading on mechanical behavior of silica-epoxy nanocomposites. This paper reviews the most important research done on the effect of nanoparticle loading on mechanical properties of silica-epoxy nanocomposites. While the main focus is the tensile behavior of nanocomposite, the compressive behavior and flexural behavior were also reviewed. Finally, some of the published experimental data were combined in the graphs, using dimensionless parameters. Later, the best fitted curves were used to derive some empirical formulas for mechanical properties of silica-epoxy nanocomposites as functions of weight or volume fraction of nanoparticles.

Various heterogeneous catalysts are often used to produce biodiesel from non-edible crude oils. In this study a highly active heterogeneous calcium oxide (CaO) nanocatalyst with a diameter and surface area of 66 ± 3 nm and 90.61 m2/g, respectively, was synthesized from Polymedosa erosa (P. erosa) seashells through a calcination-hydration-dehydration technique. The nano-CaO catalysis impact was investigated in a two-step transesterification of triglycerides from crude Jatropha oil as a biodiesel along with other reaction parameters such as catalyst ratio, reaction time, and methanol to oil ratio. Fourier transform infrared spectroscopy, transmission electron microscope, X-ray diffraction, and Brunauer-Emmett-Teller spectrographic techniques were utilized to evaluate the CaO nanocatalyst spectral and structural characteristics. The effect of the transesterification parameters on reaction kinetics and Jatropha biodiesel (JB) yield were analyzed by employing a three-factor-five-level response surface methodology model based on a full factorial, two-block, central composite design. The adequacy of the predicted model was verified, and a 98.54% JB yield was reported at optimal parametric conditions, i.e., 0.02:1 (w/w) catalyst ratio, 133.1 min reaction time, and 5.15:1 mol/mol of methanol to the pretreated oil. An average of 95.8% JB yield was obtained from the catalyst reusability up to the sixth cycle. Fuel property test results of JB were found to be highly commensurate with the biodiesel standard EN 14214.