Recent development and future trends in coir fiber‐reinforced green polymer composites: Review and evaluation

Development of natural fiber composites with thermoplastics and thermosets finds applications in various fields, from agriculture to automotive. It can reduce the dependency on petroleum resources which causes several environmental problems. Natural fibers are renewable and biodegradable that reduces carbon footprint to the environment. Coir fibers are natural fibers used in the development of composites offers comparable properties with other mineral fillers. This article reviews different methods of coir fiber modification include alkali treatment, silane treatment, hydrogen peroxide treatment, sodium hypochlorite treatment, sodium periodate treatment coupled with p‐aminophenol and urea, treatment with benzene diazonium salt and maleated coupling agent. It also reviews composites of coir fiber with thermoplastic, rubber and thermoset plastics. Hybrid composites based on coir fiber are also being discussed. Thermoplastic composites such as biodegradable (PLA, PBS) and petroleum‐based polymers (PE, PP) and thermoset polymers include polyurethane, epoxy and polyester based composites also reviewed. Degradation and biodegradation studies were reviewed in the case of biodegradable polymers. Hybrid fibers of coir with other natural and mineral fibers have recently been used in composite industry has also been reviewed. All these composites show better properties. It can be used in different applications in the field of automobile, building and construction, consumer products and furniture. POLYM. COMPOS., 37:3296–3309, 2016. © 2015 Society of Plastics Engineers     

Reinforcing effect and isothermal crystallization kinetics of poly(3‐hydroxybutyrate) nanocomposites blended with organically modified montmorillonite

Organically modified montmorillonite (OMMT) has been incorporated up to 7 wt% in poly(3‐hydroxybutyrate) (PHB) by melt compounding in a twin screw extruder. PHB nanocomposites reinforced with C93A showed significant increase in tensile and flexural modulus and impact strength comparatively. Wide angle X‐ray diffraction showed an increase in overall d‐spacing indicating intercalated structure. The intercalation morphology was further supported by transmission electron microscope images indicating formation of intercalated structure in case of PHB/OMMT and a mixture of Intercalated/exfoliated structure in case of PHB/TMI‐MMT nanocomposites. Thermogravimetric analyses indicate that the thermal stability of PHB/TMI‐MMT nanocomposites is higher among all other nanocomposites under investigation and virgin PHB. Differential scanning calorimetry (DSC) analysis of PHB nanocomposites shows marginal increase in glass transition temperature and decrease in crystallization temperature compared to virgin PHB. The isothermal crystallization kinetics of PHB/C93A nanocomposites was investigated by DSC in the temperature range of 100–120°C and the development of relative crystallinity with the crystallization time was analyzed by Avrami equation. POLYM. COMPOS., 35:999–1012, 2014. © 2013 Society of Plastics Engineers     

Synthesis of SiO2-Nanoparticles from Rice Husk Ash and its Comparison with Commercial Amorphous Silica through Material Characterization

Silicon - Silica is a major inorganic component of rice husk and present in the form of nanoparticle in it. Therefore, it is possible to extract high purity amorphous silica nanoparticles by simple...     

Influence of Coir Fiber Geometry on Mechanical Properties of SiC Filled Epoxy Composites

Silicon - The objective of this study is to attempt the possibility to employ eco-friendly fiber in composite material for engineering applications. Also, evaluate its mechanical properties like...     

Numerical analysis of the effect of tool wear on surface integrity during hard turning

Journal of Mechanical Science and Technology - The white layer formed during hard turning deteriorates surface integrity, thereby severely affecting the fatigue life of machined parts. A 2D...     

Enhanced dielectric,thermal stability,and energy storage properties in compositionally engineered lead-free ceramics at morphotropic phase boundary

Structural inhomogeneity at morphotropic phase boundary (MPB) offers a novel paradigm to explore and modulate the physical properties of dielectric materials to design next-generation multifunctional devices. In this work, two lead free materials at MPB; Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) and (Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ (BNTBT), are combined together to synthesize polycrystalline composite samples of (1-x) BCZT-xBNTBT with x = 0.0, 0.25, 0.50, 0.75, and 1.0. Structural investigations using XRD show the coexistence of double phases for pristine BCZT (tetragonal (P4mm) + rhombohedral (R3m)), and for pristine BNTBT (tetragonal (P4bm) + rhombohedral (R3c)). However, all the doped samples with x = 0.25, 0.5, and 0.75 display a coexistence of triple phases with P4mm, P4bm, and R3c symmetries. Detailed dielectric study reveals a normal ferroelectric to macroscopic ergodic relaxor crossover for samples with x = 0.25 and 0.75. Intriguingly, sample x = 0.25 displays a coexistence of high dielectric constant (4050), ultralow dielectric loss (≤0.02), high temperature thermal stability of permittivity (variation ≤ ±15%) in a temperature range 135 °C–450 °C, large recoverable energy density (W_rec = 423 mJ/cm³) with ultrahigh energy storage efficiency (η = 95.4%) at low applied electric field - 23 kV/cm. Nevertheless, at similar applied field strength, the obtained values of W_rec and η exceed most of the selected lead-free energy storage materials. This work may pave a new path to design superior high-temperature dielectrics, through intermixing of MPBs, for energy storage applications.     

Evaluation of a novel 8-channel RX coil for speech production MRI at 0.55 T

Magnetic Resonance Materials in Physics, Biology and Medicine - Speech production MRI benefits from lower magnetic fields due to reduced off-resonance effects at air-tissue interfaces and from the...     

Design,fabrication and testing of reduced graphene oxide strain gauge based pressure sensor with increased sensitivity

Microsystem Technologies - Pressure sensors with high sensitivity, repeatable output, wide sensing range, suitable for mass production and which can be manufactured cost effectively are highly...     

Dielectric and impedance properties of LiCa2Nb5O15 ceramics

Polycrystalline sample of LiCa₂Nb₅O₁₅ was prepared by a high-temperature solid-state reaction technique. Structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscope (SEM). X-ray studies reveal that the material has orthorhombic structure at room temperature. Electrical properties of the material have been studied using a complex impedance spectroscopy (CIS) technique in a wide temperature (31–500 °C) and frequency (10²–10⁶ Hz) ranges. The complex impedance plots reveal the main contribution of bulk effects in it. The bulk resistance, evaluated from complex impedance spectrum, has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR) behavior. Variation of dc conductivity (bulk) with temperature demonstrates that the compound exhibits Arrhenius type of electrical conductivity.     

Effect of cloisite 30B clay and sisal fiber on dynamic mechanical and fracture behavior of unsaturated polyester toughened epoxy network

This study examined the dynamic mechanical properties of sisal fiber reinforced unsaturated polyester (UP) toughened epoxy nanocomposites. The chemical structures changes in Epoxy, UP and UP toughened epoxy (Epoxy/UP) systems were characterized by Proton Nuclear magnetic resonance (¹HNMR) spectroscopy. The morphological alterations of the nanocomposites were analyzed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The untreated, chemically treated fibers, nanoclays, and the fiber reinforced Epoxy/UP nanocomposites were confirmed by FTIR spectrometer. The obtained mechanical results showed that alkali‐silane treated fibers improve the tensile strength (96%) and flexural strength (60%) of the Epoxy/UP nanocomposite than that of Epoxy/UP blend due to the strong interfacial bonding between the sisal fiber and matrix. The fracture toughness (K_IC) and fracture energy (G_IC) of treated sisal fiber reinforced DGEBA/UP/C30B nanocomposites found to be higher than that of untreated sisal fiber nanocomposites. The dynamic mechanical analysis (DMA) reveals that the fiber reinforced Epoxy/UP nanocomposites contains 30 wt% treated fiber and 1 wt% nanoclays, exhibits the highest storage modulus and better glass transition temperature (T_g) among the other kind of systems. The surface morphology of the fibers, fractured surface of the resins and composites were confirmed by scanning electron microscope (SEM). POLYM. COMPOS., 37:2832–2846, 2016. © 2015 Society of Plastics Engineers