Yoshito Andou

Modification of Oil Palm Mesocarp Fiber Characteristics Using Superheated Steam Treatment

In this study, oil palm mesocarp fiber (OPMF) was treated with superheated steam (SHS) in order to modify its characteristics for biocomposite applications. Treatment was conducted at temperatures 190–230 °C for 1, 2 and 3 h. SHS-treated OPMF was evaluated for its chemical composition, thermal stability, morphology and crystallinity. OPMF treated at 230 °C exhibited lower hemicellulose content (9%) compared to the untreated OPMF (33%). Improved thermal stability of OPMF was found after the SHS treatment. Moreover, SEM and ICP analyses of SHS-treated OPMF showed that silica bodies were removed from OPMF after the SHS treatment. XRD results exhibited that OPMF crystallinity increased after SHS treatment, indicating tougher fiber properties. Hemicellulose removal makes the fiber surface more hydrophobic, whereby silica removal increases the surface roughness of the fiber. Overall, the results obtained herewith suggested that SHS is an effective treatment method for surface modification and subsequently improving the characteristics of the natural fiber. Most importantly, the use of novel, eco-friendly SHS may contribute to the green and sustainable treatment for surface modification of natural fiber.

Biomass-based composites from poly(lactic acid) and wood flour by vapor-phase assisted surface polymerization.

To prepare biomass-based composites in an environmentally benign manner, vapor-phase assisted surface polymerization (VASP) was applied to prepare the composites from wood flour and poly(l-lactic acid) (PLLA) without solvent. VASP of l,l-lactide successfully proceeded on the wood flour surfaces, resulting in surface coverage by newly generated PLLA. For obtained PLLA/wood flour composites, it was clarified that grafting of PLLA on wood flour surfaces had occurred to form covalently bonded composites, with the accumulated PLLA layers having crystallized in situ during VASP. Resulting PLLA layers showed very high crystallinity of 79.2% and a high melting point close to the equilibrium melting point. Moreover, thermal degradation behavior of the composites suggested a cooperative degradation manner of the components.

Enhanced biocatalytic esterification with lipase-immobilized chitosan/graphene oxide beads.

In this work, lipase from Candida rugosa was immobilized onto chitosan/graphene oxide beads. This was to provide an enzyme-immobilizing carrier with excellent enzyme immobilization activity for an enzyme group requiring hydrophilicity on the immobilizing carrier. In addition, this work involved a process for the preparation of an enzymatically active product insoluble in a reaction medium consisting of lauric acid and oleyl alcohol as reactants and hexane as a solvent. This product enabled the stability of the enzyme under the working conditions and allowed the enzyme to be readily isolated from the support. In particular, this meant that an enzymatic reaction could be stopped by the simple mechanical separation of the “insoluble” enzyme from the reaction medium. Chitosan was incorporated with graphene oxide because the latter was able to enhance the physical strength of the chitosan beads by its superior mechanical integrity and low thermal conductivity. The X-ray diffraction pattern showed that the graphene oxide was successfully embedded within the structure of the chitosan. Further, the lipase incorporation on the beads was confirmed by a thermo-gravimetric analysis. The lipase immobilization on the beads involved the functionalization with coupling agents, N-hydroxysulfosuccinimide sodium (NHS) and 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC), and it possessed a high enzyme activity of 64 U. The overall esterification conversion of the prepared product was 78% at 60°C, and it attained conversions of 98% and 88% with commercially available lipozyme and novozyme, respectively, under similar experimental conditions.

Electrospun nanofiber membranes as ultrathin flexible supercapacitors

A highly flexible electrochemical supercapacitor electrode was developed with a novel metal oxide-reinforced nanofiber electrode by utilizing a solution-based electrospinning technique. The facile fabrication steps involved the introduction of metal precursors into a polymeric solution, which was subjected to an in situ electrospinning process. The electrospun polymeric web with metallic ingredients was then subjected to an oxidative stabilization process that induced the formation of metal oxide nanoparticles within the polymer structure. Finally, the metal oxide nanoparticles incorporated with nanofibers were obtained using a carbonization process, thus converting the polymer backbones into a carbon-rich conductive nanofiber structure. The fabricated nanofibers were decorated and implanted with metal oxide nanoparticles that had a surface-decorated structure morphology due to the solubility of the precursors in the reaction solution. The electrochemical performance of the fabricated metal oxide reinforced with nanofiber electrodes was investigated as an electrochemical system, and the novel morphology significantly improved the specific capacitance compared to a pristine carbon nanofiber membrane. As a result of the uniform dispersion of metal oxide nanoparticles throughout the surface of the nanofibers, the overall capacitive behavior of the membrane was enhanced. Furthermore, a fabricated free-standing flexible device that utilized the optimized nanofiber electrode demonstrated high stability even after it was subjected to various bending operations and curvatures. These promising results showed the potential applications of these lightweight, conductive nanofiber electrodes in flexible and versatile electronic devices.

Successful scaling-up of self-sustained pyrolysis of oil palm biomass under pool-type reactor

An appropriate technology for waste utilisation, especially for a large amount of abundant pressed-shredded oil palm empty fruit bunch (OFEFB), is important for the oil palm industry. Self-sustained pyrolysis, whereby oil palm biomass was combusted by itself to provide the heat for pyrolysis without an electrical heater, is more preferable owing to its simplicity, ease of operation and low energy requirement. In this study, biochar production under self-sustained pyrolysis of oil palm biomass in the form of oil palm empty fruit bunch was tested in a 3-t large-scale pool-type reactor. During the pyrolysis process, the biomass was loaded layer by layer when the smoke appeared on the top, to minimise the entrance of oxygen. This method had significantly increased the yield of biochar. In our previous report, we have tested on a 30-kg pilot-scale capacity under self-sustained pyrolysis and found that the higher heating value (HHV) obtained was 22.6–24.7 MJ kg−1 with a 23.5%−25.0% yield. In this scaled-up study, a 3-t large-scale procedure produced HHV of 22.0–24.3 MJ kg−1 with a 30%−34% yield based on a wet-weight basis. The maximum self-sustained pyrolysis temperature for the large-scale procedure can reach between 600 °C and 700 °C. We concluded that large-scale biochar production under self-sustained pyrolysis was successfully conducted owing to the comparable biochar produced, compared with medium-scale and other studies with an electrical heating element, making it an appropriate technology for waste utilisation, particularly for the oil palm industry.

Enhancement of compatibility based on vapor-phase-assisted surface polymerization (VASP) method for polymer composites with agricultural wastes

Cellulosic substances in polymer matrices are immiscible and non-dispersive because of mismatch between their surface properties. In order to fabricate a natural fiber-reinforced plastic, hydrophilic cellulosic substances should be modified to hydrophobicity to make it miscible and dispersible to polymer matrices. Herein, this work shows potential application of vapor-phase-assisted surface treatment as a new modification approach for cellulosic substances. Cellulosic substances were modified to improve the compatibility in the polymer matrix. The modified cellulose substrates were characterized by Fourier transform infrared spectrometer spectroscopy, thermogravimetric analysis, and scanning electron microscope, and the resulting shows the grafting polymer on cellulosic substances indeed. To more enhance compatibility in polymer matrix, grafting of the methacryloyl groups on cellulose substance was prepared through gaseous methacrylic anhydride on cellulose surface, and then higher modified cellulose substance was carried out with vapor-phase graft polymerization of methyl methacrylate finally. The vapor-phase-assisted surface treatments could highly modify the cellulose surface compared to conventional method in liquid process.

Modification of Carbon-Based Electroactive Materials for Supercapacitor Applications

Relentless efforts have been underway to improve the energy storage capability and cyclic stability of supercapacitors without sacrificing their shelf life. Supercapacitors, also known as electrochemical capacitors, can deliver significantly more power than batteries or fuel cells, making them indispensable in high power density applications. The selection of electroactive materials for supercapacitors is attributed to the high specific capacitance of supercapacitors. Activated carbon and carbon nanotubes have been widely explored as electroactive materials in supercapacitor applications because of their unique combination of features, which include a high surface area, high electrical conductivity, controlled pore size distribution, and excellent electrochemical properties. Recently, graphene has attracted tremendous interest for supercapacitor research because of its exceptionally high charge carrier mobility, high conductivity, excellent mechanical properties, high surface area, good chemical stability, and great flexibility compared to other carbon-based materials. Therefore, this chapter discusses different types of carbon-based materials that have been studied as electroactive materials for the electrodes of supercapacitors, along with their electrochemical performances (i.e., specific capacitance, retention value, and impedance) in supercapacitor applications.

Simple Manufacture of Surface-Modified Nanolignocellulose Fiber via Vapor-Phase-Assisted Surface Polymerization

This work tackles the disadvantages in the production of functionalized nanofibers from biomass and offers a new methodology to nanofiber-reinforced composite manufacturing. A vapor-phase-assisted surface polymerization (VASP) method has been used to develop surface-modified lignocellulosic nanofibers. Through the vaporized monomers during polymerization, the polymer chains can be introduced deep within oil palm mesocarp fibers (OPMFs) due to their unique porous structure. After OPMFs are modified with polymer chains, the simple Mortar grinder mill–ionic liquid (M-IL) method provides fibrillation from the macro- to nanoscale, retaining the grafted polymer chains. This approach for the functionalization of biomass could lead to the large-scale fabrication of surface-modified nanofibers for reinforced materials and promote innovative implementations of the renewable biomass resource.

Design of biodegradable PCL/PI films as a joining tape for grafting plant

ABSTRACT In this study, novel eco-friendly blends based on environmental-friendly polymers and compatibilizers, such as poly(ϵ-caprolactone) (PCL), cis-1,4-polyisoprene (PI), soybean lecithin (SOLE) and acrylated-epoxidized soybean oil (AESO), have been prepared in order to suggest a biodegradable joining tool used for plant grafting in agriculture, which will be competitive from the environment and economic points of view against conventional nonbiodegradable tools. PCL/PI blends, in which the portion of PCL was 75 and 50, were mixed with a compatibilizer by a melt-blending technique. The resulting blends were investigated by thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy and also their mechanical properties were determined. Afterwards, the blend films were buried in the soil. Remarkable level of weight loss was achieved in 6 weeks, ∼46%. The results showed that the addition of SOLE helped to improve the compatibility between PCL and PI due to its amphipathic property, and, besides, accelerated the weight loss of the films in soil, increasing microorganism growth on the film.

Melt-Processable Nanocomposites Grafting-From Platelet Surfaces by Vapor-Assisted Surface Polymerization

One issue accompanying the melt-processing polymer/clay nanocomposites is the reaggregation of silicate platelets, which induces decreases in advantages of nanocomposites. To address this issue, vapor-assisted surface polymerization (VASP) method was applied with an initiator-attached and copolymerizable surfactant moiety-bound A-C18/C6MMT to obtain the exfoliated and intercalated nanocomposites using methylmethacrylate and styrene as vinyl monomers, respectively. The melt processing of the nanocomposites was carried out by a melt-compression molding method at 200°C. From XRD measurements, the C18/C6MMT-based nanocomposites showed no change in d-spacing even after melt processing, indicating the maintenance of the exfoliation and intercalation states. This maintenance must result from polymer chains grafting from the silicate layer surfaces, thus clearly confirming the anchoring effect of the copolymerizable surfactant moiety units.