Supachok Tanpichai

Effective Young’s Modulus of Bacterial and Microfibrillated Cellulose Fibrils in Fibrous Networks

The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at ≈ 1095 cm(-1). We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peaks wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79-88 and 29-36 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poissons ratio for MFC networks and BC networks. Discussion of this in-plane auxetic behavior is given.

Micromechanics of TEMPO-Oxidized Fibrillated Cellulose Composites

Composites of poly(lactic) acid (PLA) reinforced with TEMPO-oxidized fibrillated cellulose (TOFC) were prepared to 15, 20, 25, and 30% fiber weight fractions. To aid dispersion and to improve stress transfer, we acetylated the TOFC prior to the fabrication of TOFC-PLA composite films. Raman spectroscopy was employed to study the deformation micromechanics in these systems. Microtensile specimens were prepared from the films and deformed in tension with Raman spectra being collected simultaneously during deformation. A shift in a Raman peak initially located at ~1095 cm(-1), assigned to C-O-C stretching of the cellulose backbone, was observed upon deformation, indicating stress transfer from the matrix to the TOFC reinforcement. The highest band shift rate, with respect to strain, was observed in composites having a 30% weight fraction of TOFC. These composites also displayed a significantly higher strain to failure compared to pure acetylated TOFC film, and to the composites having lower weight fractions of TOFC. The stress-transfer processes that occur in microfibrillated cellulose composites are discussed with reference to the micromechanical data presented. It is shown that these TOFC-based composite materials are progressively dominated by the mechanics of the networks, and a shear-lag type stress transfer between fibers.

Keratin Extracted from Chicken Feather Waste: Extraction, Preparation, and Structural Characterization of the Keratin and Keratin/Biopolymer Films and Electrospuns

In this work, keratin was extracted from chicken feather waste via an environment-friendly method, sulphitolysis method, by using various sodium metabisulphite contents (0.0–0.5xa0M). Percentage yield and molecular weight of the extracted keratin were characterized by gravimetry and gel electrophoresis (SDS-PAGE), respectively. It was found that the yield increased, with the increase of sodium meta-bisulphite content, to the maximum value of 87.6xa0% yield, by using sodium meta-bisulphite content at 0.2xa0M. Molecular weight range of the product also decreased with the increase of the sodium meta-bisulphite content. The extracted keratin, with highest molecular weight ranged between 12 and 20xa0kDa, was further used for fabricating into fibers by using the electrospinning process. It was found that pure keratin solution could not be electrospun into fiber. However, by blending keratin with more than 10xa0wt% PLA, the fibers can be prepared. Results from FTIR and DSC also reveal that the crystal structure of the keratin changed from the β-sheet structure (rigid and small displacement characteristic) to the α-helix structure (elastic and large displacement characteristic) after keratin/PLA blends (10–50xa0wt% keratin) were prepared by the electrospinning method.

Effects of two different cellulose nanofiber types on properties of poly(vinyl alcohol) composite films

This work concerns a study on the effects of fiber types and content of cellulose nanofiber on mechanical, thermal, and optical properties polyvinyl alcohol (PVA) composites. Two different types of cellulose nanofibers, which are nanofibrillated cellulose (NFC) and bacterial cellulose (BC), were prepared under various mechanical treatment times and then incorporated into the PVA prior to the fabrication of composite films. It was found that tensile modulus of the PVA film increased with nanofibers content at the expense of its percentage elongation value. DSC thermograms indicate that percentage crystallinity of PVA increased after adding 2-4 wt% of the fibers. This contributed to the bettermechanical properties of the composites. Tensile toughness values of the PVA/BC nanocomposite films were also superior to those of the PVA/NFC system containing the same fiber loading. SEM images of the composite films reveal that tensile fractured surface of PVA/BC experienced more ductile deformation than the PVA/NFC analogue. The above discrepancies were discussed in the light of differences between the two types of fibers in terms of diameter and their intrinsic properties. Lastly, percentage total visible light transmittance values of the PVA composite films were greater than 90%, regardless of the fiber type and content.

Effect of clay content on morphology and processability of electrospun keratin/poly(lactic acid) nanofiber.

This research work has concerned the development of volatile organic compounds (VOCs) removal filters from biomaterials, based on keratin extracted from chicken feather waste and poly(lactic acid) (PLA) (50/50%w/w) blend. Clay (Na-montmorillonite) was also added to the blend solution prior to carrying out an electro-spinning process. The aim of this study was to investigate the effect of clay content on viscosity, conductivity, and morphology of the electrospun fibers. Scanning electron micrographs showed that smooth and bead-free fibers were obtained when clay content used was below 2 pph. XRD patterns of the electrospun fibers indicated that the clay was intercalated and exfoliated within the polymers matrix. Percentage crystallinity of keratin in the blend increased after adding the clay, as evidenced from FTIR spectra and DSC thermograms. Transmission electron micrographs revealed a kind of core-shell structure with clay being predominately resided within the keratin rich shell and at the interfacial region. Filtration performance of the electrospun keratin/PLA fibers, described in terms of pressure drop and its capability of removing methylene blue, were also explored. Overall, our results demonstrated that it was possible to improve process-ability, morphology and filtration efficiency of the electrospun keratin fibers by adding a suitable amount of clay.

Microfibrillated Cellulose Reinforced Poly(vinyl alcohol) Composites

Microfibrillated cellulose (MFC) was successfully prepared from lyocell fibers using combined homogenization and sonication treatments. MFC fibrils with a mean diameter of ~365 nm were observed, after the lyocell fibers with diameters of ~10 μm were mechanically treated for 60 min. Poly (vinyl alcohol) (PVA) composites reinforced with MFC were then fabricated using a solvent casting method. Physical and mechanical properties of the MFC reinforced PVA composites were investigated. An increase of ~13 and ~34 % of tensile strength and Youngs modulus was observed for the 3 wt% MFC reinforced composites, compared to those of the pure PVA. Raman spectroscopy was also employed to study the deformation micromechanics of the MFC reinforced PVA composites. The position of the Raman peak initially located at 1095 cm-1, corresponding to the C-O ring stretching and C-O-C glycosidic bond stretching modes, was recorded. During tensile deformation, this peak was observed to shift towards a lower wavenumber position, indicating stress-transfer between the resin and the fibrils.

Mechanical Properties of All-Cellulose Composites Made from Pineapple Leaf Microfibers

Pineapple leaf microfibers were firstly prepared using steam explosion, and all-cellulose composites were subsequently prepared using a surface selective dissolution process with the solvent of lithium chloride and N,N-dimethylacetamide (LiCl/DMAc). Mechanical properties and surface morphology of all-cellulose composites with immersion times of pineapple leaf microfibers in the solvent of LiCl/DMAc were investigated using tensile testing and scanning electron microscopy, respectively. The tensile strength of the all-cellulose composites with 120 min-immersion time was approximately 28 times higher than that of the pineapple leaf microfiber mats. These biocomposites made from pineapple leaf microfibers could be one of the potential alternatives to replace glass fiber reinforced composites.

Reinforcing abilities of microfibers and nanofibrillated cellulose in poly(lactic acid) composites

Abstract The reinforcing abilities of cellulose microfibers and nanofibrillated cellulose (NFC) in poly(lactic acid) (PLA) were evaluated. NFC successfully prepared from regenerated cellulose fibers using high-speed blending for 60 min was introduced in a PLA matrix. The physical and mechanical properties of NFC-reinforced PLA composites were investigated in comparison with those of the composites with microfibers. NFC fibrils with diameters in the range of 100–500 nm were disintegrated from micron-sized regenerated fibers. A slight decrease in the degree of crystallinity and degradation temperature obtained for NFC after mechanical treatment was found compared with untreated microfibers. The introduction of NFC in the PLA effectively increased the tensile strength and Young’s modulus of the composites by 18% and 42%, respectively. The use of micron-sized fibers to reinforce PLA, on the other hand, showed a slight improvement in Young’s modulus (13%). The improvement in the mechanical properties of the composites reinforced with NFC was found because of the higher surface area of NFC and better interaction between the matrix and NFC fibrils. This allowed stress to transfer from the matrix to the reinforcement. NFC prepared using the high-speed blending could be an alternative to use as reinforcement in composites.

Transparency, moisture barrier property, and performance of the alternative solar cell encapsulants based on PU/PVDC blend reinforced with different types of cellulose nanocrystals

Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25xa0wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNCm) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNCw). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517xa0gxa0m−2xa0day−1 was the PU/PVDC film reinforced with 0.1xa0wt% of CNCm. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14xa0days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

All-cellulose composite laminates prepared from pineapple leaf fibers treated with steam explosion and alkaline treatment

Pineapple leaf fibers with diameters of 43u2009±u20090.1u2009µm were treated by two different approaches: the alkaline treatment and the combination of the steam explosion and alkaline treatment. The observations revealed the steam explosion process efficiently provided 3.4u2009µm diameter fibers with a less amount of lignin and a higher proportion of cellulose, compared with the alkaline-treated fibers. The steam-exploded fibers showed higher crystallinity and more thermal stabilities than the alkaline-treated fibers. No structural change from cellulose I to cellulose II was detected from both treated pineapple leaf fibers. Subsequently, all-cellulose composite laminates were prepared from these two types of treated pineapple leaf fibers mats. The higher tensile strength and modulus were obtained from the steam-exploded pineapple leaf fibers composite laminates due to larger surface areas of the fibers interacted with the cellulose matrix. Fracture morphology of the composites was studied after tensile deformation. The combination mechanism of fiber breakage and fiber pull-out deformation was observed from the steam-exploded pineapple leaf fibers composite laminates, whereas only fiber pull-out mechanism was found from the alkaline-treated pineapple leaf fibers composite laminates. The fiber width and amounts of the matrix filling in pores in a mat were found to dominate the mechanical properties of the all-cellulose composites.