Structural and Compositional Changes of Bamboo fibers during Super-Heated Steam Treatment and Thereby Composite Preparation

Structural and compositional changes of bamboo fibers, which were prepared through super-heated steam (SHS) treatment at normal pressure and fine grinding, were investigated by infra-red spectroscopy, thermogravimetry, viscosity-average molecular weight (Mv) measurement, and X-ray fluorescence analysis. SHS-treated Moso bamboo resulted in preferential decomposition of hemicellulose without any decrease in the Mv of cellulose crystalline. The SHS-treated bamboo was easily ground to obtain various short bamboo fibers (sBF) suitable for conventional melt processing of composites with polypropylene. The sBF showed good melt-processability and contributed to the mechanical performance of the composites moldings, resulting in 290% increases in flexural modulus

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

Tar-free and Benzo[a]pyrene-free Hydrothermal Liquefaction of Bamboo and Antibacterial Property of Recovered Vinegar

Bamboo, which was treated using superheated steam controlled at a low temperature range, gave tar-free and benzo[a]pyrene-free vinegar. The vinegar’s selective antibacterial activity against Staphylococcus aureus concerned with the atopic dermatitis and Bacillus cereus causing food poisoning in humans was confirmed, while no effect was found against Escherichia coli and Bacillus subtilis as being indigenous bacteria in natural environments

Tar-free and benzo[a]pyrene-free hydrothermal liquefaction of bamboo and antibacterial property of recovered vinegar

Bamboo, which was treated using superheated steam controlled at a low temperature range, gave tar-free and benzo[a]pyrene-free vinegar. The vinegar’s selective antibacterial activity against Staphylococcus aureus concerned with the atopic dermatitis and Bacillus cereus causing food poisoning in humans was confirmed, while no effect was found against Escherichia coli and Bacillus subtilis as being indigenous bacteria in natural environments

Auto-Drawing and Functionalization by Vapor-Phase Assisted Polymerization on Solid Surface

Formation of two- and three-dimensional micro architectures with chemical functions was verified by photo-vapor phase assisted surface polymerization (VASP) of functional monomer vapors combined with an auto-drawing system manipulated by prescribed programs. The surface modification by the photo-VASP of styrene vapor progressed rapidly, and a fine lines-pattern of photo-mask was transcribed as the corresponding polymer accumulations on poly(methyl methacrylate) (PMMA) substrate surfaces. Substrate surface modified by photo-VASP of acrylic acid showed reversible changes in hydrophilic/hydrophobic properties according to repeating external chemical stimuli. The successive auto-drawing by photo-VASP of three kinds of monomer vapors was examined under spot illumination from a fine optical fiber on an X-Y stage manipulated by a prescribed program, resulting in the production of a pre-designed functional structure by successful accumulations of corresponding polymers on the substrate surface

Short Bamboo Fibers Coated by Lignin during Super-Heated Steam Treatment and Bio-composites using Same

In order to apply short bamboo fiber (sBF) as a functional reinforcement of bio-composites having specific electrical properties, lignin-surfaced sBF was prepared via super-heated steam (SHS) treatment of bamboo. The sBF was easily isolated from the intrinsic fibrovascular bundle structure of bamboo after SHS treatment and pulverization. The isolated sBF was surfaced by brown-colored hydrophobic compounds, which were lignin-derived compounds generated during the SHS treatment. The functional bio-composites were prepared from the SHS-treated sBF and polypropylene and showed specific antistatic properties. Surface electrical resistance values of the composites decreased significantly with increase in the aspect ratio (AR) value of sBF. It is considered that the lignin-derived surfacing of sBF functions as an electron carrier in the composite, in particular, the longer sBF acts as an effective bridge for transporting electrons over long distances along conductive paths. From a cross-sectional microscopic image of the bio-composite, orientated sBFs were observed in its surface layer, supporting the suggestion of conductive path formation. Further, it was confirmed that the reinforcing effect of the presence of sBF was increased with increasing AR value

Thermal Stability of Poly (L-lactide): Influence of End Protection by Acetyl Group

Thermal stability of end-protected poly (L-lactide) (PLLA) was studied by dynamic thermal degradation and pyrolyzate analyses. The treatment of PLLA by acetic anhydride resulted in the acetylation of end hydroxyl groups, and at the same time a decrease in the residual Sn content in the polymer. The thermal degradation of the acetylated PLLA-Ac showed a shift to a 40-50°C higher degradation temperature range than that of untreated, high Sn content PLLA, but exhibited nearly the same degradation behavior as the untreated PLLA with a comparable Sn content. Purified metal-free PLLA-H showed good thermal stability, having the highest degradation temperature range. Interestingly, despite the end-protection, the acetylated metal-free PLLA-H/Ac decomposed at almost the same temperature as that of PLLA-H. From pyrolyzate and kinetic analyses, it was found that the contribution of the hydroxyl-end acetylation to the stability of PLLA was negligible, except for the stabilization effect due to the elimination of residual Sn during the acetylation process

Effects of Chain End Structures on Pyrolysis of Poly(L-lactic acid) Containing Tin Atoms

Thermal degradation of high molecular weight PLLA containing residual tin atoms was investigated as a means of controlling the reaction for feedstock recycling to L,L-lactide. To clarify the pyrolysis mechanism of the PLLA, three samples with different chain end structures were prepared, namely, as-polymerized PLLA-ap, precipitated-with-methanol PLLA-pr, and purified PLLA-H. From pyrolyzate and kinetic analyses, typical degradation mechanisms of Sn-containing PLLA were clarified. In other words, it was assumed that the pyrolysis of PLLA-ap proceeds through a zero-order weight loss process with the apparent Ea = 80-90 kJ mol-1, and with the occurrence of backbiting and transesterification reactions caused by Sn-alkoxide chain ends. The pyrolysis of PLLA-pr was also assumed to proceed via a zero-order weight loss process with apparent Ea = 120-130 kJ mol-1, with the proposed mechanism being Sn-catalyzed selective lactide elimination caused by Sn-carboxylate chain ends. Both pyrolysis of PLLA-ap and PLLA-pr produced L,L-lactide selectively. These degradation mechanisms and products are in contrast to those of PLLA-H, in which a large amount of diastereoisomers and cyclic oligomers were formed by random degradation. From this study, the complicated PLLA pyrolysis behavior as reported previously could be explained properly

Racemization on Thermal Degradation of Poly(L-lactide) with Calcium Salt End Structure

Poly(L-lactide) with calcium salt end structure (PLLA-Ca) is a promising material for PLLA recycling because of the ease of lactide recovery through the unzipping depolymerization process. However, the pyrolysis of PLLA-Ca also causes meso-lactide to form. In this article, the racemization in PLLA-Ca pyrolysis was analyzed in detail with Py-MS, Py-GC/MS, and a glass tube oven. The results suggested that at a temperature lower than 250°C, nucleophilic attack by a carboxylate anion end on an asymmetrical methyne carbon in a penultimate lactate unit occurred, resulting in the predominant formation of meso-lactide. On the other hand, also at temperatures over 320°C, by-reactions, such as enolization reactions, caused the meso-lactide to form, but not dominantly. In the temperature range of 250-320°C, L,L-lactide was produced exclusively, because unzipping depolymerization proceeded as the main reaction. This is a very significant result for PLLA recycling, because PLLA-Ca is an easily recyclable material, which depolymerizes based on the 1st-order weight loss process