KOBUNSHI RONBUNSHU

Original Papers

Study on the Use of Supercritical Carbon Dioxide as a Solvent to Prepare Novel, Efficient Controlled-Release Materials

Chikara TSUTSUMI, Ami TSUZUKI, Teruyuki HARA, Yuushou NAKAYAMA, Takesh ...

2014 Volume 71 Issue 1 Pages 1-10
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.1

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In order to develop a novel controlled-release materials, we previously attempted to impregnate poly(L-lactide) (poly(L-LA)), poly(L-LA-ran-CL) (CL: ε-caprolactone) and poly(L-LA-ran-TEMC) (TEMC: tetramethylene carbonate) with low boiling point organic compounds using supercritical carbon dioxide (scCO₂) as the solvent. In this work, the factors influencing the impregnation of poly(L-lactic acid) copolymers with various compounds in scCO₂ was investigated. The effects of temperature, pressure and time on the impregnation process were evaluated, using synthetic poly(L-LA-ran-CL), poly(L-LA-ran-TEMC) or poly(L-LA-ran-DXO) (DXO: 1,5-dioxepan-2-one) as the base polymers. Preparation of the controlled-release materials was carried out using essential oil from Thujopsis dolabrata var. hondae in scCO₂ at 14 MPa, 40°C for 3 h. The oil content was highest for poly(L-LA-ran-CL) and lowest for poly(L-LA-ran-DXO). The mechanical properties of those impregnated were evaluated by a tensile testing machine. Although the tensile strength and elastic modulus of poly(L-LA-ran-TEMC) and poly(L-LA-ran-DXO) increased greatly by impregnation in scCO₂, the elongation decreased conversely. Poly(L-LA-ran-DXO) could easily be hydrolyzed in saturated calcium chloride solution, and the containing oil was also released earlier than for other polymers.

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Preparation of Chondroitin Sulfate/Chitosan Composite Fibers by Spinning from Aqueous Solution Interfaces

Kazutoshi IIJIMA, Kazuya YUYAMA, Kotaro ASAINE, Kanta IRIE, Mineo HASH ...

2014 Volume 71 Issue 1 Pages 11-16
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.11

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We developed processes to obtain water-insoluble fibers from polyion complexes (PIC) of chondroitin sulfate C (CS) and chitosan (CHI) by utilizing interface-spinning methods. A CS solution was gently placed on a CHI solution, which resulted in formation of films made of PIC at the solution interfaces. Fibers were spun by withdrawing the films from the interfaces, then dried by passing through an acetone bath and finally rolled up. We evaluated the morphology and strength of the prepared fibers. Several meters-long CS/CHI composite fibers having several tens of micrometers diameter were successfully obtained through this process. Interestingly, it was found that tensile strength increased as the molecular weight of CHI increased. Swelling-stretching treatment made these fibers denser and stronger than before treatment. The experimental results revealed that these fibers made of CS/CHI had mechanical properties sufficient for structural materials.

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Polyion Complex Formation from Marine Biomass by Reactive Processing

Takayuki TSUKEGI, Jauzein VINCENT, Minato WAKISAKA, Haruo NISHIDA

2014 Volume 71 Issue 1 Pages 17-22
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.17

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Alginic acid from seaweed and chitosan derived from shrimp and crab shells are well known as abundant biopolymers of marine origin. Alginic acid as a polyanion and chitosan as a polycation produce a polyelectrolyte complex (PIC) by ionic crosslinking. So far, PIC has been prepared by alternate lamination or casting methods. In this study, a novel continuous preparation method of PIC was demonstrated with an extruder and a hot press. It was confirmed that homogeneous PIC sheets were prepared conveniently. Moreover, by adding various plasticizers it was shown that mechanical properties of PIC were controllable in a range of hard and soft materials.

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Thermal Oxidation Degradation Mechanism of Polyethylene by FT-IR Imaging

Kiyomi OKADA, Tetsuya TSUJII, Kazushi YAMADA, Hiroyuki NISHIMURA

2014 Volume 71 Issue 1 Pages 23-30
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.23

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The deterioration mechanism of polyethylene with increased temperature resistance (PERT) used for hot water supply plumbing was investigated. The deterioration in 120°C air was analyzed by using FT-IR. The following results were found (1) Degradation begins from the place where orientation relaxes gently and the amount of antioxidants decreases. The degradation by oxidation starts from surface. It advances along the surface, but does not advance that much into the bulk. (2) The progress of surface deterioration can be evaluated by the ratio acid to aldehyde peak of the carbonyl group. (3) It is necessary to evaluate not only the amount of carbonyl groups, at around 1600 cm⁻¹ but also its type (acid or aldehyde). The above result correlate with the results of tensile-strength tests and thermal measurements. The deterioration process of PERT can be analyzed more clearly by the FT-IR imaging method and visualization in two dimensions.

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Development of Biocomposites Containing Erianthus Arudinaceus as Cellulose Resource Crops

Hee-sung LEE, Minato WAKISAKA, Norio NAGASAWA, Haruo NISHIDA, Yoshito ...

2014 Volume 71 Issue 1 Pages 31-37
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.31

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Fiber reinforced plastics using natural fibers are attracting keen interest as renewable materials and for efficient CO₂ fixation. We focused on Erianthus arudinaceus as a cellulose resource crop for enhancing the mechanical properties and the thermal stability of biocomposites and improving the interfacial adhesion between polypropylene (PP) and Erianthus fiber (ETF). To achieve this purpose, we proposed classifications of fiber size after grinding. Maleic anhydride-polypropylene (MAPP) is used as a compatibilizer in the polymer matrix. The ETF/PP and ETF/PP/MAPP composites were prepared using a twin screw extrusion followed by injection molding. Tensile strength and flexural strength of ETF/PP composites revealed a weak adhesion between matrix and wood fibers. However, the ETF/PP/MAPP composites show improved tensile strength and flexural strength. Moreover, we examined the influence of ETF fiber size in biocomposites on mechanical strength and thermal degradation stability.

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Optimization of Screw Design on Fiber Breakage and Dispersion in Injection Molded Bamboo-Fiber-Reinforced Polypropylene

Akira INOUE, Tatsuya TANAKA, Yoshihiko ARAO, Hiroshi TAGUCHI, Yasutake ...

2014 Volume 71 Issue 1 Pages 38-46
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.38

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Injection molding of fiber-reinforced thermoplastics (FRTP) leads to fiber breakage and in turn deterioration of mechanical properties of the molded parts. In this paper, we propose an effective screw geometry for improving both fiber dispersion and residual fiber length. By evaluating four types of screws by investigation of the molded specimens, we found that the screw geometry in the compression zone had a dominant effect on the residual fiber length, and that choosing the proper geometry for the melting and mixing process was the most important factor for improving both fiber dispersion and residual fiber length. The screw improves both properties at the same time owing to the appropriateness of its geometry for both the melting and mixing zone. Our experimental observations were compared with the results of flow analysis and consistency was observed.

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Relationship between Transparency and Morphology of Cast Films Composed of a Mixture of Poly-D-Lactic Acid and Poly-L-Lactic Acid

Yuichiro KOIDE, Hiroki IKAKE, Yoshio MUROGA, Shigeru SHIMIZU

2014 Volume 71 Issue 1 Pages 47-51
Published: January 25, 2014
Released on J-STAGE: January 24, 2014

DOIhttps://doi.org/10.1295/koron.71.47

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Two kinds of cast films, mix-PLA(DOX) film and mix-PLA(CHL) film, were prepared with an equal-weight mixture of poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) by using 1,4-dioxane (DOX) or chloroform (CHL) as casting solvent, and it is clarified that mix-PLA(DOX) films are opaque, whereas mix-PLA(CHL) films are transparent. The relation between the transparency of these mix-PLA films and their morphology was studied by wide-angle X-ray diffraction, differential scanning calorimetry, and small-angle X-ray scattering. It is shown that the transparency does not depend on the crystallinity of sc-PLA, but on the macrostructure of the stereo-complex composed of PLLA and PDLA, sc-PLA, which is reflected in crystal size, lamella thickness and long period and their distribution. The transparency is lowered as the macrostructure becomes more disturbed or disordered. Moreover, it is shown that mix-PLA(CHL) films have good transmittance comparable to that of poly(methyl methacrylate) or polycarbonate and better thermal-resistance.

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