Thermal Degradation Behavior of Poly (lactic acid) Stereocomplex

Thermal degradation of poly(lactic acid) stereocomplex (scPLA) was investigated to clarify the pyrolysis mechanism. Three scPLA samples with different chain end structures were prepared, namely, as-polymerized scPLA-ap, precipitated-with-methanol scPLA-pr, and purified metal-free scPLA-H. From the analyses of thermal degradation kinetics and pyrolyzates of the scPLA samples, typical degradation mechanisms of these scPLAs were proposed as follows: The pyrolysis of scPLA-ap proceeds through main unzipping depolymerization caused by Sn-alkoxide chain ends with apparent Ea = 80-100kJ mol-1, showing zero-order weight loss behavior. The pyrolysis of scPLA-pr also proceeds via a zero-order weight loss process consisting of main Sn-catalyzed selective lactide elimination with apparent Ea = 100-120kJ mol-1 caused by Sn-carboxylate chain ends. The pyrolyzates from scPLA-ap and scPLA–pr were predominantly L,L-/D,D-lactides. In the case of scPLA-H, random degradation is a main process, producing a large amount of meso-lactide and cyclic oligomers. These degradation mechanisms were nearly the same as those of the corresponding PLLAs, except that the scPLA-ap pyrolysis started at higher temperature due to the higher melting point of scPLA

Biodegradability of Plastics

Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed

Pyrolysis Kinetics of Poly(L-lactide) with Carboxyl and Calcium Salt End Structures

To clarify the pyrolysis mechanism of poly(L-lactide), which has been reported as complex, the thermal decomposition of carboxyl type and calcium ion end capped PLLA (PLLA-H and PLLA-Ca, respectively) was investigated by means of thermogravimetric analysis (TG), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The TG data revealed that PLLA-Ca has a lower pyrolysis temperature (220~360°C) than that of carboxyl type PLLA-H (280~370°C). The apparent activation energy of the decomposition reaction was estimated from TG curves at different heating rates by plural methods to be 176 and 98 kJ mol-1 for PLLA-H and PLLA-Ca, respectively. Further kinetic studies indicated that PLLA-H degraded mainly through a random reaction with a pre-exponential factor A=2.0×1012 s-1, whereas PLLA-Ca degraded by way of a 1st-order reaction with A=8.4×105 s-1. Pyrolysis products of PLLA-H were composed of lactides and other cyclic oligomers, while the degradation products of PLLA-Ca were principally lactides. The main reaction pathway for PLLA-H pyrolysis was regarded as the random transesterification, whereas for PLLA-Ca pyrolysis the unzipping depolymerization process was dominant

シカク ショウガイシャ ヘ ノ シンキュウ キョウイク ニ オケル オントロジー ベース キョウザイ ノ ユウコウセイ

我々は視覚障害者向けの鍼灸、特に経絡と経穴に関する教育材料の研究に取り組んだ。この教材では、鍼灸分野における概念間の関係の体系的な理解を可能にすべく、オントロジーを用いた。オントロジーの概念図によりオントロジー教材を作成し、これを鍼灸の講義で使用した群とオントロジー教材未使用群とで経絡・経穴の試験の結果を比較し、その有効性を解析した。その結果、オントロジー教材を使用した学生の経絡・経穴の試験の得点は、オントロジー教材未使用群の学生の得点よりも有意(P < 0.001)に高く、経絡と経穴の学習にオントロジー教材有効である事が明らかになった。この結果は、オントロジーの視覚障害者教育への利用が視覚障害者の鍼灸理論の学習へも有効であることを示唆している。In this study we developed learning material of acupuncture - acupoints and meridians - for visually impaired people. For this learning material, we used ontology to construct the relations between the concepts in the acupuncture and moxibustion field which also enables tactical understanding similarly as visual understanding. We then used our learning material in the acupuncture lecture for the visually impaired students, and quantitatively analysed its efficacy to compare the results with the group which did not use the learning material. As a result, the students, who used our learning material, scored significantly higher in the examination than the students of non-use group (P < 0.001), suggesting that our learning material was effective for learning of acupuncture theory

Biodegradability of Plastics

Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed