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Improvement of Mechanical and Thermal Properties of Poly(lactic acid) with Polymer Blends
Get PDF京都工芸繊維大学博士（工学）ポリ乳酸（PLA）はバイオマスから製造されるバイオベースポリマーとして、高い機械的特性を有している。しかし、PLAは脆くて耐熱性に劣るという欠点もある。そこで、この研究の目的は、生分解性ポリマーとして高い強度を持つポリブチレンサクシネート-co-アジペート（PBSA)をブレンドすることによって、PLAの物性を改善することである。二軸押出機でPLAとPBSAをブレンドし、レオロジー及び熱的特性の測定を行った。さらに、射出成型によるテストピースの作製と溶融紡糸による繊維化を行い、衝撃強度及び引張強度の測定を行った。その結果、PBSAの割合が低い場合には、PBSAはPLAに良好に分散し、PBSAの割合が高いときには大きな滴状となった。射出成型物の機械的物性はPLAマトリックス中のPBSAの分散状態に依存していた。PBSAが良好にPLAマトリックスに分散するほど、耐衝撃強度も改善された。しかし、繊維の機械的強度はPBSAをブレンドすることによって低下した。 ポリエチレングリコール（PEG）がポリ乳酸とポリブチレンサクシネート（PBS)のブレンドの物性に与える影響を解明した。DMAによる測定より、PLA単味のTgとPBSブレンド中におけるTgは等しかったが、PEGの添加によりそれらの値は異なった。この現象はPBSでは見られなかった。この事から、ブレンド体においてPEGはPLA相からPBS相に異動していると考えられる。引張強度とヤング率はPEGの添加量が増加するに従い減少した。このことは、PEGがポリマーブレンド中で可塑剤として働いていることを意味している。SEMによる破断面の観察では、PEGの添加はPLAの物性を脆弱性から延伸性へと変化させていることを示している。 PLAとポリブチレンサクシネート（PBS)は良好な混和性を示した。PLAとPBSのブレンド体（PLA-PBS）の機械的、及び熱的特性はポリマーの結晶性と関連している。ポリ乳酸（PLA）とポリブチレンサクシネート（PBS)のブレンドにタルクを添加し、溶媒法及びキャスティング法によってフィルムを製作した。等温結晶化の動力学および球晶の形態の観察を行い、アブラミモデルによる解析を行った。ブレンド体におけるポリ乳酸とPBSの重量比は80：20及び60：40とした。一方タルクの添加量は0から5 phrとした。タルクの分散性はPLAの等温結晶化率および結晶の広がりに強く依存し、PBSの場合が大きな球晶に成長するのと対比的であった。PLA単体とPLA-PBSブレンド中におけるPLAを比較すると、ブレンド比率80:20ではタルクの添加により明らかに結晶化は促進された。一方、ブレンド比率60:40では、低温においてPBSの結晶化挙動が観察された。PLA-PBSブレンドにおいて、アブラミ式のｎ値は2.4から4.7であった。これは、結晶が三次元で成長していることを示している
Impact Property of Flexible Epoxy Treated Natural Fiber Reinforced PLA Composites
No full textAbstractThe modification is required for more practical applications due to the brittleness of PLA polymer. The improvement of the impact properties of PLA is an addition of fillers or reinforcements. Bamboo fiber, vetiver grass fiber and coconut fiber were used as alternative reinforcements in PLA composites. Injection molded of untreated and flexible epoxy treated composites at various reinforcement content was prepared. The impact strength of natural fiber reinforced PLA composite decreased with the increased of fiber content. The maximum reduction in impact strength was 23.8, 27.3 and 56.2% for bamboo fiber/PLA, vetiver grass fiber/PLA and coconut fiber/PLA composites, respectively. The flexible epoxy surface treatment improved impact property of bamboo fiber/PLA and coconut fiber/PLA composites when compared against the untreated composites. Unlike the other combinations, treated vetiver grass fiber/PLA composite showed less improvement in impact strength when compared with other natural fibers. Bamboo fiber proved to be the most effective reinforcement among all studied reinforcements
Mechanical Property of Surface Modified Natural Fiber Reinforced PLA Biocomposites
No full textAbstractNatural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fiber reinforced polymer composites. This paper is focused on the tensile properties of natural fiber reinforced polylactic acid composites. The untreated and flexible epoxy treated bamboo fiber, vetiver grass fiber and coconut fiber were used as reinforcement for PLA biocomposites. The stiffness of untreated biocomposites increased significantly with increasing of fiber content. However, the tensile strength decreased with increasing of fiber content. The flexible epoxy surface treatment reduced the stiffness of all composites while it considerably increased tensile strength when compared against the untreated composites. In addition, it can be seen that the effects of flexible epoxy treated on the tensile strength improvement were dependent upon the type of natural fiber. The tensile strength of bamboo fiber and coconut fiber reinforced PLA composites were significantly improved by the flexible epoxy surface treatment. Unlike the other combinations, vetiver grass fiber reinforced PLA composite showed less improvement in tensile strength when comparing with other natural fibers. Bamboo fiber proved to be the most effective reinforcement compared to other reinforcements
Biodegradation in Landfilled of Biodegradable Micro-braided Yarn
No full textAbstractBiodegradable polymer yarns of polymer blends of poly(lactic acid) (PLA) and poly(butylene succinate-co-adipate) (PBSA) reinforced with natural fiber were prepared by a micro braiding technique. The biodegradation of the micro-braid yarn was studied by field tests. The yarn are prepared from polymer blends of PLA:PBSA with ratios of 100:0, 90:10, and 85:15 (wt%) by a single screw extruder. Braided samples were prepared using jute as a braided core fiber. The mechanical property analysis showed tensile strength of polymer yarn with jute fiber higher than polymer yarn without jute. Biodegradation of micro-braiding yarn with and without jute fiber was studied by buried under controlled conditions compared with cellulose. The field biodegradation test was carried out for 28 days with period of 7 days sampling. It was found that humidity and soil temperature affected the biodegradability of polymers. Analysis of samples confirmed that buried at low temperature position showed higher degradation than at high temperature. High humidity enhanced the degradability due to hydrolysis reaction. Micro-braided polymer yarns of PLA:PBSA (85:15) and PLA:PBSA (85:15)/jute showed similar biodegradability confirmed that the mechanism of biodegradation from surface of the yarn was priority
Effect of Compatibilizer on PLA/PP Blend for Injection Molding
No full textAbstractPolymer blends of poly(lactic acid) and polypropylene were prepared for the application to injection molding products. Due to the phase separation of PLA and PP, the addition of polypropylene-graft-maleic anhydride (PP-g-MAH) as a compatibilizer was studied. The polymer blends were comprised of PLA:PP ratios 80:20 and 20:80 with addition of 1, 3 and 5 wt% of PP-g-MAH. The product samples were processed dry blend with injection molding process and the products were subjected to thermal, mechanical properties and morphology analysis. The thermal analysis confirmed that addition of PP-g-MAH has no effect on crystalline melting temperature of the polymer components as well as no effect on the mechanical properties. The morphology study of the polymer blends confirmed the adhesion of PLA and PP by assistance of PP-g-MAH. The addition of more amount of PP-g-MAH resulted in high polarity of a compatibilizer and decreased the compatibility with PLA. The tensile strength of polymer blends increased with increasing amounts of PLA. The research results confirmed the application of polymer blend system to injection molding process
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Preparation of Biodegradable Polymer Copolyesteramides from L-Lactic Acid Oligomers and Polyamide Monomers
No full textAbstractBiodegradable copolyesteramide was synthesized from L-lactic acid oligomers and polyamide monomers to improve the properties of poly(lactic acid). The oligomer was synthesized from L-lactic acid using direct polycondensation process at 170 oC, 30 torr for 7h. p-Toluenesulfonic acid used as a catalyst. From 1H NMR analysis the oligomers have degree of polymerization of ca. 5. The L-lactic acid oligomer (OLLA) was subjected to reacted with ɛ-caprolactam (CLM) with different ratios: 90:10, 80:20, 70:30 and 60:40 using SnCl2·2H2O as a catalyst at 130, 150 and 170 oC pressure 30 torr for 3h. The synthesized polymers were subjected to thermal property analysis using DSC technique and analyzed the functional groups with FT-IR. It was found that the melting temperature of the polymers increased with increasing amounts of CLM but decreased when the amount of CLM exceeded 30 percent. FT-IR analysis confirmed structure of copolyesteramide comprised of amide ide units and lactate unit
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