• Title/Summary/Keyword: Composition Technology

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Synthesis and Non-Isothermal Crystallization Behavior of Poly (ethylene-co-1,4-butylene terephthalate)s

  • Jinshu Yu;Deri Zhou;Weimin Chai;Lee, Byeongdu;Le, Seung-Woo;Jinhwan Yoon;Moonhor Ree
    • Macromolecular Research
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    • v.11 no.1
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    • pp.25-35
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    • 2003

  • A series of random poly(ethylene-co-1,4-butylene terephthalate)s (PEBTs), as well as poly(ethylene terephthalate) (PET) and poly(1,4-butylene terephthalate) (PBT), were synthesized by the bulk polycondensation. Their composition, molecular weight, and thermal properties were determined. All the copolymers are crystallizable, regardless of the compositions, which may originate from both even-atomic-numbered ethylene terephthalate and butylenes terephthalate units that undergo inherently crystallization. Non-isothermal crystallization exotherms were measured over the cooling rate of 2.5-20.0 K/min by calorimetry and then analyzed reasonably by the modified Avrami method rather than the Ozawa method. The results suggest that the primary crystallizations in the copolymers and the homopolymers follow a heterogeneous nucleation and spherulitic growth mechanism. However, when the cooling rate increases and the content of comonomer unit (ethylene glycol or 1,4-butylene glycol) increases, the crystallization behavior still becomes deviated slightly from the prediction of the modified Avrami analysis, which is due to the involvement of secondary crystallization and the formation of relatively low crystallinity. Overall, the crystallization rate is accelerated by increasing cooling rate but still depended on the composition. In addition, the activation energy in the non-isothermal crystallization was estimated.

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Species Composition and Community Structure of Macrobenthos during Fall on the Dokdo Coast, Korea (가을철 독도 연안에 출현하는 대형저서동물의 종 조성 및 군집 구조)

  • Kang, Su Min;Lee, Hyung-Gon;Kim, Sang Lyeol;Choi, Jin-Woo;Park, Chan Hong;Yu, Ok Hwan
    • Ocean and Polar Research
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    • v.41 no.2
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    • pp.47-61
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    • 2019

  • The Dokdo coast is known for its high biodiversity. However, few studies have examined the biodiversity and macrobenthic community on the subtidal soft-bottom. Therefore, we collected macrobenthos (> 1 mm) using a Smith-McIntyre grab ($0.1m^2$) at 15 stations along the Dokdo coast in September 2016. The sediments consisted of badly sorted (1.7) coarse sand with gravel and the mean sediment grain size was $-0.4{\phi}$. In total, 177 macrobenthic species were collected; their mean density was $1,566ind./m^2$. The number of species and density of macrobenthic fauna decreased significantly with the mean grain size. The dominant species were the amphipods Melita denticulata (16.5%) and Melita shimizui (5.5%), polychaete Salvatoria clavata (5.4%), bivalve Glycymeris aspersa (4.4%), and ophiuroid Ophionereis dubia (4.3%). The dominant macrobenthos species on the subtidal soft-bottom differed from the coastal areas of the East Sea, suggesting that the difference in the sediment grain size affected the macrobenthos. Cluster analysis was performed to divide the study area into four groups, and environmental factors which correlated with species composition and distribution in the study area were the combination of the four parameters of salinity, dissolved oxygen, total organic carbon and depth. A future seasonal investigation is needed to understand the species composition and characteristics of the Dokdo macrobenthos.

  • https://doi.org/10.4217/OPR.2019.41.2.047 인용 PDF KSCI HTML