1,720,954 research outputs found
Trade-offs Between Limonene & Geraniol-Based Reprocessable and Non-Reprocessable Epoxy Thermosets: Role of Aliphatic Diamines in Polymer Networks Design.
No full textThe growing demand for sustainable materials, driven by environmental concerns and the rapid depletion of fossil fuels, has garnered significant attention in bio-based thermosets fabrication. Petroleum-derived thermosetting polymers can be replaced with renewable alternatives such as limonene and geraniol-derived epoxy prepolymers. The present study focuses on the synthesis and characterization of limonene and geraniol-based epoxy prepolymers over a two-step process and their thermally crosslinked thermosets using different aliphatic diamines. Incorporating cystamine, a disulfide-containing diamine, introduced a covalent adaptable network via disulfide metathesis, achieving a reprocessable thermoset with self-healing capabilities, recyclability, and extended lifespan. In contrast, traditional aliphatic diamines produced a permanently crosslinked thermoset with superior mechanical strength, thermal stability, and chemical resistance, ideal for high-performance applications requiring durability with maximum tensile strength of 11.62 MPa and 17.9 MPa for limonene and geraniol derived epoxy thermoset, respectively. Differential scanning calorimetry (DSC) elucidated the curing kinetics and crosslinking behavior, while thermogravimetric analysis (TGA) confirmed excellent thermal stability. Dynamic mechanical analysis (DMA) and tensile testing also demonstrated desirable mechanical properties. The glass transition temperature (Tg) of the limonene- and geraniol-derived malleable thermosets was determined by dynamic mechanical analysis (DMA) at 18C and 25℃, respectively. Above these temperatures, the malleable thermosets exhibited dynamic behavior facilitated by disulfide bond exchange. In addition, the developed materials displayed maximum tensile strengths of 3.1 MPa and 3.66 MPa, highlighting their mechanical robustness and potential for reprocessable applications
Self-healable and Reprocessable Epoxy Vitrimer derived from Epoxidized Hemp Seed Oil and Dynamic Imine Bonds
No full textVitrimers are a class of covalently cross-linked polymers that undergo dynamic bond exchange, enabling self-healing, reprocessability, and recyclability while retaining the mechanical robustness of thermosets. This research focuses on the synthesis and characterization of a fully bio-based vitrimer derived from epoxidized hemp seed oil (EHSO) and vanillin-based imine cross-linkers. The synthesis involves the epoxidation of hemp seed oil followed by curing with dynamic Schiff-base (imine) cross-linkers synthesized from vanillin and aliphatic diamines. The imine bonds introduce network adaptability, allowing topological rearrangement under external stimuli such as heat, thereby facilitating material reconfiguration and repair. To optimize vitrimer properties, a systematic study is conducted on cross-linker structure, catalyst selection, and curing conditions. Characterization techniques such as Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy confirm the successful synthesis of precursors. Gel permeation chromatography (GPC) and epoxy oxygen content (%EOC) analysis validate network formation, while rheological studies, stress relaxation experiments, and mechanical testing evaluate viscoelastic behavior, self-healing efficiency, and mechanical strength. The developed vitrimer presents a sustainable alternative to conventional thermosets, exhibiting tunable mechanical and thermal properties suited for applications in coatings, adhesives, and composite materials, by integrating renewable feedstocks and dynamic covalent chemistry, this research advances the development of bio-based high-performance polymers, contributing to environmentally friendly material innovations. The findings demonstrate the potential of hemp-seed-oil-derived vitrimers in circular economy frameworks, emphasizing their role in reducing polymer waste and enhancing material sustainability
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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