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Synthesis of a Degradable High-Performance Epoxy-Ended Hyperbranched Polyester.

ABSTRACT: Degradation and recycling of cured thermosetting epoxy resins are major challenges to the industry. Here, a low-viscosity, degradable epoxy-ended hyperbranched polyester (DEHP) is synthesized by a reaction between epichlorohydrin and a carboxyl-ended hyperbranched polyester (DCHP) obtained from an esterification between citric acid and maleic anhydride. The chemical structures of DCHP and DEHP were characterized by Fourier transform infrared and 1H NMR. DEHP has a positive effect on reinforcing and toughening of the diglycidyl ether of bisphenol-A (DGEBA). With an increase in the content and molecular weight of DEHP, the mechanical performances of the cured DEHP/DGEBA composites, including the tensile, flexural, and impact strengths, increase first and then decrease. The improvements on the tensile, flexural, and impact strengths were 34.2-43.4%, 35.6-48.1%, and 117.9-137.8%, respectively. Moreover, the DEHP also promotes degradation of the cured DEHP/DGEBA composites. The degree of degradation of the cured DEHP/DGEBA composites increases with an increase of the DEHP content and molecular weight. The composites containing 12 wt % DEHP can be degraded completely in only about 2 h at about 90 °C, compared with the degradation degree (35%) of cured DGEBA, indicating good degradation and recycling properties of the DEHP.

SUBMITTER: Yu Q

PROVIDER: S-EPMC6640995 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Synthesis of a Degradable High-Performance Epoxy-Ended Hyperbranched Polyester.

Yu Qian Q Liang Yeyun Y Cheng Juan J Chen Sufang S Zhang Aiqing A Miao Menghe M Zhang Daohong D

ACS omega 20170407 4

Degradation and recycling of cured thermosetting epoxy resins are major challenges to the industry. Here, a low-viscosity, degradable epoxy-ended hyperbranched polyester (DEHP) is synthesized by a reaction between epichlorohydrin and a carboxyl-ended hyperbranched polyester (DCHP) obtained from an esterification between citric acid and maleic anhydride. The chemical structures of DCHP and DEHP were characterized by Fourier transform infrared and <sup>1</sup>H NMR. DEHP has a positive effect on r ...[more]

PMID: 31457508

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Project description:Histological examination of bone microstructure provides insight into extant and extinct vertebrate physiology. Fossil specimens sampled for histological examination are typically first embedded in an inexpensive polyester resin and then cut into thin sections, mounted on slides, and polished for viewing. Modern undecalcified bone is chemically processed prior to embedding in plastic resin, sectioning, mounting, and polishing. Conversely, small fossil material and modern undecalcified bone are typically embedded in higher priced epoxy resin because these specimen types require final sections near or below 100 µm thick. Anecdotal evidence suggests thin sections made of polyester resin embedded material polished thinner than 100 µm increases likelihood of sample peeling, material loss, and is unsuitable for modern tissue and small fossil material. To test this assertion, a sample of modern bones and fossil bones, teeth, and scales were embedded in either polyester resin or epoxy resin. Embedded specimens were sectioned and mounted following standard published protocol. Thin sections were ground on a lapidary wheel using decreasing grit sizes until tissue microstructure was completely discernible when viewed under a polarizing light microscope. Additionally, eight prepared thin sections (four from polyester resin embedded specimens and four from epoxy resin embedded specimens) were continuously ground on a lapidary wheel using 600 grit carbide paper until peeling occurred or material integrity was lost. Slide thickness when peeling occurred was measured for comparing slide thickness when specimen integrity was lost between the two resin types. Final slide thickness ranged from 38 µm to 247 µm when tissue was identifiable using a polarizing microscope. Finished slide thickness varied between resin types despite similar tissue visibility. However, finished slide thickness appears more dependent on hard tissue composition than resin type. Additionally, we did not find a difference of slide thickness when material was lost between resin types. The results of this preliminary study suggest that polyester resins can be used for embedding undecalcified modern hard tissues and fossilized hard tissues without loss of tissue visibility or material integrity, at least in the short term.

Dataset Information

Synthesis of a Degradable High-Performance Epoxy-Ended Hyperbranched Polyester.

Publications

Synthesis of a Degradable High-Performance Epoxy-Ended Hyperbranched Polyester.

Similar Datasets

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