Interest in producing chemicals and thermosets from sustainable
resources is growing, yet their moderate performance drastically undermines
their potential applicability. Herein, an aryl dinitrile epoxy precursor
(DVN-EP) was developed from vanillin. After curing with 4,4′-diaminodiphenyl
sulfone (DDS), cyano-containing resin (DVN-EP/DDS) was produced with
eminent comprehensive properties on account of the dual-cross-linked
network formed by the epoxy-amine reaction and the further cyclotrimerization
of cyano groups. In particular, the glass transition temperature,
storage modulus, char yield (at 800 °C in N2), and
Young’s modulus of the DVN-EP/DDS were 201 °C, 2795 MPa,
47.4%, and 5034 MPa, respectively, all much higher than those of the
cyano-free counterpart (DMG-EP/DDS). Moreover, the cyano dipole–dipole
pairings combined with the H-bonding interactions contributed to a
tremendously increased lap shear strength of up to 7.18 MPa as well
as good energy dissipation and damping capacity. The rationally designed
dual-cross-linked network strengthening mechanism reported here offers
an important and universal strategy for significantly enhancing the
comprehensive properties of thermosets.
Fluid dynamic is an important course in engineering undergraduate education. In this article, a case study that running the fluid dynamic course to sophomore students of civil engineering by the author is conducted. Even though running into several problems when imparting knowledge towards non-major junior undergraduate students within limited teaching hours, the author solved them by thoughtfully selecting textbooks, dividing levels for the course and guiding the target for students. The target echelon and concept map theories are employed, as well as attaching importance to experimental session in order for the students' practical ability. The methods mentioned above are attested effective in teaching practice, which has accumulated precious experience for running the fluid dynamic course to engineering undergraduate students in limited teaching hour.
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