Yuanjun Song

Surface Characteristics of Rare Earth Treated Carbon Fibers and Interfacial Properties of Composites

Abstract Effect of rare earth treatment on surface physicochemical properties of carbon fibers and interfacial properties of carbon fiber/epoxy composites was investigated, and the interfacial adhesion mechanism of treated carbon fiber/epoxy composite was analyzed. It was found that rare earth treatment led to an increase of fiber surface roughness, improvement of oxygen-containing groups, and introduction of rare earth element on the carbon fiber surface. As a result, coordination linkages between fibers and rare earth, and between rare earth and resin matrix were formed separately, thereby the interlaminar shear strength (ILSS) of composites increased, which indicated the improvement of the interfacial adhesion between fibers and matrix resin resulting from the increase of carboxyl and carbonyl.

A Simple and Efficient Route for Preparing 2,3,5,6- Tetraaminopyridine Hydrochloride Salt

A simple and efficient route for preparing 2,3,5,6-tetraaminopyridine hydrochloride salt (TAP·3HCl·H2O) was introduced in this paper. The title compound was synthesized, as usual, in two steps (nitration and hydrogenation) with a total yield of 90%. The use of an oleum and fuming nitric acid mixture in the nitration step improved the yield and purity of the intermediate product. A highly efficient hydrogenation using a H2/Pd/C/C2H5OH system was developed. The products were characterized by TG, IR, 1H-NMR, 13C-NMR, HPLC and elemental analysis.

Mechanical reinforcement of PBO fibers by dicarboxylic acid functionalized carbon nanotubes through in situ copolymerization

To make stronger poly(p-phenylene benzobisoxazole) (PBO) fibers, we designed and synthesized a series of CNTs & PBO copolymer fibers based on dicarboxylic acid functionalized CNTs (CNTs I–III). The aim of introducting three dicarboxylic acids including two flexible (I, II) and one rigid chain (III) functionalized CNTs is to overcome the limited dispersivity and reactivity of CNTs in the PBO polymerization system. The CNTs I–III as well as pure terephthalatic acid (TPA) were further covalently incorporated with the monomer 4,6-diaminoresorcinol dihydrochloride (DADHC) via in situ polymerization to obtain copolymers of CNTs I & PBO, CNTs II & PBO and CNTs III & PBO, respectively. Then continuous CNTs I–III & PBO copolymer fibers have been fabricated through a dry-jet wet spinning process. The chemical structure and morphology of CNTs I–III & PBO copolymer fibers were characterized by FTIR, WAXD, SEM and TEM. The mechanical and thermal properties of CNTs I–III & PBO copolymer fibers were characterized by TG and tensile testing, compared with PBO, and the properties have been enhanced. As a result, dicarboxylic acids on CNTs improves the dispersion of CNTs in the PBO matrix, provide high reaction activity and an efficient load transfer between CNTs reinforcement and PBO matrix, which may be the main reasons for improving the mechanical and thermal properties.