Jiaoqiang Zhang

Investigation of Tribological Properties of PI/FEP Laminated Composites Under Dry Sliding, Water- and Oil-Lubricated Conditions

Polyimide/fluorinated ethylene propylene (PI/FEP) laminated composites were fabricated by means of hot-press molding. The friction and wear behavior of high performance PI/FEP laminated composites has been comparatively evaluated under dry sliding, water- and oil-lubricated conditions. The worn surface morphologies of samples under different lubrication conditions were examined by scanning electron microscope and the wear mechanisms were comparatively discussed. As the results, PI/FEP laminated composites sliding against stainless steel under water lubrication registered lower friction coefficients, but higher wear rates than those under dry sliding. The friction coefficients and wear rates of samples under liquid paraffin-lubricated condition were lowest in three sliding conditions. The lateral surface of samples exhibited better wear resistance than parallel surface did under dry sliding.

Synthesis and Properties of Semicrystalline Copolyimides Based on 4,4′-Diaminodiphenylether and 1,3-Bis(4-aminophenoxy) Benzene

Copolyimides were prepared from 4,4′-diaminodiphenylether (4,4′-ODA), 1,3-bis(4-aminophenoxy) benzene (TPER), and pyromellitic dianhydride (PMDA) through a three-step imidization process with different monomer compositions. The copolymerization disrupted the molecular regularity and decreased the intermolecular interaction of the polyimide chains. The X-ray diffraction (XRD) results indicated the prepared copolyimides showed the same semicrystalline character, but had various crystallinity and crystal forms. The copolymerization also changed the crystal morphologies of the polyimides. With increasing TPER ratio, the copolyimides started to form spherulites and hedrites, which then tended to grow more perfectly as the TPER ratio was further increased. The solubility of the copolyimides and their dependence on the crystallnity and the chain flexibility was investigated. These copolyimides exhibited excellent thermal and thermo-oxidative stability.

Preparation and properties of Nano-SiO2/TDE-85/BMI/BADCy composites

A new type of the nanometer particles and epoxy/bismaleimide-triazine nanocomposites were prepared using a nanometer silica (nano-SiO2), a 4,5-epoxycyclohexane 1,2-dicarboxylic acid dilycidyl (TDE-85) epoxy resin, a 4,4′-bismaleimidodiphenymethane (BMI) and a bisphenol a dicyanate (BADCy). The properties of nano-SiO2/TDE-85/BMI/BADCy composites, such as mechanical and thermal properties, were systemically investigated in detail by mechanical measurement, scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The experimental results showed that the addition of the appropriate amount of nano-SiO2 could improve the impact strength and the flexural strength of the nano-SiO2/TDE-85/BMI/BADCy composites. Simultaneously, the thermal stability of the blends was found to be higher than that of the TDE-85/BMI/BADCy copolymers.