Min Chao

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.

Synthesis and Characterization of Novel Sulfone-containing Polyimides Molding Powder Derived from 2, 2-Bis[4-(4-aminophenoxy) phenyl] Sulfone and Aromatic Dianhydrides

A novel sulfone ether diamine was successfully synthesized by aromatic nucleophilic chloro-displacement reaction of 4-chloronitrobenzene with the 4, 4′-dihydroxydiphenylsulfone, followed by a catalytic reduction. Two kinds of aromatic polyimides molding powder containing sulfone and ether linkages was prepared from the resulting diamine with pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylic dianhydride (BTDA) by a new three-step imidization procedure. The monomer and polyimides powder obtained were characterized by various methods. The monomer was synthesized with high purity and yield. The novel polyimides powder exhibited semi-crystalline character, good solubility in organic solvents, as well as high Tg value and excellent thermal stability in N2 and air.

Synthesis and Characterization of Polyimides Derived from Novel 1,3-Bis(4-Aminophenoxy)Benzene

A novel aromatic ether diamine 1,3-bis(4-aminophenoxy)benzene (TPER) was synthesized. Four kinds of polyimides were prepared with obtained TPER, 4,4’-diaminodiphenyl(ODA), pyromellitic dianhydride (PMDA) and end capped with phthalic anhydride(PA). The imidization process was solution imidization followed by solid-phase thermal imidization. The results of DSC, 1H-NMR and FTIR analysis showed that high purity TPER had been successfully synthesized. FTIR spectras of polyimides indicated the imidization process could reduce the final imidization temperature. The inherent viscosities([η]) showed molecular weight could be controlled via the introduction of flexible diamine and end capping agent. And all polyimides exhibited excellent thermal stability.

Preparation and Characterization of Micro-coiled Carbon Fibers: Preparation and Characterization of Micro-coiled Carbon Fibers

Carbon microcoils (CMCs) were synthesized by the catalytic decomposition of acetylene using nickel sulfide particles as the catalyst which prepared by solvothermal method. The morphology and microstructure of the catalyst and micro-coiled carbon fibers were examined by SEM, FT-IR and XRD. The results showed that the catalyst was regular hexagonal phase nickel sulfide with its diameter of 1−2 μm and a smooth surface. CMCs have double helix structure, rectangular cross-section and identical coil diameter. The molecular structure of CMCs contained both unsaturated -C=C- and saturated -CH2- and -CH3 groups. The microstructure of CMCs was of poor degree of order with a low graphitization degree, containing a certain amount of amorphous carbon and crystal defects.