Feng-Yih Wang

Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6/clay nanocomposites

Carbon fiber and glass fiber reinforced polyamide-6 and polyamide-6/clay nanocomposites were prepared. Results show that the mechanical and thermal properties of the polyamide-6/clay nanocomposites are superior to those of polyamide-6 composite in terms of the heat distortion temperature, tensile and flexural strength and modulus without sacrificing their impact strength. This may be due to the nanoscale effects, and the strong interaction force existed between the polyamide-6 matrix and the clay interface. The mechanical properties of neat polyamide-6/clay nanocomposites are better than those of 10 wt.% glass fiber or carbon fiber reinforced polyamide-6. The effect of nanoscale clay on toughness is more significant than that of the fiber.

Thermo-oxidative degradation of novel epoxy containing silicon and phosphorous nanocomposites

Abstract Modified epoxy nanocomposites containing silicon and phosphorous was prepared and compared with pure epoxy. The study of thermo-oxidative degradation of modified epoxy nanocomposites and pure epoxy has been utilized by thermal analysis. The thermal stability of modified epoxy nanocomposites is not superior to that of the pure epoxy at low temperature, however, the char yield of modified epoxy nanocomposites is higher than that of the pure epoxy at 800 °C in air atmosphere. The modified epoxy nanocomposites possess better thermal stability at high temperature range. The values of the limiting oxygen index of pure epoxy and modified epoxy nanocomposites are 24 and 32, respectively. This indicates that modified epoxy nanocomposites possesses better flame retardance. By the Kissinger’s method, the activation energies of thermo-oxidative degradation for epoxy nanocomposites are less than those of thermo-oxidative degradation for pure epoxy in first stage of thermo-oxidative degradation. However, the activation energies of thermo-oxidative degradation for epoxy nanocomposites are more than those of thermo-oxidative degradation for pure epoxy in second stage of thermo-oxidative degradation.

Processability, morphology and mechanical properties of wood flour reinforced high density polyethylene composites

Abstract Wood flour reinforced high density polyethylene (HDPE) composites have been prepared and their rheological properties measured. The melt viscosity decreased as the processing temperature increased and the wood flour content decreased. A power law model was used to describe the pseudoplasticity of these melts. Adding wood flour to HDPE produced an increase in tensile strength and modulus. Composites compounded in a twin screw extruder and treated with a coupling agent (vinyltrimethoxysilane) or a compatibliser (HDPE grafted with maleic anhydride) exhibited better mechanical properties than the corresponding unmodified composites because of improved dispersion and good adhesion between the wood fibre and the polyalkene matrix. Scanning electron microscopy of the fracture surfaces of these composites showed that both the coupling agent and compatibiliser gave superior interfacial strength between the wood fibre and the polyalkene matrix.

Thermodynamic properties affect the molecular motion of novolac type phenolic resin blended with polyamide

Abstract The effect of association reaction length on the substantial increase of molecular motion as well as entropy (−TΔSm) of phenolic–polyamide blends is investigated with the 13C solid-state NMR and DSC. The H-bonding strength by forming the phenolic–polyamide interaction is great enough to overcome the breaking off the self-association of phenolic. With respect to decreasing the association reaction, the polyamide resonance intensity of 13C solid-state NMR spectra is weakened due to the reduction of the cross-polarization efficiency at a high mobile sample. The glass transition temperature of phenolic–polyamide blend as well as TH1ρ value from NMR experiments is also decreased. The decreasing strength of H-bonding resulting from blending causes higher entropy (−TΔSm) and higher molecular mobility of the phenolic–polyamide blends. Accordingly, the polyamide-66 possesses higher H-bonding force and exhibits more mobile role in this phenolic/polyamide blends family. It can be concluded that the molecular segmental motion and entropy are progressively decreased while increasing the inter-association force of the polyamide within the miscible window.

Thermal degradation behaviors of poly (dimethylsiloxane)-urethane-graft-poly (methyl methacrylate) copolymers based on various diisocyanates

The thermal decomposition behaviors of slightly crosslinked poly(dimethylsiloxane)-urethane-graft-poly(methyl methacrylate) (PDMS-urethane-g-PMMA) copolymers based on two diisocyanates: 2,4-toluene diisocyanate (2,4-TDI) and m-xylene diisocyanate (m-XDI) are discussed. By analyzing the residues of the decomposed copolymers and thermal degradation behaviors of copolymers, it was proposed that poly(dimethylsiloxane) (PDMS) in the copolymers traps free radicals generated from the thermal decomposition of the copolymer and reduces the rate of thermal decomposition. In addition, the crosslinking structure of PDMS can also reduce the evaporation of volatiles from the thermal decomposition process.