Papers by Author: Yan Ping Wang

Abstract: The hierarchical hydroxyapatite (HAP), such as needle-shaped, spherical and flower-like, was successfully synthesized by a homogenous precipitation method with poly (styrene)-block-poly (acrylic acid) (PS-b-PAA)_. The self-assembled “crew-cut” micelles of amphiphilic block copolymer were found to play an important role in directing the nucleation and growth of HAP crystals. The morphology, crystal phrase and chemical structure of HAP crystal were investigated by scanning electron microscope (SEM), X-ray diffractions (XRD) and Fourier transform infrared spectroscopy (FT-IR) respectively.

Abstract: In this study, oligomer Joncryl^TM ADR was used to extend the chains and improve the mechanical properties. The chain extender multifunction epoxide was used with concentrations of 0.5 and 0.9 wt %. Pure and modified PLAs were characterized using DSC, MFI and FT-IR. The DSC results showed that Tg shifted to the high temperature and T_m increased slightly after chain extending. The MFI of the blends decreased with increasing the content of the CE which means the increase of molecular weight. The coupling between epoxy groups of CE and end groups of PLA was confirmed by FTIR tests. This coupling led to significant improvement in tensile strength and modulus.

Abstract: PET/60HBA-MWNTs Liquid Crystalline Polyester (LCP) composite was synthesis by melting polymerization process with a novel method of reacting in acetic anhydride solution. FTIR, XRD, POM, TGA and mechanical properties tests were applied for the characterization of modification of nanotube, crystallization property, thermal and mechanical properties. The results indicate that thermal and mechanical properties of LCP polyester are all enhanced with 0.3wt% MWNTs addition. The degradation temperature (T_d) increased for 8°C and the modules, strength and breaking elongation are increased by 39.0%, 62.3% and 46.4% respectively.

Abstract: Calcium carbonate (CaCO₃) was mineralized in N,N-dimethylformamide (DMF)-H₂O mixed solvents in the presence of polystyrene-b-poly (vinyl pyrrolidone) (PS-b-PNVP) block copolymer. The morphologies of PS-b-PNVP micelles and CaCO₃ crystals were characterized by TEM and SEM. By varying the volume ratio of DMF-H₂O, the CaCO₃ crystals with different morphologies and phases were obtained. It was convinced that the morphology of crew cut micelles played a key role in the morphological formation of CaCO₃.

Abstract: The polymerization of para-acetoxybenzoic acid (PABA) and poly (ethylene terephthalate) to generate high molecular weight semi-aromatic copolyester was conducted successfully in the presence of acetic anhydride. The influence of acetic anhydride on the copolymerization was studied. The addition of acetic anhydride (2:1 mol AC₂O /PET) in the polymerization system afforded the polymerized copolyester with an increased intrinsic viscosities (by 112.5%) and a decreased amount of insoluble fraction (by 80%). ¹H-NMR analysis indicated that mole ratio of PET repeat unit and PHB was 42:58 with the addition of acetic anhydride, which was quite similar to the theoretical ratio and higher than traditional synthesized PET/PHB. The results show that the addition of acetic anhydride is effective not only in increasing the molecular weight but also in increasing benzene ring content in the copolyester.

Abstract: Thermal stability can reflect the thermal degradation speed of polymers during the melt processing. In this paper, we used Kissinger, Flynn-Wall-Ozawa and Coats-Redfern method to study the kinetics of non-isothermal degradation of PFA. The thermal degradation activation energy obtained from the Kissinger method, Flynn-Wall-Ozawa method and Coats-Redfern method is 228.5 kJ/mol, 213.9 kJ/mol and 237.4 kJ/mol respectively. The Flynn-Wall-Ozawa method indicates the thermal degradation reaction PFA is a secondary reaction.

Abstract: The impact performance of PE can be greatly enhanced by the use of functionalized conch powder, while maintaining high tensile strength thus giving this study high potentiality for its practical applications. The conch powder was treated by titanate coupling agent NDZ-201 before use and the influence of different proportions of conch powder on the mechanical properties of PE/conch powder composite is discussed in this article. The impact strength has a maximum value of 63.4kJ/m2 and the frictional loss records a minimum of 4.27×10-1mm3/(Nm)-1 and 42.2% lower than that of pure PE.

Abstract: Capillary rheometer was used to conduct preliminary study on the rheological behavior of SKYPEL thermoplastic polyester elastomer (TPEE). SKYPEL TPEE is a kind of non-Newtonian fluid and displays typical shear thinning behavior. Non-Newtonian index of the three samples varies from 0.69 to 0.77. With increasing temperature, the structure viscosity of the sample decreased and among them G172D is the smallest one under the same temperature.

Abstract: Melt-blown generated PBT nonwoven fabrics usually have small fibril diameter, high flexibility, well heat and oil resistance. Therefore, they would have promising application such as vehicle filtering media. The rheological behavior of PBT with High Melt Flow Index for Melt-blown is investigated in this paper. It is a direction of the technology design and fabrication parameters .The relation of apparent viscosity and shear rate is analyzed, as well as flow activation energy and Non-Newtonian indexes. The results suggest that PBT with High Melt Flow Index is Non-Newtonian fluid. Apparent viscosity and flow activation energy show gradually decrease with increasing shear rate, exhibiting typical shear-thinning behavior.

Abstract: The non-isothermal crystallization process of PBT with high melt flow index has been investigated by DSC, and the nonisothermal crystallization process of PBT with high melt flow index was studied by Ozawa equation and Jeziorny equation respectively. It was found that Ozawa equation, rather than Jeziorny equation, could appropriately be applied to study the non-isothermal crystallization process of PBT with high melt flow index. The Avrami index, obtained by Ozawa equation, varied between 1.06-1.80 with the change in temperature.