Papers by Author: Yi Min 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: 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: This paper adopted the air plasma treatment on ultra-high molecular weight polyethylene fiber surface modification. SEM, tensile test and fiber bundle pull out test were used to characterize the influence of processing time and voltage on the effect of fiber surface modification. The results showed that the optimum conditions of surface modification were obtained by the processing parameters of pressure 15Pa, time 5 minutes and voltage 15V. At this point, the bonding strength was increased by about 82.4%, and the breaking strengthreduced by 9.7%.

Abstract: Polyamide 5,6 (PA56) fibers were successfully prepared by melt-spinning technique. PA56 fibers were subjected to hot drawing process at different draw ratio and temperature. The effect of the drawing conditions on their mechanical properties such as tenacity, tensile modulus and breaking elongation were investigated by means of tensile test measurements. The results revealed that the tenacity and tensile modulus were found to be increased, while the elongation at break decreased with the draw ratio. The improvements of the mechanical properties could be attributed to the enhanced of the molecular orientation along the fiber axis and an increase in crystallinity. On the other hand, the PA56 fibers mechanical properties do not show significant difference with the drawing temperatures.

Abstract: Hydroxyl-terminated hyperbranched polyesters (HBPET) with aromatic-aliphatic structure were synthesized by melt polycondensation of isophthalic acid and pentaerythritol via A₂+ B₄ approach, at three different monomer mole ratios (A₂/B₄ =1:1, 1.5:1, 2:1, respectively). Fourier transform infrared (FTIR) spectroscopy indicated that the expected HBPET. The degree of branching of the HBPET was estimated to be between 0.39–0.45 by ¹H-NMR and ¹³C-NMR measurement. The thermogravimetric analysis ( TGA ) measurement revealed that HBPET had a 10 % weight-loss at 350°C in N₂.

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.