Advanced Materials Research Vols. 712-715

Abstract: Rosin, an abundant renewable natural resin obtained from exudation of pine trees, has attracted a great deal of attention because of its utilization as a feedstock for the preparation of polymers in the age of the depletion of fossil fuels. Dehydroabietic acid (DA) is one of important resin acid that could be produced with large scale and high purity. In this paper, we reported a new synthetic strategy to prepare a novel resin acid based monomer with acrylic group (DAHA) by sequential reaction of DA with 1,6-hexanediol and acryloyl chloride. The structure and properties of DAHA and DA monoester of 1,6-hexanediol (DAH), an intermediate compound, were characterized by FT-IR, ¹H NMR, ¹³C NMR, MS, DSC and GPC. The results showed that DAHA has high purity and could undergo free radical polymerization. DAHA is a soft monomer with the glass transition temperature of-23.52 °C and can impart flexibility to the polymer integrated. This study illustrates a new synthetic strategy to prepare a new class of resin acid based monomer.

Abstract: In this article, a series of novel phenolic resin modified with cardanol were synthesized. The influence of reaction condition and cardanol content on the structure and properties of phenolic resin was evaluated. The nanocomposite phenolic foam was then prepared by infusing the organo-modified montmorillonite (OMMT) in the synthesis step of cardanol phenolic resin to produce nanocomposite phenolic foams. These phenolic foams were characterized by FTIR, XRD, SEM and TGA. And the mechanical properties and fire performance of these nanocomposite foams were also measured. The results showed that the cardanol component could reduce the crosslink density of phenolic foam and thus improve the mechanical properties; the OMMT platelets were 3~10μm in diameter and 40~50nm in thick. These platelets can exfoliated and dispersed well in the nanocomposite due to the hydrogen-bonding between organo-modifier and phenolic matrix and improve the thermal stability, fire resistance and also the mechanical properties of nanocomposite foam.

Abstract: This paper is concerned with the design of a new wideband 1-3-2 piezoelectric composite with multi-mode. The equivalent parameters of 1-3-2 piezoelectric composite with multi-mode are derived from series-parallel theory and uniform field theory. By using numerical calculation, the law of bandwidth varying with the cutting depth is obtained and compared with experiments. The computations show agreement with the experimental results. The results prove that the new wideband 1-3-2 piezoelectric composite with multi-mode can expand bandwidth efficiently, which can be expanded to 28.728 kHz that is 5 times the bandwidth of traditional 1-3-2 piezoelectric composite.

Abstract: Narrowly-distributed poly (methyl methacrylate)/polyacrylonitrile (PMMA/PAN) core-shell particles with a target use as the precursor for fabricating carbon microspheres and carbon nanotubes (CNTs) were prepared using the seed adsorption method. PMMA, acrylonitril (AN) and potassium persulfate (KPS) were used as the seed latex, the second-stage monomer (shell monomer) and the initiator, respectively. The effect of process parameters, such as monomer adsorption time, monomer/initiator stoichiometry, presence of surfactant as well as reaction temperature and stirring strength etc., on the morphology and size distribution of the PMMA/PAN composite particles was studied. The process condition under which uniform PMMA/PAN composite particles can form was then identified. Morphological observation by SEM revealed that upon the formation of the core-shell structure, smooth surface of PMMA spheres changed into rambutan-like rough structures.

Abstract: A core-shell nanocomposite particle with polystyrene sphere core and polythiophene overlayer shell was synthesized through thiophene chemical oxidative polymerization using uniquely structured polystyrene latexes template. The morphology of polythiophene shell, which has nanorods shaped or featureless surface morphology, can be simply controlled through varying the dosage and feeding methods of oxidizers.

Abstract: Carbon black was activated and then filled into polypropylene to prepare conductive composites, of which the electrical properties, including impedance Z, phase angelθ and dissipation factor tgδ, as a function of frequency and carbon black concentration were investigated using impedance analyzer. The percolation threshold of 5wt% carbon black concentration was obtained. It was found that the variation of AC electrical properties as a function of frequency is dramatic and dependent on the carbon black concentration. It was also found that dependence of the real part and the imaginary part of impedance on frequency decreases with the increased concentration of carbon black, while that of phase angle and dissipation factor increases. Based on the corresponding results, the conductive network model and the corresponding equivalent circuit were constructed.

Abstract: Carbon black was first activated by grafting and coupling respectively. Then the grafted carbon black, coupled carbon black, together with the unmodified carbon black was filled into polypropylene to prepare three kinds of composites respectively. The measurements of Fourier Transform Infrared Spectroscopy (FTIR) and alternating current (AC) electrical properties were performed on the composites. And the effect of CB activation on the AC electrical properties was analyzed. Seen from the result of FTIR spectra it can be found that different groups are bonded to the surface of carbon black after activation. For the corresponding conductive composites,it was found that the value of percolation threshold decreases and the electrical conductivity improves consequently after the carbon black activation. The influence of carbon black activation on the AC electrical properties of the composites and their variation with frequency was analyzed. The AC conduction mechanism was discussed and the conduction model was constructed based on the analysis.

Abstract: Poly (TBAM-AM-NMMAD) random-block copolymer were prepared by aqueous micellar copolymerization using AIBA (V50), ammonium persulfate (J) and sodium bisulfite (D) as initiator and SDS as surfactant in the mixture solvent of deionized water. The structure of Poly (TBAM-AM-NMMAD) was characterized by solid state ¹³C-NMR and FTIR spectroscopy and the dynamic viscosity was measured by the NDJ-1 viscometer. The experimental results and analysis shows poly (AM-TBAM-NMMAD) random-block copolymer which had been endowed with high rheological properties was successfully synthesized by controlling the abundance of initiator based on the method of orthogonal experiment.

Abstract: The organically modified montmorrillonite (OMMT)/phosphorus polymeic flame retardant (PFR)/polyamide 6(PA6) nanocomposites were prepared via melt intercalation on a twin-screw extruder. The structure formed in nanocomposite system was investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). Properties such as flame retardancy, notched impact strength, tensile strength, elongation at break and flexural modulus were studied by limited oxygen index (LOI) approach, UL94, and mechanical property test. The results of the studies indicated that flame retardancy and mechanical properties of PA6 nanocomposites were all reinforced due to addition of OMMT and PFR.

Abstract: Solving the internal stresses of continuous fiber reinforced composite materials is a complex problem, which was studied usally by experimental or numerical calculation method. This paper proposed the equal strain method with virtual external force compensation instead of considering the shear stress in the calculation of the stress in the fiber and matrix of composite materials. By the equal strain method, the formula of longitudinal elastic modulus of continuous fiber reinforced composite materials is derived. The same result was given by other literatures with other methods, which indirectly proved correctness of the equal strain method. Further the internal stress calculation formulaes of the fiber and matrix are derived. The formulaes show that the internal stress of fiber (or matrix) is proportional to the external load and the elastic modulus of the fiber (or matrix), and is inversely proportional to the elastic modulus of the composite material.