Materials Science Forum Vol. 815

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Abstract: The phase compositions of a Mg-2Dy-0.5Zn (at.%) alloy under different solid solution temperature was investigated by differential thermal analysis (DSC), X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results indicated that the as-cast sample was mainly composed of an 18R long period stacking ordered (LPSO) phase and Mg matrix. The disappearance of 18R-LPSO phase, together with the presence of 14H-LPSO phase, occurred when solid solution treatment (SST) was at 535 °C. When the temperature was higher than 535 °C, the 18R-LPSO phase was detected again companied with a new Mg8ZnDy eutectic phase.
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Abstract: Three kinds of poly (3-alkylthiophene), such as poly (3-butylthiophene) (P3BT), poly (3-hexylthiophene) (P3HT) and poly (3-dodecylthiophene) (P3DDT) were prepared by the Grignard Metathesis Method (GRIM). Their chemical structures are characterized by FTIR, 1H-NMR and GPC. 1H-NMR result shows that regioregular structure of these polymers is relatively higher. The GPC results show that the molecular weight of the polymers is 8.42×104, 1.06×105 and 1.21×104 g/mol with molecular weight distributions of 1.41, 2.18 and 1.18, respectively. The DSC result shows that the glass transition temperature of three kinds of polymers is 120.8, 146, 118 °C, respectively. UV absorption spectrum and fluorescence spectroscopy of three polymers in THF solution show that the maximum absorption wavelength is 448 nm, 470 nm, 390 nm, and the maximum emission wavelength is 531, 535, 527 nm with the band gap of 2.06, 1.86, 2.21 eV, respectively.
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Abstract: Poly (3,4-ethylenedioxythiophene) (PEDOT) has been synthesized through a facile solid-state polymerization (SSP) approach. The polymerization was simply initiated by sintering the monomer, 2,5-dibro-3,4-ethylenedioxythiophene (DBEDOT), at the temperature of 80 °C. The SSP-PEDOT with the heating time for 24 hours has the maximum value of dielectric loss tangent (tanδε) in the frequency range of 2-18 GHz, which revealed that this sample has the best electromagnetic energy absorption ability. When the thickness of the sample reached 2 mm, the bandwidth with the reflection loss (RL) deeper than −10 dB is nearly 5.9 GHz (From 10.0 GHz to 15.9 GHz), and the maximum value of RL is about −50.1 dB at 11.2 GHz. These results demonstrate that SSP initiated at low temperature shows multi-practical application in the areas of military camouflage, and electronic devices protection.
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Abstract: In this study, Ultra-high molecular weight polyethylene (UHMWPE) particles were surface treated by F2/N2 and F2/O2/N2 two direct fluorination routes. A great number of polar groups are grafted on the surface of UHMWPE particles after direct fluorination confirmed by FT-IR and X-ray photoelectron spectroscopy (XPS) characterization. Two kinds of surface modified UHMWPE particles were blended with thermoplastic polyurethane (TPU) by dissolving in solvent. The scanning electron microscope (SEM) demonstrates that the interfacial interaction degree between the two polymer phases is correlated with the chemical composition of a fluorinated surface layer. The TPU composite with the UHMWPE particle treated by F2/O2/N2 route obtains excellent tribological performance enhancement with significant decrease in wear loss, ranging from 192.9 mm3 to 97.8 mm3, about 49.3% reduction compared with the virgin TPU.
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Abstract: Poly (arylene sulfide sulfone)/glass fiber cloth composites (PASS/GFC) were prepared through compression moulding. The optimum processing conditions including temperature, time and pressure were discussed in detail. The cross-linking reaction, mechanical and dynamic mechanical properties were also characterized. The results showed that the optimum processing temperature, pressure and time were 325 °C, 5 MPa and 15 min, respectively. The thioether group (-S-) was oxidized and converted to sulfoxide (-SO-) and sulfone (-SO2-) groups during the crosslinking reaction proved by Fourier transform infrared spectrometer. The mechanical and dynamic mechanical analysis measurements showed that mechanical properties, including tensile, bending, impact and storage modulus increased continuously with an increase of the GFC contents.
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Abstract: Polymer blending is a very important and widely used method for the modification of polymer materials. However, little attention has been paid to the Semi-aromatic Polyamides with PPS blends. In this article, we investigate the properties of Poly (phenylene sulfide) (PPS) blends with Poly (hexamethylene terephthalamide/hexamethylene hexanediamide) (nylon 6T/66). The structure, mechanical properties of nylon 6T/66 and (PPS) blends were studied by scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TG). The results indicate that the blends have good thermal stability and the tensile strength, flexural strength and flexural modulus of the blends are better than the PA6T/66 but worse than that of the PPS.
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Abstract: In this paper, we investigated the effects of a coupling agent (KH560) on the mechanical properties of long glass fiber (LGF) reinforced polyphenylene sulfide (PPS) composites. The LGF reinforced PPS composites were prepared utilizing our self-designed mold. It’s found that KH560 was beneficial for improving the mechanical properties of the composites. Meanwhile, the fiber lengths of glass fibers in the original injection molded sample and near the fracture surface were measured under the optical microscope. Comparing to the untreated sample, the sample with KH560 possessed higher proportion of fiber length on 0.75-1.25 mm. It suggested that KH560 could protect glass fibers from broken. Meanwhile, near the fracture surface, two composites possessed similar proportions of fiber length on 0-0.75 mm. That indicated KH560 improved the interfacial bonding between glass fiber and PPS. Scanning electron microscopy (SEM) images showed that more resin adsorbed on the fiber surface, which was consistent with the above phenomena.
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Abstract: Modified aramid (PBIA) containing benzimidazole units in the main chain were synthesized and the corresponding PBIA fibers were prepared by wet spinning and then annealed at different temperatures. The mechanical properties and the structure of copolyamide PBIA fibers were investigated for different annealing temperatures. The results of thermogravimetric analysis showed that the decomplexation reaction between HCl and benzimidazole occurred during the annealing process and HCl was completely removed at 320°C. The decomplexation of HCl also leads to the formation of hydrogen bonds between benzimidazole fragments, resulting in the rearrangement of the molecular chain and a more ordered macromolecular structure. The mechanical properties, chain orientation could be significantly improved when the samples were annealed in the temperature range from 280 to 320 °C. In addition, the analysis of self-elongation during the annealing process further indicates that the macromolecular chains were more ordered after the decomplexation of HCl. In addition, the PBIA fibers firstly annealed at 300°C which the decomplexation reaction between HCl and benzimidazole occurred, and then annealed at 400°C, resulting the higher PBIA fibers are obtained.
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Abstract: The carbon fiber (CF) reinforced polyphenylene sulfide (PPS) composite was modified by aminated polyphenylene sulfide (PPS-NH2) with different mass fractions. The quantified influence of aminated PPS on PPS/CF composites was investigated. The PPS/CF composite with 7wt% PPS-NH2 showed the best mechanical properties. The tensile strength, flexural strength, flexural modulus and impact strength of the composites increased by 12.5%, 13.0%, 38.5% and 31.5%, respectively. PPS-NH2 hardly influenced the melting process of PPS/CF composite. But the crystallization temperature (Tc) of PPS were obviously increased with the present of aminated PPS.
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Abstract: In this paper, N-methyl-2-pyrrolidone (NMP) induced crystallization behavior of PASS was found and studied. To study NMP induced crystallization of PASS, Differential Scanning Calorimeter (DSC), X-Ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were employed. The results showed that the crystal induced by NMP was consistent with precipitates obtained in solution, and was the eutectic of PASS and NMP. With the induction time increased, crystalline region continued to improve and the crystal size became bigger.
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