Co-reporter:Shengnan Zhang;Hai Wang;Duigong Xu;Wenxiao Yang;Ping Tang
Journal of Applied Polymer Science 2016 Volume 133( Issue 26) pp:
Publication Date(Web):
DOI:10.1002/app.43605
ABSTRACT
The crystallization behavior of poly(vinylidene fluoride) (PVDF) and transcrystallization in carbon fiber (CF)/PVDF composite were investigated under a temperature gradient. The crystallization temperature (Tc) was controlled in the range of 110–180 °C. For neat PVDF, the results showed that exclusive γ phase formed at Tc above 164 °C, but coexisted with α phase at Tc ranging from 137 to 160 °C. The promotion of γ phase to nucleation of α phase at low Tc was observed for the first time. For CF/PVDF composite, a cylindrical transcrystalline (TC) layer formed on the surface of CF when Tc was between 137 and 172 °C. The TC layer was exclusively composed of γ phase at Tc above 164 °C. The hybrid nucleation was dominated by γ phase though some α phase nuclei emerged on the surface of CF when Tc was in the range of 144–160 °C. As Tc decreased, competition between the hybrid nucleation of α and γ phase became more intense. The γ phase nuclei was soon circumscribed by the rapidly developed α phase when Tc was below 144 °C. Furthermore, some α phase nuclei were induced at the surface of the γ phase TC layer, and developed into α phase TC layer when Tc was in the range of 146–156 °C, which resulted in a doubled TC layer of α and γ phase at the interface of the composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43605.
Co-reporter:Shengnan Zhang;Duigong Xu;Wenxiao Yang;Ping Tang
Macromolecular Symposia 2016 Volume 365( Issue 1) pp:10-16
Publication Date(Web):
DOI:10.1002/masy.201650026
Summary
Thin film of carbon fiber (CF) and poly (L-lactic acid) (PLLA) composite was prepared by a solution casting technique. Influence of crystallization temperature (Tc) on morphology of transcrystalline (TC) on the interface between CF and PLLA was investigated under a temperature-controlled gradient (T-gradient) stage with temperature ranging from 90 °C to 140 °C. Morphology of TC was observed by polarized optical microscope (POM). Typical TC structure isothermally crystallized on the T-gradient stage was obtained at the surface of CF when Tc = 111 ∼ 132 °C. As Tc decreased from 132 to 111 °C, nuclei density on the surface of single fiber increased while the thickness of TC layer decreased. Crystallization kinetics of TC was investigated through isothermal crystalization under POM equipped with a temperature-controlled stage. As Tc decreased, the nucleation rate of TC increased and the growth rate of TC decreased. Furthermore, it revealed that the thickness of TC layer was conducted by the competition between heterogeneous nucleation on the surface of fiber and homogeneous nucleation in the bulk matrix around the fiber. The nucleation rate of TC structure was much higher than homogeneous nucleation rate of spherulites in the bulk matrix when Tc was above 118 °C. In this case, TC had enough space to develop perpendicular to fiber axis. Consequently, thickness of TC layer was larger at higher crystallization temperature. On the contrary, transcrystallization was suppressed by homogeneous crystallization when Tc was below 118 °C due to enhanced nucleation ability of spherulites.
Co-reporter:Ping Tang, Rong Zhang, Zhiqiang Chen, Bo Yang, Yuezhen Bin
Composites Part A: Applied Science and Manufacturing 2015 Volume 78() pp:174-180
Publication Date(Web):November 2015
DOI:10.1016/j.compositesa.2015.07.021
High-density polyethylene composite films filled with various contents of carbon fiber (CF) were manufactured by melt mixing. The electrical and self-heating properties of the composite films were investigated. The composite films containing 10 wt% CF were exposed to γ-ray irradiation. The structural, morphological, and self-heating properties of the irradiated composite films were examined. The results indicated that the surface temperature (Ts) of the composite films was strongly dependent on the applied voltage and filler content. The Ts of the irradiated composite films was higher than that of the non-irradiated films, which contributed to the lower thermal expansion and the higher degree of crystallization of the irradiated composite films. In addition, the mechanical properties of the irradiated composite films were significantly improved. Using a rechargeable battery as the applied voltage source to evaluate the self-heating property of the irradiated composite films, a heating temperature of 54.2 °C was achieved, which lasted for 6 h.
Co-reporter:Duigong Xu;Kohji Tashiro
Journal of Polymer Science Part B: Polymer Physics 2015 Volume 53( Issue 4) pp:253-261
Publication Date(Web):
DOI:10.1002/polb.23620
ABSTRACT
Temperature dependences of spherulite morphology and crystal orientation of poly(vinylidene fluoride) (PVDF) were systematically investigated via a combinatorial method. The method created a temperature gradient ranging from 130 to 200 °C. Results show that the preferential orientation of the crystallites changes with the crystallization temperature. The crystallization at 169 °C gives the most highly developed crystalline state of PVDF crystalline form II (α form), in which the spherulite size is maximal, and the crystallite sizes are also the longest, about 200 nm along the b axes. Besides, the a-axis is almost parallel to the film normal. It indicates that the crystallization rate is the highest in the b-axis direction. The perferential orientation at higher temperatures may be attributed to the confined 2D growth of the PVDF spherulites in the thin film, whereas the spherulites grow in the 3D mode at lower temperatures. The crystallization behavior revealed in the method is consistent with the results of melt isothermal crystallization experiments. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 253–261
Co-reporter:Ping Tang;Rong Zhang;Ran Shi
Journal of Materials Science 2015 Volume 50( Issue 4) pp:1565-1574
Publication Date(Web):2015 February
DOI:10.1007/s10853-014-8716-z
High-density polyethylene (HDPE) composite films filled with carbon fibers (CF), carbon nanotubes (CNT) as well as hybrid filler of CF and CNT were prepared by melt mixing. The electrical and self-heating properties of the composite films were investigated. Results showed that: when the total content of filler was the same, (i) the electrical resistivity of composite films filled with hybrid fillers was lower than those with single filler; (ii) the composite films filled with hybrid fillers displayed more excellent self-heating performance such as a higher surface temperature (Ts), a more rapid temperature response, and a better thermal stability. This indicates the synergetic effect of combination of CNT and CF on improvement of the electrical and self-heating properties of HDPE-based composite films. The synergy can be considered to be the result of the fibrous filler CF acting as long distance charge transporters and the CNT serving as an interconnection between the fibers by forming local conductive paths.
Co-reporter:Rong Zhang, Ping Tang, Jianfeng Li, Duigong Xu, Yuezhen Bin
Polymer 2014 Volume 55(Issue 8) pp:2103-2112
Publication Date(Web):10 April 2014
DOI:10.1016/j.polymer.2014.02.065
Composites of carbon fibers (CF) filled with ultrahigh molecule weight polyethylene/low density polyethylene blend matrix (UHMWPE/LDPE) were prepared by kneading method. The positive temperature coefficient (PTC) effect of electrical resistivity of UHMWPE/LDPE/CF composites was investigated by direct current (DC) and alternating current (AC) measurements over the frequency range of 100–106.5 Hz from 30 to 150 °C. The onsets of PTC effect were found to be strongly depended upon the CF content even the melting behaviors were almost same for all composites. To interpret this phenomenon, a master curve of temperature–frequency–resistivity superposition was constructed for composites with different CF contents based on the AC resistivity. The CF content dependence of correlation length was related to the onset of PTC effect. The transitions of conductor–insulator were studied quantitatively by complex planes of AC impedance, and the calculated capacitances and resistances showed a similar PTC effect under DC. Based on the analysis of AC capacitance, the average distances between CFs were calculated using a plane capacitance model which varied with CF concentration and temperature, and the tendency was consistent to the PTC effect.
Co-reporter:Ran Shi;Hai Wang;Ping Tang
Frontiers of Chemical Science and Engineering 2014 Volume 8( Issue 2) pp:171-178
Publication Date(Web):2014 June
DOI:10.1007/s11705-014-1428-8
To improve the dispersibility of carbon nanotubes (CNTs), poly(vinylferrocene-co-styrene) (poly (Vf-co-St)), was grafted onto the surface of CNTs by a ligand-exchange reaction. Poly(Vf-co-St) was obtained by a radical copolymerization reaction using styrene and vinylferrocene as the monomers. The vinylferrocene was synthesized from ferrocene via a Friedel-Crafts acylation. The molecular weight, molecular weight distribution, and amount of Vf in the poly(Vf-co-St) were 1.32 × 104, 1.69 and 17.6% respectively. The degree of grafting of the copolymer onto the CNTs surface was calculated from thermogravimetric analysis and varied from 27.1% to 79.7%. The addition of the poly(Vf-co-St) greatly promoted the dispersibility of the modified CNTs in anhydrous alcohol. The electrical conductivity of composites prepared from the polymer-grafted CNTs and copolymer (acrylonitrile, 1,3-butadiene and styrene, ABS) strongly depended on the degree of grafting. These results show that the amount of polymer grafted onto the surface of CNTs can be controlled and that the electrical properties of composites prepared with these grafted polymers can be tuned.
Co-reporter:Duigong Xu, Yanan Song, Xiaomei Shi, Ping Tang, Masaru Matsuo, Yuezhen Bin
Polymer 2013 Volume 54(Issue 15) pp:4037-4044
Publication Date(Web):8 July 2013
DOI:10.1016/j.polymer.2013.05.058
Temperature dependence of lamellae orientation of a branched low molecular weight polyethylene (B-LMWPE)/ultra-high molecular weight polyethylene (UHMWPE) blend film has been studied by using transmission electron microscopy (TEM), two-dimensional wide angle X-ray diffraction (2D-WAXD) and two-dimensional small angle X-ray scattering (2D-SAXS). The film was prepared by solution casting under a controlled temperature gradient (T-gradient). TEM and X-ray scattering observations demonstrate that no clear lamellar crystal exists in B-LMWPE-rich phase while a large amount of lamellae are found in UHMWPE-rich phase. And these lamellae show a significant temperature dependence of preferred orientation. Results of 2D-WAXD and 2D-SAXS indicate that the lamellae stack regularly and preferentially parallel to the film surface at lower temperatures. At the temperatures near to the transition region, namely near to the gelation temperature, a part of the lamellae become to orient in an irregular way. At higher temperatures, almost all of the lamellae preferentially orient along the normal to the film surface and they randomly distribute around that direction. It's worth noting that the preferred orientation of the lamellae may influence the drawability of B-LMWPE/UHMWPE blend films.
Co-reporter:Yanan Song, Kohji Tashiro, Duigong Xu, Jun Liu, Yuezhen Bin
Polymer 2013 Volume 54(Issue 13) pp:3417-3425
Publication Date(Web):7 June 2013
DOI:10.1016/j.polymer.2013.04.054
Co-reporter:Qian Yu, Yanan Song, Xiaomei Shi, Chunye Xu, Yuezhen Bin
Carbohydrate Polymers 2011 Volume 84(Issue 1) pp:465-470
Publication Date(Web):11 February 2011
DOI:10.1016/j.carbpol.2010.12.006
Novel crosslinked blend films of N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride (HTCC) and poly(vinyl alcohol) (PVA) were prepared by mixing their aqueous solutions followed by crosslinking with glutaraldehyde (GA). The effects of the GA content and ratio of HTCC to PVA on the appearance, swelling, gel content, morphology and antibacterial activities of blend films were studied and a possible mechanism of crosslinking was proposed based on the results. It was found that the equilibrium degree of swelling (ESD) increased with the increasing content of HTCC, but decreased with the content of GA. The ESD was a maximum (212%) when the ratio of HTCC/PVA/GA was 60/40/2 (wt). Antibacterial activities against Staphylococcus aureus and Escherichia coli of the blend films were weakened slightly by crosslinking, but still showed substantial antibacterial activity. These results demonstrate that, not only the PVA, but also the HTCC reacted with GA. It was the amino groups on HTCC that was un-substituted by quaternary ammonium salt, which reacted with the aldehyde groups on GA.
Co-reporter:Ru Chen;Yumiko Nakano;Naoko Kurata
Colloid and Polymer Science 2010 Volume 288( Issue 3) pp:307-316
Publication Date(Web):2010 February
DOI:10.1007/s00396-009-2173-2
In an attempt to improve the mechanical property of polyethylene composite at high temperature, crosslinking of ultrahigh-molecular-weight polyethylene (UHMWPE) and carbon fiber (CF) blends was carried out by using dicumyl peroxide (DCP). The specimens were prepared by gelation/crystallization from solutions. The effect of chemical crosslinking on mechanical and electrical properties of UHMWPE/CF blends with composition of 1/0, 1/0.25, and 1/1 (w/w) were investigated in detail. Electrical conductivity and thermal mechanical properties of the blends with the 1/1 composition were greatly improved by incorporation of enough content of CF and adequate crosslinking network formation. Surprisingly, the Young’s modulus of the 1/1 blend reached 20 GPa at room temperature (20 °C). On the other hand, heat treatment at 135 °C played an important role for obtaining a high PTC effect for the UHMWPE-CF blend in which the PTC intensity reached 107.
Co-reporter:Duigong Xu, Yuezhen Bin and Ping Tang
Macromolecules 2010 Volume 43(Issue 12) pp:5323-5329
Publication Date(Web):May 19, 2010
DOI:10.1021/ma100056j
Crystallization and phase separation of polyethylene blend were first studied under a controlled temperature gradient (T-gradient) condition. Branched low molecular weight polyethylene (B-LMWPE) and ultrahigh molecular weight polyethylene (UHMWPE) blend films were prepared by casting the blend solutions on the T-gradient stage and then evaporating the solvent. The morphological evolution of blend films was investigated in detail. The blend films showed a continuous gradients surface. With increasing temperature, the degrees of crystallinity for both of the B-LMWPE and UHMWPE decreased in the blend films. The results indicated that phase separation behavior of B-LMWPE and UHMWPE blend with composition 10/1 or 5/1 occurred in both of solution and gel, and the phase separation was prior to crystallization. It is suggested that phase separation should induce molecular ordering and crystallization in the B-LMWPE/UHMWPE blend in the initial stage, and the phase separation and crystallization compete with each other in the later period. Another fact is that high viscosity of blend solution plays a more important role in phase separation rather than in crystallization, and it will be the main disincentive in inhibiting the Marangoni phenomenon when the composition of UHMWPE increases in the blend.
Co-reporter:Pengju Lv, Yuezhen Bin, Yongqiang Li, Ru Chen, Xuan Wang, Baoyan Zhao
Polymer 2009 50(24) pp: 5675-5680
Publication Date(Web):
DOI:10.1016/j.polymer.2009.10.004
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