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Cao X.-W.,South China University of Technology | Lin H.,South China University of Technology | Luo J.,South China University of Technology | He G.-J.,South China University of Technology | And 2 more authors.
Journal of Macromolecular Science, Part B: Physics | Year: 2014

Three types of polypropylene, namely propylene homopolymer (HPP), block copolymer of propylene with ethylene (CPP-B) and random copolymer of propylene with ethylene (CPP-R), were melted and isothermally crystallized in a self-designed vessel under supercritical carbon dioxide (Sc-CO2) atmosphere. The melting behavior and crystalline forms of crystallized samples were investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results showed that the presence of Sc-CO2 could improve the crystallinity for all three polypropylenes, and the promoting effect was more obivious with increasing CO2 pressure. In addition, it was observed that γ-crystals could be obtained in the CPP-B and CPP-R samples crystallized under Sc-CO2, while no γ-crystals were formed in HPP under the given conditions. The relative content of γ-crystals obtained in CPP-R samples was much higher than that of CPP-B, and 100% γ-phase could be formed in the CPP-R sample when subjected to 14 MPa Sc-CO2. © 2014 Taylor & Francis Group, LLC. Source


Du Y.,Wuyi University | Shi S.,Wuyi University | Yin X.,South China University of Technology | Xu B.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2016

Polymer mixing properties processed by three kinds of novel blending unit, namely barrier unit, chaos unit and vane unit, were simulated and compared through using Polyflow as polymer fluid dynamic software. The results show that mixing index of vane unit is larger than that of barrier unit and chaos unit, material in the runner of three kinds of novel blending unit suffers stretching action mainly, and vane unit is of the largest stretching action strength in the runner. Residence time expectations of chaos unit, barrier unit and vane unit are about 4 s, 5 s and 6 s respectively, and distribution mixing effect of vane unit is better. Stretching action in vane unit is obviously higher than in barrier unit and chaos unit. The transient mixing efficiency order of three kinds of novel blending unit is vane unit, barrier unit and chaos unit. Time averaged mixing efficiency of barrier unit is higher than that of chaos unit. With the increasing of axial distance, the influence of vane unit on mixing properties is more obvious. © 2016, Chengdu University of Science and Technology. All right reserved. Source


He G.-J.,South China University of Technology | Zheng T.-T.,South China University of Technology | Ke D.-M.,South China University of Technology | Cao X.-W.,South China University of Technology | And 2 more authors.
RSC Advances | Year: 2015

In this work, rapid ozone degradation of polypropylene (PP) was developed for the aim of rheology control using a reactive extrusion process. Experiments were carried out in a co-rotating intermeshed twin-screw extruder with varied polymer throughput and reaction temperature. Ozone was introduced into the extruder to rapidly oxidize molten PP in just several seconds period. The oxidized PP was characterized through melt flow index (MFI), rheological measurement, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy tests. The influence of reactive temperature and polymer throughput on the degradation reaction was studied. It was noted that molten PP could be fast and successfully degraded during this reactive extrusion process. The oxidized PP had higher MFI than that of the origin PP resin, indicating the decrease of molecular weight of PP. Carbonyl groups were formed on the PP molecular chains. This rapid oxidization process has higher reaction efficiency than the ozone degradation of PP in solid state and no harmful byproduct would be generated from this ozonizing reaction. © The Royal Society of Chemistry 2015. Source


Xu B.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities | Feng Y.,South China University of Technology | Cheng J.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities | Yu H.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities | He L.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities
Huagong Xuebao/CIESC Journal | Year: 2014

Numerical investigation was conducted to study the mixing behavior of Stokes flows in a rectangular cavity stirred by alternating motion of three square rods. The square loops of rod moved in two different ways that a Pseudo-Anosov map could be built in the flow domain in the augmented phase space. The finite volume method was used to solve the flow field with the periodic boundary conditions of the rod motion being imposed by the mesh supposition technique. The flow domain was meshed by staggered grids and the discretization schemes for control equations were accurate to the second-order resulting from the use of central differencing. Fluid particle tracking was conducted by a fourth-order Runge-Kutta scheme. The Poincaré section was obtained to reveal the size of the domain in which the Pseudo-Anosov map almost covered the whole cavity region except for four corner zones. The evolution patterns of tracers from different initial positions were computed to characterize the mixing process. Tracer interface stretches experienced exponential increases and had the larger power index than that predicted by the Pseudo-Anosov(pA) map matrix, which was due to the local secondary folding caused by the details of flow field, such as shapes of rods, rod trajectories and so on. ©All Rights Reserved Source


Luo J.-S.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities | Luo J.-S.,Wuyi University | Xu B.-P.,Technology Development Center for Polymer Processing Engineering of Guangdong Colleges and Universities | Xu B.-P.,Wuyi University | And 3 more authors.
Fibers and Polymers | Year: 2015

Thermoplastic polyurethane (TPU)/polypropylene (PP) blends of different weight ratios were prepared with a self-made co-rotating non-twin screws extruder (NTSE), which rotates at a speed ratio of 2.0, and a traditional twin-screw extruder (TSE), which rotates at a speed ratio of 1.0. The mechanical properties, phase morphology and thermal stabilities were investigated to characterize the effect of different processing methods. The experimental results revealed that the samples prepared with a NTSE had superior mechanical properties compared to those of the samples prepared with a TSE. High-resolution scanning electron microscopy showed a structure feature of fiber morphology of TPU/PP blends prepared with a NTSE and the particle size of dispersed phase of blends prepared with NTSE is smaller than that prepared with TSE, indicating that the NTSE is more efficient in mixing for immiscible polymer blends. Furthermore, thermogravimetric analysis curves indicated the strong interaction of the TPU/PP blends influenced by the flow field in NTSE, compared to that of TSE-extruded. © 2015, The Korean Fiber Society and Springer Science+Business Media Dordrecht. Source

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