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Lu X.,South China University of Technology | Lu X.,National certified Enterprise Technology Center | Zhao J.,South China University of Technology | Yang X.,National certified Enterprise Technology Center | Xiao P.,National certified Enterprise Technology Center
Polymer Testing | Year: 2017

Phase morphology exerts a tremendous influence on the properties of polymer blends. The development of the blend morphology depends not only on the intrinsic structure of the component polymers but also on extrinsic factors such as viscosity ratio, shearing force and temperature in the melt processing. In this study, various poly (butylene adipate-co-terephthalate) (PBAT) materials with different melt viscosity were prepared, and then poly (lactic acid) (PLA)/PBAT blends with different viscosity ratio were prepared in a counter-rotating twin-screw extruder under constant processing conditions. The influence of viscosity ratio on the morphology, mechanical, thermal and rheological properties of PLA/PBAT (70/30 w/w) blends was investigated. The experimental results showed that the morphology and properties of PLA/PBAT blends strongly depended on the viscosity ratio. Finer size PBAT phase were observed for viscosity ratio less than 1 (λ < 1) compared to samples with λ > 1. It was found that the interfacial tensions of PLA and PBAT were significantly different when the viscosity ratio was changed, the lowest interfacial tensions (0.12 mN/m) was obtained when the viscosity was 0.77. Additionally, the maximal tensile strength in PLA/PBAT blends were obtained when the viscosity ratio was 0.44, while the maximal impact properties were obtained when the viscosity ratio was 1.95. © 2017 Elsevier Ltd

Lu X.,Shanghai JiaoTong University | Lu X.,National certified Enterprise Technology Center | Zhang H.,Shanghai JiaoTong University | Zhang Y.,Shanghai JiaoTong University
Journal of Polymer Research | Year: 2014

Ester-exchange reaction was a useful method to improve the compatibility of polymer blends. In this article, ester-amide exchange reaction between Nylon 1010 and Ethylene-vinyl acetate rubber (EVM) was studied in the presence of different Ti and Zn derivatives as catalysts. The chemical reactions were studied by1H NMR. Catalytic activities of Ti(OBu)4, TiO(OOCCH3)2, ZnO and Zn(OOCCH3)2 were compared and Ti(OBu)4 showed the highest catalytic reactivity. Melt flow index (MFI) of Nylon 1010/EVM blends indicated that crosslinking and degradation took place in the reactive blends. Gel permeation chromatography (GPC) provided the evidence for the degradation behavior during melt blending. SEM images showed that the compatibility of the blends was improved at the presence of catalyst. SAXS results showed that the long period of Nylon 1010/EVM decreased after adding Ti(OBu)4, implying the formation of imperfect crystallites in Nylon 1010/EVM/Ti(OBu)4 blend. © 2014, Springer Science+Business Media Dordrecht.

Yin C.,Pennsylvania State University | Yin C.,National certified Enterprise Technology Center | Yin C.,Donghua University | Miranda D.F.,Pennsylvania State University | And 3 more authors.
Polymer (United Kingdom) | Year: 2016

This paper presents an investigation of semi-crystalline poly[tetrafluoroethylene -co-(perfluoropropylvinylether)] (PFA) films uniaxially drawn at two temperatures. The extent of crystal unit cell orientation increased significantly with drawing at both draw temperatures as expected, but crystallinity was found to increase with draw ratio only at the lower draw temperature, remaining unchanged at the higher temperature. Considering the evolution of small-angle X-ray scattering patterns as a function of deformation, a model for the changes in PFA lamellar microstructure on drawing was developed. The observed mechanical α and γ relaxations of PFA were assigned to relaxation of rigid and mobile amorphous segments, respectively. Drawing at 200 °C to a draw ratio of 7 leads to a ∼40 °C increase in the α transition temperature compared to the unoriented film, and the findings support the key role of molecular orientation in suppressing the cooperative motions of non-crystalline segments in drawn polymers. © 2016 Elsevier Ltd

Du H.,Sichuan University | Zhang Y.,Sichuan University | Zhang Y.,National Certified Enterprise Technology Center | Liu H.,Sichuan University | And 4 more authors.
Polymer (United Kingdom) | Year: 2014

In the work, ethylene-octene copolymer (POE) toughened isotatic polypropylene (PP) blends with different phase morphologies and crystalline structures were successfully fabricated and their influence on the toughness of PP blends was discussed. POE domains not only played the role of stress concentration to induce stress field around them, but also acted as stress deliverer to transmit stress to the deep into the PP matrix. Elongated domains transmitted stress better, but spherical ones induced a larger stress field. As for the crystalline structure of PP matrix, compared with the "bundle-like" β-crystals, well-developed β-spherulites could induce a larger stress field. The toughness of the blends with different combinations of phase morphology and crystalline structure was also discussed. Only the blend with elongated POE domains and well-developed β-spherulites could achieve super-high toughness. To achieve this goal requires simultaneous optimization of nucleating agent content, POE content and composition, and processing conditions. This work provides a good example to better understand the influence of phase morphology of rubbers and crystalline structure of matrix in rubber-toughed polymer system. © 2014 Elsevier Ltd. All rights reserved.

Li L.,Sun Yat Sen University | Li L.,National certified Enterprise Technology Center | Ruan W.-H.,National certified Enterprise Technology Center | Zhang M.-Q.,National certified Enterprise Technology Center | Rong M.-Z.,National certified Enterprise Technology Center
Express Polymer Letters | Year: 2015

A ternary system based on blends of poly(vinylidene fluoride)(PVDF) and polycaprolactone (PCL) and made the multi-walled carbon nanotubes (MWNT) selective distribution in PCL phases via melt blending has been studied. The studies on conductivity of MWNT/PCL/PVDF composites with different proportions of PVDF and PCL showed that the conductivity was good in the mass ratio range of PVDF/PCL from 70/30 to 40/60 and that of other matching was poor. The scanning electron microscope (SEM) observation of the composites revealed co-continuous morphologies of PVDF and PCL were formed in composites under suitable proportion of PVDF to PCL. The interfacial tensions of PVDF and PCL melts was tested at mixing temperature of 200°C, the calculated wetting coefficient indicated that MWNT would selectively distribute in PCL phase owing to interfacial effects. Transmission electron microscope (TEM) observation further confirmed that co-continuous morphologies of PVDF and PCL could appear with the increase of PCL content, as indicated by MWNT selective localization in PCL.As the result, the desired structure of double percolation was built in MWNT/PCL/PVDF composites, which have much higher conductivity than that of PVDF or PCL composites with the same MWNT content. Through a strategy of selective localization of MWNT, PVDF based material with low percolation threshold (<0.5 wt%) was acquired which held promise for potential use in large-scale industrial applications. © BME-PT.

Liu D.,Beijing University of Chemical Technology | Li Y.,Beijing University of Chemical Technology | Li Y.,National Certified Enterprise Technology Center | Deng J.,Beijing University of Chemical Technology | Yang W.,Beijing University of Chemical Technology
Polymer (United Kingdom) | Year: 2014

This paper reports helix-sense-selective polymerizations (HSSPs) of achiral acetylene monomer performed in chiral micelles, by which optically active helical polymer emulsions were directly obtained. The chiral micelles were constructed by chiral emulsifiers, in which achiral acetylene underwent HSSPs in the presence of catalyst [(nbd)RhCl]2. The chiral emulsifiers possessed different alkyl chain lengths and different amino acid groups, and their effects on HSSPs were investigated in detail. The obtained polymer emulsions were characterized by TEM, circular dichroism and UV-vis absorption spectroscopy techniques. It is demonstrated that the polymer chains constructing the emulsions adopted helical structures of predominantly one-handed screw sense, from which the emulsions exhibited remarkable optical activity. © 2014 Elsevier Ltd. All rights reserved.

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