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Chivatanasoontorn V.,Kyoto Institute of Technology | Yamada K.,Osaka Municipal Technical Research Institute | Kotaki M.,Kyoto Institute of Technology | Kotaki M.,Kaneka Americas Holding Inc.
Polymer (United Kingdom) | Year: 2015

Abstract Raman spectroscopy and wide-angle X-ray diffraction (WAXD) were used to evaluate microstructures, i.e. molecular orientation, crystalline orientation and the relative amount of β-phase crystal (K), near the surface of injection molded polypropylene (PP). It was found that highly ordered structure near the surface (0-30 μm) was formed when ultra-high injection speed (1000 mm/s or γ = 1670 s-1) was utilized. Subsequently, increase of relative amount of β-phase crystal near the surface was achieved. The relationship between the microstructures and surface mechanical properties measured by micro-cutting method and progressive load scratch tests was investigated. The highly oriented PP showed higher surface mechanical properties due to the increase in degree of molecular and crystalline orientation. The increased scratch properties were considered to be also affected by higher β-phase crystal content. © 2015 Elsevier Ltd.

Itoh H.,Kyoto Institute of Technology | Li Y.,Kyoto Institute of Technology | Chan K.H.K.,Kyoto Institute of Technology | Kotaki M.,Kaneka Americas Holding Inc. | Kotaki M.,Kyoto Institute of Technology
Polymer Bulletin | Year: 2016

Electrospinning has been recognized as a simple and straightforward technique for the production of nanometer and micron-scaled polymer fibers. The technique utilizes electrical forces to stretch and thin fine polymer solution jet drawn from the orifice of a nozzle. Due to the electrical nature of the spinning process, the electrical and ionic conductivity of the polymer solution was proposed to play an important influence on both the process and fiber morphology. This study aims to increase mechanical properties and control nanofiber morphology using a mass production electrospinning technique known as free surface electrospinning. It is found that development of ribbon-shaped fibers was due to thick polymer jets ejected from Taylor cones on the electrode of free surface electrospinning and fast solvent evaporation rate caused by high solution conductivity. Tensile testing of the nanofiber mats indicated higher tensile strength for nanofiber mat spun with solution of enhanced solvent conductivity. Correlating with internal structure characterized in terms of thermally properties and d-spacing, the increased mechanical properties of nanofibers from high conductivity solution were proposed to be attributed to the presence of ribbon-shaped fibers. © 2016 Springer-Verlag Berlin Heidelberg

Li P.,Texas A&M University | Huang T.-C.,Texas A&M University | White K.L.,Texas A&M University | Hawkins S.,Texas A&M University | And 3 more authors.
RSC Advances | Year: 2015

Epoxy nanocomposite spray-coatings containing large aspect ratio modified graphene (MG) were successfully prepared in a facile manner. The individually exfoliated MG nanosheets form liquid crystalline mesophases in the epoxy precursor at low loadings. The epoxy/MG nanocomposite films exhibit significantly improved gas barrier properties even in humid conditions. The spray-coating method allows for the preparation of high MG content nanocomposites in large scale without compromising processability. Implication of the present finding for fabrication of high-performance graphene-based packaging films with multi-functionality is discussed. © 2015 The Royal Society of Chemistry.

Chouwatat P.,Kyoto Institute of Technology | Nojima S.,Kyushu University | Higaki Y.,Kyushu University | Kojio K.,Kyushu University | And 4 more authors.
Polymer (United Kingdom) | Year: 2016

An effect of surface segregation of polyhedral oligomeric silsesquioxanes (POSS) on surface physical properties was investigated. Hard coating layer with various MA8POSS loadings was prepared on a bilayer of soft layer and PMMA substrate via a UV curing process. The scratch resistance of the coating layer showed specific properties. When MA8POSS loadings in the coating layers were less than 10 wt %, the coating layers showed a great performance in scratch resistance. While MA8POSS loadings were higher than 10 wt %, the surface performance was deteriorated. This is because the outermost surface of the coating layer was covered by MA8POSS molecules when the MA8POSS loadings were higher than 10 wt %, resulting in uncompleted curing reaction caused by large steric hindrance of MA8POSS. © 2015 Elsevier Ltd. All rights reserved.

Li P.,Texas A&M University | Yao H.,Texas A&M University | Wong M.,Texas A&M University | Sugiyama H.,Kaneka Corporation | And 2 more authors.
Journal of Materials Science | Year: 2014

Thermally stable and highly conductive films have been prepared based on thermally reduced graphene oxide and exfoliated α-zirconium phosphate nanoplatelet (ZrP) hybrids. Exfoliated ZrP and graphene oxide (GO) were first mixed in aqueous solution to form a stable dispersion and then cast into free-standing films through flow-directed assembly. Upon annealing at 750 °C in Argon atmosphere, significant amounts of oxidized species were removed from the GO and a noticeable recovery of sp2 structure of the reduced GO sheets was observed. With the incorporation of the inorganic nanoplatelets, the thermal stability and structural integrity of the hybrid films were greatly improved, while the good electrical conductivity of the reduced GO was maintained. Potential applications for graphene-based hybrid films based on the current approach are discussed. © 2013 Springer Science+Business Media New York.

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