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Preparation of New Bioactive Hybrid Bone Cements Containing Bis-GMA Derivatives as a Prepolymer
Park, Bang-Ju,Park, Kwideok,Ahn, Kwang-Duk,Chin, Yong-Ok,Han, Dong Keun Wiley - VCHVerlag GmbH & Co. KGaA 2006 Macromolecular Materials & Engineering Vol.291 No.6
<P>Summary: Novel organic-inorganic hybrid bioactive bone cements containing bisphenol-A-glycidyl methacrylate (Bis-GMA) derivatives and a bioactive inorganic filler were prepared for orthopedic applications. The Bis-GMA derivatives, such as 3MA and a 3MA mixture (3MA mix), were synthesized by blocking one or two of the hydroxyl groups of the Bis-GMA so as to use it as a prepolymer. Four organic prepolymers, such as Bis-GMA, 3MA, 3MA 50 and 3MA mix, and an inorganic filler, AW-GC, were used for the preparation of the bioactive bone cements and their characteristics were evaluated. As compared with the Bis-GMA control, the new bioactive bone cements containing the Bis-GMA derivatives exhibited appropriate curing times, low polymerization shrinkage, low water absorption and solubility as well as high mechanical properties. In particular, the bioactive bone cement containing 3MA mix and AW-GC had higher bending and compressive strengths than the Bis-GMA one.</P><P> <img src='wiley_img/14387492-2006-291-6-MAME200500408-gra001.gif' alt='wiley_img/14387492-2006-291-6-MAME200500408-gra001'> Graphic Curing time and polymerization shrinkage on various prepolymers of bioactive bone cements. </P>
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Chung, Jae Woo,Oh, Kwang Sei,Kwak, Seung-Yeop Wiley - VCHVerlag GmbH & Co. KGaA 2007 Macromolecular Materials & Engineering Vol.292 No.5
<P>Poly(ϵ-caprolactone) nanocomposites, PCLOC25A and PCLOC30B, with organoclays (OCs) having nonpolar and polar organic modifiers, respectively, were prepared by the melt mixing method and additional heat treatment. WXRD analysis revealed that both nanocomposites were exfoliated, irrespective of the OC polarity. However, WXRD failed to show the degree of exfoliation of the nanocomposites, because the d<SUB>001</SUB> peaks disappeared. Thus, dynamic mechanical analysis (DMA) was carried out to compare the degree of exfoliation of the PCL nanocomposites. From DMA, PCLOC30B showed higher elasticity, storage moduli, viscosity, and activation energy than PCLOC25A, indicating that PCLOC30B had a more exfoliated structure than PCLOC25A. This is due to the polar interaction in PCLOC30B, as verified by the plots of a<SUB>T</SUB> versus temperature. Thus, it was confirmed that DMA provides an alternative approach to evaluating the degree of exfoliation of nanocomposites.</P><P> <img src='wiley_img_2010/14387492-2007-292-5-MAME200600451-gra001.gif' alt='wiley_img_2010/14387492-2007-292-5-MAME200600451-gra001'> </P>
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A Novel Fabrication Method for Poly(propylene)/Clay Nanocomposites by Continuous Processing
Kim, Do Hoon,Park, Jun Uk,Cho, Kwang Soo,Ahn, Kyung Hyun,Lee, Seung Jong Wiley - VCHVerlag GmbH & Co. KGaA 2006 Macromolecular Materials & Engineering Vol.291 No.9
<P>Summary: It is well known that poly(propylene)/clay (PP/clay) nanocomposite forms an exfoliated structure when mixed with maleic anhydride-functionalized polypropylene (MAPP). This can be easily achieved by melt processing, however, the use of functionalized chemicals like MAPP costs a lot preventing its commercial application. Recently, it was reported that the exfoliated structure of PP/clay nanocomposite could be obtained without using any compatibilizer such as MAPP when exposed to the electric field. They could regulate the degree of dispersion and exfoliation by controlling the amount of clay loading, the strength of electric field, the time exposed to the electric field, etc. However, this was accomplished by applying the electric field on a rheometer for a long time. It will be practically attractive if we produce PP/clay nanocomposites via continuous processing like extrusion. A new design concept is required for this purpose. In this study, we present a novel method to continuously produce PP/clay nanocomposites using the electric melt pipe equipped with a twin-screw extruder. Rheology, XRD, and SEM measurements confirm the formation of nanocomposites. Thermal- and dynamic-mechanical analysis also shows the enhancement of the properties. Though, in this study, only a partial intercalation was achieved through continuous processing, it shows a possibility to produce nanocomposites by this approach. As this is a physical process that can be adapted to the conventional extrusion, the approach suggested in this study may be extended to other polymer/clay nanocomposite systems as well.</P><P> <img src='wiley_img/14387492-2006-291-9-MAME200600169-gra001.gif' alt='wiley_img/14387492-2006-291-9-MAME200600169-gra001'> Graphic Schematic diagram of electric melt pipe equipped with a twin-screw extruder. </P>
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Chi, Jun Ho,Park, Se Hee,Lee, Chang-Lyoul,Kim, Jang Joo,Jung, Jin Chul Wiley - VCHVerlag GmbH & Co. KGaA 2007 Macromolecular Materials & Engineering Vol.292 No.7
<P>Two new polyimides (ODA-PI and HDA-PI) having 1,4-phenylenediethynylene unit and octyloxy groups were synthesized. Judging from inherent viscosities of their precursor PAAs (1.42 and 1.62 dL · g<SUP>−1</SUP>), the two PIs were very high in molecular weight. Casting and thermal imidization of PAAs results polyimides with good-quality films. They were stable up to 364 °C and showed no crystallites. UV-vis and PL spectra in NMP solutions of both PIs showed maxima at 442 and 501 nm, respectively, while PL spectra in ≈10 µm thick films exhibited a maximum at 540 nm. CV indicates that two PIs were electrochemically active in redox region. The devices with construction of ITO/PEDOT/PIs/BAlq<SUB>3</SUB>/LiF/Al exhibited turn-on voltages of 6.5 V in ODA-PI and 7.5 V in HDA-PI and emitted a bright bluish-green light. ODA-PI and HDA-PI showed maximum luminescence of 256 and 316 cd · cm<SUP>−2</SUP>, respectively, at the same voltage of 12 V.</P><P> <img src='wiley_img/14387492-2007-292-7-MAME200700067-gra001.gif' alt='wiley_img/14387492-2007-292-7-MAME200700067-gra001'> </P>
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Kim, Sumin,Kim, Jin-A.,An, Jae-Yoon,Kim, Hee-Soo,Kim, Hyun-Joong,Deng, Yuhe,Feng, Qian,Luo, Jiayan Wiley - VCHVerlag GmbH & Co. KGaA 2007 Macromolecular Materials & Engineering Vol.292 No.12
<P>The effect of wood species on the TVOC emission factor and the physico-mechanical properties of GPBs is investigated. Of the two wood species, the water absorption was higher for the GPBs made using Eucalyptus sp. than for those using Pinus massoniana. The Eucalyptus sp. GPBs pressed at room temperature, 40 and 60 °C all demonstrated higher moisture absorption than commercial GPBs. The TVOC emission factor decreased with increasing press temperature, especially for Eucalyptus sp. but remained under ‘excellent’ grade as defined by the KACA. From these results, GPB with higher content of wood particles should be considered for the replacement of wood-based panels such as particleboard and medium density fiberboard (MDF).</P><P> <img src='wiley_img_2010/14387492-2007-292-12-MAME200700192-gra001.gif' alt='wiley_img_2010/14387492-2007-292-12-MAME200700192-gra001'> </P>
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