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Blends Decreased (blend + decreased)
Selected AbstractsOnium salt reduces the inhibitory polymerization effect from an organic solvent in a model dental adhesive resinJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Fabrício A. Ogliari Abstract This study evaluated the effect of organic solvent concentration on the polymerization kinetics for a model dental adhesive resin containing a ternary photoinitiator system. A monomer blend based on the bis-GMA, TEGDMA, and HEMA was used as a model dental adhesive resin, which was polymerized using a binary system [camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system [CQ, EDAB, and diphenyliodonium hexafluorphosphate (DPIHFP)]. Additionally, these blends had 0, 10, 20, 30, and 40 wt % ethanol added. Real-time Fourier transform infrared spectroscopy was used to investigate the polymerization reaction over photoactivation time. Data were plotted, and Hill's three-parameter nonlinear regression was performed for curve fitting. The addition of a solvent to the monomer blends decreased the polymerization kinetics, directly affecting the rate of polymerization, delaying vitrification, and attenuating the Trommsdorf effect. The introduction of DPIHFP displayed a strong increase in reaction kinetics, reducing the solvent inhibition effect. After 10 s of photoactivation, the binary system obtained in 0, 10, 20, 30, and 40% of ethanol, a degree of conversion of 44.6, 26.3, 13.4, 1.15, and 0.0%, respectively, whereas when a ternary system was used, the values were 54.6, 40.5, 27.4, 14.5, and 3.4%. An improvement was observed in the polymerization kinetics of a model dental adhesive resin when using a ternary photoinitiation system, making the material less sensitive to the residual presence of a solvent before photoactivation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Effect of EPDM on Morphology, Mechanical Properties, Crystallization Behavior and Viscoelastic Properties of iPP+HDPE BlendsMACROMOLECULAR SYMPOSIA, Issue 1 2007Nina Vranjes Abstract Summary: Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE) with and without ethylene-propylene-diene (EPDM) terpolymer as compatibilizer were systematically investigated to determine the influence of the EPDM on blends properties. The morphology was studied by Scanning Electron Microscopy (SEM). Mechanical properties of investigated systems: tensile strength at break, elongation at break, yield stress and Izod impact strength were determined. Crystallization behavior was determined by Differential Scanning Calorimetry (DSC). Dynamic Mechanical Analysis (DMA) was used to determined the storage modulus (E,), loss modulus (E,), and loss tangent (tan ,). The PP+HDPE blend revealed poor adhesion between PP and HDPE phases. Finer morphology was obtained by EPDM addition in PP+HDPE blends and better interfacial adhesion. Addition of HDPE to PP decreased tensile strength at break, elongation and yield stress. Decrease of tensile strength and yield stress is faster with EPDM addition in PP+HDPE blends. Elongation at break and impact strength was significantly increased with EPDM addition. The addition of EPDM in PP+HDPE blends did not significantly change melting points of PP phase, while melting points of HDPE phase was slightly decreased in PP+HDPE+EPDM blends. The EPDM addition increased the percentage of crystallization (Xc) of PP in PP+HDPE blends. The increase of Xc of HDPE was found in the blend with HDPE as matrix. Dynamical mechanical analysis showed glass transitions of PP and HDPE phase, as well as the relaxation transitions of their crystalline phase. By addition of EPDM glass transitions (Tg) of HDPE and PP phases in PP+HDPE blends decreased. Storage modulus (E,) vs. temperatures (T) curves are in the region between E,/T curves of neat PP and HDPE. The decrease of E, values at 25,°C with EPDM addition in PP+HDPE blends is more pronounced. [source] Rheological behavior of LDPE/CaCO3 blends containing EAAPOLYMER COMPOSITES, Issue 9 2009Aiqin Dong Calcium carbonate (CaCO3) filler particles were surface treated with organic titanate (TTS), a coupling agent. The composites were prepared by blending low-density polyethylene (LDPE) with the surface-modified fillers at various weight ratios. Ethylene-acrylic acid copolymer (EAA) was added to improve the adhesion of LDPE to fillers. A capillary rheometer was used to evaluate rheological properties of the LDPE/CaCO3/EAA blends. The blends were shown to be pseudoplastic with shear thinning behavior. When CaCO3 was modified by TTS (<2 wt%), the viscosity of the blends decreased quickly, and, addition of a small amount of EAA (<6 wt%) could also decrease the viscosity of the blends. The thermal behavior of these materials is evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The addition of a small amount of EAA and TTS enhances the stabilization of the blends, which could be explained by the "ball belling" action. The effects of temperature, TTS content, CaCO3 granule size, and content on the rheological property were also studied. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Reactive compatibilization of biodegradable poly(lactic acid)/poly(,-caprolactone) blends with reactive processing agentsPOLYMER ENGINEERING & SCIENCE, Issue 7 2008Masaki Harada Poly(lactic acid) (PLA) blended with poly(,-caprolactone) (PCL) was prepared with various reactive processing agents. Four isocyanates-lysine triisocyanate (LTI); lysine diisocyanate (LDI); 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione (Duranate TPA-100); 1,3,5-tris(6-isocyanatohexyl)biuret (Duranate 24A-100)-and an industrial epoxide-trimethylolpropane triglycidyl ether (Epiclon 725)-were used as reactive processing agents. PLA/PCL blended in the presence of LTI had the highest torque in a mixer test. The test specimens were prepared by injection molding. The mechanical properties, thermal properties, molecular weight, melt viscosity, phase behavior, and morphology were investigated using tensile strength, impact strength, differential scanning calorimetry, melt mass-flow rate measurements, capillary rheometery, gel permeation chromatography, laser scanning confocal microscopy (LSCM), and visco-elasticity atomic force microscopy (VE-AFM). The impact strength increased considerably at 20 wt% PCL. The nominal tensile strain of PLA/PCL blended with LTI increased by 270%. The MFR values of PLA/PCL blends decreased with increasing LTI. Similar results were observed for shear viscosity. LSCM measurements showed that the diameters of PCL were dispersed about 0.4 ,m in the presence of LTI. VE-AFM showed that spherical particles with diameters of 50 nm were PCL-rich domain. These results indicate that isocyanate groups of LTI react with both terminal hydroxyl or carboxyl groups of polymers, and the compatibility of PLA/PCL blends improves with LTI by reactive processing. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effect of poly(acrylic acid)-g-PCL microstructure on the mechanical properties of starch/PCL blend compatibilized with poly(acrylic acid)-g-PCLPOLYMER ENGINEERING & SCIENCE, Issue 3 2001Chang-Hyeon Kim Poly(acrylic acid)-g-polycaprolactone (PAA-g-PCL) graft copolymer was synthesized and starch/PCL blends compatibilized with PAA-g-PCL were prepared. The mechanical properties of the starch/PCL blends compatibilized with various PAA-g-PCLs that have different graft degrees and graft lengths were investigated. As the graft degree of the PAA-g-PCLs that have the same graft length increased, the modulus and the strength of the blends decreased. However, the elongation at break and the tensile toughness of the blends showed a maximum at a certain graft degree (10.8 mol%) owing to the better compatibilizing effect compared to the low (3.9 mol%) and the high (23.4 mol%) graft degree of PAA-g-PCL. It was also found that the modulus and the strength of the blends increased with the increase of graft length of the PAA-g-PCLs that have the same graft degree (,11 mol%). However, the blend compatibilized with the short graft length (M.W. of PCL graft: 530) exhibited the highest value of the elongation at break and the tensile toughness. This result is attributed to the self-crystallization of PAA-g-PCL in the blend that has longer PCL grafts. 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