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Modifying Agents (modifying + agent)
Selected AbstractsPreparation and characterization of polypropylene/solid-state organomodified montmorillonite nanocompositesPOLYMER COMPOSITES, Issue 4 2008Sun Yu-hai A novel organomodified montmorillonite prepared by solid-state method and its nanocomposites with polypropylene were studied. The interaction between modifying agent and montmorillonite was investigated by X-ray diffraction (XRD) analysis, contact angle determination, and Fourier-transform infrared spectroscopy. The results showed that the modifying agent behaves as an effective intercalating agent, enlarging the interlayer spacing of montmorillonite and making montmorillonite more hydrophobic. Polypropylene/solid-state organomodified montmorillonite composites were prepared by melt-mixing method. The dispersion of the silicates was investigated by XRD analysis and transmission electron microscopy. It was found that the nanocomposites are formed with solid-state organomodified montmorillonite and polypropylene. The thermogravimetric analysis and differential scanning calorimetry results showed that the organoclay could enhance the thermal stability and decrease the relative crystallinity of polypropylene. Mechanical and rheological tests indicated that the organoclay improves the mechanical properties but has no obvious effect on rheological properties of polypropylene. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Influence of polyethersulfone modification of a tetrafunctional epoxy matrix on the fracture behavior of composite laminates based on woven carbon fibersPOLYMER COMPOSITES, Issue 5 2004B. Fernández In this study, the influence of poly(ethersulfone) (PES) as a modifying agent of a tetrafunctional epoxy matrix (TGDDM) on the mechanical behavior of composite laminates based on woven carbon fibers has been investigated. Dynamic mechanical experiments were performed on neat matrix resins and on their corresponding laminate composites. Mode-I and Mode-II fracture toughness tests for the bulk matrices and their composites, respectively, and also flexural and short beam shear tests (SBS) were carried out. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the morphologies obtained. A nanoscopic phase separation was obtained after PES addition, which was not able to stabilize the fracture process, leading, as a consequence, to a poor extent of improvement on fracture toughness properties. Polym. Compos. 25:480,488, 2004. © 2004 Society of Plastics Engineers. [source] Synthesis and characterization of poly(butyl acrylate- co -ethylhexyl acrylate)/ poly(vinyl chloride)[P(BA-EHA)/PVC] novel core-shell modifier and its impact modification for a poly(vinyl chloride)-based blendPOLYMER ENGINEERING & SCIENCE, Issue 6 2010Mingwang Pan Synthesis of poly(butyl acrylate-co-ethylhexyl acrylate)-core/poly(vinyl chloride)-shell [P(BA-EHA)/PVC] used as a modifying agent of PVC via semicontinuous seeded emulsion copolymerization is reported here. Diameter distributions and morphology of the composite latex particles were characterized with the aid of particle size analyzer and transmission electron microscopy (TEM). The grafting efficiency (GE) and grafting ratio (GR) of vinyl chloride (VC) grafted onto the P(BA-EHA) with varying content of crosslinking agent and core-shell ratios were investigated. TEM studies indicated that the P(BA-EHA)/PVC latex particles have core-shell structure, and the P(BA-EHA) rubbery particles in blending materials were uniformly dispersed in PVC matrix. Dynamic mechanical analysis (DMA) results revealed that the compatibility between the P(BA-EHA) and the PVC matrix was significantly improved due to the presence of the P(BA-EHA)-grafted-VC copolymer. The notched impact strength of the blending material with 3 wt% of rubber content was seven times that of the PVC. Linear regressions of mechanical properties as loading of the modifier were made. The resulting data of notched impact strength and elongation at break for the blending materials deviated significantly from regression lines within 3,4.5 wt% of the P(BA-EHA) content. The PVC blends modified by the modifier exhibited good toughness and easy processability. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Development of a robust once-a-day glipizide matrix systemJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2007Shahla Jamzad The robustness of a new hydroxypropylmethylcellulose (HPMC) based modified release glipizide (10 mg) formulation was studied. The tablet formulations were prepared by dry blending the ingredients and direct compression, incorporating a range of release modifying agents up to ± 20% w/w relative to an optimized formulation. The dissolution was assessed in 900 mL pH 6.8 buffer at 75 rev min,1 paddle speed. Calculated difference and similarity factors (f1 and f2) and results of analysis of variance suggest that the overall release profiles were similar. Compositional changes up to ± 20% w/w and a reduction of drug dose to half did not change the general release pattern of this low dose/pH-dependent drug in a significant way. It is concluded that the drug release from the developed matrix systems is highly dependent on the kinetics of hydration and erosion, and that the proposed compositional changes within ± 20% w/w did not alter this relationship. The particulate systems used were characterized by determining the Carr index, Hausner ratio and the rheological properties using a texture analyser. Results indicate that the release is reproducible and the system has potential for successful scale-up operation, while complying with recommended Food and Drug Administration guidelines "Scale Up and Post Approval Changes". [source] Effect of bifunctional modifiers of the clay on the morphology of novolac cured epoxy resin/clay nanocompositesPOLYMER COMPOSITES, Issue 10 2008Tsung-Yen Tsai Montmorillonite type clay, (PK-802) is modified by the bifunctional modifiers (2-phenylimidazole/benzalkonium chloride, PI/BEN or 2-methylimidazole/benzalkonium chloride, MI/BEN) with different ratio, which contain a curing agent, BEN, and the promoters/accelerator (PI and MI). These two modifying agents are simultaneously intercalated into the gallery space of pure PK-802. The novolac cured epoxy nanocomposites are prepared with this modified clay by crosslinking polymerization reaction. Wide-angle X-ray diffraction is used to measure the resulting d -spacing of modified PK-802 and the nanocomposites. Thermo-gravimetric analysis is used to characterize the thermal properties of the nanocomposites. The morphology of the nanocomposites is investigated using transmission electron microscopy techniques. Well dispersion of clay into the novolac cured epoxy-clay nanocomposites resulted when simultaneously both the modifying agents with 5:5 mole ratios are used to modify the clay instead of using single modified agent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Chemoselective synthesis of peptides containing major advanced glycation end-products of lysine and arginineCHEMICAL BIOLOGY & DRUG DESIGN, Issue 3 2005P. Gruber Abstract:, Useful methodologies have been developed, enabling the straightforward synthesis of peptides containing N, -(carboxymethyl)- l -lysine (CML) and N, -(carboxyethyl)- l -lysine (CEL), the major glycation end-products of lysine. These lysine derivatives were successfully incorporated into growing peptide chains via standard Fmoc/Ot -Bu peptide synthesis procedures. For the synthesis of peptides containing major glycation end-products of arginine, synthetic routes have been developed enabling the transformation of ornithine residues in peptides into the well-known arginine-derived advanced glycation end-products (AGEs) Glarg, carboxymethyl- l -arginine (CMA), MG-H1, MG-H2, MG-H3, and carboxyethyl- l -arginine (CEA), respectively, by means of special modifying agents. Furthermore, it was shown that Glarg-containing peptides become quantitatively hydrolyzed into CMA-peptides under physiologic conditions. A similar reaction was observed in case of a MG-H3-peptide, which turned into a CEA-peptide under these conditions. [source] Lipids, lipid modifying agents and cardiovascular risk: a review of the evidenceCLINICAL ENDOCRINOLOGY, Issue 6 2009David Preiss Summary It is well-established that serum total-cholesterol, LDL-cholesterol, low HDL-cholesterol and calculated indices such as total cholesterol : HDL-cholesterol ratio or less commonly used indices such as non-HDL cholesterol are strongly predictive of cardiovascular events. Serum triglycerides, by contrast, are only modestly associated with coronary heart disease (CHD) in multivariate analysis and incorporation of triglycerides into prediction algorithms is therefore unlikely to improve their prediction capability. Meta-analysis of studies including > 90 000 subjects has provided robust evidence that statins reduce important clinical end-points. These included a 12% fall in all-cause mortality, 19% fall in CHD mortality and 23% fall in CHD mortality or myocardial infarction. Furthermore there are high quality data showing additional benefit of intensive statin therapy over standard statin therapy for secondary prevention of cardiovascular disease. However, meta-analysis of 10 fibrate trials has shown inconsistent evidence of vascular benefit and non-cardiovascular mortality has been slightly but consistently elevated in most fibrate trials and in meta-analysis. The general use of fibrates for cardiovascular risk reduction can therefore not be supported at present. Other second line agents such as bile acid sequestrants, nicotinic acid and omega-3 fatty acid supplements have been evaluated in a few randomized controlled studies in which cardiovascular benefit has been found but clearly further data are required to properly establish their use in clinical practice. Ongoing studies such as ACCORD, IMPROVE-IT, ASCEND, ORIGIN and HPS2-THRIVE should assist in answering outstanding questions over the next 5 years. [source] | |||||||||||||