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Modulus Decreased (modulus + decreased)
Selected AbstractsApplication of ultrasonic shear rheometer to characterize rheological properties of high protein concentration solutions at microliter volumeJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2005Atul Saluja Abstract The purpose of this work was to conduct preliminary rheological analysis on high protein concentration solutions by using the technique of ultrasonic shear rheometry at megahertz frequencies. The work was aimed at establishing the viability of the technique for analyzing protein solution rheology as well as obtaining an initial understanding of the effect of solution conditions on solution rheology of a model protein. Bovine serum albumin (BSA) was used for this study, and rheological analysis was conducted at 20 ,L sample volume between pH 2.0 and 9.0 at different ionic strengths at 25°C using 5 and 10 MHz quartz crystals. Significant differences in storage modulus among solutions at pH 5.0, 7.0, and 9.0 could only be detected at 10 MHz, and the errors associated with measurements were smaller as compared to those at 5 MHz for all the solutions studied. Solutions at pH 2.0 and 3.0 showed a time-dependent change in solution rheology. For solutions at pH 5.0, 7.0, and 9.0, which did not show time dependence in solution rheology, loss modulus data at lower concentrations correlated well with the dilute solution data in the literature. At higher concentrations, pH 5.0 solutions exhibited a higher loss modulus than pH 7.0 and pH 9.0 solutions. Storage modulus decreased with increasing ionic strength, unlike loss modulus, which did not show any change, except at pI of protein when no effect was observed. The results show the potential of high frequency rheometry for analyzing subtle differences in rheology of pharmaceutically relevant protein solutions at microliter volume. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:1161,1168, 2005 [source] Evaluation of the Effectiveness of New Compatibilizers Based on EBAGMA-LDPE and EBAGMA-PET Masterbatches for LDPE/PET BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2010Aida Benhamida Abstract The present paper is aimed to evaluate the efficiency of two masterbatches, i.e., EBAGMA/LDPE (MB1) and EBAGMA/PET (MB2) with 50/50 w/w composition, prepared by melt mixing and used as new compatibilizers for blends of LDPE/PET. The morphology, the mechanical and the thermal properties of LDPE/PET/MB1 and LDPE/PET/MB2 ternary blends have been investigated. Morphological investigation by SEM of LDPE/PET/MB1 ternary blends showed a finer dispersion of PET in LDPE matrix with a better interfacial adhesion compared to those of both LDPE/PET/MB2 and binary LDPE/PET blends. The results also indicated a substantial improvement in both elongation at break and impact strength, while the Young's modulus decreased. Moreover, the thermal properties showed a decrease of the crystallization phenomena of PET in LDPE/PET/MB1 blend, thus confirming the good dispersion of PET particles into the continuous phase of LDPE matrix, leading to the conclusion that MB1 could be an efficient compatibilizer for LDPE/PET system. [source] Mechanical properties of Al2O3/polymethylmethacrylate nanocompositesPOLYMER COMPOSITES, Issue 6 2002Benjamin J. Ash Alumina/polymethylmethacrylate (PMMA) nanocomposites were produced by incorporating alumina nanoparticles, synthesized using the forced gas condensation method, into methylmethacrylate. The particles were dispersed using sonication and the composites were polymerized using free radical polymerization. At an optimum weight percent, the resulting nanocomposites showed, on average, a 600% increase in the strain-to-failure and the appearance of a well-defined yield point when tested in uniaxial tension. Concurrently, the glass transition temperature (Tg) of the nanocomposites dropped by as much as 25°C, while the ultimate strength and the Young's modulus decreased by 20% and 15%, respectively. For comparison, composites containing micron size alumina particles were synthesized and displayed neither phenomenon. Solid-state deuterium NMR results showed enhanced chain mobility at room temperature in the nanocomposites and corroborate the observed Tg depression indicating considerable main chain motion at temperatures well below those observed in the neat polymer. A hypothesis is presented to relate the thermal and mechanical behavior observed in the composites to the higher chain mobility and Tg depression seen in recent ultrathin polymer film research. [source] Tribological behaviors of aligned carbon nanotube/fullerene-epoxy nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2008Huan Wang The tribological properties of aligned CNT/fullerene-epoxy nanocomposites were studied by nanoscratch, nanowear, and nano-indentation tests. Compared with neat epoxy, aligned CNT/fullerene-epoxy nanocomposites showed lower friction coefficient in scratch tests, a reduction of 38.1 and 26.2%, respectively. In addition, the aligned CNT-epoxy composite showed better wear resistance and its hardness and Young's modulus increased by 29.4 and 16.8%, respectively. In contrast, for a fullerene-epoxy nanocomposite with 10 wt% fullerenes, the hardness decreased by 50% and the Young's modulus decreased by more than 60% when compared with the neat epoxy. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] | ||||||||||