Home About us Contact
|
Home About us Contact | ||
|
|
||
Slow Cooling Rate (slow + cooling_rate)
Selected AbstractsEffect of the preparation conditions on the permeation of ultrahigh-molecular-weight polyethylene/silicon dioxide hybrid membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Nana Li Abstract Porous ultrahigh-molecular-weight polyethylene/SiO2 membranes were prepared by thermally induced phase separation (TIPS) with white mineral oil as the diluent and SiO2 as an additive. Influential factors, including extraction method, SiO2 content, and cooling rate, were investigated. The results suggest that the both porosity and pure water flux of the membranes by extraction of the solvent naphtha in the tension state with alcohol were the best among our research. With increasing SiO2 content, the porosity, pure water flux, and pore diameter increased. However, with excessive SiO2 content, defects formed easily. Moreover, SiO2 improved the pressure resistance of the membranes. The cooling rate directly effected the crystal structure. A slow cooling rate was good for crystal growth and the integration of the diluent. Therefore, the porosity, pure water flux, and bubble-point pore diameter increased with decreasing cooling rate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Unique Orientation Textures Induced by Confined Crystal Growth of Poly(vinylidene fluoride) in Oriented Blends with Polyamide 6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2007Akira Kaito Abstract Unique orientation textures have been induced by the confined crystal growth of PVDF in drawn films of PVDF/PA6 blends. Oriented films of PVDF/PA6 blends were prepared by uniaxially drawing melt-mixed blends. The drawn films with fixed lengths were heat-treated at 180,°C for 3 minutes to melt the PVDF component, followed by non-isothermal crystallization of PVDF at a cooling rate of 0.5,°C,·,min,1. The crystal orientation was studied by WAXD. When PVDF was melted and recrystallized in the drawn films of the PVDF/PA6,=,50/50 blend at a slow cooling rate, the crystal b- axis of the , -crystalline form of PVDF was oriented in the drawing direction, forming orthogonal orientation textures. SEM showed that stretched domains of PVDF with diameters of 0.2,0.5 µm were dispersed in the PA6 phase in the drawn films of the PVDF/PA6,=,50/50 blend. Spatial confinement of the crystal growth resulted in the alignment of the crystal b- axis along the long axis of the domains, because PVDF is crystallized in thin cylindrical domains. The orientation behavior is different from the oriented crystallization of PVDF/PA11 (Y. Li, A. Kaito, Macromol. Rapid Commun. 2003, 24, 255), in which transcrystallization from the interface causes the a- axis orientation to be in the drawing direction. It is thought that the domain size influenced the mechanism of oriented crystallization and the resultant crystal orientation. [source] Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2008Cristian Hedesiu Abstract Changes in phase composition and chain mobility in injection-molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time-domain 1H solid-state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection-molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi-rigid and amorphous fractions. [source] Effect of cooling rate and crack propagation direction on the mode 1 interlaminar fracture toughness of biaxial noncrimp warp-knitted fabric composites made of glass/PP commingled yarnPOLYMER COMPOSITES, Issue 3 2008Yantao Wang The mode 1 interlaminar fracture toughness of biaxial (±45°) noncrimp warp-knitted fabric composites made of glass/PP commingled yarn was investigated. The crack propagation along the warp and weft directions, respectively, was considered for the composites cooled at two different rates during laminate molding. The interlaminar fracture toughness was characterized by determining the critical strain energy release rate (GIC) of initiation and propagation measured from the double cantilever beam tests. In the case of a slow cooling rate (1°C/min), most specimens possess pure interlaminar crack propagation and direction-independence characteristics. Nevertheless, the high-cooled (10°C/min) specimens fractured in both directions suffer extensive intraply damage (crack branching, debonding, and bridging of 45°-oriented interfacial yarns) and knit thread breakage, leading to GIC of propagation two times higher than that of the slow-cooled specimens, and the clear difference in the GIC values of initiation between the two directions may be due to the contribution of the knit thread breakage to the fracture energy. POLYM. COMPOS., 2008 © 2007 Society of Plastics Engineers [source] Cryopreservation of isolated blastomeres and embryonic stem-like cells of Leopard danio, Brachydanio frankeiAQUACULTURE RESEARCH, Issue 4 2010Padmanav Routray Abstract This study aimed at developing a suitable cryopreservation protocol for embryonic stem (ES)-like cells of a tiny freshwater fish Leopard danio (Brachydanio frankei). Embryonic stem (ES)-like cells derived from blastomeres of the early blastulae stage of the developing embryo were cultured in vitro in a medium containing Leibowitz-15 supplemented with 10% foetal bovine serum, leopard danio embryo extract, sodium bicarbonate, sodium selenite, basic fibroblast growth factor, epidermal growth factor and leukaemia inhibitory factor. The ES-like cells showed properties similar to ES cells in other species. They were morphologically small, round to polygonal and present in patches and extensively expressed alkaline phosphatase and stage-specific embryonic antigen. The toxicity and chilling sensitivity of these cells were determined using ethylene glycol (EG), propylene glycol (PG) and glycerol as cryoprotective agents at molar concentrations of 0.6, 1.0, 1.4, 1.8 and 2.0. Among them, 1.8 M EG showed 70% significant viable ES-like cells (P<0.05). The post-thawed cells retained similar properties of non-cryopreserved ES-like cells with a viability rate of 65%. Similarly, blastomeres cryopreserved following the slow cooling rate with EG and PG yielded a viability of more than 70%. [source] Do physical forces contribute to cryodamage?BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Joseph Saragusty Abstract To achieve the ultimate goal of both cryosurgery and cryopreservation, a thorough understanding of the processes responsible for cell and tissue damage is desired. The general belief is that cells are damaged primarily due to osmotic effects at slow cooling rates and intracellular ice formation at high cooling rates, together termed the "two factor theory." The present study deals with a third, largely ignored component,mechanical damage. Using pooled bull sperm cells as a model and directional freezing in large volumes, samples were frozen in the presence or absence of glass balls of three different diameters: 70,110, 250,500, and 1,000,1,250,µm, as a means of altering the surface area with which the cells come in contact. Post-thaw evaluation included motility at 0,h and after 3,h at 37°C, viability, acrosome integrity, and hypoosmotic swelling test. Interactions among glass balls, sperm cells, and ice crystals were observed by directional freezing cryomicroscopy. Intra-container pressure in relation to volume was also evaluated. The series of studies presented here indicate that the higher the surface area with which the cells come in contact, the greater the damage, possibly because the cells are squeezed between the ice crystals and the surface. We further demonstrate that with a decrease in volume, and thus increase in surface area-to-volume ratio, the intra-container pressure during freezing increases. It is suggested that large volume freezing, given that heat dissipation is solved, will inflict less cryodamage to the cells than the current practice of small volume freezing. Biotechnol. Bioeng. 2009; 104: 719,728 © 2009 Wiley Periodicals, Inc. [source] | ||||||||||