Changes in the degree of polymerization and acid and base contents occurring at room temperature in caprolactam polymers

1974 ◽  
Vol 39 (1) ◽  
pp. 257-266 ◽  
Author(s):  
B. Lánská ◽  
J. Šebenda
Keyword(s):  
Room Temperature ◽  
Degree Of Polymerization ◽  
Acid And Base

CARBON NANOTUBE-GRAFT-POLY(CITRIC ACID) NANOCOMPOSITES

NANO ◽  
2008 ◽  
Vol 03 (01) ◽  
pp. 37-44 ◽  
Author(s):  
MOHSEN ADELI ◽  
ALI BAHARI ◽  
HODA HEKMATARA
Keyword(s):  
Carbon Nanotubes ◽  
Silver Nanoparticles ◽  
Citric Acid ◽  
Room Temperature ◽  
Water Solution ◽  
Degree Of Polymerization ◽  
Multi Wall Carbon Nanotubes ◽  
Hyperbranched Poly ◽  
Acid Ratio ◽  
Biodegradable Nanocomposites

Novel biodegradable nanocomposites containing multi wall carbon nanotubes (MWCNT) and poly(citric acid) (PCA) were successfully synthesized. For preparation of nanocomposites, MWCNT was opened using a mixture of sulfuric and nitric acid and its derivative containing – COOH and – OH functional groups was obtained. Polycondensation of monohydrate citric acid in the presence of functionalized MWCNT in the melting state was lead to nanotube-graft-poly(citric acid) (CNT-g-PCA) nanocomposites. The degree of polymerization of grafted hyperbranched poly(citric acid) onto the CNTs was controlled using CNT/citric acid ratio. The CNT-g-PCA were soluble in water freely and stirring their water solution and silver nitrate at room temperature lead to the CNT-g-PCA containing encapsulated silver nanoparticles in their polymeric shell. The structure of nanocomposites was characterized by TEM, DLS and spectroscopy methods.

Influence of Aluminum Hydroxide Particles on the Properties of Polyurethane Based on Unsaturated Polyester

2013 ◽  
Vol 721 ◽  
pp. 210-214
Author(s):  
Xiong Wu ◽  
Bai Jie Zhou ◽  
Fan Zhuo Meng ◽  
Qian Hu ◽  
Ji Lin Pan
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Aluminum Hydroxide ◽  
Room Temperature ◽  
Polyester Resin ◽  
Unsaturated Polyester ◽  
Fracture Morphology ◽  
Cross Linking ◽  
Acid And Base ◽  
Different Content

A polyurethane based on unsaturated polyesters (PUP) was prepared, which can be cured and cross-linking reaction under room temperature. The polyurethane-based resin exhibited excellent endurance to acid and base relative to traditional unsaturated polyester resin. Different content and particle size of aluminum hydroxide particles were added into the PUP to improve the properties of final materials. Experiment results showed that proper content and size of aluminum hydroxide particles can improve the mechanic properties, thermal stability and electrical insulation of PUP materials to some extent. Such result was confirmed by the fracture morphology of the samples because of the well dispersion of aluminum hydroxide particles into PUP phase.

Dissolution Condition Effect on Cellulose in Ionic Liquid and the Recycling of Ionic Liquid

2014 ◽  
Vol 644-650 ◽  
pp. 5207-5210
Author(s):  
Yan Hao ◽  
Ting Ting Li ◽  
Xue Lian Ma ◽  
Gui Bao Guo
Keyword(s):  
Ionic Liquid ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Degree Of Polymerization ◽  
Room Temperature Ionic Liquids ◽  
Dissolution Time ◽  
Vacuum Drying ◽  
Regenerated Cellulose ◽  
Condition Effect ◽  
Homogeneous Modification

Recently, room temperature ionic liquids (RTILs) have been widely used in dissolution, homogeneous modification of cellulose. Cellulose only could be dissolved in RTILs at elevated temperature. Herein, effect of dissolution condition on microcrystalline cellulose in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid was studied. The results indicated that the degree of polymerization (DP) of regenerated cellulose decreased from 161 to 83 with the increasing of dissolution temperature in the range of 70 °C to 110 °C, whereas the DP was affected by dissolution time slightly. Moreover, after dissolution [Bmim]Cl could be recycled by distillation and vacuum drying. The recycled [Bmim]Cl also had good dissolving capability of cellulose, and its FTIR spectra was similar to that of original [Bmim]Cl.

Polyphosphate Chain Stability in Magnesia-Polyphosphate Cements

1991 ◽  
Vol 245 ◽  
Author(s):  
E. D. Dimotakis ◽  
W. G. Klemperer ◽  
J. F. Young
Keyword(s):  
Nmr Spectroscopy ◽  
Aqueous Solutions ◽  
General Formula ◽  
Chain Length ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Degree Of Polymerization ◽  
Mas Nmr ◽  
Average Degree ◽  
Cement Pastes

ABSTRACTPolyphosphates of the general formula NanH2PnO3n+1·H2O, n = 6, 15, 70, where n is the average degree of polymerization, have been synthesized and characterized by 31P NMR and HPLC. Aqueous solutions of these polyphosphates react at room temperature with magnesia to form cement pastes that harden to amorphous materials. The compressive strengths and porosities obtained are similar to those of MgO-(NH4)H2P3O10-H2O cements. Although polyphosphate chain length does not have a significant effect on the strength of the cement, 31P MAS-NMR spectroscopy showed that the degree of polyphosphate chain degradation decreases as the average degree of polymerization, n, increases.

The kinetics of the spontaneous, proton- and AlIII-catalysed hydrolysis of 1,5-anhydrocellobiitol — Models for cellulose depolymerization in paper aging and alkaline pulping, and a benchmark for cellulase efficiency

2005 ◽  
Vol 83 (9) ◽  
pp. 1516-1524 ◽  
Author(s):  
John William Baty ◽  
Michael L Sinnott
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Cellulose Hydrolysis ◽  
Degree Of Polymerization ◽  
Kraft Pulping ◽  
Paper Strength ◽  
Cellulose Fibres ◽  
Low Temperature Storage ◽  
Cellulose Depolymerization ◽  
Kinetics Of

The kinetics of the spontaneous, proton- and AlIII-catalysed hydrolyses of the C1—O4′ bond in 1,5-anhydrocellobiitol have been measured at elevated temperatures (125.0–220.0 °C). Data for the first two processes extrapolate to the expression k = (8.6 ± 2.1 × 10–16) + (1.4 ± 0.2 × 10–9-pH) s–1 at 25 °C. These room-temperature figures were used to model cellulose depolymerization by the af Ekenstam equation. The spontaneous process is too slow to contribute to loss of paper strength on aging, and even the acid-catalysed process is significant only below ~pH 4.0. However, the spontaneous hydrolysis readily accounts for the reduction of cellulose degree of polymerization (DP) during alkaline (e.g., kraft) pulping of cellulose fibres. Efficient electrophilic catalysis by AlIII was observed at 150.0 °C in 0.1 mol/L succinate buffers of room temperature pH 3.05 and 3.35 (k2 = 8.1 ± 0.4 × 10–3 and 4.2 ± 0.2 × 10–3 (mol/L) –1 s–1, respectively). The apparent activation energy of the AlIII-catalysed process was 31 ± 4 kJ mol-1, lower than that of the proton-catalysed path, suggesting the electrophilic catalysis increases in importance as the temperature approaches ambient. Consequently, it appears that the culprit in the impermanence of “rosin-alum” -sized paper is AlIII, directly acting as a Lewis acid, not the AlIII hydration sphere as a Brønsted acid. Conservation measures should either address this or be generic (e.g., low-temperature storage). Key words: cellulose, hydrolysis, kraft pulping, paper conservation, rosin-alum sizing.

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Hepatocyte Alterations in Guinea Pigs FED Polychlorinated Biphenyls (PCBs), Dibenzodioxins (PCDD), AND DIBENZOFURANS (PCDF)

1982 ◽  
Vol 40 ◽  
pp. 56-57
Author(s):  
J. N. Turner ◽  
D. N. Collins
Keyword(s):  
Guinea Pigs ◽  
Room Temperature ◽  
Dose Group ◽  
Methyl Cellulose ◽  
Uranyl Acetate ◽  
Target Organ ◽  
Office Building ◽  
Lead Citrate ◽  
Control Groups ◽  
Cooling Fluid

A fire involving an electric service transformer and its cooling fluid, a mixture of PCBs and chlorinated benzenes, contaminated an office building with a fine soot. Chemical analysis showed PCDDs and PCDFs including the highly toxic tetra isomers. Guinea pigs were chosen as an experimental animal to test the soot's toxicity because of their sensitivity to these compounds, and the liver was examined because it is a target organ. The soot was suspended in 0.75% methyl cellulose and administered in a single dose by gavage at levels of 1,10,100, and 500mgm soot/kgm body weight. Each dose group was composed of 6 males and 6 females. Control groups included 12 (6 male, 6 female) animals fed activated carbon in methyl cellulose, 6 males fed methyl cellulose, and 16 males and 10 females untreated. The guinea pigs were sacrificed at 42 days by suffocation in CO2. Liver samples were immediately immersed and minced in 2% gluteraldehyde in cacadylate buffer at pH 7.4 and 4°C. After overnight fixation, samples were postfixed in 1% OsO4 in cacodylate for 1 hr at room temperature, embedded in epon, sectioned and stained with uranyl acetate and lead citrate.

Domain Formation in Synthetic Quartz

1971 ◽  
Vol 29 ◽  
pp. 156-157
Author(s):  
Joseph J. Comer
Keyword(s):  
Electron Beam ◽  
Room Temperature ◽  
Domain Formation ◽  
Synthetic Quartz ◽  
Transmission Electron ◽  
Black Spots ◽  
Diffraction Mode ◽  
Domain Boundaries ◽  
Kikuchi Lines ◽  
Straight Lines

Domains visible by transmission electron microscopy, believed to be Dauphiné inversion twins, were found in some specimens of synthetic quartz heated to 680°C and cooled to room temperature. With the electron beam close to parallel to the [0001] direction the domain boundaries appeared as straight lines normal to <100> and <410> or <510> directions. In the selected area diffraction mode, a shift of the Kikuchi lines was observed when the electron beam was made to traverse the specimen across a boundary. This shift indicates a change in orientation which accounts for the visibility of the domain by diffraction contrast when the specimen is tilted. Upon exposure to a 100 KV electron beam with a flux of 5x 1018 electrons/cm2sec the boundaries are rapidly decorated by radiation damage centers appearing as black spots. Similar crystallographio boundaries were sometimes found in unannealed (0001) quartz damaged by electrons.

A Liquid Nitrogen Cooled Stage for STEM

1974 ◽  
Vol 32 ◽  
pp. 444-445
Author(s):  
Louis T. Germinario
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Liquid Nitrogen ◽  
Room Temperature ◽  
Objective Lens ◽  
Thermal Drift ◽  
Specimen Holder ◽  
Resolution Capability ◽  
Focal Position

A liquid nitrogen stage has been developed for the JEOL JEM-100B electron microscope equipped with a scanning attachment. The design is a modification of the standard JEM-100B SEM specimen holder with specimen cooling to any temperatures In the range ~ 55°K to room temperature. Since the specimen plane is maintained at the ‘high resolution’ focal position of the objective lens and ‘bumping’ and thermal drift la minimized by supercooling the liquid nitrogen, the high resolution capability of the microscope is maintained (Fig.4).

Cryogenic atomic force microscopy

1991 ◽  
Vol 49 ◽  
pp. 54-55
Author(s):  
K. A. Fisher ◽  
M. G. L. Gustafsson ◽  
M. B. Shattuck ◽  
J. Clarke
Keyword(s):  
Room Temperature ◽  
Rapid Freezing ◽  
Cryogenic Temperatures ◽  
Soft Or ◽  
Electrically Conductive ◽  
Force Microscopy ◽  
Flexible Molecules ◽  
Advantages And Disadvantages ◽  
Atomic Force ◽  
Chemical Perturbation

The atomic force microscope (AFM) is capable of imaging electrically conductive and non-conductive surfaces at atomic resolution. When used to image biological samples, however, lateral resolution is often limited to nanometer levels, due primarily to AFM tip/sample interactions. Several approaches to immobilize and stabilize soft or flexible molecules for AFM have been examined, notably, tethering coating, and freezing. Although each approach has its advantages and disadvantages, rapid freezing techniques have the special advantage of avoiding chemical perturbation, and minimizing physical disruption of the sample. Scanning with an AFM at cryogenic temperatures has the potential to image frozen biomolecules at high resolution. We have constructed a force microscope capable of operating immersed in liquid n-pentane and have tested its performance at room temperature with carbon and metal-coated samples, and at 143° K with uncoated ferritin and purple membrane (PM).

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