scholarly journals Flow properties of polymeric systems. XX. Shear rate–temperature superposition for low molecular weight polyethylenes

1968 ◽  
Vol 12 (12) ◽  
pp. 2739-2740 ◽  
Author(s):  
Julian F. Johnson
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Low Molecular Weight ◽  
Flow Properties ◽  
Polymeric Systems ◽  
Temperature Superposition

scholarly journals Certain Rheological Aspects of Functionalized Guar Gum

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Meenu Kapoor ◽  
Dhriti Khandal ◽  
Ruchi Gupta ◽  
Pinklesh Arora ◽  
Geetha Seshadri ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Guar Gum ◽  
Loss Modulus ◽  
Industrial Applications ◽  
Green Technology ◽  
Low Molecular Weight ◽  
Radiation Processing ◽  
Industrial Sectors ◽  
Wide Acceptance

Guar gum and its derivatives are highly important industrial hydrocolloids as they find applications in various industrial sectors. Guar is a polymer of high molecular weight and its aqueous solutions exhibit unique rheological properties, which has led to its wide acceptance by the industry. In certain industrial applications low molecular weight guar and its derivatives are needed, and conventionally chemical depolymerisation of guar is carried out for this purpose. Radiation processing is a novel and green technology for carrying out depolymerization and can be an ideal substitute for chemical depolymerisation technique. In order to study the effect of radiation on guar derivatives, three types of derivatives have been taken in the present study: carboxymethyl, hydroxyethyl, and methyl guar. The effect of 1–50 KGy radiation dose on the rheological behavior of these derivatives has been studied, and the results have been described in the present paper. The effect on storage and loss modulus with respect to frequency and effect on viscosity with respect to shear rate have been discussed in detail.

Influence of Chemical Nature on Flow Behavior of Polymers. I. Shear Rate and Temperature Dependence

1970 ◽  
Vol 43 (5) ◽  
pp. 1109-1115 ◽  
Author(s):  
E. A. Collins ◽  
T. Mass ◽  
W. H. Bauer
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Chemical Nature ◽  
Flow Behavior ◽  
Capillary Viscometer ◽  
Low Molecular Weight ◽  
Flow Activation Energy ◽  
Flow Activation ◽  
Made In ◽  
Low Shear

Abstract The flow behavior of low molecular weight liquid polybutadiene polymers was studied as a function of shear rate, temperature, and molecular structure. Measurements were made in the temperature range 15 to 50° C and shear rate range 1 to 15,000 sec−1 with a cone and plate and a capillary viscometer. Limiting low shear viscosity, flow activation energy, and critical shear rate marking onset of shear rate thinning were found to be strongly dependent upon the presence of functional groups such as hydroxyl, carboxyl, and nitrile. The modifying groups showed a greater effect than the molecular weight upon the properties measured.

scholarly journals Low Molecular Weight Oligomers of Poly(alkylene succinate) Polyesters as Plasticizers in Poly(vinyl alcohol) Based Pharmaceutical Applications

Polymers ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 146
Author(s):  
Artemis Palamidi ◽  
Afroditi Kapourani ◽  
Evi Christodoulou ◽  
Panagiotis A. Klonos ◽  
Konstantinos N. Kontogiannopoulos ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Vinyl Alcohol ◽  
Size Exclusion ◽  
Poly Vinyl Alcohol ◽  
Flow Index ◽  
Low Molecular Weight ◽  
Processing Temperature ◽  
Melt Flow ◽  
Flow Properties ◽  
Pharmaceutical Applications

The plasticizing effect of three low molecular weight oligomers of aliphatic poly(alkylene succinate) polyesters, namely poly(butylene succinate) (PBSu), poly(ethylene succinate) (PESu), and poly(propylene succinate) (PPSu), on partially hydrolyzed poly(vinyl alcohol) (PVA) used in melt-based pharmaceutical applications, was evaluated for the first time. Initially, the three aliphatic polyesters were prepared by the melt polycondensation process and characterized by differential scanning calorimetry (DSC), 1H NMR, intrinsic viscosity, and size exclusion chromatography (SEC). Subsequently, their effect on the thermophysical and physicochemical properties of PVA was thoroughly evaluated. According to the obtained results, PVA was completely miscible with all three polyesters, while PESu induced PVA’s thermal degradation, with the phenomenon starting from ~220 °C, in contrast to PBSu and PPSu, where a thermal profile similar to PVA was observed. Furthermore, molecular interactions between PVA and the prepared poly(alkylene succinate) polyesters were revealed by DSC, ATR-FTIR, and molecular dynamics simulations. Finally, melt flow index (MFI) measurements showed that, in contrast to PBSu, the use of PESu or PPSu significantly improved PVA’s melt flow properties. Hence, according to findings of the present work, only the use of low molecular weight PPSu is suitable in order to reduce processing temperature of PVA and improve its melt flow properties (plasticizing ability) without affecting its thermal decomposition.

scholarly journals Geometric and mechano-sorption modification of fumed nanosilica in the gaseous dispersion media

2019 ◽  
Vol 20 (1) ◽  
pp. 22-26 ◽  
Author(s):  
E.F. Voronin ◽  
L.V. Nosach ◽  
V.M. Gun’ko ◽  
B. Charmas
Keyword(s):  
Molecular Weight ◽  
Bioactive Compounds ◽  
Inorganic Salts ◽  
Low Molecular Weight ◽  
Polymeric Systems ◽  
Low Molecular Weight Compounds ◽  
Dispersion Media ◽  
Gaseous Dispersion

Methods of geometric and solvate-stymulated mechano-sorption-activated modification of fumed nanosilica in the gaseous dispersion media were developed and used to prepare functionalyzed nanofillers for polymeric systems. Non-volatile high- and low-molecular weight compounds (such as polymers, organic bioactive compounds, organic and inorganic salts) can be used as modifiers of nanofillers.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment
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