Identification of Elastomers in Tire Sections by Total Thermal Analysis. IV. Innerliner

1975 ◽  
Vol 48 (4) ◽  
pp. 653-660 ◽  
Author(s):  
A. K. Sircar ◽  
T. G. Lamond
Keyword(s):  
Exothermic Reaction ◽  
Minor Component ◽  
Peak Temperature ◽  
Thermal Methods ◽  
Important Conclusion ◽  
Diffusion Controlled ◽  
Wide Range ◽  
Secondary Reactions ◽  
Size Characteristic ◽  
A Minor

Abstract Butyl and halogenated butyls are clearly indicated by both DSC and DTG in nitrogen. Binary NR/CIIR blends are also easily characterized by combined DSC and DTG techniques. In ternary SBR/CIIR/NR blends, only CIIR and NR show up in DTG curves when SBR occurs as a minor component. Minor indication of SBR is obtained from DSC curves. Thermal methods fail to distinguish between BUR and CIIR. In elastomer blends, DTG peak temperatures may vary over a wide range depending on the type of the second elastomer. The NR peak temperature (365°C), for example, is lowered by blending with SBR, BR (345–350°C) or CR (325–348°C). These latter elastomers degrade by exothermic reaction. An increase in peak temperature was observed in association with the polymers which degrade by endothermic reaction (EPDM, 369–374°C; CIIR, 373–377°C). This may be caused by abstraction of heat by the second elastomer in the overall decomposition process. Another important conclusion drawn from the blends studies in this series is that thermal stability of the polymers is not materially affected by the presence of another polymer, thus giving rise to the weight-loss peaks at well-defined temperatures, characteristic of each polymer. Thermooxidative stability, however, is very much dependent on the type and composition of the polymers present. The effect of secondary reactions on the degradation curves is also considerably greater in the oxidizing atmosphere. Thermooxidative degradation is very much dependent on sample size, characteristic of a diffusion-controlled reaction. However, it provides auxiliary evidence for idsntification. Except for SBR/BR blends, which show a single Tg changing with composition, all other elastomer blends show transitions at the respective temperatures, indicating the inherent incompatibility of elastomers. However, a second or third transition is not observed when (a) the proportion of the polymer is too small and (b) Tg'a are too close to each other. Thus, obtaining a single glass transition temperature in a polymer blend is not always a proof of its compatibility, as has been claimed so often.

scholarly journals The molecular structure of plant sporopollenin

2018 ◽  
Author(s):  
Fu-Shuang Li ◽  
Pyae Phyo ◽  
Joseph Jacobowitz ◽  
Mei Hong ◽  
Jing-Ke Weng
Keyword(s):  
Molecular Structure ◽  
Minor Component ◽  
Pollen Grains ◽  
Outer Wall ◽  
Land Plant ◽  
Spores And Pollen ◽  
Biomimetic Polymers ◽  
Wide Range ◽  
Nmr Techniques ◽  
A Minor

Sporopollenin is a ubiquitous and extremely chemically inert biopolymer that constitutes the outer wall of all land-plant spores and pollen grains. Sporopollenin protects the vulnerable plant gametes against a wide range of environmental assaults, and is considered as a prerequisite for the migration of early plants onto land. Despite its importance, the chemical structure of plant sporopollenin has remained elusive. Using a newly developed thioacidolysis degradative method together with state-of-the-art solid-state NMR techniques, we determined the detailed molecular structure of pine sporopollenin. We show that pine sporopollenin is primarily composed of aliphatic-polyketide-derived polyvinyl alcohol units and 7-O-p-coumaroylated C16 aliphatic units, crosslinked through a distinctive m-dioxane moiety featuring an acetal. Naringenin was also identified as a minor component of pine sporopollenin. This discovery answers the long-standing question about the chemical makeup of plant sporopollenin, laying the foundation for future investigations of sporopollenin biosynthesis and for design of new biomimetic polymers with desirable inert properties.

Precursor and processing effects on BaPbO3 formation kinetics

2006 ◽  
Vol 21 (3) ◽  
pp. 584-596 ◽  
Author(s):  
Jun-ichi Tani ◽  
Guerman Popov ◽  
Paul R. Mort ◽  
Richard E. Riman
Keyword(s):  
Phase Boundary ◽  
Reaction Temperature ◽  
Formation Rate ◽  
Exothermic Reaction ◽  
Three Dimensional ◽  
Interface Reaction ◽  
Diffusion Controlled ◽  
Wide Range ◽  
Lead Oxides ◽  
Nitrate System

The synthesis of BaPbO3 from a wide range of mixtures containing metalorganic precursors, nitrate precursors, lead oxides, barium oxide and peroxide was investigated, and the kinetics was analyzed using the Johnson–Mehl–Avrami (JMA) equation. It was found that Ba and Pb stearate soaps and Pb oxalate that were used as metalorganic precursors formed BaCO3 and PbO or Pb3O4 after firing at 440 °C. The formation rate of BaPbO3 from a metalorganic precursor system is not higher than that from the conventional BaCO3–PbO system and does not depend on mixing methods or the kinds of metalorganic precursors but instead on the synthesis atmosphere. In the case of the BaCO3–PbO system, the Avrami exponent (n) is ∼1, indicating that the reaction is controlled by the phase-boundary-contraction interface reaction. For the BaO2–PbO2 system, n has two values ∼1 and ∼0.3, depending on the reaction temperature and time, indicating that the reaction is either controlled by the phase-boundary-contraction interface reaction or diffusion-controlled reaction. In the Ba nitrate–Pb nitrate system, phase-pure BaPbO3 is obtained at 550 °C, which is 250 °C lower than in the case of the BaCO3–PbO system. The value of n for the nitrate system is ∼1.5, indicating that the reaction is controlled by a three-dimensional (3D) diffusion-controlled nucleation mechanism. In the BaO–PbO system, the formation of BaPbO3 started at 350 °C by an exothermic reaction and the content of BaPbO3 in the product was ∼40 wt%, which is independent of reaction temperature as well as time in the temperature range of 350–500 °C.

Conversion of dense lodgepole pine stands in west-central British Columbia into young lodgepole pine plantations using prescribed fire. 1. Biomass consumption during burning treatments

1992 ◽  
Vol 22 (4) ◽  
pp. 572-581 ◽  
Author(s):  
B. Blackwell ◽  
M.C. Feller ◽  
R. Trowbridge
Keyword(s):  
Forest Floor ◽  
Lodgepole Pine ◽  
Fire Severity ◽  
Minor Component ◽  
Understory Vegetation ◽  
Fuel Load ◽  
Fuel Moisture ◽  
Wide Range ◽  
A Minor ◽  
Moisture Conditions

The ecological effects of different treatments used to convert dense Pinuscontorta var. latifolia Engelm. stands into young P. contorta plantations are determined. The treatments used were felling the trees with a bulldozer and either broadcast burning the slash or bulldozing the slash into windrows, which were then burned. Burns were conducted under different fuel moisture conditions and state of fuel curing to achieve four classes of fire severity. The preburn surface fuel load was relatively high due largely to fallen dead woody materials (10−21 kg/m2). The biomass of the forest floor (5−10 kg/m2) was similar to that of the tree slash (5−13 kg/m2), while the understory vegetation was a minor component (0.3−0.5 kg/m2). The quantity of slash and understory vegetation consumed by burning increased with the preburn mass of the same components. Forest floor consumption depended primarily on the preburn forest floor mass for windrow burns and on forest floor moisture content as well as preburn forest floor mass for broadcast burns. Fire severity generally did not have a strong influence on biomass consumption, although it did significantly influence forest floor consumption. There was a general trend, however, of increasing biomass consumption in broadcast burns with increasing fire severity. Windrow burning consumed more biomass than did broadcast burning under similar weather and fuel moisture conditions. Windrow burning resulted in uniformly high biomass consumption that was relatively independent of fuel moisture over the wide range of fuel moistures studied.

scholarly journals Two Distinct Mechanisms Ensure Transcriptional Polarity in Double-Stranded RNA Bacteriophages

2003 ◽  
Vol 77 (2) ◽  
pp. 1195-1203 ◽  
Author(s):  
Hongyan Yang ◽  
Eugene V. Makeyev ◽  
Sarah J. Butcher ◽  
Aušra Gaidelytė ◽  
Dennis H. Bamford
Keyword(s):  
Minor Component ◽  
Rna Transcription ◽  
Double Stranded Rna ◽  
Complex Particle ◽  
Wide Range ◽  
Dsrna Viruses ◽  
Strand Initiation ◽  
A Minor

ABSTRACT In most double-stranded RNA (dsRNA) viruses, RNA transcription occurs inside a polymerase (Pol) complex particle, which contains an RNA-dependent RNA Pol subunit as a minor component. Only plus- but not minus-sense copies of genomic segments are produced during this reaction. In the case of φ6, a dsRNA bacteriophage from the Cystoviridae family, isolated Pol synthesizes predominantly plus strands using virus-specific dsRNAs in vitro, thus suggesting that Pol template preferences determine the transcriptional polarity. Here, we dissect transcription reactions catalyzed by Pol complexes and Pol subunits of two other cystoviruses, φ8 and φ13. While both Pol complexes synthesize exclusively plus strands over a wide range of conditions, isolated Pol subunits can be stimulated by Mn2+ to produce minus-sense copies on φ13 dsRNA templates. Importantly, all three Pol subunits become more prone to the native-like plus-strand synthesis when the dsRNA templates (including φ13 dsRNA) are activated by denaturation before the reaction. Based on these and earlier observations, we propose a model of transcriptional polarity in Cystoviridae controlled on two independent levels: Pol affinity to plus-strand initiation sites and accessibility of these sites to the Pol in a single-stranded form.

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

scholarly journals Friction of Metals: A Review of Microstructural Evolution and Nanoscale Phenomena in Shearing Contacts

2021 ◽  
Vol 69 (4) ◽  
Author(s):  
Michael Chandross ◽  
Nicolas Argibay
Keyword(s):  
Shear Strength ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Low Friction ◽  
Friction Behavior ◽  
Important Conclusion ◽  
Fundamental Properties ◽  
Wide Range ◽  
Boundary Sliding ◽  
Metal Interfaces

AbstractThe friction behavior of metals is directly linked to the mechanisms that accommodate deformation. We examine the links between mechanisms of strengthening, deformation, and the wide range of friction behaviors that are exhibited by shearing metal interfaces. Specifically, the focus is on understanding the shear strength of nanocrystalline and nanostructured metals, and conditions that lead to low friction coefficients. Grain boundary sliding and the breakdown of Hall–Petch strengthening at the shearing interface are found to generally and predictably explain the low friction of these materials. While the following is meant to serve as a general discussion of the strength of metals in the context of tribological applications, one important conclusion is that tribological research methods also provide opportunities for probing the fundamental properties and deformation mechanisms of metals.

Petrography and provenance of the Marambio Group, Vega Island, Antarctica

1994 ◽  
Vol 6 (4) ◽  
pp. 517-527 ◽  
Author(s):  
Duncan Pirrie
Keyword(s):  
Late Cretaceous ◽  
Sedimentary Rocks ◽  
Clay Mineralogy ◽  
Minor Component ◽  
Source Area ◽  
Low Grade ◽  
Western Margin ◽  
Sediment Input ◽  
A Minor ◽  
Sandstone Petrography

Late Cretaceous sedimentary rocks assigned to the Santa Marta (Herbert Sound Member) and López de Bertodano (Cape Lamb and Sandwich Bluff members) formations of the Marambio Group, crop out on Cape Lamb, Vega Island. Although previous studies have recognized that these sedimentary rocks were derived from the northern Antarctic Peninsula region, the work presented here allows the provenance and palaeogeographical evolution of the region to be described in detail. On the basis of both sandstone petrography and clay mineralogy, the Herbert Sound and Cape Lamb members reflect sediment input from a low relief source area, with sand grade sediment sourced from low grade metasediments, and clay grade sediment ultimately derived from the weathering of an andesitic source area. In contrast, the Sandwich Bluff Member reflects a switch to a predominantly andesitic volcaniclastic source. However, this sediment was largely derived from older volcanic suites due to renewed source area uplift, with only a minor component from coeval volcanism. Regional uplift of both the arc terrane and the western margin of the James Ross Basin was likely during the Maastrichtian.

scholarly journals Species pattern of phosphatidylinositol from lung surfactant and a comparison of the species pattern of phosphatidylinositol and phosphatidylglycerol synthesized de novo in lung microsomal fractions

1988 ◽  
Vol 254 (1) ◽  
pp. 67-71 ◽  
Author(s):  
B Rüstow ◽  
Y Nakagawa ◽  
H Rabe ◽  
K Waku ◽  
D Kunze
Keyword(s):  
Lung Function ◽  
Molecular Species ◽  
De Novo ◽  
Lung Surfactant ◽  
Minor Component ◽  
Main Species ◽  
Surfactant Phospholipids ◽  
Species Pattern ◽  
A Minor

1. Phosphatidylinositol (PI) is a minor component of lung surfactant which may be able to replace the functionally important phosphatidylglycerol (PG) [Beppu, Clements & Goerke (1983) J. Appl. Physiol. 55, 496-502] without disturbing lung function. The dipalmitoyl species is one of the main species for both PI (14.4%) and PG (16.9%). Besides the C16:0--C16:0 species, the C16:0--C18:0, C16:0--C18:1, C16:0--C18:2 and C18:0--C18:1 species showed comparable proportions in the PG and PI fractions. These similarities of the species patterns and the acidic character of both phospholipids could explain why surfactant PG may be replaced by PI. 2. PI and PG were radiolabelled by incubation of microsomal fractions with [14C]glycerol 3-phosphate (Gro3P). For 11 out of 14 molecular species of PI and PG we measured comparable proportions of radioactivity. The radioactivity of these 11 species accounted together for more than 80% of the total. The addition of inositol to the incubation system decreased the incorporation in vitro of Gro3P into PG and CDP-DG (diacylglycerol) of lung microsomes (microsomal fractions), but did not change the distribution of radioactivity among the molecular species of PG. These results supported the idea that both acidic surfactant phospholipids may be synthesized de novo from a common CDP-DG pool in lung microsomes.

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