Labile Cross Links in Low Unsaturation Elastomers. II. Effect of Chain and Cross-Link Structure on Thermal and Oxidative Stability

1968 ◽  
Vol 2 (6) ◽  
pp. 1149-1168
Author(s):  
Peter F. Lyons ◽  
Timothy C. P. Lee ◽  
Arthur V. Tobolsky
Keyword(s):  
Oxidative Stability ◽  
Cross Link ◽  
Link Structure ◽  
Thermal And Oxidative Stability ◽  
Cross Links

scholarly journals Linear Dynamic Viscoelasticity of Dual Cross-Link Poly(Vinyl Alcohol) Hydrogel with Determined Borate Ion Concentration

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 71
Author(s):  
Takuro Taniguchi ◽  
Kenji Urayama
Keyword(s):  
Vinyl Alcohol ◽  
Ion Concentration ◽  
Poly Vinyl Alcohol ◽  
Relaxation Dynamics ◽  
Cross Link ◽  
Dynamic Viscoelasticity ◽  
Linear Dynamic ◽  
Cross Links ◽  
Pva Gel ◽  
Pva Hydrogel

We investigated the linear dynamic viscoelasticity of dual cross-link (DC) poly(vinyl alcohol) (PVA) (DC-PVA) hydrogels with permanent and transient cross-links. The concentrations of incorporated borate ions to form transient cross-links in the DC-PVA hydrogels (CBIN) were determined by the azomethine-H method. The dynamic viscoelasticity of the DC-PVA hydrogel cannot be described by a simple sum of the dynamic viscoelasticity of the PVA gel with the same permanent cross-link concentration and the PVA aqueous solution with the same borate ion concentration (CB = CBIN) as in the DC-PVA gel. The DC-PVA hydrogel exhibited a considerably higher relaxation strength, indicating that the introduction of permanent cross-links into temporary networks increases the number of viscoelastic chains with finite relaxation times. In contrast, the relaxation frequency (ωc) (given by the frequency at the maximum of loss modulus) for the DC-PVA hydrogel was slightly lower but comparable to that for a dilute PVA solution with the same CB. This signifies that the relaxation dynamics of the DC-PVA hydrogels is essentially governed by the lifetime of an interchain transient cross-link (di-diol complex of boron). The effect of permanent cross-linking on the relaxation dynamics was observed in the finite broadening of the relaxation-time distribution in the long time region.

scholarly journals Microtubules and microtubule-associated proteins from the nematode Caenorhabditis elegans: periodic cross-links connect microtubules in vitro.

1986 ◽  
Vol 103 (1) ◽  
pp. 23-31 ◽  
Author(s):  
E J Aamodt ◽  
J G Culotti
Keyword(s):  
Caenorhabditis Elegans ◽  
Apparent Molecular Weight ◽  
Cross Link ◽  
Nematode Caenorhabditis Elegans ◽  
Microtubule Associated Proteins ◽  
C Elegans ◽  
Associated Proteins ◽  
Cross Links ◽  
The Cross

The nematode Caenorhabditis elegans should be an excellent model system in which to study the role of microtubules in mitosis, embryogenesis, morphogenesis, and nerve function. It may be studied by the use of biochemical, genetic, molecular biological, and cell biological approaches. We have purified microtubules and microtubule-associated proteins (MAPs) from C. elegans by the use of the anti-tumor drug taxol (Vallee, R. B., 1982, J. Cell Biol., 92:435-44). Approximately 0.2 mg of microtubules and 0.03 mg of MAPs were isolated from each gram of C. elegans. The C. elegans microtubules were smaller in diameter than bovine microtubules assembled in vitro in the same buffer. They contained primarily 9-11 protofilaments, while the bovine microtubules contained 13 protofilaments. The principal MAP had an apparent molecular weight of 32,000 and the minor MAPs were 30,000, 45,000, 47,000, 50,000, 57,000, and 100,000-110,000 mol wt as determined by SDS-gel electrophoresis. The microtubules were observed, by electron microscopy of negatively stained preparations, to be connected by stretches of highly periodic cross-links. The cross-links connected the adjacent protofilaments of aligned microtubules, and occurred at a frequency of one cross-link every 7.7 +/- 0.9 nm, or one cross-link per tubulin dimer along the protofilament. The cross-links were removed when the MAPs were extracted from the microtubules with 0.4 M NaCl. The cross-links then re-formed when the microtubules and the MAPs were recombined in a low salt buffer. These results strongly suggest that the cross-links are composed of MAPs.

Analysis of thermal and oxidative stability of biodiesel from Jatropha curcas L. and beef tallow

2012 ◽  
Vol 113 (2) ◽  
pp. 437-442 ◽  
Author(s):  
Erisandro S. Silva ◽  
Marta M. Conceição ◽  
Eduardo H. S. Cavalcanti ◽  
Valter J. Fernandes ◽  
Ana C. D. Medeiros ◽  
...  
Keyword(s):  
Oxidative Stability ◽  
Beef Tallow ◽  
Jatropha Curcas ◽  
Jatropha Curcas L ◽  
Thermal And Oxidative Stability

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

2016 ◽  
Vol 89 (4) ◽  
pp. 671-688 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Experimental Validation ◽  
Main Chain ◽  
Sol Gel ◽  
Chain Scission ◽  
Cross Linking ◽  
Cross Link ◽  
Practical Reality ◽  
Cross Links ◽  
The Cross ◽  
Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

Synthesis, Characterization and Thermooxidative Properties of Hybrid Block Poly(silane-b-arylacetylene)

2014 ◽  
Vol 1004-1005 ◽  
pp. 527-532
Author(s):  
Ying Jie Xu ◽  
Hui Min Qi ◽  
Ya Ping Zhu ◽  
Fan Wang
Keyword(s):  
Weight Loss ◽  
Oxidative Stability ◽  
Lewis Acid ◽  
Grignard Reagent ◽  
Room Temperature ◽  
Condensation Polymerization ◽  
Thermooxidative Stability ◽  
Thermal Cure ◽  
Inorganic Hybrid ◽  
Thermal And Oxidative Stability

Organic-inorganic hybrid block Poly (silane-b-arylacetylene) (PSbA) have been synthesized through condensation polymerization between chloro-terminated polysilane and diethynylbenzene Grignard reagent, and chloro-terminated polysilane was synthesized through condensation polymerization of dichloromethylvinylsilane in the presence of Mg metal and Lewis acid (ZnCl2, LiCl). The structures of PSbAs were characterized by FTIR, 1H, 13C, 29Si NMR, and GPC. The PSbAs are orange viscous liquid and can be soluble in common organic solvents at room temperature. The thermal cure behavior of PSbAs was determined by DSC, and the thermal and oxidative stability of the cured PSbAs were investigated using TGA. The results showed that the cured PSbAs exhibit high thermal and thermooxidative stability. The degradation temperatures at 5% weight loss for the cured PSbAs are 470-533°C under N2 and 378-456°C under air, and the residue yields at 1000°C are 77.9-82.8% under N2 and 40.4-50.5% under air.

Role of the FAD-dependent polyamine oxidase in the selective formation of N1,N8-bis(γ- glutamyl)spermidine protein cross-links1

2007 ◽  
Vol 35 (2) ◽  
pp. 396-400 ◽  
Author(s):  
A. Lentini ◽  
P. Mattioli ◽  
B. Provenzano ◽  
A. Abbruzzese ◽  
M. Caraglia ◽  
...  
Keyword(s):  
Stratum Corneum ◽  
Polyamine Oxidase ◽  
Polyamine Metabolism ◽  
Suitable Model ◽  
Cross Link ◽  
Cellular Mechanisms ◽  
Preferential Formation ◽  
Cross Links ◽  
Selective Formation

Protein-bound γ-glutamylpolyamines have highlighted a new pathway in polyamine metabolism. Human foreskin keratinocytes offer a suitable model for this study. Indeed, they develop polymerized envelopes, as they differentiate, rich in ϵ-(γ-glutamyl)lysine and N1,N8-bis(γ-glutamyl)spermidine cross-links. We have found that the selective oxidation of N1-(γ-glutamyl)spermidine and N-(γ-glutamyl)spermine by FAD-dependent polyamine oxidase (PAO) may be one of the cellular mechanisms regulating the preferential formation of a sterically defined bis(γ-glutamyl)spermidine cross-link. The significance of this finding is unknown, but it suggests that the target of this PAO-modulation is to achieve the biochemical prerequisite for production of a normal epidermal stratum corneum.

scholarly journals Magnetic composites based on NR and strontium ferrite

2019 ◽  
Vol 12 (1) ◽  
pp. 63-69
Author(s):  
Ján Kruželák ◽  
Andrea Kvasničáková ◽  
Rastislav Dosoudil ◽  
Ivan Hudec
Keyword(s):  
Carbon Black ◽  
Strontium Ferrite ◽  
Rubber Matrix ◽  
Cross Link ◽  
Magnetic Composites ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
The Cross ◽  
Thermo Physical Properties

Abstract Two types of composites based on natural rubber (NR) and strontium ferrite were tested in this study. Composites of the first type were prepared by incorporation of strontium ferrite in the concentration range ranging from 0 to 100 phr (parts per hundred rubber) into pure NR based rubber matrix, while with those of the second type, strontium ferrite was dosed in the same concentration level into NR based rubber batch with constant amount of carbon black — 25 phr. For rubber matrices cross-linking, a standard sulfur based curing system was used. This work is focused on the effect of magnetic filler content on physico-mechanical, magnetic and thermo-physical properties of composite materials. Subsequently, the cross-link density and the structure of the formed sulfidic cross-links were examined. The results showed that the cross-link density of both types of composites increased with the increasing content of magnetic filler, while the structure of the sulfidic cross-links was almost not influenced by the amount of strontium ferrite. Tensile strength of rubber composites with pure rubber matrix was slightly improved by the incorporation of ferrite, while in case of composites based on a carbon black batch, the incorporation of magnetic filler resulted in the decrease of this characteristic. The presence of magnetic filler in both types of composites leads to a significant increase of the remanent magnetic induction.

N,N′-Ethylene-bis(iodoacetamide) as a probe for structural and functional characteristics of brine shrimp, squid, and bovine tubulins

1985 ◽  
Vol 63 (6) ◽  
pp. 439-447 ◽  
Author(s):  
Richard F. Luduena ◽  
Mary Carmen Roach ◽  
Thomas H. MacRae ◽  
George M. Langford
Keyword(s):  
Electrophoretic Mobility ◽  
Brine Shrimp ◽  
Sodium Dodecyl ◽  
Bovine Brain ◽  
Cross Link ◽  
Unique Effect ◽  
Ligand Binding Sites ◽  
Cross Links ◽  
Sulfate Formation ◽  
Brain Tubulin

We have developed a simple probe for certain functionally significant features of the tubulin molecule. When bovine brain tubulin is treated with N,N′-ethylene-bis(iodoacetamide) (EBI), two intrachain cross-links, designated βs and β*, are formed in β-tubulin, each one with a unique effect on the electrophoretic mobility of β on gels containing sodium dodecyl sulfate. Formation of the β* cross-link, which involves at least one assembly-critical sulfhydryl, is completely inhibited by colchicine and its congeners, while that of βs is inhibited completely by maytansine and GTP and partly by vinblastine. To see how conserved this complex pattern is in evolution we examined tubulins from the brine shrimp Artemia and the squid Loligo. In both tubulins EBI forms the β* cross-link in a reaction inhibitable by colchicine, podophyllotoxin, and nocodazole. In each tubulin, EBI appears to form a second intrachain cross-link in a reaction that can be inhibited completely by maytansine and GTP and partly by vinblastine. In Artemia, this cross-link alters the electrophoretic mobility to a slightly smaller extent than is the case for βs in bovine brain, but in Loligo the alteration is much greater. It seems that the ligand-binding sites, the critical sulfhydryls, and their spatial interrelationships are strongly conserved and that the βs sulfhydryls or the sequence between them are less strongly conserved in evolution.

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