Unsaturation of Synthetic Rubberlike Materials

1943 ◽  
Vol 16 (2) ◽  
pp. 280-285
Author(s):  
La Verne E. Cheyney ◽  
Everett J. Kelley
Keyword(s):  
Natural Rubber ◽  
Negative Influence ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Iodine Chloride ◽  
Cross Linkage ◽  
History Of ◽  
Interesting Correlation ◽  
Rubberlike Materials

Abstract The quantitative determination of rubber unsaturation has concerned numerous investigators. The use of iodine chloride as a reagent for this purpose (the well-known Wijs method) has achieved favor in recent years. Under the proper experimental conditions, addition has been shown to be quantitative, and substitution reactions can be kept at a minimum. This procedure has likewise been rather extensively employed as a measure of the residual unsaturation of various rubber derivatives. This reagent does not, however, add quantitatively to all unsaturated compounds, regardless of structure. The presence of a negative substituent on one or more of the unsaturated carbon atoms inhibits the reaction; in fact, it may entirely prevent it, as in the cases of maleic or fumaric acids or dichloroethylene. In other compounds extensive substitution may occur along with addition, as in the case of the unsaturated terpenes. The unsaturation of the polymerized diolefins should be of considerable interest, especially in comparison with natural rubber. It should be of special interest to study the comparative reactions with iodine chloride, which has become practically a standard reagent for rubber. Kemp and Mueller mention that polychloroprene, to which they erroneously refer as polyvinyl chloride, adds iodine chloride to only 30 per cent of theory. This could be due to two causes—the negative influence of the chlorine attached to an unsaturated carbon, and/or possible cross-linkage between chains (cyclization). It is well established that polychloroprene is much less reactive chemically toward other reagents than is natural rubber. It is unfortunate that Kemp and Mueller did not state with more detail the history of the sample studied, as such a result might have shown some interesting correlation with the experiments reported in this paper.

Studies on Polystomella Lamarck (Foraminifera)

1942 ◽  
Vol 25 (3) ◽  
pp. 607-666 ◽  
Author(s):  
Margaret W. Jepps
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Canal System ◽  
Experimental Conditions ◽  
Complete Life Cycle ◽  
Laboratory Cultures ◽  
History Of ◽  
Nuclear Changes ◽  
Opening Up

Part I. After a brief statement of the present unsatisfactory position regarding the life history of Polystomella crispa, an account is given of experiments with various fixatives on P. crispa, collected near Drake's Island, Plymouth. A method is described for the cultivation of Polystomella in diatom cultures, especially with Navicula mutica var., with which a flagellate (Bodo sp.) was constantly present. The identification of individual Foraminifera, and determination of growth, were often possible by some irregularity in the shell, or by noting the attachment of one or more stalked egg cocoons of an unknown turbellarian worm. The feeding of Polystomella on diatoms seized by the pseudopodia outside the shell is described; the structures previously taken for ingested algal cells inside the shell are shown to be foraminal plugs (‘bouchons’ of le Calvez) which are discarded from time to time and thrown out of the shell along with the excretory granules (xanthosomes), mostly via the canal system.Part II. Notes are given on the microspheric form and its reproduction, through the spring and summer, by schizogony. The rearing of two broods in laboratory cultures is described, with an account of the formation of a new chamber to the shell. It is concluded that a complete life cycle consisting of one microspheric and one megalospheric phase occupies a period of about two years.Part III. Sporulation of the megalospheric form is described as seen during life; and various factors are discussed which might affect the process. The relatively small size of the reproducing Polystomella with which Lister worked is ascribed to their having lived under less favourable conditions. From a study of stained preparations, certain details are added concerning the opening up of the shell, presumably to facilitate the eventual escape of the flagellate swarm spores; also concerning the accompanying cytoplasmic and nuclear changes. Some account is given of the form and structure of the swarm spores, both alive and in permanent preparations. Experiments are described which constitute an attempt to carry the life cycle beyond the stage of sporulation. They are so far unsuccessful, with one possible exception, under all the various experimental conditions which are briefly discussed in their turn.

DETERMINING MATERIAL PROPERTIES OF NATURAL RUBBER USING FEWER MATERIAL MODULI IN VIRTUE OF A NOVEL CONSTITUTIVE APPROACH FOR ELASTIC BODIES

2018 ◽  
Vol 91 (2) ◽  
pp. 375-389 ◽  
Author(s):  
A. Muliana ◽  
K. R. Rajagopal ◽  
D. Tscharnuter ◽  
B. Schrittesser ◽  
G. Saccomandi
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
Material Properties ◽  
Biaxial Loading ◽  
Uniaxial Stretching ◽  
Insignificant Change ◽  
Elastic Bodies ◽  
In Virtue Of ◽  
Rubberlike Materials

ABSTRACT We discuss the development of a method for the determination of the material properties of rubber and rubberlike materials within the context of a novel constitutive framework that has been put into place recently. The new constitutive framework leads to fewer material moduli than the models that are currently in vogue. We corroborate the predictions of our model against the experimental data of Treloar as well as Jones and Treloar for uniaxial and biaxial loadings and also with regard to new experimental results that have been generated by us for uniaxial stretching of natural rubber. We record both the axial and lateral responses of the specimens. This allows us to also examine the compressibility of the natural rubber specimens. Finally, we also characterize the response of compressible elastic bodies both under the assumption that the motion is isochoric, as the experiments suggest insignificant change in volume, as well as without resorting to such an assumption, when subjected to biaxial loading.

The Determination of Unsaturation in Butadiene Synthetic Rubber

1948 ◽  
Vol 21 (4) ◽  
pp. 830-834
Author(s):  
P. P. Kobeko ◽  
E. K. Moskvina
Keyword(s):  
Carbon Tetrachloride ◽  
Natural Rubber ◽  
Carbon Disulfide ◽  
Addition Product ◽  
Butadiene Rubber ◽  
Synthetic Rubber ◽  
Iodine Chloride ◽  
Hydrolysis Of

Abstract 1. It has been found that synthetic rubber does not precipitate from a solution of dichloromethane by the addition of Wijs reagent, whereas natural rubber does precipitate under the same conditions. The reverse relation occurs with carbon disulfide as solvent. 2. A method has been developed for the determination of the unsaturation of butadiene rubber in solution in dichloromethane by the use of Wijs reagent. 3. It has been demonstrated that, by the use of a solution of iodine chloride in carbon tetrachloride, the reaction with rubber is complicated by the hydrolysis of iodine chloride during titration, but not by the substitution of hydrogen by halogen nor by the hydrolysis of the rubber-halogen addition product. 4. The possibility of obtaining accurate values for unsaturation by a calculation of this hydrolysis is demonstrated. 5. Two methods have been developed for the determination of the unsaturation of natural and butadiene rubbers.

Determination of the Iodine Number of Raw Rubber

1929 ◽  
Vol 2 (3) ◽  
pp. 362-364
Author(s):  
Adolf Gorgas
Keyword(s):  
Acetic Acid ◽  
Iodine Number ◽  
Carbon Disulfide ◽  
Convenient Method ◽  
The State ◽  
Hydrogen Halide ◽  
Potassium Iodate ◽  
Substitution Reactions ◽  
Iodine Chloride

Abstract In the course of an investigation dealing with the nature of the state of unsaturation of raw rubber, it became necessary to have available a precise and convenient method for determining the iodine number of raw rubber. Though iodine reacts only slowly with unsaturated compounds, chlorine and bromine form both addition and substitution products. In the substitution reactions, the hydrogen halide is evolved, and by addition of potassium iodate, e.g., in the method of MacIlhiney, it is possible to determine the hydroden halide formed and thus the quantity of halogen substituted. In all methods, however, where extensive substitution as well as addition take place, the results are variable and uncertain. Accordingly in the chemistry of fats where the iodine number is of the greatest importance, iodine halides have been used for determining the iodine number, for under certain conditions there is very little substitution. Thus Hübl, Waller and Wijs solutions contain iodine chloride and Hanus solution contains iodine bromine. The Hanus method has in fact to a great extent replaced all other methods For determining the iodine number of rubber, the Wijs method in the form in which it was modified by Kemp is probably used more than any other. In the Kemp method about 0.1 gram of rubber is swollen in 75 cc. of carbon disulfide, and is then allowed to react for 2 hours at 0° C. with 25 cc. of Wijs solution, i.e., 0.5 N iodine chloride in acetic acid.

scholarly journals Novel Reagents for the Spectrophotometric Determination of Isoniazid

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Divya N. Shetty ◽  
Badiadka Narayana ◽  
Seranthimata Samshuddin
Keyword(s):  
Spectrophotometric Determination ◽  
Pharmaceutical Products ◽  
Molar Absorptivity ◽  
Basic Medium ◽  
Antitubercular Drug ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Simple Method ◽  
Bulk Drug

Isoniazid is an antitubercular drug, widely used for tuberculosis. Owing to its importance in therapeutics, the present study aims to develop simple method for the spectrophotometric determination of isoniazid (INH). Two novel reagents, epichlorohydrine (ECH) and 4-hydroxyphenaylchloride (HPC) are used for the spectrophotometric determination of INH. Based on the nucleophilic substitution reactions of INH with EPI & HPC in basic medium, rapid, simple, inexpensive, precise, and accurate visible spectrophotometric method is proposed for the determination of INH in bulk drug and in formulations. Method involves the reaction of INH with EPI and HPC in basic medium to form yellow-colored chromogen, measuring the absorbances at 405 and 402 nm for INH-EPI & INH-HPC, respectively. The optimum experimental conditions have been studied. The absorbance was found to increase linearly with the concentration of the drug and formed the basis for quantification. The calibration graphs were linear from 2.00–22.00 μg mL−1 and 20.00–120.00 μg mL−1 for INH-EPI & INH-HPC, respectively. The apparent molar absorptivity and Sandell's sensitivity are calculated to be 0.51×104 & 0.10×104 L mol−1 cm−1 and 0.027 & 0.134 μg cm−2 for INH-EPI & INH-HPC, respectively. The procedure is used to determine INH in pharmaceutical products. The associated pharmaceutical materials do not interfere in the measurements.

State-by-State Use of AMA Guides

2019 ◽  
Vol 24 (5) ◽  
pp. 3-7, 16
Keyword(s):  
Expert Testimony ◽  
Narrow Range ◽  
The United States ◽  
Workers Compensation ◽  
Federal Employees ◽  
Permanent Disability ◽  
Sixth Edition ◽  
History Of ◽  
Canadian Provinces

Abstract This article presents a history of the origins and development of the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), from the publication of an article titled “A Guide to the Evaluation of Permanent Impairment of the Extremities and Back” (1958) until a compendium of thirteen guides was published in book form in 1971. The most recent, sixth edition, appeared in 2008. Over time, the AMA Guides has been widely used by US states for workers’ compensation and also by the Federal Employees Compensation Act, the Longshore and Harbor Workers’ Compensation Act, as well as by Canadian provinces and other jurisdictions around the world. In the United States, almost twenty states have developed some form of their own impairment rating system, but some have a narrow range and scope and advise evaluators to consult the AMA Guides for a final determination of permanent disability. An evaluator's impairment evaluation report should clearly document the rater's review of prior medical and treatment records, clinical evaluation, analysis of the findings, and a discussion of how the final impairment rating was calculated. The resulting report is the rating physician's expert testimony to help adjudicate the claim. A table shows the edition of the AMA Guides used in each state and the enabling statute/code, with comments.

Antithrombin-mediated Inhibition of Factor Vlla-Tissue Factor Complex by the Synthetic Pentasaccharide Representing the Heparin Binding Site to Antithrombin

1996 ◽  
Vol 76 (01) ◽  
pp. 005-008 ◽  
Author(s):  
Jean Claude Lormeau ◽  
Jean Pascal Herault ◽  
Jean Marc Herbert
Keyword(s):  
Binding Site ◽  
Tissue Factor ◽  
Residual Activity ◽  
Coagulation Factors ◽  
Heparin Binding ◽  
Experimental Conditions ◽  
First Order ◽  
Heparin Binding Site ◽  
Coagulant Activity

SummaryWe examined the effect of the synthetic pentasaccharide representing the minimal binding site of heparin to antithrombin on the antithrombin-mediated inactivation of factor Vila bound to tissue factor. This effect was compared to the effect of unfractionated heparin. Using purified recombinant human coagulation factors and either a clotting or an amidolytic assay for the determination of the residual activity of factor Vila, we showed that the pentasaccharide was an efficient antithrombin-dependent inhibitor of the coagulant activity of tissue factor-factor Vila complex. In our experimental conditions, assuming a mean MW of 14,000 for heparin, the molar pseudo-first order rate constants for ATIII-mediated FVIIa inhibition by ATIII-binding heparin and by the synthetic pentasaccharide were found to be similar with respective values of 104,000 ± 10,500 min-1 and 112,000 ± 12,000 min-1 (mean ± s.e.m., n = 3)

Implications of the Intergenerational Linking Functions for the Parental Selfdyad in the Treatment of a Narcissistic Adolescent

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Richard M. Zeitner
Keyword(s):  
Negative Influence ◽  
History Of

In this paper the author presents a case of a narcissistic adolescent boy with crippling anxieties and multiple inhibitions, where the contributing intergenerational history of self-difficulties had infiltrated the parental couple's "selfdyad" in a way that could not be adequately contained. Having lost much of the capacity for the mutual selfobject relatedness that is required for a good enough selfdyad regulation, the parents' introjects were then split off and re-projected into their child. The author demonstrates a way of working in the treatment with the use of multiple psychoanalytic therapies, individual, couple, and family modalities. Furthermore, he elaborates a rationale for such a format, especially for those cases in which the intergenerational family projection-linking functions are especially salient and continue to exert a negative influence on the identified patient.

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