The Kinetics and Occurrence of Optimum Vulcanization

1956 ◽  
Vol 29 (2) ◽  
pp. 555-567
Author(s):  
B. A. Dogadkin
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Structure Formation ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Smooth Curves ◽  
Intermolecular Reaction ◽  
Physical And Chemical ◽  
Kinetics Of ◽  
And Chemical Properties

Abstract The fundamental reaction of vulcanization is the combination of a vulcanizing agent with rubber. The kinetics of this reaction is expressed by smooth curves. Simultaneously with the combining of the vulcanizing agent, in fact as a result of it, changes take place in a number of physical and chemical properties of rubber—solubility, modulus, tensile strength, and other indexes. Unlike the kinetics of combination of the vulcanizing agent, the changes in these properties are most often represented by curves having a maximum or minimum which characterizes the phenomenon of optimum vulcanization. The extreme form which curves of changes of physical and chemical properties of rubber assume during vulcanization can be explained, in our opinion, by the fact that, during vulcanization, there is a competition between opposing reactions, of which one set are reactions of structure formation (i.e., increase of the molecular weight and the intensity of intermolecular reaction), and the others are destruction reactions. Thus, during vulcanization under factory conditions, at least two reactions take place: (1) the reaction between rubber and sulfur, and (2) the reaction between rubber and molecular oxygen introduced into the vulcanization mix by milling with the ingredients. The amount of oxvgen present here in moles approaches the molar concentration of sulfur.

Isolation and identification of the high molecular weight saturated fatty acids of butterfat

1959 ◽  
Vol 26 (2) ◽  
pp. 190-195 ◽  
Author(s):  
R. P. Hansen ◽  
F. B. Shorland ◽  
N. June Cooke
Keyword(s):  
Molecular Weight ◽  
Saturated Fatty Acids ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Octadecanoic Acid ◽  
Isolation And Identification ◽  
Docosanoic Acid ◽  
Physical And Chemical ◽  
Tetracosanoic Acid ◽  
And Chemical Properties

Butterfat has been shown to contain the normal odd-numbered saturated acids n-nonadecanoic acid (C19), n-heneicosanoic acid (C21), and n-tricosanoic acids (C23).The presence of the normal even-numbered acids n-octadecanoic acid (C18), n-docosanoic acid (C22), n-tetracosanoic acid (C24) and n-hexacosanoic acid (C26) is conclusively established.n-Eicosanoic acid (C20) formerly assumed to be present in butterfat has been isolated and identified by its physical and chemical properties.

scholarly journals Physico-Chemical Properties of Purified Carboxylesterase from the Seeds of Tamarindus indica

2021 ◽  
pp. 42-58
Author(s):  
S. Kantharaju ◽  
M. Mylarappa
Keyword(s):  
Molecular Weight ◽  
Gel Filtration ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Tamarindus Indica ◽  
Physico Chemical ◽  
Sds Page ◽  
Physical And Chemical ◽  
Naphthyl Acetate ◽  
And Chemical Properties

The present work is focus on physical and chemical properties of purified Carboxylesterase using the Seeds of Tamarindus Indica.The esterases are extracted from the germinating tamarind seeds using 50 mM phosphate buffer, pH 7 and purified. The Km with α-naphthyl acetate, β-naphthyl acetate and α-naphthyl butyrate as the substrates is 28.6 μM, 22.2 μM and 26.7 μM respectively. The Vmax for the same substrates is 7.1 x 10-3 µmole/min, 7.41 x 10-3 µmole/min and 8.00 x 10-3 µmole/min respectively. The enzymes optimally active at pH 7.0 and are stable between pH 5.0 to 8.0. The optimum temperature of esterase activity is 40˚C. The molecular weight of 27.5 kD as determined by SDS-PAGE, both in the presence and absence of β-mercaptothanol and is in close agreement with the molecular weight determined by gel-filtration on Sephadex G-100 (26.9 kD).

scholarly journals Karakteristik Sifat Fisik dan Kimia Edible Film Pati Sagu Rumbia (Metroxylon sagu Rottb) untuk Bahan Baku Cangkang Kapsul (Characteristics of Physical and Chemical Properties of Edible Film of Rumbia Sago Starch for Capsule Shell Material)

2018 ◽  
Vol 10 (2) ◽  
pp. 55-62
Author(s):  
Hamlan Ihsan ◽  
Nadra Khairiah ◽  
Rufida Rufida
Keyword(s):  
Tensile Strength ◽  
Water Content ◽  
Chemical Properties ◽  
Quality Standard ◽  
Edible Film ◽  
Physical And Chemical Properties ◽  
Sago Starch ◽  
Metroxylon Sagu ◽  
Physical And Chemical ◽  
And Chemical Properties

The purpose of this research was to analyze the physical and chemical properties of sago starch edible film (Metroxylon sagu Rottb) as capsule shells material. The research was started with the extraction of the rumbia starch, and was followed with the production of edible film added with modified carrageenan concentrations (20% and 30% w/w) to the main compound. Organoleptic test showed that the color and odor of the films were normal. Water content of wet sago and dry sago was 12.55%, and 5.38%, respectively. Although the addition of carrageenan increased the water content but still corresponded with SNI gelatin quality standard with a maximum of water content of 16%. The ash content of fresh sago and dry sago was 0.36% and 1.09%, respectively, and the content increased significantly with the addition of carrageenan. The pH of all varied samples was 5.5 – 7.0, and the pH was in accordance with SNI. Meanwhile, the heavy metal content of the samples measured by means of AAS was negative. Based on viscosity testing withBrookfield method, high carrageenan concentration led to low viscosit. tensile strength test based on ASTM D 882-2002 gave positive results for dry sago (21.05 kg/cm2) whereas fresh sago with modified 20% and 30% carrageenan had tensile strength of 5.33 kg/cm2 and 18.18 kg/cm2, respectively. The results showed that sago starch had the potential as a raw material for producing soft capsules by modified composition to enhance physical and mechanical properties in order to meet the quality standard of edible film.

scholarly journals Modeling of pharmacokinetic processes of distribution of cisplatin in tumor tissues

2020 ◽  
pp. 106-108
Author(s):  
Д.А. Гиневский ◽  
П.В. Ижевский ◽  
И.Н. Шейно ◽  
Д.Г. Левитова
Keyword(s):  
In Silico ◽  
Chemical Properties ◽  
Malignant Neoplasms ◽  
Physical And Chemical Properties ◽  
Chemotherapeutic Drug ◽  
Tissue Organization ◽  
Tumor Tissues ◽  
Physical And Chemical ◽  
Kinetics Of ◽  
And Chemical Properties

Разработана математическая модель пространственно-временного распределения радиомодифицирующего агента химиотерапевтического препарата цисплатина с заданными физико-химическими свойствами на тканевом и клеточном уровнях организации биологической ткани. Эксперимент in silico позволил получить данные о кинетике внутриклеточного распределения цисплатина. Модель может быть адаптирована для определения 3D кинетики наночастиц, а также других препаратов для диагностики или терапии злокачественных новообразований. A mathematical model of the space-time distribution of a radiomodifying agent - a chemotherapeutic drug - cisplatin with specified physical and chemical properties at the tissue and cellular levels of the biological tissue organization has been developed. The in silico experiment provided data on the kinetics of the intracellular distribution of cisplatin. The model can be adapted to determine the 3D kinetics of nanoparticles, as well as other drugs for the diagnosis or therapy of malignant neoplasms.

scholarly journals Comparative Study of the Mucoadhesive Properties of Polymers for Pharmaceutical Use

2020 ◽  
Vol 8 (A) ◽  
pp. 639-645
Author(s):  
Elena Bakhrushina ◽  
Maria Anurova ◽  
Natalia Demina ◽  
Alena Kashperko ◽  
Olga Rastopchina ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Xanthan Gum ◽  
Average Molecular Weight ◽  
Negative Relationship ◽  
Chemical Properties ◽  
Drug Formulation ◽  
Movement Speed ◽  
Physical And Chemical Properties ◽  
Physical And Chemical ◽  
And Chemical Properties

BACKGROUND: In recent years, mucoadhesive dosage forms due to their advantages have attracted the interest of researchers and developers. Polymeric excipients are included into the drug composition to give adhesion to the mucous membrane. AIM: The aim of this research was to select a specific brand of pharmaceutical quality polymer that is promising for inclusion in the drug formulation. METHODS: The article presents the results of studying the mucoadhesive properties of polymers on two models using mucin: By measuring the amount of adhesion and by the evaluation the sample movement speed. RESULTS: According to the combination of two indicators, the highest mucoadhesive properties were shown by the brands of hydroxypropylmethylcellulose and xanthan gum. In addition, it was noted that hydroxyethylcellulose (HEC), sodium alginate, and hydroxypropylmethylcellulose (HPMC) also have good mucoadhesive properties. Polyethylene glycols proved to have the weakest mucoadhesive properties. The negative relationship between the average molecular weight and the sample movement speed of the HEC and HPMC was established. Obtained data showed no direct influence of the polymer average molecular weight on the amount of adhesion. It was also noted that there is no strong correlation between the amount of adhesion and the sample movement speed of the experimental samples. CONCLUSION: Based on the results of the study, it was suggested that the complex influences of the physical and chemical properties of the polymer on its mucoadhesive properties.

Low molecular weight complexed poly(3-hydroxybutyrate): a dynamic and versatile molecule in vivo

1995 ◽  
Vol 41 (13) ◽  
pp. 50-54 ◽  
Author(s):  
Rosetta N. Reusch
Keyword(s):  
Molecular Weight ◽  
Chemical Properties ◽  
Low Molecular Weight ◽  
Physical And Chemical Properties ◽  
Biological Cells ◽  
Ion Conducting ◽  
Physical And Chemical ◽  
Electron Donating Groups ◽  
And Chemical Properties

It is increasingly clear that poly(3-hydroxybutyrate) (PHB) is not just an inert storage polymer, confined to certain bacteria, but a ubiquitous, interactive, solvating biopolymer involved in important physiological functions. Low molecular weight PHB, complexed to other macromolecules (c-PHB), is widely distributed in biological cells, being found in representative organisms of nearly all phyla. Complexation modifies the physical and chemical properties of c-PHB, allowing it to pervade aqueous as well as hydrophobic regions of the cell, and as a result c-PHB can be found in cytoplasm and intracellular fluids as well as in membranes and lipoproteins. The lipidic homopolymer associates with other macromolecules primarily via its ester carbonyl oxygens, which can act as hydrogen-bond acceptors or as ligands for coordinate bonds to cations. The spacing of the electron-donating groups along the flexible backbone allows for multiple bonding interactions, and forms the basis for the ability of c-PHB to bind to proteins, or to form ion-conducting complexes with salts. The singular ability of c-PHB to dissolve salts and facilitate their transfer across hydrophobic barriers defines a potential physiological niche for c-PHB in cell metabolism.Key words: polyhydroxybutyrate, polyphosphate, polymer electrolyte, ion transport.

Sign in / Sign up

Export Citation Format

Share Document