Mechanochemical Reactions Leading to Reinforcement in Rubbers

1960 ◽  
Vol 33 (4) ◽  
pp. 929-939
Author(s):  
R. J. Ceresa
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Covalent Bond ◽  
Vinyl Monomers ◽  
Research Association ◽  
Block Copolymerization ◽  
Wide Range ◽  
Carbon Gel ◽  
Internal Mixer ◽  
Mechanochemical Reactions

Abstract The development of the single rotor internal mixer (at the British Rubber Producers' Research Association) has facilitated the research into mechanochemical reactions of a wide range of high polymers. The term “mechanochemical” has been applied to reactions such as mastication, the mechanism of which involves the primary step of mechanical scission of a polymer chain into polymeric free radicals at a carbon to carbon or other covalent bond. The processes which have been studied previously include the cold mastication of rubberlike polymers, the formation of carbon gel, the interpolymerization of two elastomers during blending, and block copolymerization by the cold mastication of polymers plasticized by vinyl monomers. The evidence for the polymeric free radical nature of these reactions has recently been reviewed.

Nature of Chemisorptive Mechanisms in Rubber Reinforcement

1957 ◽  
Vol 30 (2) ◽  
pp. 596-609 ◽  
Author(s):  
V. A. Garten ◽  
G. K. Sutherland
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Active Sites ◽  
Rubber Matrix ◽  
Excess Oxygen ◽  
Radical Intermediates ◽  
Chemical Bond Formation ◽  
Crosslinked Networks ◽  
Carbon Gel ◽  
State Of Research

Abstract The present state of research in the field of reinforcing rubber fillers is reviewed and it is pointed out that although a strong school of thought still maintains that the strength of bonding depends on particle size, there are many observations indicating the presence of reactive sites and suggesting the possibility of strong bonds of a chemical nature between filler and rubber matrix. The phenomenon of carbon-gel formation as foremost among these, is discussed as lending fresh support to the idea of chemical bond formation. This effect, known to be most pronounced in the presence of an unsaturated matrix is correlated with the mechanism of vulcanization as proceeding via free radical intermediates. It is suggested that the formation of chemical bonds between pigment and rubber constitutes an integral part of the chemical crosslink formation commenced on the rubber mill and completed by vulcanization. This hypothesis is corroborated by results obtained during studies on the reactivity of pigment surfaces towards simple inorganic and organic free radicals. It is shown that active pigments react with free radicals with the formation of nonionic bonds. Hydrophilic blacks have been prepared by treatment with persulfate. Similarly, electrochemically produced stearate free radicals have been reacted with the surface to form hydrophobic carbons. The “benzidine ”blue free radical, being the monooxidation product of benzidine, reacted easily with less active pigments and thus provided a useful measure of activity. From the experiments with free radicals, the number of active sites for various fillers has been calculated and shown to cover a range of 0.01–3.1 per 100 sq. A˚. Multifunctional polystyrene radicals, obtained in the presence of excess oxygen, yielded crosslinked networks with carbon blacks which resisted solvent extraction. These are considered to be complete analogues to carbon gel. The statistical mechanics of the rubber network has been developed to include crosslink formation as caused by rubber-filler interaction. It is shown that the mechanical properties of a rubber compound that are controlled solely by the network structure are directly proportional to σ/r, the ratio between the number of active sites per unit area and the particle radius. Abrasion does not appear to be only a mechanical phenomenon.

scholarly journals NF-κB signaling pathway and free radical impact.

2012 ◽  
Vol 59 (3) ◽  
Author(s):  
Agnieszka Siomek
Keyword(s):  
Oxidative Stress ◽  
Transcription Factor ◽  
Free Radicals ◽  
Free Radical ◽  
Ionizing Radiation ◽  
Physiological Role ◽  
Growth And Survival ◽  
Wide Range ◽  
The Impact ◽  
And Oxidative Stress

The activation of NF-κB transcription factor is critical for a wide range of processes such as immunity, inflammation, cell development, growth and survival. It is activated by a variety of stimuli including cytokines, ionizing radiation and oxidative stress. Redox modulations of NF-κB pathway have been widely demonstrated. Studies carried out during last years have advanced our knowledge about possible connections between NF-κB pathway and the impact of free radicals. This review is an endeavor to gather recent results focused on this issue, although an important question, whether oxidative stress plays a physiological role in NF-κB activation, seems to be still unanswered.

Medical Applications of Water-Soluble Polyhydroxylated Fullerene Derivatives

1994 ◽  
Vol 359 ◽  
Author(s):  
Long Y. Chiang ◽  
Fung-Jou Lu ◽  
Jaw-Town Lin
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Water Soluble ◽  
Free Radical Scavengers ◽  
Medical Applications ◽  
Radical Scavengers ◽  
Fullerene Derivatives ◽  
Wide Range ◽  
Positive Results

ABSTRACTThe promising positive results in reducing superoxide free radicals (O2-.), generated by invitro xanthine and xanthine oxidase, have been demonstrated in the evaluation of potential uses of novel water-soluble [60] fullerenols as free radical scavengers. Observation reveals the inherent application of fullerenols in a wide range of medical and clinical areas as preventive alternatives for a long-term medical treatment.

Study of antioxidant potential in leaves, stems, nuts of Juglans regia L.

2012 ◽  
Vol 1 (10) ◽  
pp. 79 ◽  
Author(s):  
G. Raja* ◽  
Ivvala Anand Shaker ◽  
Inampudi Sailaja ◽  
R. Swaminathan ◽  
S. Saleem Basha ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Juglans Regia ◽  
Radical Scavenging ◽  
Antioxidant Compounds ◽  
Free Radical Damage ◽  
Radical Damage

Natural antioxidants can protect the human body from free radicals and retard the progress of many chronic diseases as well as lipid oxidative rancidity in foods. The role of antioxidants has protected effect against free radical damage that may cause many diseases including cancer. Primary sources of naturally occurring antioxidants are known as whole grains, fruits, and vegetables. Several studies suggest that regular consumption of nuts, mostly walnuts, may have beneficial effects against oxidative stress mediated diseases such as cardiovascular disease and cancer. The role of antioxidants has attracted much interest with respect to their protective effect against free radical damage that may cause many diseases including cancer. Juglans regia L. (walnut) contains antioxidant compounds, which are thought to contribute to their biological properties. Polyphenols, flavonoids and flavonols concentrations and antioxidant activity of Leaves, Stems and Nuts extract of Juglans regia L. as evaluated using DPPH, ABTS, Nitric acid, hydroxyl and superoxide radical scavenging activity, lipid peroxidation and total oxidation activity were determined. The antioxidant activities of Leaves, Stems and Nuts extract of Juglans regia L. were concentration dependent in different experimental models and it was observed that free radicals were scavenged by the test compounds in all the models.

THE KINETICS OF THE THERMAL REACTIONS OF ETHYLENE OXIDE

1963 ◽  
Vol 41 (12) ◽  
pp. 2956-2961 ◽  
Author(s):  
M. Lynne Neufeld ◽  
Arthur T. Blades
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Ethylene Oxide ◽  
Thermal Reactions ◽  
Kinetics Of

The thermal reactions of ethylene oxide in the presence of an excess of propylene have been studied as a function of pressure and it has been found that there are two sets of products, acetaldehyde and free radicals, presumably methyl and formyl. These products are believed to arise from an excited acetaldehyde intermediate. Some evidence has been obtained for the occurrence of a surface-catalyzed rearrangement to acetaldehyde but the free radical products are uninfluenced by surface.

Metal-Free Cascade Methylation/Cyclization of N-Alkyl-N-methacryloylbenzamides with Dicumyl Peroxide

Synlett ◽  
2017 ◽  
Vol 29 (05) ◽  
pp. 617-620 ◽  
Author(s):  
Yan-Ning Niu ◽  
Xiao-Feng Xia ◽  
Yuan Yuan
Keyword(s):  
Free Radical ◽  
Dicumyl Peroxide ◽  
Metal Free ◽  
Wide Range ◽  
Radical Cascade ◽  
Convenient Access

A metal-free radical cascade methylation/cyclization of a wide range of N-alkyl-N-methacryloylbenzamides by using dicumyl peroxide as the methylating reagent provides a convenient access to a series of methylated isoquinoline-1,3-diones in moderate yields.

scholarly journals Mechanistic Insight into Antimicrobial and Antioxidant Potential of Jasminum Species: A Herbal Approach for Disease Management

Plants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1089
Author(s):  
Acharya Balkrishna ◽  
Akansha Rohela ◽  
Abhishek Kumar ◽  
Ashwani Kumar ◽  
Vedpriya Arya ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Drug Resistance ◽  
Free Radicals ◽  
Free Radical ◽  
Microbial Pathogens ◽  
Free Radical Scavengers ◽  
Bioactive Constituents ◽  
Global Issues ◽  
Iridoid Glucosides ◽  
Insight Into

Drug resistance among microbial pathogens and oxidative stress caused by reactive oxygen species are two of the most challenging global issues. Firstly, drug-resistant pathogens cause several fatalities every year. Secondly aging and a variety of diseases, such as cardiovascular disease and cancer, are associated with free radical generated oxidative stress. The treatments currently available are limited, ineffective, or less efficient, so there is an immediate need to tackle these issues by looking for new therapies to resolve resistance and neutralize the harmful effects of free radicals. In the 21st century, the best way to save humans from them could be by using plants as well as their bioactive constituents. In this specific context, Jasminum is a major plant genus that is used in the Ayurvedic system of medicine to treat a variety of ailments. The information in this review was gathered from a variety of sources, including books, websites, and databases such as Science Direct, PubMed, and Google Scholar. In this review, a total of 14 species of Jasminum have been found to be efficient and effective against a wide variety of microbial pathogens. In addition, 14 species were found to be active free radical scavengers. The review is also focused on the disorders related to oxidative stress, and it was concluded that Jasminum grandiflorum and J. sambac normalized various parameters that were elevated by free radical generation. Alkaloids, flavonoids (rutoside), terpenes, phenols, and iridoid glucosides are among the main phytoconstituents found in various Jasminum species. Furthermore, this review also provides insight into the mechanistic basis of drug resistance, the generation of free radicals, and the role of Jasminum plants in combating resistance and neutralizing free radicals.

Sign in / Sign up

Export Citation Format

Share Document