Bisalkylation Theory of Neoprene Vulcanization

1955 ◽  
Vol 28 (4) ◽  
pp. 1021-1031 ◽  
Author(s):  
Peter Kovacic
Keyword(s):  
Zinc Oxide ◽  
Natural Rubber ◽  
Organic Compounds ◽  
Chlorine Atom ◽  
Structural Difference ◽  
General Purpose ◽  
Active Chlorine ◽  
Functional Difference ◽  
Methyl Group ◽  
The Difference

Abstract Among the organic compounds that are recommended for use with magnesia and zinc oxide as vulcanizing agents for Neoprene are ethylenethiourea (2-imidazolidinethione), p,p′-diaminodiphenylmethane and the di-o-tolylguanidine salt of dicatechol borate. In the absence of sulfur, these agents in combination with zinc oxide do not vulcanize natural rubber. This points up a marked difference in the way these elastomers vulcanize. Although a major structural difference is the chlorine atom in Neoprene in place of the side methyl group in natural rubber, the small amount of tertiary allylic chlorine formed by 1,2-polymerization is the important functional difference. The labile chlorine amounts to about 1.5 per cent of the total chlorine in a general-purpose Neoprene made at 40° C, such as Neoprene Type W used in this work. In Neoprene latex, this active chlorine is gradually liberated, and the polymer becomes cross-linked. This paper demonstrates the importance of the labile chlorine in the vulcanization of dry Neoprene, accounts for the difference in the vulcanization of Neoprene and natural rubber, and suggests a bisalkylation theory of Neoprene vulcanization.

Processing Characteristics of Synthetic Rubbers and Their Use in the Manufacture of Extruded Products

1944 ◽  
Vol 17 (4) ◽  
pp. 932-940 ◽  
Author(s):  
A. E. Juve
Keyword(s):  
Natural Rubber ◽  
Present Situation ◽  
General Purpose ◽  
High Dispersion ◽  
High Recovery ◽  
Vulcanized Rubber ◽  
Roll Mill ◽  
The Difference ◽  
Extruded Products ◽  
Internal Mixer

Abstract The difference in processing behavior between synthetic rubbers and natural rubber becomes evident when production facilities designed for processing natural rubber are used for synthetic rubbers. All the synthetic rubbers in one respect or another are harder to process than natural rubber. Under circumstances other than the present emergency, processing equipment suitable for handling the synthetic rubbers would gradually be evolved. In the present situation, synthetic rubbers must be processed with equipment already available. In this discussion natural rubber and the general purpose synthetic rubbers, GR-S, GR-M and GR-I, will be considered. The processing of dry rubber consists essentially of the incorporation of vulcanizing agents, pigments, oils, and other ingredients by a process of kneading, followed by the forming of the mix by extrusion or calendering into shapes suitable for fabrication preparatory to final cure. The mixing step, which is accomplished on a two-roll mill or in an internal mixer, requires that the rubber be within a plasticity range that will permit satisfactory dispersion of the ingredients. If the plasticity is too low the rubber tends to crumble, and if it is too high dispersion is poor. Crude natural rubber is quite tough, and before breakdown has some of the properties of vulcanized rubber, such as high recovery after moderate distortion. In the crude state it is extremely difficult to obtain satisfactory dispersion of pigments. It is therefore necessary to soften it by mastication or other means so that the pigments are more readily incorporated and power requirements are lowered. In addition, its nerve or tendency to recover after distortion is greatly reduced. Synthetic rubbers, in general, differ from natural rubber in their susceptibility to softening by mastication, and they show different relationships between nerve and plasticity than does natural rubber.

Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples

1996 ◽  
Vol 54 ◽  
pp. 174-175
Author(s):  
P. Sadhukhan ◽  
J. B. Zimmerman
Keyword(s):  
Zinc Oxide ◽  
Electron Microscope ◽  
Carbon Black ◽  
Natural Rubber ◽  
Transmission Electron Microscope ◽  
Rolling Resistance ◽  
Synthetic Polymers ◽  
Nitrogen Atmosphere ◽  
Transmission Electron ◽  
Curing Agents

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.

scholarly journals Force Generation on the Hallux Is More Affected by the Ankle Joint Angle than the Lesser Toes: An In Vivo Human Study

Biology ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 48
Author(s):  
Junya Saeki ◽  
Soichiro Iwanuma ◽  
Suguru Torii
Keyword(s):  
Repeated Measures ◽  
Joint Angle ◽  
Plantar Flexion ◽  
Human Study ◽  
Force Generation ◽  
Functional Difference ◽  
Multiple Comparison Test ◽  
The Difference ◽  
Metatarsophalangeal Joints

The structure of the first toe is independent of that of the other toes, while the functional difference remains unclear. The purpose of this study was to investigate the difference in the force generation characteristics between the plantar-flexion of the first and second–fifth metatarsophalangeal joints (MTPJs) by comparing the maximal voluntary plantar-flexion torques (MVC torque) at different MTPJs and ankle positions. The MVC torques of the first and second–fifth MTPJs were measured at 0°, 15°, 30°, and 45° dorsiflexed positions of the MTPJs, and at 20° plantar-flexed, neutral, and 20° dorsiflexed positions of the ankle. Two-way repeated measures analyses of variance with Holm’s multiple comparison test (MTPJ position × ankle position) were performed. When the MTPJ was dorsiflexed at 0°, 15°, and 30°, the MVC torque of the first MTPJ when the ankle was dorsiflexed at 20° was higher than that when the ankle was plantar-flexed at 20°. However, the ankle position had no significant effect on the MVC torque of the second–fifth MTPJ. Thus, the MVC torque of the first MTPJ was more affected by the ankle position than the second–fifth MTPJs.

scholarly journals Elemental composition and clustering behaviour of α-pinene oxidation products for different oxidation conditions

2015 ◽  
Vol 15 (8) ◽  
pp. 4145-4159 ◽  
Author(s):  
A. P. Praplan ◽  
S. Schobesberger ◽  
F. Bianchi ◽  
M. P. Rissanen ◽  
M. Ehn ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Organic Compounds ◽  
Atmospheric Pressure ◽  
Molar Mass ◽  
Oxidation Products ◽  
Neutral Species ◽  
Mass Spectrometers ◽  
Comprehensive Picture ◽  
The Difference ◽  
Chemical Ionisation

Abstract. This study presents the difference between oxidised organic compounds formed by α-pinene oxidation under various conditions in the CLOUD environmental chamber: (1) pure ozonolysis (in the presence of hydrogen as hydroxyl radical (OH) scavenger) and (2) OH oxidation (initiated by nitrous acid (HONO) photolysis by ultraviolet light) in the absence of ozone. We discuss results from three Atmospheric Pressure interface Time-of-Flight (APi-TOF) mass spectrometers measuring simultaneously the composition of naturally charged as well as neutral species (via chemical ionisation with nitrate). Natural chemical ionisation takes place in the CLOUD chamber and organic oxidised compounds form clusters with nitrate, bisulfate, bisulfate/sulfuric acid clusters, ammonium, and dimethylaminium, or get protonated. The results from this study show that this process is selective for various oxidised organic compounds with low molar mass and ions, so that in order to obtain a comprehensive picture of the elemental composition of oxidation products and their clustering behaviour, several instruments must be used. We compare oxidation products containing 10 and 20 carbon atoms and show that highly oxidised organic compounds are formed in the early stages of the oxidation.

scholarly journals IFITM1 expression determines extracellular vesicle uptake in colorectal cancer

2021 ◽  
Author(s):  
Andrea Kelemen ◽  
Idan Carmi ◽  
Ádám Oszvald ◽  
Péter Lőrincz ◽  
Gábor Petővári ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Transmembrane Protein ◽  
Extracellular Vesicle ◽  
Cellular Heterogeneity ◽  
Functional Difference ◽  
Proliferating Cells ◽  
Antiviral Responses ◽  
The Difference ◽  
Functional Relevance ◽  
Therapeutic Tools

AbstractThe majority of colorectal cancer (CRC) patients carry mutations in the APC gene, which lead to the unregulated activation of the Wnt pathway. Extracellular vesicles (EV) are considered potential therapeutic tools. Although CRC is a genetically heterogeneous disease, the significance of the intra-tumor heterogeneity in EV uptake of CRC cells is not yet known. By using mouse and patient-derived organoids, the currently available best model of capturing cellular heterogeneity, we found that Apc mutation induced the expression of interferon-induced transmembrane protein 1 (Ifitm1), a membrane protein that plays a major role in cellular antiviral responses. Importantly, organoids derived from IFITM1high CRC cells contained more proliferating cells and they had a markedly reduced uptake of fibroblast EVs as compared to IFITM1low/− cells. In contrast, there was no difference in the intensity of EV release between CRC subpopulations with high and low IFITM1 levels. Importantly, the difference in cell proliferation between these two subpopulations disappeared in the presence of fibroblast-derived EVs, proving the functional relevance of the enhanced EV uptake by IFITM1low CRC cells. Furthermore, inactivating IFITM1 resulted in an enhanced EV uptake, highlighting the importance of this molecule in establishing the cellular difference for EV effects. Collectively, we identified CRC cells with functional difference in their EV uptake ability that must be taken into consideration when using EVs as therapeutic tools for targeting cancer cells.

scholarly journals Does corporate ownership affect capital structures and adjustment of capital structures — evidences from Chinese listed companies

2009 ◽  
Vol 6 (4) ◽  
pp. 532-541 ◽  
Author(s):  
Zhengwei Wang ◽  
Wei Lin ◽  
Michael Keefe
Keyword(s):  
Capital Structure ◽  
Transition Economy ◽  
Structural Difference ◽  
Firm Characteristics ◽  
Financial Friction ◽  
Listed Firms ◽  
Optimal Capital Structure ◽  
Study Results ◽  
Optimal Capital ◽  
The Difference

In Chinese transition economy, compared with state-owned firms, private firms face higher financial friction in financing activities, but have more incentive to adjust toward optimal capital structure to maximize the shareholders‟ benefit. Based on panel data of China’s listed firms from 1998 to 2007, we compare the capital structures of state-owned and privately-owned listed firms. The empirical results show that there is structural difference in static capital structure between state-owned and private listed firms while controlling for firm characteristics. We then investigate the difference in dynamics of the capital structure between these two groups of firms. Further study results tell us that the adjustment to an optimal capital structure to be faster for the private firm than for the state-owned firm.

Evaluation of wastewater characterization methods

2005 ◽  
Vol 52 (10-11) ◽  
pp. 61-68 ◽  
Author(s):  
E.-H. Choi ◽  
B. Klapwijk ◽  
A. Mels ◽  
H. Brouwer
Keyword(s):  
Organic Matter ◽  
Organic Compounds ◽  
Nitrate Concentration ◽  
Characterization Methods ◽  
Biochemical Characteristics ◽  
Organic Components ◽  
N Removal ◽  
Curve Fit ◽  
The Difference

Wastewater contains various organic components with different physical and biochemical characteristics. ASM No. 1 distinguishes two categories of biodegradable organic matter in wastewater, rapidly and slowly biodegradable. In general there are two methods for wastewater characterization: based on filtration in combination with a long-term BOD test or based on a respirogram. By comparing both approaches, we showed that in wastewater three categories of organic compounds with different biodegradation rates can be distinguished. These categories are referred to as readily biodegradable, rapidly hydrolysable and slowly hydrolysable organic matter. The total biodegradable COD can be found from a long-term BOD-test combined with a curve-fit and the readily biodegradable and rapidly hydrolysable from a respirogram. The slowly hydrolysable is the difference between total biodegradable COD and the sum of readily biodegradable and rapidly hydrolysable COD. Simulation with characterization based on filtration for a pre-anoxic reactor with a certain N-removal compared with the N-removal of the same plant with wastewater according to the modified characterization shows different results of each wastewater, especially with regard to the effluent nitrate concentration.

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