Study of the Influence of Microwaves in the Mechanism of Sulfenamide Accelerated Vulcanization of Natural Rubber Using Squalene as a Model Compound

2007 ◽  
Vol 80 (5) ◽  
pp. 739-750 ◽  
Author(s):  
B. Vega ◽  
N. Agulló ◽  
S. Borrós
Keyword(s):  
Natural Rubber ◽  
Model Compound ◽  
Rate Increase ◽  
Heating System ◽  
Conventional Heating ◽  
Crosslinking Degree ◽  
Reaction Rate Increase ◽  
Heating Source ◽  
Sulfur Transfer

Abstract The natural rubber vulcanization mechanism has been studied using microwaves as a heating source. The influence of such heating system on the mechanism reaction has been elucidated. In order to simplify the study of this process, squalene has been used as a Model Compound Vulcanization (MCV) for natural rubber and N-cyclohexyl-2-benzothiazolesulfenamide (CBS) as an accelerator. The accelerator fading, the crosslinking degree, the reversion process and the effect of the double bond have been studied and the results have been compared with previous results of our group using MCV with conventional heating. As well as the expected reaction rate increase, a noticeable change in the crosslink degree has been observed. Furthermore, some differences have been detected in the amount of the intermediate compounds formed during the reaction and in the sulfur transfer to the squalene chain. Strong differences have been also observed regarding the role of the activator in the vulcanization when microwaves are used.

ZINC OXIDE VERSUS MAGNESIUM OXIDE REVISITED. PART 1

2012 ◽  
Vol 85 (1) ◽  
pp. 38-55 ◽  
Author(s):  
Manuel Guzmán ◽  
Berta Vega ◽  
Núria Agulló ◽  
Ulrich Giese ◽  
Salvador Borrós
Keyword(s):  
Zinc Oxide ◽  
Environmental Impact ◽  
Natural Rubber ◽  
Metal Oxides ◽  
Environmental Effects ◽  
Model Compound ◽  
Rubber Industry ◽  
Sulfur Vulcanization ◽  
Activator System

Abstract Zinc oxide is a widely used compound in the rubber industry due to the excellent properties that it shows as activator, and consequently, its role in the mechanism of accelerated sulfur vulcanization has been extensively studied. Due to the increased concern about its environmental effects, several research studies have been carried out in order to substitute it with different metal oxides such us MgO. The effect of the activator system in order to minimize the environmental impact of the rubber goods has been explored. The work developed is presented in two parts. In Part 1, the influence of different mixtures of ZnO and MgO on the vulcanization of natural rubber has been investigated. In Part 2, model compound vulcanization has been used to study the role of MgO on the mechanism to gain a better understanding of the differences shown in Part 1.

ZINC OXIDE VERSUS MAGNESIUM OXIDE REVISITED. PART 2

2012 ◽  
Vol 85 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Manuel Guzmán ◽  
Berta Vega ◽  
Núria Agulló ◽  
Salvador Borrós
Keyword(s):  
Zinc Oxide ◽  
Environmental Impact ◽  
Natural Rubber ◽  
Metal Oxides ◽  
Environmental Effects ◽  
Model Compound ◽  
Rubber Industry ◽  
Sulfur Vulcanization ◽  
Activator System

Abstract Zinc oxide is a widely used compound in the rubber industry due to the excellent properties that it shows as an activator and, consequently, its role in the mechanism of accelerated sulfur vulcanization has been extensively studied. Due to the increased concern about its environmental effects, several research studies have been carried out in order to substitute it with different metal oxides such us MgO. The effect of the activator system in order to minimize the environmental impact of the rubber goods has been explored. The work developed is presented in two parts. In Part 1, the influence of different mixtures of ZnO and MgO in the vulcanization of natural rubber has been investigated. In Part 2 of the study, model compound vulcanization has been used to study the role of MgO on the mechanism to gain a better understanding of the differences shown in the first part.

ROLE OF THE THYROID GLAND IN DEVELOPMENT AND MAINTENANCE OF RENAL HYPERTENSION IN RATS

1960 ◽  
Vol XXXIV (III) ◽  
pp. 411-429 ◽  
Author(s):  
Melvin J. Fregly ◽  
Kenneth M. Cook
Keyword(s):  
Blood Pressure ◽  
Rate Increase ◽  
Renal Hypertension ◽  
The Other ◽  
Elevated Blood Pressure ◽  
Unit Weight ◽  
Elevated Blood ◽  
Inhibition Of Growth ◽  
Testicular Size

ABSTRACT The anti-thyroid drugs, thiouracil, propylthiouracil, and methimazole, prevented both development of elevated blood pressure and cardiac hypertrophy usually accompanying kidney encapsulation with latex envelopes. These drugs also reduced elevated blood pressure of rats with hypertension of 13 to 40 weeks' duration prior to drug administration. Addition of desiccated thyroid powder to diet containing an anti-thyroid drug overcame the anti-hypertensive effect of the latter. Withdrawal of thyroid powder only was followed by return of blood pressure to previous low level within 3 weeks. The results suggest that the anti-hypertensive effect of these drugs is related directly to the hypothyroidism produced rather than to extrathyroidal effects of the drugs. Comparison of potencies of the 3 drugs in terms of anti-hypertensive effect, inhibition of growth rate, increase in testicular size, and increase in thyroid size suggests that propylthiouracil and methimazole are equally potent per unit weight of drug. Thiouracil has approximately half the potency of the other two.

Activators in Accelerated Sulfur Vulcanization

2004 ◽  
Vol 77 (3) ◽  
pp. 512-541 ◽  
Author(s):  
Geert Heideman ◽  
Rabin N. Datta ◽  
Jacques W. M. Noordermeer ◽  
Ben van Baarle
Keyword(s):  
Reaction Mechanisms ◽  
Model Compound ◽  
Background Information ◽  
Zinc Compounds ◽  
Chemical Mechanisms ◽  
Sulfur Vulcanization ◽  
Multifunctional Additives ◽  
Vulcanization Process

Abstract This review provides relevant background information about the vulcanization process, as well as the chemistry of thiuram- and sulfenamide-accelerated sulfur vulcanization with emphasis on the role of activators, to lay a base for further research. It commences with an introduction of sulfur vulcanization and a summary of the reaction mechanisms as described in literature, followed by the role of activators, particularly ZnO. The various possibilities to reduce ZnO levels in rubber compounding, that have been proposed in literature, are reviewed. A totally different approach to reduce ZnO is described in the paragraphs about the various possible roles of multifunctional additives (MFA) in rubber vulcanization. Another paragraph is dedicated to the role of amines in rubber vulcanization, in order to provide some insight in the underlying chemical mechanisms of MFA systems. Furthermore, an overview of Model Compound Vulcanization (MCV) with respect to different models and activator/accelerator systems is given. In the last part of this review, the various functions of ZnO in rubber are summarized. It clearly reveals that the role of ZnO and zinc compounds is very complex and still deserves further clarification.

scholarly journals Biocomposites of Epoxidized Natural Rubber/Poly(lactic acid) Modified with Natural Fillers (Part I)

2021 ◽  
Vol 22 (6) ◽  
pp. 3150
Author(s):  
Anna Masek ◽  
Stefan Cichosz ◽  
Małgorzata Piotrowska
Keyword(s):  
Tensile Strength ◽  
Lactic Acid ◽  
Natural Rubber ◽  
Epoxidized Natural Rubber ◽  
Poly Lactic Acid ◽  
Uv Aging ◽  
High Elasticity ◽  
Natural Fillers ◽  
Natural Additives

The study aimed to prepare sustainable and degradable elastic blends of epoxidized natural rubber (ENR) with poly(lactic acid) (PLA) that were reinforced with flax fiber (FF) and montmorillonite (MMT), simultaneously filling the gap in the literature regarding the PLA-containing polymer blends filled with natural additives. The performed study reveals that FF incorporation into ENR/PLA blend may cause a significant improvement in tensile strength from (10 ± 1) MPa for the reference material to (19 ± 2) MPa for the fibers-filled blend. Additionally, it was found that MMT employment in the role of the filler might contribute to ENR/PLA plasticization and considerably promote the blend elongation up to 600%. This proves the successful creation of the unique and eco-friendly PLA-containing polymer blend exhibiting high elasticity. Moreover, thanks to the performed accelerated thermo-oxidative and ultraviolet (UV) aging, it was established that MMT incorporation may delay the degradation of ENR/PLA blends under the abovementioned conditions. Additionally, mold tests revealed that plant-derived fiber addition might highly enhance the ENR/PLA blend’s biodeterioration potential enabling faster and more efficient growth of microorganisms. Therefore, materials presented in this research may become competitive and eco-friendly alternatives to commonly utilized petro-based polymeric products.

Microwave-Assisted Grafting to MCM-41 Silica and its Application as Catalyst in Flow Chemistry

2011 ◽  
Vol 64 (11) ◽  
pp. 1522 ◽  
Author(s):  
Manuela Oliverio ◽  
Antonio Procopio ◽  
Toma N. Glasnov ◽  
Walter Goessler ◽  
C. Oliver Kappe
Keyword(s):  
Continuous Flow ◽  
Rate Increase ◽  
Flow Chemistry ◽  
Conventional Heating ◽  
Kinetic Effect ◽  
Microwave Technology ◽  
Microwave Assisted ◽  
Technology Control ◽  
First Time ◽  
Mcm 41

Finding environmentally gentle methods to graft Lewis acid on the surface of mesoporous materials is a topic of current interest. Herein we describe the optimization of a preparation procedure of a mesoporous silica-supported ErIII catalyst using the microwave-assisted post-calcination functionalization of Mobil Composition of Matter-41 silica as the key step. The required time for functionalization was reduced from several hours to 10 min using sealed-vessel microwave technology. Control experiments using conventional heating at the same temperature demonstrated that the rate increase is owing to a simple thermal/kinetic effect as a result of the higher reaction temperature. The resulting ErIII catalyst was tested for the first time as a catalyst in the continuous flow deprotection of benzaldehyde dimethylacetal and a complete leaching study was performed.

scholarly journals Exhaustive laccase-catalysed oxidation of a lignin model compound (vanillyl glycol) produces methanol and polymeric quinoid products

1985 ◽  
Vol 229 (1) ◽  
pp. 277-279 ◽  
Author(s):  
K Lundquist ◽  
P Kristersson
Keyword(s):  
Model Compound ◽  
Polymerization Process ◽  
Lignin Biodegradation ◽  
Simultaneous Formation ◽  
Initial Formation ◽  
Lignin Model Compound ◽  
Catalysed Oxidation ◽  
Visible Spectra ◽  
Lignin Model

Laccase-catalysed oxidation of the lignin-related phenol vanillyl glycol results in the initial formation of dimers and subsequent polymerization. The polymerization is accompanied by a liberation of methanol corresponding to 15-20% demethylation. Visible spectra together with reduction experiments suggest the simultaneous formation of o-quinones. The participation of quinone formation in the polymerization process and the possible role of such intermediates in lignin biodegradation is discussed.

Radical Mechanisms in Saturated and Olefinic Systems. II. Disubstitutive Carbon-Carbon Cross-Linking by Tertiary Alkoxy Radicals in Isoprenic Olefins and Rubber

1951 ◽  
Vol 24 (4) ◽  
pp. 777-786
Author(s):  
E. H. Farmer ◽  
C. G. Moore
Keyword(s):  
Natural Rubber ◽  
Cross Linking ◽  
Chain Molecules ◽  
Alkoxy Radicals ◽  
Full Extent ◽  
Carbon Chains ◽  
Butyl Peroxide ◽  
High Degree ◽  
Vulcanization Process

Abstract The high degree of dehydrogenation effected by tert.-butoxy radicals at the α-methylenic groups of olefins enables these radicals to be used for the carbon-to-carbon cross-linking of unsaturated carbon chains, and especially of the polyisoprenic chains of natural rubber. Such cross-linking amounts to a vulcanization process in which the connecting links between chain molecules are just C—C bonds, which may be expected to have appropriate attributes. An examination has first been made of the cross-linking produced by tert.- butoxy radicals (from di-tert.-butyl peroxide) at 140° between the short iso-prenic chains in 1-methylcyclohexene, 4-methylhept-3-ene, 2,6-dimethylocta-2, 6-diene, and digeranyl. Cross-linking proceeds efficiently in each case, and the points of union in these isoprene units which become directly joined are not confined to original α-methylenic carbon atoms. Where the reagent radicals are in considerable deficit, e.g., one per two or three of the isoprene units present, those olefin molecules which are attacked become linked together mostly by single unions to form aggregates containing two, three or four molecules; but in the tetraisoprenic olefins the extent to which more than one union is formed between some of the directly linked molecules becomes appreciable. In natural rubber, cross-linking occurs smoothly and to nearly the full extent corresponding to the (in practice restricted) proportion of peroxidic reagent employed. Good vulcanizates can be so obtained in which the tensile stength is found to increase towards a maximum and then to decline rapidly as the degree of cross-linking steadily increases. Thus to obtain vulcanizates of the optimum physical characteristics, the degree of cross-linking must be suitably chosen. The role of the peroxidic reagent is almost entirely non-additive and non-degradative.

scholarly journals Efficient central heating and modern heat sources

2013 ◽  
Vol 7 (4) ◽  
pp. 28-33
Author(s):  
Monika Pawlita
Keyword(s):  
Energy Saving ◽  
Calorific Value ◽  
Cost Effective ◽  
Weather Conditions ◽  
Heating System ◽  
Heat Pumps ◽  
Single Family ◽  
Heating Source ◽  
The Cost ◽  
Family House

Background: The methods of heating houses with system components determine the energy-saving systems. Energy-saving solutions allow to maintain comfortable conditions in the house, while minimizing the cost associated with its operation and at the same time helping to protect natural environment. The examples of such solutions include condensing boilers, heat pumps and solar collectors.Material and methods: The object of the analysis in this paper is typical single-family house occupying the area of 150 m². The comparison of analyzed heating system for a single-family house, including modern energy sources, allows the assessment of the most cost-effective method of heating. Results: Choosing rational method of heating for a single-family house is dictated mainly by economic reasons. The efficiency of the heating sources is also very important. In addition, an important factor is a heating period, which depends on the weather conditions in a given year.Conclusions: The costs of fuel/energy are still growing. Fuel selection is determined mainly by fuel calorific value and the price. To select the type of the heating source one must take into account the cost of kWh of heat.

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