The Cyclization of Natural Rubber

1963 ◽  
Vol 36 (4) ◽  
pp. 1005-1018 ◽  
Author(s):  
D. F. Lee ◽  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Natural Rubber ◽  
Empirical Formula ◽  
Chemical Reactivity ◽  
Bond Formation ◽  
The Other ◽  
Acid Catalysts ◽  
Double Bonds ◽  
Partial Loss ◽  
Other Hand

Abstract The resinification of natural rubber by acid catalysts has been investigated since the beginnings in 1937 of interest in the chemical reactivity of rubber. During the reaction there is a partial loss in unsaturation but no change in the empirical formula of the rubber, C5H8. No general agreement exists on the decrease in unsaturation, values from 40 to 90% of the original having been quoted. (see PDF for diagram) The reduction in the number of double bonds has been attributed to an intramolecular bond formation leading to formation of cyclic structures. D'Ianni, Naples, Marsh, and Zarney have suggested the generally favored structure I, formed by reaction between pairs of adjacent isoprene units of the rubber chain. Van Veersen on the other hand, has proposed the more highly condensed polycyclic structure II. with the cyclization proceeding along the chain to involve a number of adjacent isoprene groups.

Reactions of macroions with ester and carboxylic groups of polymers

1987 ◽  
Vol 52 (9) ◽  
pp. 2194-2203
Author(s):  
Miloslav Kučera ◽  
Dušan Kimmer ◽  
Karla Majerová ◽  
Josef Majer
Keyword(s):  
Maleic Anhydride ◽  
Acrylic Acid ◽  
Methyl Methacrylate ◽  
Bond Formation ◽  
Covalent Bond ◽  
The Other ◽  
Poly Methyl Methacrylate ◽  
Other Hand ◽  
Carboxylic Groups ◽  
Poly Acrylic Acid

In the reaction of dianions with poly(methyl methacrylate), only an insignificant amount of insoluble crosslinked product is obtained. If, however, the concentration of grafting dianions approaches that of ester groups, the amount of poly(methyl methacrylate) which may thus be crosslinked becomes quite significant. Dications, too, can bring about crosslinking of only an insignificant number of poly(methyl methacrylate) chains. Carboxylic groups in poly(acrylic acid) react with dianions and dications in an anhydrous medium similarly to ester groups. On the other hand, in the presence of a cocatalytic amount of water dications are more readily bound to carboxylic groups, forming a covalent bond. The relatively highest efficiency was observed in the bond formation between dication and the poly[styrene-alt-(maleic anhydride)], both in an anhydrous medium and in the presence of H2O.

Borierungsreaktionen an den N-Oxiden und -Iminen ungesättigter Stickstoffbasen / Boration Reactions with the N-Oxides and m-Imines of Unsaturated Nitrogen Bases

1980 ◽  
Vol 35 (5) ◽  
pp. 568-577 ◽  
Author(s):  
Peter Paetzold ◽  
Günther Schimmel
Keyword(s):  
Nitrous Oxide ◽  
Liquid Phase ◽  
Gas Phase ◽  
The Other ◽  
Double Bonds ◽  
Similar Reduction ◽  
Nitrogen Bases ◽  
Other Hand

1,3-Dipolar reagents with an unsaturated CNO- or CNN-skeleton undergo 1,3-organoboration by triorganoboranes. On the other hand, the unsaturated NNO-skeletons in azoxybenzene or nitrous-oxide are reduced to the corresponding NN-fragment by trialkylboranes. The 1,3-addition of aminoborane Cl2BNMe2 to the aldimineoxide PhHC = NMe-0 represents one of the rare examples of analogous reactivity of BN- and CC-double bonds. O-Borylhydroxylamines PhHCR-NMe-OBR2 are reduced by BR′3 to PhHCR-NMe-BR′2 and R′0-BR2. Similar reduction products are isolated from liquid-phase thermolysis of PhHCEt-NMe-OBEt2 (16), whereas gas-phase thermolysis of 16 gives PhCH = NMe, (EtBO)3, and C4H10.

The Load Dependence of Side Force and Self-Aligning Torque of Pneumatic Tires

1970 ◽  
Vol 43 (5) ◽  
pp. 995-1004
Author(s):  
A. Schallamach
Keyword(s):  
Experimental Data ◽  
Natural Rubber ◽  
The Other ◽  
Research Association ◽  
Side Force ◽  
Load Dependence ◽  
Other Hand ◽  
Force Curves ◽  
Theoretical Side ◽  
Pneumatic Tires

Abstract A conclusion to be drawn from this analysis of the load dependence of side force and self-aligning torque of pneumatic tires is that agreement between experimental and theoretical side force curves does not necessarily prove the soundness of the theory. On the other hand, even an inadequate theory is successful in suggesting a predictable and useful interrelation between load and slip dependence of the side force. Figure 4 demonstrates that quite a primitive transform of experimental data can lead to a unified presentation of its load and slip dependence although the resulting curve deviates quantitatively from theory in this particular case. This work forms part of a program of research undertaken by the Natural Rubber Producers' Research Association.

Thermomechanical Effects Associated With Crystallization of Rubber Under Stretch and During Slow Extension

1997 ◽  
Vol 119 (3) ◽  
pp. 298-304 ◽  
Author(s):  
Mehrdad Negahban
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Thermodynamic Model ◽  
The Other ◽  
Equilibrium Stress ◽  
Rubber Sample ◽  
Other Hand ◽  
The Difference ◽  
Thermomechanical Effects

A natural rubber sample which crystallizes after stretching normally shows stress relaxation associated with this crystallization and normally ends up at a stress lower than that of the fully amorphous rubber before crystallization. On the other hand, a natural rubber sample which crystallizes during stretching becomes more rigid as a result of the crystallization and the stress required to extend it to a given stretch increases substantially above the stress needed to extend the fully amorphous rubber to the same elongation. Even though the former effect has been modeled and studied by the likes of Flory (1947), the latter effect has not yet been properly modeled or studied. The difference between crystallization during or after stretching will be studied in this article based on a thermodynamic model developed by the author to capture the thermomechanical effects of crystallization in natural rubber. The two limit cases of very rapid and very slow extension to a given stretch are singled out for comparison of the equilibrium stress.

Behavior of Different Fractions of Purified Hevea Rubber during Vulcanization

1949 ◽  
Vol 22 (4) ◽  
pp. 994-999
Author(s):  
G. T. Verghese
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
The Other ◽  
Stress Strain ◽  
Strain Behavior ◽  
Other Hand ◽  
The Difference

Abstract Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :

The Structure of Synthetic Types of Rubber. Polychloroprenes

1937 ◽  
Vol 10 (1) ◽  
pp. 126-134 ◽  
Author(s):  
A. L. Klebanskii ◽  
V. G. Vasil'eva
Keyword(s):  
Natural Rubber ◽  
Levulinic Acid ◽  
Ring Structure ◽  
The Other ◽  
Exact Methods ◽  
Open Chain ◽  
Chain Formation ◽  
Other Hand ◽  
Decisive Evidence ◽  
Natural And Synthetic

Abstract Ozonization is one of the most successful and most exact methods for determining the structure of rubber. It was this method which was first used by Harries and his numerous collaborators for determining the structures of various types of natural and synthetic rubbers. By ozonizing solutions of natural rubber, Harries obtained ozonides, the decomposition of which yielded levulinic acid and levulinic aldehyde. This was proof that the combination of isoprene residues in the rubber molecule is in the 1,4-1,4 position, and it also showed the nature of the base molecules of rubber and the manner in which they are united in chain formation. On the other hand, these investigations did not give any decisive evidence as to whether the rubber molecule is an open chain or has a ring structure. At the beginning of his investigations in this field, Harries assigned to the hydrocarbon which is the fundamental constituent of the rubber molecule the following formula:

Failure Properties of Natural Rubber Double Networks

1995 ◽  
Vol 68 (1) ◽  
pp. 124-131 ◽  
Author(s):  
P. G. Santangelo ◽  
C. M. Roland
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
The Other ◽  
Direction Transverse ◽  
Mechanical Fatigue ◽  
Other Hand ◽  
Failure Properties ◽  
The Difference ◽  
Double Networks

Abstract When measured parallel to the curing deformation, double networks of natural rubber have a higher modulus than single networks of equal crosslink density. The difference is greater at higher strains. Despite the higher modulus, the mechanical fatigue lifetimes of double networks were found to be as much as a factor of ten higher than for conventionally crosslinked NR. The double network's tensile strength, on the other hand, was slightly lower. In contrast to these results, the modulus and tensile strength in the direction transverse to the curing strain are minimally affected by the presence of a composite network.

scholarly journals Chemical Reactivity of Isoproturon, Diuron, Linuron, and Chlorotoluron Herbicides in Aqueous Phase: A Theoretical Quantum Study Employing Global and Local Reactivity Descriptors

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Luis Humberto Mendoza-Huizar
Keyword(s):  
Free Radical ◽  
Aqueous Phase ◽  
Chemical Reactivity ◽  
The Other ◽  
Reactivity Descriptors ◽  
Local Reactivity ◽  
Other Hand ◽  
Aqueous Conditions ◽  
Global And Local ◽  
Local Reactivity Descriptors

We have calculated global and local DFT reactivity descriptors for isoproturon, diuron, linuron, and chlorotoluron herbicides at the MP2/6-311++G(2d,2p) level of theory. The results suggest that, in aqueous conditions, chlorotoluron, linuron, and diuron herbicides may be degraded by elimination of urea moiety through electrophilic attacks. On the other hand, electrophilic, nucleophilic, and free radical attacks on isoproturon may cause the elimination of isopropyl fragment.

scholarly journals ANALISIS KETERKAITAN PENDAPATAN DENGAN MUTU BOKAR YANG DIHASILKAN PETANI KARET RAKYAT DI PROVINSI JAMBI

2018 ◽  
Vol 1 (1) ◽  
pp. 19-37
Author(s):  
Dompak Napitupulu ◽  
Endy Efran
Keyword(s):  
Natural Rubber ◽  
Secondary Data ◽  
The Other ◽  
Average Price ◽  
Smallholder Farmer ◽  
Weak Correlation ◽  
Rubber Market ◽  
Average Grade ◽  
Other Hand

ome research showed that the quality of natural rubber produced by smallholder in Jambi Province is getting worst, while the international rubber market on the other hand needs higher quality. This research is aimed to find out whether the natural rubber price received by farmer is linked to the rubber quality marketed in Jambi Province. The research was undertaken in four regency main rubber producing samples. Data was both primary and secondary data. The research found that the natural rubber was marketed in monopolistic manner, in which the natural rubber price was mainly controlled by trader. Majority (81,33 %) smallholder farmer sold their natural rubber to certain local trader. The natural rubber quality was range from low (50.09 %) to medium (76,14 %) grade, with the average grade was 62,27 %. Furthermore, the research was also showed that the price ranges from Rp. 5000/Kg to Rp. 10.800/Kg and the average price was Rp. 7.499,02/Kg. The research was also found that there is a weak correlation between price paid to the farmer and the natural rubber quality sold by the farmer in Jambi Province.

scholarly journals Indonesian natural rubber export potential in European market

2021 ◽  
Vol 305 ◽  
pp. 02003
Author(s):  
Aura Dhamira ◽  
Imade Yoga Prasada
Keyword(s):  
Natural Rubber ◽  
World Market ◽  
The Other ◽  
European Countries ◽  
Competitive Advantages ◽  
Other Hand ◽  
The World ◽  
European Markets ◽  
Star Position ◽  
Export Product

Indonesia is one of the largest natural rubber exporters in the world. On the other hand, the potential for natural rubber in the world market is enormous. The Asian continent is the largest market for Indonesian natural rubber, followed by American and European markets. Currently there have been many studies on the competitiveness of Indonesian natural rubber exports to the international market, but so far there has not been much research on the competitiveness and potential of rubber exports specifically to European countries. This study aims to determine the competitiveness and the potential of Indonesian natural rubber in European countries, namely Germany, France, and Spain. The method used in this study is descriptive analytics, meanwhile Revealed Comparative Advantage (RCA) was used to determine Indonesia’s competitiveness in each of the partner countries, on the other hand Export Product Dynamic (EPD) was used to determine the performance of Indonesian natural rubber in partner countries. The RCA index shows that Indonesia has competitive advantages in the partner countries, and the EPD matrix indicated that Indonesia is in a rising star position in the German, French and Spanish markets. To strengthen this position, Indonesia needs to increase their export value through the increase in production.

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