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:

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.

Comparative Study on Effect of Natural and Synthetic Antioxidants on Curing Characteristic and Properties of Different Natural Rubber Origin Compounds

2013 ◽  
Vol 812 ◽  
pp. 93-99
Author(s):  
N.H.H. Shuhaimi ◽  
Nadras Othman ◽  
Hanafi Ismail ◽  
S. Sasidharan
Keyword(s):  
Molecular Weight ◽  
Fatigue Life ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Processing Time ◽  
The Other ◽  
Synthetic Antioxidants ◽  
Compression Set ◽  
Rubber Compounds ◽  
Natural And Synthetic

Effect of natural and synthetic antioxidants on curing characteristic and properties of different natural rubber (NR) origin compounds were performed in this study. The evaluations of natural antioxidant (NA) performance in different NR origins were conducted and the changes in curing characteristic, crosslink density, fatigue life and compression set were recorded. The results indicated that Standard Thailand Rubber (STR) compound has longer processing time in curing characteristic due to a longer chain which is high molecular weight. Because of that, crosslink density, fatigue life cycle (Kc) and compression set (%) of STR compound show better result compared to other origins. On the other hand, NR compounds with NA have show better fatigue and compression set compared with trimethylquinoline (TMQ) especially for STR 5L. Thus, NA can be used as an alternative to the commercial antioxidant in all rubber compounds.

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 :

Synthesis of Some Stable 7-Halo-1,4-thiazepines. Potential Substituted Penam Precursors

1971 ◽  
Vol 49 (23) ◽  
pp. 3866-3876 ◽  
Author(s):  
P. Blondeau ◽  
R. Gauthier C. Berse ◽  
D. Gravel
Keyword(s):  
Dimethyl Acetal ◽  
The Other ◽  
Open Chain ◽  
The Third ◽  
Other Hand

The synthesis of some new 3-carbomethoxy-5-oxoperhydro-1,4-thiazepines is described. Halogenation studies led to the preparation of three potential substituted penam ring precursors: 6,7-dibromo-3-carbomethoxy-5-oxoperhydro-1,4-thiazepine, 3-carbomethoxy-6,7-dichloro-5-oxoperhydro-1,4-thiazepine, and 3-carbomethoxy-7-chloro-6,6-dimethyl-5-oxoperhydro-1,4-thiazepine. Preliminary studies on the reactivity of these α-halothioethers showed that methanolysis to the corresponding methoxy-thiazepines may be carried out in nearly quantitative yields in the case of the first two derivatives; the third compound, on the other hand, led to an open-chain dehydrohalogenated product where C-7 is converted to the corresponding dimethyl acetal.

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 Examining Semitic Rhetoric: A Qur’anic Sciences Perspective

2020 ◽  
Vol 28 (2) ◽  
pp. 127
Author(s):  
Aqdi Rofiq Asnawi ◽  
Idri Idri
Keyword(s):  
Research Methods ◽  
Comparative Research ◽  
Ring Structure ◽  
The Other ◽  
Analytic Method ◽  
Other Hand ◽  
New Interpretation ◽  
Semitic Rhetoric

In his study of Qur’anic structure, Michel Cuypers applied Semitic Rhetoric that has been used to analyze Biblical structure. Despite having received positive responses from Gabriel Said Reynolds and others, Cuypers’ method was criticized by Nicolai Sinai for ignoring rhyme in the Qur’an and overdoing in maintaining the existence of the ring structure in the Qur’an. This paper, then, attempts to examine this analytic method from the perspective of the Qur’anic sciences’ (‘ulu>m al-Qur’a>n). This study aims to determine proportionally the characteristics of the method and the effect it produces by using descriptive-analytic and comparative research methods. This paper argues that there are subjectivity and inconsistency in dividing the text and determining the structure of its composition, as in the study of surah al-Qa>ri‘ah by Cuypers, and an ignorance of the information about reasons for the revelations (asba>b al-nuzu>l) and Prophet’s explanation about verses. However, the application of this method can lead to a new interpretation of the Qur’an, namely by using the information in the Qur’an itself, indicators of wording around it (siya>q), and verse correlation (muna>saba>t). On the other hand, this method supports the authenticity and coherence of the Qur’anic text, which has become a debate among the Orientalists.

Activation processing of cathepsin H impairs recognition by its propeptide

2005 ◽  
Vol 386 (9) ◽  
Author(s):  
Martin Horn ◽  
Lucie Dolečková-Marešová ◽  
Lubomír Rulíšek ◽  
Martin Máša ◽  
Olga Vasiljeva ◽  
...  
Keyword(s):  
General Rule ◽  
The Other ◽  
Binding Region ◽  
Inhibitory Potency ◽  
Inhibitory Interaction ◽  
Chain Formation ◽  
Cysteine Cathepsins ◽  
Other Hand ◽  
Cathepsin H ◽  
Endopeptidase Activity

AbstractFree propeptides are known to function as inhibitors of the parental mature cysteine cathepsins. This general rule, however, does not apply to the aminopeptidase cathepsin H. Screening of propeptide fragments for their inhibitory potency revealed no significant effect on the native mature cathepsin H. On the other hand, inhibitory interaction was established with recombinant cathepsin H that displays endopeptidase activity due to a lack of the mini-chain. This finding suggests that the propeptide-binding region is structurally rearranged during maturation processing and mini-chain formation, which impairs the effective recognition of mature cathepsin H by its own propeptide.

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.

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