Quantitative Characterization of Cure. II. Use of Modulus as a Measure of the State of Cure of Pure-Gum Natural-Rubber Vulcanizates

1952 ◽  
Vol 25 (3) ◽  
pp. 439-446 ◽  
Author(s):  
W. P. Fletcher ◽  
Geoffrey Gee ◽  
S. H. Morrell
Keyword(s):  
Natural Rubber ◽  
The State ◽  
Quantitative Characterization ◽  
Natural Rubber Vulcanizates ◽  
Practical Disadvantage ◽  
Practical Measure

Abstract The purpose of this investigation was to develop methods of measuring state of cure which involved only measurements normally available or very readily made. Swelling measurements, although suitable in theory, suffer the practical disadvantage of being time-consuming, but it is shown that they can be replaced very satisfactorily by modulus at 100 per cent elongation. This is a good practical measure of state of cure for most purposes, and simple corrections are developed which extend its range of usefulness. An easily constructed machine is described for the accurate measure of modulus at small elongations.

Quantitative Characterization of Cure. III. Relation between Compound Viscosity and Vulcanizate Stiffness in Pure-Gum Natural-Rubber Vulcanizates

1952 ◽  
Vol 25 (3) ◽  
pp. 446-454 ◽  
Author(s):  
R. F. Blackwell ◽  
W. P. Fletcher ◽  
Geoffrey Gee
Keyword(s):  
Natural Rubber ◽  
Considerable Reduction ◽  
Test Compound ◽  
Quantitative Characterization ◽  
Mooney Viscosity ◽  
Natural Rubber Vulcanizates ◽  
The Relationship

Abstract The aim of this investigation was to study the dependence of vulcanizate stiffness on the compound Mooney viscosity, and if possible to derive a method by which account could be taken of variations in viscosity in order to reduce the so-called mixing error in batches of test compound. Investigations covering a range of compounds, raw rubbers, and curing times gave results which for the practical range indicated a relation between modulus at 100 per cent elongation and Mooney viscosity. Using the relationship thus established, a method of adjusting modulus results to correspond to a standard Mooney viscosity was derived. Application of the scheme to batches of ACS1 compound mixed from parts of the same lot of homogeneous raw rubber led to a considerable reduction in the range of modulus values.

Structural Characterization of Filled Vulcanizates Part 1. Determination of the Concentration of Chemical Crosslinks in Natural Rubber Vulcanizates Containing High Abrasion Furnace Black

1967 ◽  
Vol 40 (3) ◽  
pp. 866-882 ◽  
Author(s):  
M. Porter
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Volume Fraction ◽  
Exponential Relationship ◽  
Furnace Black ◽  
Simple Linear Relationship ◽  
Chemical Crosslinks ◽  
Natural Rubber Vulcanizates

Abstract The degree to which HAF black restricts the swelling of natural rubber vulcanizates in n-decane has been determined using a vulcanizing system in which the stoichiometry of crosslinking is unaffected by the carbon black. The dependence of the degree of restriction, as measured by the ratio of the volume fractions of rubber in the filled and unfilled vulcanizates swollen to equilibrium, on the concentration of carbon black follows an exponential relationship previously proposed by Lorenz and Parks. This is found to be equivalent to a simple linear relationship between the apparent and actual crosslink concentrations: napparent/nactual=1+Kϕ, where K is a constant characteristic of the filler and φ is its volume fraction in the vulcanizate. The relation has been used to determine actual crosslink concentrations in filled natural rubber vulcanizates. HAF black is found to cause increases of up to 25 per cent in the yield of polymer to polymer crosslinks in conventional sulfur vulcanizing systems, accompanied by changes in rate of cure and of crosslink reversion. All these are small compared with the effect of the filler on many physical properties.

Quantitative Characterization of Cure. I. Relationship between Modulus and Strain of Pure-Gum Natural-Rubber Vulcanizates

1952 ◽  
Vol 25 (3) ◽  
pp. 430-439 ◽  
Author(s):  
R. F. Blackwell
Keyword(s):  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Quantitative Characterization ◽  
Strain Data ◽  
Tentative Explanation ◽  
Natural Rubber Vulcanizates ◽  
The Relationship ◽  
Mooney Equation

Abstract The object of this investigation was to determine whether the relationship between strain (elongation) and modulus is sufficiently close for one to be calculated from the other. Stress-strain data have been recorded for loads of 2–10 kg. per sq. cm. for a series of ACS1 and other pure-gum compounds. It is shown that the strain at a fixed stress (5 kg. per sq. cm.) is uniquely related to the load required to produce an elongation of 100 per cent. A tentative explanation of this observation is given in terms of the Mooney equation for the stress-strain curve. It is shown that the second constant of this equation does not vary greatly from rubber to rubber.

The CBS-Accelerated Sulfuration of Natural Rubber and Cis-1,4-Polybutadiene

1972 ◽  
Vol 45 (1) ◽  
pp. 182-192 ◽  
Author(s):  
T. D. Skinner
Keyword(s):  
Natural Rubber ◽  
Zinc Sulfide ◽  
Chain Length ◽  
Network Formation ◽  
Reaction Times ◽  
Substantial Fraction ◽  
Chemical Complexity ◽  
Cure Time ◽  
Natural Rubber Vulcanizates

Abstract The results of characterization of the natural rubber vulcanizates are consistent with the results of characterization of the sulfidic products from 2-methylpent-2-ene. In both the model olefin system and the rubber system the initially formed crosslinks are polysulfidic but these are subsequently reduced to di- and monosulfidic crosslinks as the cure time is increased. Similar amounts of zinc sulfide are formed during the sulfuration of 2-methylpent-2-ene and during the vulcanization of natural rubber. The efficiency of sulfur utilization for crosslinking in natural rubber is approximately half that in comparable sulfurations of 2-methylpent-2-ene, i.e. approximately twice as many sulfur atoms are needed to obtain a chemical crosslink in natural rubber as are needed to obtain a crosslink in 2-methylpent-2-ene. This is presumed to be a consequence of the intra-molecular sulfuration that occurs in natural rubber. There is no evidence to indicate the presence of vicinal crosslinks in the natural rubber vulcanizates. Hence in agreement with the views of other workers it is concluded that the crosslinks present in accelerated sulfur vulcanizates of natural rubber are tetrafunctional and dialkenyl. The results of the characterization of the polybutadiene vulcanizates are not fully supported by the results of the model olefin studies. In the vulcanization of polybutadiene the initially formed crosslinks are polysulfidic. As vulcanization proceeds, the chemical complexity of the network increases. After long reaction times, however, no significant amount of monosulfidic crosslinks are present in the network and very little of the reacted sulfur is present in the form of zinc sulfide. Nitrogen analyses of the polybutadiene vulcanizates showed that a substantial fraction of the accelerator, equivalent to 80–90% of the available 2-thiobenzothiazole groups, become combined in the network during vulcanization. It is proposed that the combination of accelerator with polybutadiene prevents the desulfuration of dialkenyl polysulfides to dialkenyl monosulfides (the normally observed pathway of accelerated sulfuration of natural rubber) and allows vicinal crosslinking to proceed. Some support for this proposal is that vicinal crosslinks and a substantial amount of nitrogenous product are formed during the accelerated sulfuration of cyclohexene. The findings of Gregg and Katrenick on the MBTS accelerated sulfuration of cis-cis-1,5-cyclooctadiene are also consistent with this proposal. The nitrogen analyses of the polybutadiene vulcanizates indicate that very little of the accelerator is permanently combined in the network during the initial stages of network formation. Hence by comparison with the observed pattern of sulfuration of hex-3-ene, where it was shown that negligible amounts of nitrogenous product are present, it is proposed that dialkenyl (tetrafunctional) polysulfidic crosslinks are initially introduced into the polybutadiene network. The polysulfidic crosslinks then presumably undergo desulfuration reactions leading to dialkenyl crosslinks of reduced sulfur chain length until the desulfurating agent is, in effect, removed from the system by the 2-thio-benzothiazole groups becoming combined in the network. Once most of these groups have combined, after ca. 60 min. at 140° C, the desulfuration reactions are probably less important than the reactions leading to vicinal crosslinking, and it is likely that a well cured-polybutadiene vulcanizate contains a substantial fraction of vicinal crosslinks.

PREPARATION AND CHARACTERIZATION OF BROMINATED NATURAL RUBBER APPLIED IN SILICA-FILLED NATURAL RUBBER VULCANIZATES

2016 ◽  
Vol 89 (3) ◽  
pp. 406-418 ◽  
Author(s):  
Nuchanart Onchoy ◽  
Pranee Phinyocheep
Keyword(s):  
Natural Rubber ◽  
Bromine Atom ◽  
Proton Nuclear Magnetic Resonance ◽  
Strong Emission ◽  
X Ray ◽  
Rubber Compounds ◽  
Silica Filler ◽  
Natural Rubber Vulcanizates

ABSTRACT Functionalization of NR with a bromine atom was developed and explored for its application in a silica-reinforced NR system. Two possible pathways were investigated: the direct addition of a bromine atom using N-bromosuccinimide (NBS) with FeCl2 as a catalyst in the latex phase (NR–Br); and an indirect method using a ring opening of epoxidized natural rubber (ENR) with 2-bromopropionic acid (ENR–Br). The chemical structure, including determination of the bromine contents, was analyzed with proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. The occurrence of bromine in NR–Br was confirmed using scanning electron microscopy with energy dispersive x-ray spectroscopy. Strong emission peaks for Br Kα at 1.5 eV was evidenced. Moreover, glass transition temperature of modified NRs increased after bromination. Two types of brominated NR, that is, NR–Br and ENR–Br containing 2 and 4 mol% of bromine function, respectively, were used in a range of 1–5 phr in the silica-reinforced NR system with silica loading of 10 and 30 phr. Both cure and mechanical properties of the rubber compounds were investigated. The incorporation of the bromine function in NR of both ENR–Br and NR–Br enhanced the cure reactivity of the NR–silica vulcanization system. The modified NRs may have a role as a coupling agent between the NR and the silica filler.

Synthesis and characterization of water swellable natural rubber vulcanizates

2013 ◽  
Vol 49 (5) ◽  
pp. 1098-1110 ◽  
Author(s):  
Charoen Nakason ◽  
Yeampon Nakaramontri ◽  
Azizon Kaesaman ◽  
Wiyong Kangwansukpamonkon ◽  
Suda Kiatkamjornwong
Keyword(s):  
Natural Rubber ◽  
Synthesis And Characterization ◽  
Natural Rubber Vulcanizates

Characterization of the natural rubber vulcanizates obtained by different accelerators

1996 ◽  
Vol 32 (12) ◽  
pp. 1395-1401 ◽  
Author(s):  
J. Travas-sejdic ◽  
J. Jelencic ◽  
M. Bravar ◽  
Z. Fröbe
Keyword(s):  
Natural Rubber ◽  
Natural Rubber Vulcanizates

Structure and Properties of Natural Rubber and Modified Montmorillonite Nanocomposites

2003 ◽  
Vol 76 (2) ◽  
pp. 406-418 ◽  
Author(s):  
Rathanawan Magaraphan ◽  
Woothichai Thaijaroen ◽  
Ratree Lim-ochakun
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Clay Content ◽  
Silicate Layer ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Silicate Layers ◽  
High Structure ◽  
Natural Rubber Vulcanizates

Abstract Montmorillonite clay was organically modified by primary and quaternary ammonium salts (having C12-C18). The modified clay was added to a solution of natural rubber in toluene at various contents. Characterization of the structure of the nanocomposites was performed by using x-ray diffraction and transmission electron microscope. The results showed that the silicate layers of the clay were expanded so that the exfoliated nanocomposites were obtained at clay content below 10 phr; above that the nanocomposites became partially exfoliated. Moreover, long primary amine showed more improved mechanical properties than the quaternary one (at the same carbon numbers). The longer organic modifying agents resulted in better expansion of silicate layer distance indicating more intercalation of natural rubber molecules in between clay galleries. The curing properties were also improved. It was found that a small loading of 7 phr is enough to bring good mechanical properties in comparison to those of high structure silica filled and carbon black filled natural rubber vulcanizates.

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