Some Properties of Vulcanized Rubber under Strain. Degree of Crystallization as Calculated from Temperature Coefficient of Elastic Tension

1951 ◽  
Vol 24 (4) ◽  
pp. 845-852
Author(s):  
B. B. S. T. Boonstra
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Thermodynamic Calculation ◽  
Energy Change ◽  
Thermodynamic Evaluation ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Calorimetric Measurements ◽  
Degree Of Crystallization

Abstract To elucidate the crystallization phenomenon in natural rubber and to investigate the applicability of thermodynamic calculation to measurements of the elastic tension as a function of temperature, it seemed necessary to check whether crystallization determined by x-ray analysis (and combined with density) lined up reasonably with the percentage of crystallization computed from the energy change found by applying thermodynamics to stretched vulcanized rubber) on stretching. Calorimetric measurements were desirable, as no accurate figures are available for the heat of crystallization of rubber crystallites. The heat of melting of rubber crystallites was determined to about 66 joules per gram, which is of the same order as that of isoprene. The spreading in the results was large; the determination is based on the degree of crystallization found by x-ray analysis of raw rubber. The heat of crystallization on stretching, found by thermodynamic evaluation of the elastic tension and its temperature coefficient, is combined with the value of 66 joules for the heat of melting of the pure rubber crystallites. The degree of crystallization calculated in this way agrees reasonably well with the direct x-ray measurements of Goppel and Arlman. Crystallization as determined by x-ray analysis and that responsible for the energy change on stretching are much the same. This also means that thermodynamic evaluation of the change of stress with temperature is justified if pufficient relaxation of stress has taken place.

The Degree of Crystallinity in Natural Rubber. IV. The Degree of Crystallization in Frozen Raw Rubber and Stretched Vulcanized Rubber

1950 ◽  
Vol 23 (2) ◽  
pp. 310-319 ◽  
Author(s):  
J. M. Goppel ◽  
J. J. Arlman
Keyword(s):  
Natural Rubber ◽  
Experimental Evidence ◽  
Theoretical Investigation ◽  
Degree Of Crystallinity ◽  
X Ray ◽  
Crystallization Point ◽  
Vulcanized Rubber ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract An improved x-ray technique has been worked out to determine the degree of crystallinity in natural rubber. Inaccuracies which sometimes occur in quantitative x-ray measurements were eliminated, and it has been shown that the amount of crystalline rubber, both in frozen samples of raw rubber and in stretched vulcanized rubber, could be determined fairly accurately. More experiments were carried out and the results are described. These results, which confirm the current views on the problem of crystallization, point to relatively low degress of crystallization, even in highly stretched rubber, and they agree with some other experimental evidence and with a recent theoretical investigation.

X-Ray Study of the Crystallization of Vulcanized Rubber during Stretching. II.

1951 ◽  
Vol 24 (3) ◽  
pp. 541-549 ◽  
Author(s):  
V. I. Kasotochkin ◽  
B. V. Lukin
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Crystal Formation ◽  
Oxidative Destruction ◽  
Ray Method ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Crystal Content

Abstract 1. The relation between the crystal content of stretched vulcanizates to the time of vulcanization for different mixtures of natural rubber was studied by the x-ray method. 2. It was shown that the tensile strength is a function of the crystal content of the stretched vulcanizate and of the total time of vulcanization. 3. The nature of crystal formation depends on the following factors: changes of density of the network of sulfur bridges, their distribution, the degree of oxidative destruction, and the quantity of bound sulfur which has not formed bridges between the molecular chains.

The Degree of Crystallinity in Natural Rubber. III. Correlation between X-Ray and Density Measurements

1950 ◽  
Vol 23 (2) ◽  
pp. 306-310 ◽  
Author(s):  
J. J. Arlman
Keyword(s):  
Natural Rubber ◽  
Unit Cell ◽  
Degree Of Crystallinity ◽  
X Rays ◽  
Density Measurements ◽  
X Ray ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract In 1925 Katz discovered the crystallization of stretched rubber. In the following years several investigators tried to determine the structure of rubber crystallites. The densities of the rubber crystallites calculated from the results of these investigations varied strongly. The results of x-ray and density measurements on crude rubber carried out by the author can be made to correspond only when the latter are based on the unit cell of Bunn. It is shown by experiment that, to measure the correct degree of crystallization, it is necessary to use monochromatic x-rays.

An X-Ray Study of the Proportion of Crystalline and Amorphous Components in Stretched Rubber

1941 ◽  
Vol 14 (3) ◽  
pp. 555-571 ◽  
Author(s):  
J. E. Field
Keyword(s):  
Physical Properties ◽  
Structural Characteristics ◽  
Quantitative Measure ◽  
Crystalline Material ◽  
Amorphous Halo ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Maximum Value ◽  
Degree Of Crystallization ◽  
And Performance

Abstract A method is described for obtaining a quantitative measure of crystalline hydrocarbon present in stretched rubber samples by comparing the intensities of the diffraction spots and the amorphous halo appearing in the x-ray diagrams. This method has been applied to a study of the crystallinity of stretched vulcanized rubber as it is affected by different vulcanization accelerators, variations in extension, temperature, and cure. To illustrate a connection between the physical performance of a rubber vulcanizate and its degree of crystallization, measurements were made of the relation of crystallinity to creep when the rubber was stretched to different initial elongations under constant loads. The creep as a function of the elongation has a maximum value at the same intermediate elongation for which crystallization becomes appreciable. At higher elongations, increased crystallinity results in a diminution of the creep. The ultimate strength and extensibility generally associated with stretched vulcanized rubber is the result of the combined effect of primary valence cross-linkages formed by vulcanization and the formation of crystallites caused by stretching. Crystallization is an important factor in maintaining the relatively high strengths of vulcanizates having a greater range of extensibilities. In general, the physical properties and performance of vulcanized rubber is related to the amount of crystalline material formed on stretching, which depends on the structural characteristics of the vulcanizate.

The Degree of Crystallinity in Natural Rubber. V. A Discussion of the X-Ray Results on Natural Rubber in Connection with the Work of Flory, Gee and Wildschut

1950 ◽  
Vol 23 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J. J. Arlman ◽  
J. M. Goppel
Keyword(s):  
Natural Rubber ◽  
Physical Meaning ◽  
Average Length ◽  
Degree Of Crystallinity ◽  
Recent Theory ◽  
X Ray ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract A recent theory, developed by Flory, makes it possible to calculate the degree of crystallization from thermodynamical measurements if certain parameters are properly evaluated. Such evaluation is possible by combining Wildschut's thermodynamical measurements with the x-ray results presented in previous papers. Thus the average length of molecule chains between cross-linkages can be derived; it closely corresponds to the results of swelling measurements carried out by Gee. Other parameters are also evaluated in agreement with their physical meaning.

Influence of Agitation Equipment on Reinforcing Effect and Dispersion State of Cellulose Nano-Fibers in Natural Rubber

2017 ◽  
Vol 754 ◽  
pp. 23-26
Author(s):  
Sho Omori ◽  
Takayuki Morita ◽  
Koki Matsumoto ◽  
Asahiro Nagatani ◽  
Tatsuya Tanaka
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Reinforcing Effect ◽  
X Ray ◽  
Centrifugal Mixer ◽  
Vulcanized Rubber ◽  
Biomass Resource ◽  
Dispersion State ◽  
Biomass Resources ◽  
Internal Mixer

There are many rubber products like tires, and reinforcing agents derived from fossil resources such as carbon black (CB) are used for them. However, in recent years, conversion to biomass resources has been demanded due to problems such as depletion of fossil resources. Therefore, we have studied the composite of natural rubber (NR) reinforced with cellulose nano-fibers (CNF), which has attracted attention as a next-generation biomass resource. It is very difficult to uniformly disperse CNF in the conventional kneading process. Therefore, it is preferable to agitate CNF in NR latex. Then, it is necessary to study the optimum agitation equipment of CNF. In this study, the reinforcing effect by CNF was investigated when the agitation equipment was changed. Agitation of NR latex and CNF was carried out by a hand, a homogenizer, a dispersion mixer, and planetary centrifugal mixer. Thereafter, agitated materials were dried and masterbatches were made. Furthermore, the masterbatch and vulcanizing agents were kneaded using an internal mixer. Tensile test and X-ray CT observation of the prepared vulcanized rubber sheets were carried out to evaluate the reinforcing effect and dispersion state of CNF. As a result, the planetary centrifugal mixer was most useful to uniformly disperse CNF.

On the Degree of Crystallinity in Natural Rubber. I. An Improved Method to Determine the Degree of Crystallization in Rubber

1948 ◽  
Vol 21 (4) ◽  
pp. 773-783 ◽  
Author(s):  
J. M. Goppel
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Present Article ◽  
Degree Of Crystallinity ◽  
Improved Method ◽  
Ray Method ◽  
X Ray ◽  
Degree Of Crystallization ◽  
The Degree Of Crystallinity

Abstract There are indications that the degree of crystallization in high polymeric substances is of importance in studying mechanical properties. With regard to the crystallization of rubber, few measurements have been made, mainly by Field. The results, however, are in contradiction to estimates of an earlier date, and therefore the necessity was felt to have them checked. An x-ray method, in some respecta differing from that of Field, was developed, the results of which diverged considerably from the figures reported by Field. The present article deals with a description of the method.

Acetylene Polymers and Their Derivatives. II. A New Synthetic Rubber: Chloroprene and Its Polymers

1932 ◽  
Vol 5 (1) ◽  
pp. 7-29
Author(s):  
Wallace H. Carothers ◽  
Ira Williams ◽  
Arnold M. Collins ◽  
James E. Kirby
Keyword(s):  
Particle Size ◽  
Natural Rubber ◽  
Petroleum Hydrocarbons ◽  
Tetracarboxylic Acid ◽  
Closed Vessel ◽  
X Ray Diffraction ◽  
Aqueous Emulsion ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Synthetic Rubber

Abstract Chloro-2-butadiene-1,3 (chloroprene) is described and its structure established through reactions leading to its conversion into butane-α, β,γ,δ-tetracarboxylic acid, and into β-chloroanthraquinone. Within ten days under ordinary conditions in a closed vessel containing a little air, chloroprene spontaneously changes into a transparent, resilient, strong, non-plastic, elastic mass resembling vulcanized rubber. This product is called μ-polychloroprene. By interrupting the polymerization before it has proceeded to completion one obtains a soft, plastic product (α-polymer) that resembles unvulcanized rubber. Under the action of heat the α-polymer rapidly changes to the μ-polymer. Other polymers of chloroprene described are volatile (β-) polymer, granular (ω-) polymer, and balata-like polymer. The structures of the polymers are discussed as well as the effect of conditions on the formation of each type. Unlike any previously described synthetic rubbers, μ-polychloroprene resembles natural rubber in the fact that when it is stretched its x-ray diffraction pattern shows a point diagram. The transformation of chloroprene into μ-polychloroprene occurs very rapidly in aqueous emulsion. The resulting product constitutes a synthetic (vulcanized) latex. It has a much smaller particle size than natural latex and it penetrates porous materials more readily. Chloroprene can also be polymerized in the pores of porous or bibulous materials. The materials thus become intimately impregnated with synthetic rubber. Compared with natural rubber the new synthetic rubber is more dense, more resistant to absorption or penetration by water, less strongly swelled by petroleum hydrocarbons and less permeable to many gases. It is much more resistant to attack by oxygen, ozone, hydrogen chloride, hydrogen fluoride and many other chemicals.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

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