Effect of Crosslink Structure on Properties of Natural Rubber

1970 ◽  
Vol 43 (3) ◽  
pp. 664-686 ◽  
Author(s):  
Joginder Lal
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Chemical Nature ◽  
Relative Concentration ◽  
Oxygen Absorption ◽  
Dicumyl Peroxide ◽  
High Tensile Strength ◽  
Failure Envelope ◽  
Chemical Crosslinks ◽  
Absorption Characteristics

Abstract Natural rubber-sulfur-diphenylguanidine vulcanizates were allowed to react with triphenylphosphine under nitrogen to convert polysulfidic crosslinks principally to di- and monosulfidic crosslinks and to assess the effect of this change in the chemical nature of the crosslinks on tensile strength, flex life, and oxygen absorption characteristics. The vulcanizates were analyzed for organically combined sulfur and polysulfidic sulfur. Data obtained by this approach were treated statistically and showed that polysulfidic crosslinks are not essential for attaining high tensile strength or superior flex life. In another approach, polysulfidic crosslinks were introduced into dicumyl peroxide-cured vulcanizates containing carbon-carbon crosslinks to yield two-stage vulcanizates. Data for these vulcanizates fitted the curve of tensile strength as a function of 300% modulus for the precursor samples. It was further shown that the reduced failure envelope for natural rubber gum vulcanizates is independent of the type and relative concentration of chemical crosslinks. An interesting observation was made that the tensile strengths of dicumyl peroxide-cured samples were enhanced on extraction with acetone. Vulcanizates which had lost 95–99 per cent of their polysulfidic sulfur due to reaction with triphenylphosphine exhibited significantly lower rates of oxygen absorption at 100° C as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.

The Effect of Crosslink Structure on the Tensile Strength and Oxygen Absorption Characteristics of Natural Rubber Vulcanizates

1969 ◽  
Vol 42 (5) ◽  
pp. 1412-1419
Author(s):  
J. Lal
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Chemical Nature ◽  
Oxygen Absorption ◽  
High Tensile Strength ◽  
Modulus Curve ◽  
Natural Rubber Vulcanizates ◽  
Absorption Characteristics ◽  
Control Samples

Abstract The chemical nature of crosslinks in natural rubber—sulfur—diphenylguanidine vulcanizates was modified by reaction with triphenylphosphine under nitrogen to determine the effect of this change on tensile strength and oxygen absorption characteristics of the vulcanizates. The vulcanizates were characterized by organically combined sulfur and polysulfidic sulfur. Polysulfidic crosslinks, i.e., crosslinks containing three or more sulfur atoms in the crosslink, were found not to be essential for the attainment of high tensile strength in these vulcanizates. Data for the samples which had lost significant amounts of polysulfidic crosslinks by reaction with triphenylphosphine fitted the tensile strength versus 300% modulus curve for the control samples. Vulcanizates which had been reacted with triphenylphosphine for 16 days at 80° C, had lost 95–99.6% of their polysulfidic sulfur. These triphenylphosphine-reacted vulcanizates exhibited significantly lower rates of oxygen absorption at 100° C as compared to the untreated vulcanizates. This suggests that polysulfidic structures in the original vulcanizates act as oxidation initiators.

High Quality Foams from NIR Latex

1966 ◽  
Vol 39 (3) ◽  
pp. 755-762
Author(s):  
S. N. Angove ◽  
E. S. Graham ◽  
G. Hilditch ◽  
R. A. Stewart ◽  
F. L. White
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Natural Rubber ◽  
Compression Modulus ◽  
High Modulus ◽  
High Tensile Strength ◽  
High Quality ◽  
Foam Rubber ◽  
Oil Resistance ◽  
Low Temperature Flexibility

Abstract Foam rubber properties have been measured for NIR latexes as a function of acrylonitrile content of the copolymer and as a function of ratio of NIR latex to NR latex and high modulus SBR latex. Foam rubber made from NIR latex had good aging and oil resistance, combined with the desirable high tensile strength and elongation characteristic of natural rubber foam. Resilience and low temperature flexibility of NIR foams were found to be lower than that achieved with foams of either SBR or NR latexes. Although compression modulus of NIR foam was lower than that of a high modulus SBR foam and approximately equivalent to that of NR foam, it was effectively increased by the addition of either such SBR latex or a high-styrene resin latex.

Polybutadienes of Controlled Cis, Trans and Vinyl Structures

1959 ◽  
Vol 32 (2) ◽  
pp. 614-627 ◽  
Author(s):  
J. N. Short ◽  
G. Kraus ◽  
R. P. Zelinski ◽  
F. E. Naylor
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Natural Rubber ◽  
Physical Properties ◽  
Abrasion Resistance ◽  
High Hardness ◽  
High Modulus ◽  
High Tensile Strength ◽  
Truck Tires ◽  
Wide Range

Abstract The physical properties of polybutadiene vulcanizates have been measured as a function of polymer microstructure. Although the over-all properties of any one polybutadiene are determined by the relative ratio of cis, trans and vinyl units in the polymer chain, marked changes in physical properties do not occur until a relatively pure configuration is approached or unless the raw polymer displays crystallinity. Thus, polybutadienes containing more than 85 per cent cis, trans or vinyl units are characteristically different from each other and the differences are accentuated as the isomeric forms approach 100 per cent of a given configuration. Polybutadiene of 95 per cent cis configuration displays very low heat generation and high resilience (equaling natural rubber in these properties) and excellent abrasion resistance. trans-Polybutadiene (90 per cent), a crystalline plastic in the raw state, becomes rubbery after vulcanization. Gum vulcanizates possess high tensile strength, and tread stocks display high modulus and tensile strength, high hardness and fair hysteresis properties. Vulcanizates of amorphous 94 per cent vinyl polybutadiene are characterized by fair tensile properties, low hysteresis, and poor low temperature properties. Crystalline syndiotactic polybutadiene, 70 per cent vinly, displays much higher gum and tread tensile strengths than its amorphous counterpart. Amorphous polybutadienes containing less than 70–80 per cent of any one configuration are generally similar in most properties, and resemble emulsion polybutadiene in many respects. The wide range of properties of the various polybutadienes makes them suitable for many applications. cis-Polybutadiene is an excellent tire rubber, which has given as much as 40 per cent greater abrasion resistance than natural rubber in passenger tire tests. Heavy duty 10:00 × 20 truck tires fabricated with a 1:1 blend of cis-polybutadiene and natural rubber in the treads have given slightly better abrasion ratings and lower running temperatures than control tires fabricated entirely from natural rubber. Amorphous 80 per cent cis-polybutadiene has been found to possess exceptionally good low temperature properties, far superior to present arctic-type unsaturated elastomers, trans-Polybutadienes by virtue of their high modulus, high tensile strength, and high hardness could be utilized in the preparation of hard rubber goods, floor tiles, and shoe soles. While none of these polybutadienes is yet available commercially, their unusual properties and potential applicability in many areas should lead to their manufacture in the future.

Measurement of Tensile Strength of Natural Rubber Vulcanizates at Elevated Temperature

1982 ◽  
Vol 55 (1) ◽  
pp. 66-75 ◽  
Author(s):  
C. L. M. Bell ◽  
D. Stinson ◽  
A. G. Thomas
Keyword(s):  
Tensile Strength ◽  
Elevated Temperature ◽  
Critical Temperature ◽  
Natural Rubber ◽  
Test Piece ◽  
Flaw Size ◽  
High Tensile Strength ◽  
Test Pieces ◽  
Naturally Occurring ◽  
Natural Rubber Vulcanizates

Abstract The tensile strength of test pieces made from natural rubber vulcanizates drops abruptly at a critical temperature which can vary from 40 to 130°C. This variation in critical temperature is shown here to be a result of the variation in critical cut length with temperature. When the naturally occurring flaws in the test piece are smaller than the critical cut length, high tensile strength values occur, but when the flaws are longer than the critical cut length, low tensile strength values occur. The critical cut length decreases as the temperature increases, and the abrupt drop in tensile strength occurs as the critical cut length reaches the natural flaw size in the test piece. The natural flaw size in tensile test pieces depends on the sharpness of the cutter, and for tensile strength measurements at elevated temperature, it is shown that even a slightly blunt cutter may give markedly different results from a sharp one.

Epoxidized Natural Rubber / Silica Nanoscale Organic-Inorganic Hybrid Composites Prepared by Sol-Gel Technique

2004 ◽  
Vol 77 (5) ◽  
pp. 830-846 ◽  
Author(s):  
Abhijit Bandyopadhyay ◽  
Mousumi De Sarkar ◽  
Anil K. Bhowmick
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Hybrid Composites ◽  
Sol Gel ◽  
Hybrid Nanocomposites ◽  
Dicumyl Peroxide ◽  
Inorganic Hybrid ◽  
Gel Technique ◽  
Rubber Phase

Abstract Epoxidized natural rubber (ENR) / silica organic-inorganic hybrid nanocomposites were prepared by using a sol-gel technique. Tetraethoxysilane was used as the precursor for the in-situ generation of silica. The choice of ENR as a matrix was made because of its polar nature which can interact with the in-situ generated silica. The sol-gel reaction was carried out at room temperature by dissolving the rubber in tetrahydrofuran solvent using hydrochloric acid as the catalyst. The resultant composite films appeared transparent up to 50 wt% of tetraethoxysilane loading. Dispersion of the discrete silica particles having dimensions of 15 – 100 nm was observed through transmission electron microscope. Scanning electron microscopic studies did not produce any evidence for formation of silica network within the bulk of the composite. Infrared spectroscopic studies indicated the occurrence of chemical interaction within the rubber /silica organic-inorganic interfaces which was further supported by the insolubility of the respective samples in tetrahydrofuran under the ambient conditions. Mechanical reinforcement within the hybrid nanocomposites, both at high and low temperature regions, was demonstrated through dynamic mechanical analysis. The composites exhibited superior tensile strength and tensile moduli compared to the gum rubber samples. Further reinforcement was noticed when the rubber phase in the nanocomposites was cured with either benzoyl peroxide or dicumyl peroxide. The dicumyl peroxide cured hybrid composites displayed 112% improvement in tensile strength over the control crosslinked rubber sample, probably due to synergisms of nanosilica reinforcement and crosslinking of the rubber phase in the hybrids.

Method for Estimating the Chemical Crosslink Densities of Cured Natural Rubber and Styrene-Butadiene Rubber

1994 ◽  
Vol 67 (5) ◽  
pp. 854-864 ◽  
Author(s):  
Shirley Lee ◽  
Henry Pawlowski ◽  
A. Y. Coran
Keyword(s):  
Chemical Analysis ◽  
Natural Rubber ◽  
Dynamic Properties ◽  
Loss Modulus ◽  
Styrene Butadiene Rubber ◽  
Dicumyl Peroxide ◽  
Butadiene Rubber ◽  
Chemical Crosslinks ◽  
Styrene Butadiene ◽  
Crosslink Densities

Abstract Chemical crosslink densities of gum and carbon black-filled natural rubber (NR) and styrene-butadiene rubber (SBR) were estimated by using a newly developed rheometer. The rheometer is the Rubber Process Analyzer (RPA 2000) which is designed specifically to measure dynamic properties such as shear storage modulus G′ and shear loss modulus G″ in cured and uncured rubber. It was found that the differences between the G′ values of dicumyl peroxide-cured NR and those of uncured samples yielded estimates of the crosslink densities which were nearly the same as the values inferred by chemical analysis. For TMTD-cured SBR, the same procedure yielded estimates of chemical crosslinks very close to those estimated by a tensile stress-strain method and by NMR. In addition, accelerated sulfur-cured natural rubber was also investigated. The agreement between the crosslink densities of these stocks determined from G′ values and from a solvent-swelling method was very good.

Tensile Strength of Protein-free Natural Rubber and its Vulcanizate Soaked in Water

2020 ◽  
Vol 93 (9) ◽  
pp. 293-299
Author(s):  
Luu Thanh HUYEN ◽  
Chen Ao RAN ◽  
Yoshimasa YAMAMOTO ◽  
Seiichi KAWAHARA
Keyword(s):  
Tensile Strength ◽  
Natural Rubber

LUCEFIN GROUP C30 (1.0528), C30E (1.1178), C30R (1.1179)

Alloy Digest ◽  
2020 ◽  
Vol 69 (9) ◽  
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
High Tensile Strength ◽  
Medium Carbon ◽  
Alloy Steels ◽  
Cold Worked ◽  
Lower Carbon

Abstract Lucefin Group C30, C30E, and C30R are medium-carbon, non-alloy steels that are used in the normalized, cold worked, or quenched and tempered condition. C30E and C30R may also be flame or induction hardened. C30, C30E, and C30R are widely used for small, moderately stressed parts, where higher strength levels are needed than can be achieved in the lower carbon grades, and also where toughness is more important than high tensile strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, and joining. Filing Code: CS-206. Producer or source: Lucefin S.p.A.

Sign in / Sign up

Export Citation Format

Share Document