Natural Rubber Compounds for Intermittent Low Temperature Service

1957 ◽  
Vol 30 (2) ◽  
pp. 652-666
Author(s):  
W. P. Fletcher ◽  
A. N. Gent ◽  
R. I. Wood
Keyword(s):  
Transition Temperature ◽  
Low Temperature ◽  
Natural Rubber ◽  
Physical Properties ◽  
Dynamic Stiffness ◽  
Theoretical Treatment ◽  
Rubber Compounds ◽  
Second Order Transition ◽  
General Physical ◽  
Silicone Rubbers

Abstract The changes in physical properties of rubber vulcanizates on approaching the so-called second order transition temperature are discussed and distinction is drawn between these phenomena and those associated with crystallization. A simple apparatus of the torsional pendulum type is used to determine the dynamic stiffness and hysteresis loss factor at a frequency of about 0.5 c.p.s. of vulcanizates in the temperature range 20 to −120° C. A large number of liquids are examined as potential plasticizers for lowering the rubber to glass transition temperature and a number are shown to have a high order of efficiency in this respect. Of these materials some also conform to the overriding requirements of low volatility and adequate compatibility with rubber. The loss in physical properties consequent on increase of plasticizer content is not markedly different for most of the plasticizers. Di-iso-octyl adipate is representative of the liquids which give useful low temperature plasticization and a number of commercial type compounds are developed using this plasticizer with carbon black or silica reinforcement, some of these have transition temperatures approaching those of the silicone rubbers but with a better level of general physical properties. A tentative theoretical treatment for the low temperature plasticization of nonpolar rubbers is discussed and this leads to a law which has been found to predict fairly well the transition temperature of a plasticized natural rubber compound in terms of the index of variation with temperature of the plasticizer viscosity.

A Review on Heat and Reversion Resistance Compounding

2003 ◽  
Vol 19 (3) ◽  
pp. 143-170 ◽  
Author(s):  
R. N. Datta
Keyword(s):  
Thermal Stability ◽  
Natural Rubber ◽  
Physical Properties ◽  
Dynamic Performance ◽  
Thermal Ageing ◽  
Vital Role ◽  
Performance Characteristics ◽  
Network Density ◽  
Performance Property ◽  
Rubber Compounds

When sulfur vulcanized natural rubber compounds are exposed to a thermal ageing environment significant change in physical properties and performance characteristics are observed. These changes are directly related to modifications of the original crosslink structure. Decomposition reactions tend to predominate and thus leading to reduction in crosslink density and physical properties as observed during extended cure and when using higher curing temperatures. The decrease in network density is common when vulcanizates are subject to an anaerobic ageing process. However, in the presence of oxygen, the network density is increased with the main chain modifications playing a vital role. Over the years the rubber industry has developed several compounding approaches to address the changes in crosslink structure during thermal ageing. This paper gives a review of these compounding approaches. As with many formulation changes in rubber compounding, there is a compromise that must be made when attempting to improve one performance characteristic. For example, improving the thermal stability of vulcanized natural rubber compounds by reducing the sulfur content of the crosslink through the use of the more efficient vulcanization systems will reduce dynamic performance property such as fatigue resistance. The challenge is to define a way to improve thermal stability while maintaining dynamic performance characteristics.

Recent Developments in Superior Processing Natural Rubber

1960 ◽  
Vol 33 (3) ◽  
pp. 810-824 ◽  
Author(s):  
H. C. Baker ◽  
R. M. Foden
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Operating Conditions ◽  
Lower Percentage ◽  
Die Swell ◽  
Rubber Compounds ◽  
Recent Developments ◽  
Efficient Processing ◽  
And Control

Abstract SP rubbers give greater latitude in extrusion and calendering processes by extending the range of operating conditions and giving greater scope for compounding for good physical properties. Compounds based on SP rubbers extrude smoothly with lower die swell at lower temperatures and higher viscosities. Greater productivity is obtained through the faster screw speeds which are possible with SP rubbers in many types of compound. SP rubber compounds calender with greater conformity to gage, greater ease of handling and control of shrinkage of the calendered sheet, at temperatures 10° C lower than normal. The firmer stocks given by SP rubbers and their greater resistance to degradation on milling lead to reduced wastage of unvulcanized compound in the factory, while the stricter control of processing permitted by SP rubbers results in a lower percentage of rejected articles. Evaluation of an experimentally produced SP 90 crepe has indicated the potentialities of a concentrated form of SP rubber as a more efficient processing aid than crosslinked SBR 1009 with NR and SBR.

scholarly journals Evaluation of Cooking Oil as Processing Addtive for Natural Rubber

2017 ◽  
Vol 34 (1) ◽  
pp. 17 ◽  
Author(s):  
Y. M. SYAMIN ◽  
S. AZEMI ◽  
K. DZARAINI
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Natural Rubber ◽  
Physical Properties ◽  
Aromatic Ring ◽  
Rolling Resistance ◽  
Cooking Oil ◽  
Alternative Option ◽  
Rubber Compounds ◽  
Polycyclic Aromatic

It was reported recently that high amount of aromatic ring  or number of polycyclic aromatic hydrocarbon compounds found in aromatic oil are carcinogenic. This paper discusses the work to evaluate the Malaysian cooking oil as an alternative option to be used as process oil since cooking oil is safe to use and non-toxic. The performance of cooking oil is compared againstaromatic and paraffinioils. The results showed that rubber compounds containing cooking oil produced almostsimilar cure characteristicsas those produced by aromatic and paraffinioils indicating that it did not interfere with the vulcanization reaction. The physical properties of the vulcanizates containing cooking oil were almostsimilar to those of vulcanizates containing aromatic and paraffinioils, except the rebound resilience. The vulcanizates containing cooking oil gave higher resilience than vulcanizates containing aromatic and paraffinioils. High resilience is one of the desired features for a low rolling resistance tyre. Cooking oil provided this extra advantage.

Low-Temperature Properties of Plasticized Butadiene-Styrene Copolymers

1955 ◽  
Vol 28 (2) ◽  
pp. 557-569 ◽  
Author(s):  
D. A. Henderson ◽  
L. A. McLeod
Keyword(s):  
Transition Temperature ◽  
Low Temperature ◽  
Second Order ◽  
Order Transition ◽  
Styrene Copolymers ◽  
Second Order Transition ◽  
Dibutyl Sebacate ◽  
Special Case ◽  
Measured Transition ◽  
Butadiene Styrene

Abstract The second-order transition temperatures of plasticized butadiene-styrene copolymers have been measured by dilatometric techniques. In a series of ester plasticizers, the ability of a given plasticizer to depress the second-order transition temperature of the polymer is related to the swelling effect of the plasticizer on the polymer. The special case of a crystallizing plasticizer (dibutyl sebacate) has been discussed. Common petroleum plasticizers do not appear to behave in a similar manner. The change of coefficient of expansion of the ester-plasticized copolymers is related to the measured transition temperature of the blend.

Detection of the Molecular Orientation in Nonvulcanized and Vulcanized Natural Rubber Compounds by the Low-Temperature X-Ray Method

1989 ◽  
Vol 62 (2) ◽  
pp. 179-194 ◽  
Author(s):  
Y. Udagawa ◽  
M. Ito
Keyword(s):  
Low Temperature ◽  
Carbon Black ◽  
Natural Rubber ◽  
Molecular Orientation ◽  
Ray Method ◽  
Processing Methods ◽  
X Ray ◽  
Rubber Compounds

Abstract The low-temperature x-ray method can detect the orientation of NR molecules in both vulcanizate samples and nonvulcanizate samples of NR compounds. The presence of carbon black is important for causing the orientation. NR molecules orient in the direction of stretch-relaxation in the case of uniaxially fatigued vulcanizates or in the direction of shear in the case of nonvulcanizates prepared by various processing methods. The orientation of NR molecules in nonvulcanizates usually disappears when vulcanized, but a fairly large extent of molecular orientation remains, even after vulcanization, if there exist crosslinks in the oriented nonvulcanizate and the sample is prevented from shrinkage.

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.

Heat Resistance of Neoprene-GN Vulcanizates

1944 ◽  
Vol 17 (1) ◽  
pp. 173-184
Author(s):  
D. B. Forman
Keyword(s):  
Natural Rubber ◽  
Heat Resistance ◽  
Physical Properties ◽  
High Temperatures ◽  
Continuous Exposure ◽  
Oxygen Bomb ◽  
Rubber Compounds ◽  
Active Subject ◽  
Continuous Problem

Abstract Control of heat deterioration is a continuous problem for the chemist. In the case of rubber and synthetic elastomers, the rubber chemist has charted the changes in the physical properties of vulcanized elastomers during heat aging. He has developed many methods for retarding the deterioration of rubber compounds by heat; but with the newer synthetic elastomers the development of methods of retarding deterioration by heat is now an active subject of investigation. The degree of deterioration depends on the methods of compounding and curing the different elastomers, as well as on the conditions of aging. In general, continuous exposure to high temperatures softens natural rubber but hardens synthetic elastomers. Inherently Neoprene has greater heat resistance than natural rubber. Many investigators have described the heat resistance of rubber vulcanizates, but only a few have reported on the heat resistance of Neoprene vulcanizates, and these reports have been primarily comparisons of given Neoprene vulcanizates with one or more rubber stocks. The compounding of Neoprene (Type GN) for heat resistance was discussed by Catton, Fraser, and Forman. The oxygen bomb aging of Neoprene (Types E and GN) was compared with that of various rubber compositions by Neal, Bimmerman, and Vincent.

Cure Characteristics and Ageing Resistance of Recovered Waste Pre-Vulcanized Nitrile/Epoxidized Natural Rubber Latex Blends in Nitrile Butadiene Rubber Compounds

2015 ◽  
Vol 1119 ◽  
pp. 347-351
Author(s):  
A.I.H. Dayang Habibah ◽  
V. Devaraj ◽  
H. Kamarularifin ◽  
Ibrahim Suhawati
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Natural Rubber Latex ◽  
Butadiene Rubber ◽  
Rubber Latex ◽  
Maximum Torque ◽  
Rubber Compounds ◽  
Curing Characteristics ◽  
Control Compound ◽  
Minimum Torque

Waste pre-vulcanized nitrile latex (WPNL), obtained from nitrile glove dipping tank was blended at different ratios with concentrated ENR latex processed via ultrafiltration and designated as ENRLC-SP20 and ENRLC-SP50, respectively, with the number indicating, the percentage of WPNL incorporated into the blend. The blends were prepared in the latex stage and subsequently processed into dry rubber. The rubbers were then blended with virgin nitrile rubber (NBR) at various ratios and the curing characteristics and physical properties of the blends were evaluated. The results showed the maximum torque (MH) decreases while the minimum torque (ML) increases with increasing level of SP 50 rubber. Using higher concentrations of SP-50, the results showed slight reductions in the cure (t90) and scorch time (ts2), respectively. It was also found that by increasing ratio of ENRLC-SP20 and ENRLC-SP50 improves the heat ageing resistance of NBR blends at 100°C as evidenced by the higher percentages in retention of the blends, compared to the control compound.

Thermal Expansion Measurements and Transition Temperatures, First and Second Order

1959 ◽  
Vol 32 (4) ◽  
pp. 1005-1015
Author(s):  
Mark L. Dannis
Keyword(s):  
Thermal Expansion ◽  
Transition Temperature ◽  
Physical Properties ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Second Order ◽  
Rate Of Change ◽  
Order Transition ◽  
Abrupt Changes ◽  
Second Order Transition

Abstract When any pure material goes through a change in state, its physical properties change greatly. In each phase the physical properties are relatively constant or change slowly enough with temperature that the rate of change of a property such as volume is a constant. This rate of change of volume is the thermal expansion coefficient, (∂V/V)/∂T. The thermal expansion coefficient is almost constant, experimentally, as long as the temperature range over which measurements are made does not include a phase transition. At the transition temperature, abrupt changes in volume are found as illustrated in Figure 1. Polymeric materials often show changes in physical properties not necessarily accompanied by abrupt changes in volume, even though the expansion coefficient does change. Since the expansion coefficient changes, some change in internal structure is suspected, and the name second-order transition (Tg) has been adopted. This kind of change is roughly diagrammed in Figure 2. This latter change at the second-order transition temperature can be found in every known polymer, even though many polymers possess clear, first-order, crystalline transitions as well. Hevea rubber, for example, has a crystalline melting point of 28° C, compared to its Tg about −70°. These data are shown, copied from Boyer and Spencer, as Figure 3.

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