Properties of Rubbers

Vulcanization changes the physical properties of rubbers. It increases viscosity, hardness, modulus, tensile strength, abrasion resistance, and decreases elongation at break, compression set and solubility in solvents. All those changes, except tensile strength, are proportional to the degree of cross-linking (number of crosslinks) in the rubber network. On the other hand, rubbers differ in their ease of vulcanization. Since cross-links form next to carbon-carbon double bonds. 

Thermoplastic elastomers (TPES), as the name indicates, are plastic polymers with the physical properties of rubbers. They are soft, flexible, and possess the resilience needed of rubbers. However, they are processed like thermoplastics by extrusion and injection molding. 

Poor mechanical properties of rubber products may also be due to matrix separation [257], Just as in other systems, separation gives rise to cavities and initiates failure. These processes prevail in systems with poor adhesion and become more probable with the increasing filler modulus. 

Dynamic mechanical measurements for elastomers that cover wide ranges of frequency and temperature are rather scarce. Payne and Scott [12] carried out extensive measurements of /a and /x" for unvulcanized natural mbber as a function of test frequency (Figure 1.8). He showed that the experimental relations at different temperatures could be superposed to yield master curves, as shown in Figure 1.9, using the WLF frequency-temperature equivalence, Equation 1.11. The same shift factors, log Ox. were used for both experimental quantities, /x and /x". Successful superposition in both cases confirms that the dependence of the viscoelastic properties of rubber on frequency and temperature arises from changes in the rate of Brownian motion of molecular segments with temperature. 

A.R. Payne and J.R. Scott, Dynamic and related time-dependent properties of rubber. Chap. 2 in Engineering Design with Rubber, Interscience PubUshers, New York, 1960. 

Effect of Alkoxysilane on Structure and Properties of Rubber-Sihca... 

EFFECT OF ALKOXYSILANE ON STRUCTURE AND PROPERTIES OF RUBBER-SILICA HYBRID NANOCOMPOSITES... 

Effects of Fillers on Rheological Properties of Rubber and Rubber Nanocomposites.785... 

EFFECTS OF FILLERS ON RHEOLOGICAL PROPERTIES OF RUBBER AND RUBBER NANOCOMPOSITES... 

Li, S., Lamminmaki, J., and Hanhi, K., Improvement of mechanical properties of rubber compounds using waste rubber/virgin rubber, Polym. Eng. Sci., 45, 1239, 2005. 

Duclaux declared in 1923 that it is useless to seek explanations for the properties of rubber on the basis of its molecular structure inasmuch as rubber should be regarded as a physical state rather than as a chemical compound. 

For a more extensive discussion of the physical properties of rubber, the reader is referred to The Physics of Rubber Elasticity by L. R. G. Treloar (Oxford, Clarendon Press, 1949),... 

In an attempt to introduce carboxyl groups to improve the adhesive properties of rubber, 6 1 of powdered rubber (0.1 -0.5 mm particle size) in an 8 1 flask was treated with ozonised oxygen. The gas stream, containing 5% of ozone was led to the bottom of the flask via a dip tube at the rate of 4 1/min for 2 min, when... 

The molecular weight distribution is an important parameter for controlling the rheological and processing properties of rubber ... 

Livigni, R. A. Hargis, I. G. Aggarwal, S. L. "Structure and Properties of Rubbers for Tires and New Developments for Crystallizing Butadiene Rubbers" Paper presented at Int l. Rubber Conf., Kiev, U.S.S.R., 1978. 

The deterioration of the physical properties of rubber products when exposed to service conditions also the controlled exposure of rubber samples to a variety of deteriorating influences in the evaluation of antioxidants and antiozonants. See Accelerated Ageing. 

An instrument for measuring the mechanical properties of rubbers in relation to their use as materials for the absorption and isolation of vibration. These properties are resilience, modulus (static and dynamic), kinetic energy, creep and set. The introduction of an improved version has recently been announced. 

The silicone elastomers combine the properties of rubber and silicones. They retain flexibility over 90 to 250°C temperature. 

Pickles had proposed that rubber was composed of covalently bound chains of isoprene, and that variations in the chains accounted for differences in the properties of rubbers (40). Pickles was the first to assign a chain structure of rubber on the basis of the properties of the chemically modified material. He noted that saturation of the double bond with bromine did not destroy the "colloidal nature" of the material. In a remarkably accurate proposition of structure, he made but one error. He assumed that the chain ends combined to form a ring of eight isoprene units. As we shall see later, he was not alone in this ascertation. 

ZnCFO at the contents 5,0 phr promotes to formation of morphological structure of compositions with the minimal particles size of heterophase, that is realized in the improvement of physical-mechanical properties of rubbers. 

Table 4.111 displays examples of ageing and chemical property ranges for some TPEs. These comparisons are very schematic and cannot be used for designing. Ozone resistance is a specific property of rubbers used in numerous specifications. The rating system is the same as previously 5 is always attributed to the most attractive materials. These general indications should be verified by consultation with the producer of the selected grades and by tests under operating conditions. 

Detonation and Mechanical Properties of Rubber Bonded Sheet Explosives are discussed by W. Kegler R. Schall in the 4thONRSympDeton (1965), pp 496-501... 

Influence of Rubber Properties. The physical and chemical properties of rubbers, monomers and interpolymers must be considered together, as in the main stage of the reaction all of these are present and the properties of the mixture at any moment determine the subsequent reaction. 

Swollen tensile and compression techniques avoid both of these problems since equilibrium swelling is not required, and the method is based on interfacial bond release and plasticization rather than solution thermodynamics. The technique relies upon the approach to ideal rubberlike behavior which results when lightly crosslinked polymers are swelled. At small to moderate elongations, the stress-strain properties of rubbers... 

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