Mechanical properties of rubber vulcanizates

Pictures of NBR-W-REF samples (Fig. 4a, b) present broken needles of wollastonite in the area of fracture, whereas in the case of NBR-W-48 sample (Fig. 4c, d) needles of wollastonite are non-broken but pulled out fi om rubber matrix. This change to morphology, reflected by lower rubber-filler interactions, responsible for worse mechanical properties of rubber vulcanizates (see Section 12.3.3), is undoubtedly the result of an increase of SFE polar component of filler after plasma treatment. The SEM pictures of the vulcanizates, no matter, containing virgin or modifies wollastonite particles, do not reveal any filler agglomeration. 

For rapid determination of the tan 6 at low frequencies and room temperature of the large number of rubber vulcanizates tested, we adapted the Yerzley Oscillograph. This equipment was one of the earliest instruments used for determining the dynamic mechanical properties of rubber vulcanizates. 

Song MS (1989) Studies on the relationship between the network structure and the mechanical properties of rubber vulcanizates (1) theory of elasticity for rubber vulcanizates with carbon black fillers in large deformation. Chin J Chem Eng 4(2) 162-177... 

Powders are commonly used as fillers for rubber mixes. The most popular are carbon black, silica, kaolin, or more modem like graphene, fullerenes and carbon nanotubes. The nature of their siuface is the main attribute of fillers, as surface energy and specific area determine the compatibility of filler with mb-ber matrix and the affinity to other c ingredients. One of the major problems is the tendency of fillers to agglomeration-formation of bigger secondary stmctures, associated with lower level of filler dispersion, what is reflected by the decrease of mechanical properties of rubber vulcanizates [1]. Surface modification of powder can unprove interaction between mbber matrix and filler. Application of low-temperature plasma treatment for this purpose has been drown increasing attention recently [2,3]. 

Any changes to filler particles SFE and its components effect on mechanical properties of rubber vulcanizates filled with the modified filler. Improvement of mechanical properties of the materials originates increased rubber-filler interaction and better dispersion of filler particles in rubber matrix. 

On the other hand, the mechanical properties of thermoplastic vulcanizates containing ground tire rubber have been investigated with the aim of increasing use of recycled rubber. The compositions tested included passenger car combined with EPDM, SBR rubber, isoprene rubber, and butadiene rubber. It was found that the particle size of the ground tire rubber had small effect on mechanical properties, but that the choice of the sulfur accelerator was significant [26]. 

Mechanical properties of the vulcanizates containing Zn stearate are close to the analogous characteristics of the sample compound. It is proved that Zn stearate is an effective dispersing agent for the carbon black in a wide range of concentrations within the rubber compound. Experimental results reveal that for the carbon black filled SBR compounds and the MBT Zn stearate is a suitable activator. 

Techniques for Determining the Dynamic Mechanical Properties and Some of the Functional Properties of Rubber Vulcanizates... 

After vulcanization, the chemical crosslinks network is formed, which largely enhance the mechanical properties of rubber. The poly-ZDMA nano-particles dispersed in NR matrix, yielding a pronounced Payne effect. As shown in Fig. 10, the linear viscoelastic region (LVE) of vulcanizate with high loading of ZDMA corresponded to an elastic modulus independent to deformation, which can be observed at middle strain amplitudes (even to 1°, equal to al4 %). This... 

The following is the summary of the results of the studies (31) on the effect of stereoregularity on stress-induced crystallization and mechanical properties of the vulcanizates of propylene oxide copolymers. In the studies on stress-induced crystallization, stress (cr) and birefringence (A) were measured as a function of temperature using an Instron tester fitted with a thermostatted Insulated chamber and an optical system. In an amorphous rubber, the quantity (T A/o) (where T is absolute temperature) is almost constant. Stress-induced crystallization leads to the formation of crystals oriented in the stretching direction which substantially increase the birefringence. 

Fluoroelastomers Novikova et al. [32] reported unproved physico-mechanical properties of fluoro mbbers by reinforcement with chopped polyamide fibers. Other fiber reinforcements are covered by Grinblat et al. [33]. Watson and Francis [34] described the use of aramid (Kevlar) as short fiber reinforcement for vulcanized fluoroelastomer along with polychloroprene mbber and a co-polyester TPE in terms of improvement in the wear properties of the composites. Rubber diaphragms, made up of fluorosilicone mbbers, can be reinforced using aramid fiber in order to impart better mechanical properties to the composite, though surface modification of the fiber is needed to improve the adhesion between fluorosUicone mbber and the fiber [35]. Bhattacharya et al. [36] studied the crack growth resistance of fluoroelastomer vulcanizates filled with Kevlar fiber. 

Mechanical Properties of Cryoground Rubber (CGR) Loaded NR Vulcanizates... 

Blends of elastomers are routinely used to improve processability of unvulcanized rubbers and mechanical properties of vulcanizates like automobile tires. Thus, cis-1,4-polybutdiene improves the wear resistance of natural rubber or SBR tire treads. Such blends consist of micron-sized domains. Blending is facilitated if the elastomers have similar solubility parameters and viscosities. If the vulcanizing formulation cures all components at about the same rate the cross-linked networks will be interpenetrated. Many phenolic-based adhesives are blends with other polymers. The phenolic resins grow in molecular weight and cross-link, and may react with the other polymers if these have the appropriate functionalities. As a result, the cured adhesive is likely to contain interpenetrating networks. 

Virgin EPDM rubber in a thermoplastic blend of polypropylene (PP) and EPDM rubber is substituted by ground EPDM vulcanizate of known composition, after which the mechanical properties of the compound are determined. Attempts to replace amounts greater than 45% fail due to processing difficulty [28],... 

A devulcanization process that utilizes supercritical CO2 as a devulcanization reaction medium in the presence of diphenyl disulfide as a devulcanizing reagent has been reported [45]. The process devulcanizes unfilled NR vulcanizates effectively. Further, a comparison of measured sol/gel components as well as dynamic mechanical properties of the devulcanized rubber products of filled and unfilled NR vulcanizates has indicated that the presence of carbon black in the vulcamizate does not disturb the devulcanization in supercritical CO2. 

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