Natural rubber composites silica

FIGURE 3.16 Morphology and visual appearance of acrylic rubber (ACM)-silica and epoxidized natural rubber (ENR)-silica hybrid composites prepared from different pH ranges (a) transmission electron microscopic (TEM) picture of ACM-siUca in pH 1.0-2.0, (b) scanning electron microscopic (SEM) picture of ACM-siUca in pH 5.0-6.0, (c) SEM image of ACM-siUca in pH 9.0-10.0, (d) TEM picture of ENR-silica in pH... 

FIGURE 3.17 Tensile stress-strain plots for uncross-linked acrylic rubber (ACM)-siUca and epoxidized natural rubber (ENR)-silica hybrid composites synthesized from various pH. Letter p in the legends indicates pH and the numbers following the letter are indicative of the pH ranges e.g., 1 means pH range of 1.0-2.0, similarly 3 means 3.0-4.0. (From Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Mater. Sci., 41, 5981, 2006. Courtesy of Springer.)... 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

Figure 19.8 Mechanical properties of different filler loadings of organoclay and 50 phr silica-filled natural rubber composites.

Eflfect of silica/clay filler loadings on (a) hardness, (b) tensile modulus, MlOO, (c) tensile strength, (d) elongation at break (%) and (e) abrasion loss of natural rubber composites. 

Mechanical properties of PALF-reinforced natural rubber composites were studied in Bhattacharya et al. (1986) in which PALF addition increased hardness, compression set, tear resistance, and Mooney viscosity. However, elongation at break, mill shrinkage, and Mooney scorch time decreased. The use of resorcinol, hexamethylenetetramine, and silica is essential for PALF-rubber adhesion. PALF-reinforced... 

Ismail H, Chung FL (1999) The effect of partial replacement of silica by white rice husk ash in natural rubber composites, hit J Polym Mater 43 301-312... 

A common practice to enhance the properties of rubber products is by loading large amounts of fillers that are either reinforcing or non-reinforcing. Traditionally carbon black, precipitated silica and calcium carbonate are used to reinforce the natural rubber matrix in bulk amounts, up to 80 phr in some cases. Addition of large quantities of fillers reduces the elasticity and processability and increases the weight of the natural rubber composites. 

Choi, S.-S., C. Nab, and B.-W. Jo, Properties of natural rubber composites reinforced with silica or carbon black Influence of cure accelerator content and filler dispersion. Polymer International, 2003. 52(8) 1382-1389. 

Generally speaking, commercial rubber products are manufactured as a composite from a rubber and a nano-filler, which is in a group of fillers of nanometer size (mainly, carbon black and particulate silica). For an example, a pneumatic tire for heavy-duty usages such as aircrafts and heavyweight tracks is made from natural rubber (NR) and carbon black and/or silica. Their reinforcing ability onto rubbers makes them an indispensable component in the rubber products [1,2]. 

The example chosen here to illustrate this type of composite involves a polymeric phase that exhibits rubberlike elasticity. This application is of considerable practical importance since elastomers, particularly those which cannot undergo strain-induced crystallization, are generally compounded with a reinforcing filler. The two most important examples are the addition of carbon black to natural rubber and to some synthetic elastomers and silica to polysiloxane elastomers. The advantages obtained include improved abrasion resistance, tear strength, and tensile strength. Disadvantages include increases in hysteresis (and thus heat buUd-up) and compression set (permanent deformation). 

In the rubber industry, silica is widely used as a non-black reinforcing filler to improve the mechanical properties of NR composites due to its high specific surface area, particularly tensile strength, tear resistance, abrasion resistance and hardness. Silica can be obtained by various methods, such as precipitated silica by precipitation of an aqueous sodium silicate solution, fumed silica by pyrogenic process, silica from natural resources e.g. rice husk ash and fly ash), and in situ silica or silica sol by the sol-gel process. 

Thin films of blended deuterated polystyrene (dPS) and poly(vinyl methyl ether) (PVME) were imaged as a fimction of the dPS PVME ratio. Near the critical composition of 35% dPS, an imdulating, spinodal-like structure was observed, whereas for compositions away from the critical mixture ratio, regular mounds or holes (< dPS < < crit and < dPS > (pent, respectively) were present. These variations were assigned to surface tension effects (120). Blends of PBD, SBR, isobutylene-brominated p-methylstyrene, PP, PE, natural rubber, and isoprene-styrene-isoprene block rubbers were imaged (Fig. 18). Stiff, styrenic phases and rubbery core-shell phases were evident as the authors utilized force-modulated afm to determine detailed microstructure of blends, including those with fillers such as carbon-black and silica (121). 

Zhou et al. [12] fabricated an extremely durable superhydrophobic tridecafluorooctyl triethoxysilane modified poly(dimethylsiloxane) (PDMS)/silica nanoparticle composite coating for use on different fabrics (Figure 10.5). Inspiration for the robust composite coating was obtained from a tire, a classic and highly durable nanocomposite material, where the main components are natural rubber and carbon black. 

The nonlinear viscoelastic behavior of the composites of natural rubber filled with surface-modified nanosilica was studied with reference to silica loading [191]. The effect of temperature on the nonlinear viscoelastic behavior has been investigated. It was observed that Payne effect becomes more pronounced at higher silica loading. The filler characteristics such as particle size, specific surface area, and the surface structural features were found to be the key parameters influencing the Payne effect. A nonlinear decrease in storage modulus with increasing strain was observed for unfilled compounds also. The results reveal that the mechanism includes the breakdown of different networks namely the filler — filler network, the... 

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