Natural rubber morphological

Compatibility and various other properties such as morphology, crystalline behavior, structure, mechanical properties of natural rubber-polyethylene blends were investigated by Qin et al. [39]. Polyethylene-b-polyiso-prene acts as a successful compatibilizer here. Mechanical properties of the blends were improved upon the addition of the block copolymer (Table 12). The copolymer locates at the interface, and, thus, reduces the interfacial tension that is reflected in the mechanical properties. As the amount of graft copolymer increases, tensile strength and elongation at break increase and reach a leveling off. 

The reactive extrusion of polypropylene-natural rubber blends in the presence of a peroxide (1,3-bis(/-butyl per-oxy benzene) and a coagent (trimethylol propane triacrylate) was reported by Yoon et al. [64]. The effect of the concentration of the peroxide and the coagent was evaiuated in terms of thermal, morphological, melt, and mechanical properties. The low shear viscosity of the blends increased with the increase in peroxide content initially, and beyond 0.02 phr the viscosity decreased with peroxide content (Fig. 9). The melt viscosity increased with coagent concentration at a fixed peroxide content. The morphology of the samples indicated a decrease in domain size of the dispersed NR phase with a lower content of the peroxide, while at a higher content the domain size increases. The reduction in domain size... 

FIGURE 3.12 Morphology of mbber-silica hybrid composites synthesized from solution process using different solvents (a) and (b) are the scanning electron microscopic (SEM) pictures of acrylic rubber (ACM)-silica hybrid composites prepared from THF (T) and ethyl acetate (EAc) (E) and (c) and (d) are the transmission electron microscopic (TEM) pictures of epoxidized natural rubber (ENR)-siUca hybrid composites synthesized from THF and chloroform (CH). (From Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Appl. Polym. Sci., 95, 1418, 2005 and Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Mater. Sci., 40, 53, 2005. Courtesy of Wiley InterScience and Springer, respectively.)... 

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... 

Obviously, there are many subtle differences in the structure, morphology, or network topology between radiation cured and sulfur cured elastomers, but their physical properties may be nearly equal, provided that precautions are taken to avoid the occurrence of chain scissions. A comparison of radiation cross-linked and sulfur cured natural rubber (gum and carbon-black-reinforced compounds) is in Table 5.4. ... 

Varkey, J.T. Augustine, S. Groeninckx, G. Bhagawan, S.S. Rao, S.S. Thomas, S. Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends. J. Polym. Sci. B Polym. Phys. 2000,38 (16), 2189-2211. 

FIGURE 3.21 Isothermal dielectric loss curves for a thermodynamically-miscible blend of 25% 1,2-polybutadiene with natural rubber. Notwithstanding the homogenous morphology, the respective mobiUties of the components differ, whereby two peaks are observed in the spectrum. Reprinted from Alegria et al. (1994). 

Meier [23] has derived equations relating block copolymer morphology to thermodynamics using lattice models. His model explains quantitatively the observations of Merrett [24] on the influence of preferential solvents on the mechanical properties of graft copolymers. Merrett found that, depending on the solvent used in casting films of a natural rubber/poly(methyl methacrylate) graft copolymer, he could obtain either a hard stiff film characteristic of poly(methyl methacrylate) or a soft, flexible film typical of natural rubber. He interpreted these results as follows a solvent for poly(methyl methacrylate) collapsed the... 

A.W.M. Kahar, H. Ismail, N. Othman. Effects of polyethylene-grafted maleic anhydride as a compatibilizer on the morphology and tensile properties of (thermoplastic tapioca starch)/ (high-density polyethylene)/(natural rubber) blends... 

Nakason, C., Tobprakhon, A., and Kaesaman, A. 2005. Thermoplastic vulcanizates based on poly(methyl methacrylate) /epoxidized natural rubber blends Mechanical, thermal, and morphological properties. Journal of Applied Polymer Science 98 3) 1251-1261. 

Nakason, C., Saiwaree, S., Tatun, S., and Kaesaman, A. 2006. Rheological, thermal and morphological properties of maleated natural rubber and its reactive blending with poly (methyl methacrylate). Polymer Testing 25(5) 656-667. 

Varghese, K. T., Nando, G. B., De. R R, and De, S. K. 1988. Miscible blends from rigid poly (vinyl chloride) and epoxidized natural rubber. Part 1. Phase morphology. Journal of Materials Science 23 3894 3902. 

Thitithammawong, A., Nakason, C., Sahakaro, K., Noordermer., J. (2007). Effect of different type of peroxide on rheological, mechanical, and morphological properties of thermoplastic based vulcanizates based on natural rubber/ polypropylene blends. Polym, Test, 26, 537-546... 

Polymers are very high molecular weight materials formed by smaller structural units bound together by covalent bonds. According to this definition, some natural materials such as cellulose and natural rubber are polymers. However, only the synthetic polymers will be considered in this book. These synthetic polymers are made by combination of small molecules, monomers, which form the structural units of the polymer. The reaction of monomers to form a polymer is termed polymerization. The molecular and morphological characteristics of the polymer depend on the formulation (monomers, catalysts, initiators, etc.), the polymerization process (reactor, polymerization technique) and the process conditions (concentrations, temperature, time). 

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