Double networking rubber

Mott, P. H. and Roland, C. M. Mechanical and optical behavior of double network rubbers. A/dc-... 

Roland, C. M. Warzel, M. L., Orientation Effects in Rubber Double Networks. Rubber Chem. Technol. 1990, 63, 285-297. 

Roland CM, Warzel ML (1990) Orientation effects in rubber double networks. Rubber Chem Technol 63(2) 285-297... 

Santangelo PG, Roland CM (1995) Failure properties of natural rubber double networks. Rubber Chem Technol 68(1) 124-131... 

D-TEM gave 3D images of nano-filler dispersion in NR, which clearly indicated aggregates and agglomerates of carbon black leading to a kind of network structure in NR vulcanizates. That is, filled rubbers may have double networks, one of rubber by covalent bonding and the other of nanofiller by physical interaction. The revealed 3D network structure was in conformity with many physical properties, e.g., percolation behavior of electron conductivity. 

Kaa Kaang, S., Nah, C. Fatigue crack growth of double-networked natural rubber. Polymer 39 (1998) 2209-2214. 

The value ofVjA is determined by the concentration of network knots. These knots usually have a functionality of 3 or 4. This functionality depends on the type of curing agent. Crosslinked polyurethanes cured by polyols with three OH-groups are examples of the three-functional network. Rubbers cured through double bond addition are examples of four-functional networks. 

FIGURE 15 Natural rubber sample on left is double network and on right is a conventional NR elastomer (a, b). Both are in a state of mechanical equilibrium (stress = 0). Nevertheless, as seen in (c), the double network transmits light through crossed polarizers, due to its inherent orientation. This is a violation of the stress optical rule, similar to that observed during creep recovery of uncrosslinked rubber. 

Aprem, A. S. Joseph, K. Thomas, S., Studies of Double Networks in Natural Rubber Vulcanizates. J.Appl. Polym. Sci. 2004, 91,1068-1076. 

Dry RubbGr. Because of its enhanced crystallizability, guayule rubber can exhibit superior failure properties in unfilled rubber compositions. As a double network, an elastomer cured a second time while in a deformed state guayule rubber exhibits substantially better fatigue resistance than deproteinized Hevea rubber (118). When compounded with carbon black, guayule rubber and Hevea rubber behave similarly (119). In tread and wire skim stocks, the compoimding and performance behavior of guayule rubber was comparable to that of Hevea rubber (Tables 7, 8) (120). 

Abstract The nonlinear viscoelastic behavior of cured rubber is quite different from that of uncured compound, since the presence of crosslink networks. The factors for the influence of the crosslink networks on the nonlinear viscoelastic behaviors of cured rubbers are very complex and obscure. One of the reasons is that the crosslink networks may be consisted of several different types of networks. However, there are few literatures reporting the nonlinear viscoelastic behaviors of cured mbbers with mutle-networks. We reviewed the literatures dedicated to the topic of the non-linear viscoelasticity of simplest mutle-networks—double-network and summarized the useful information as much as possible in the present paper. Song s transient double-network model, double-network formed by twice curing and the specific crosslink network formed in metal salts of unsaturated carboxylic acids reinforced rubbers are introduced in detail. 

Keywords Crosslink rubber Double-network Non-linear viscoelasticity... 

The nonlinear viscoelastic behavior of filled vulcanizates is somewhat different from that of filled compounds, since the chemical crosslink network of the rubber matrix is formed and, the physical rubber-filler networks and filler-filler networks are enhanced during curing at a relatively high temperature [7]. Speaking from a broad sense, filled vulcanizates can be viewed as a double network structure in which the nanoparticles supplement the inherent viscoelasticity of crosslink rubbers with additional physical network junctions. 

In a filled rubber, agglomeration of the particles produces a filler network, in addition to the network of covalently-bonded polymer chains. In fact, Reichert et al. [30] modeled the deformation of single network of filled rubber as a double network, adopting an approach similar to that used to analyze unfilled double networks [35-37]. This implies that double-network mbber reinforced with filler can be viewed as a composite of three distinct networks. 

Double Network in Metal Salts of Unsaturated Carboxylic Acids Reinforced Rubbers [38-59]... 

Santangelo PG, Roland CM (1994) The mechanical behavior of double network elastomers. Rubber Chem Technol 67(2) 359-365... 

Hamed GR, Huang MY (1998) Tensile and tear behavior of anisotropic double networks of a black-filled natural rubber vulcanizate. Rubber Chem Technol 71(5) 846-860... 

Kaang S, Gong D, Nah C (1997) Some physical characteristics of double-networked natural rubber. J Appl Polym Sci 65(5) 917-924... 

Aprem AS, Joseph K, Thomas S (2004) Studies on double networks in natiual rubber vulcanizates. J Appl Polym Sci 91(2) 1068-1076... 

There are some ongoing general studies of surface modification of elastomers and studies on the synthesis and characterization of double-network elastomers. Research was done on the suppression of crystallization in blended natural rubber and neoprene. Other studies of crystallization, for example, on positron emission tomography (PET), have also been done. 

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. 

If a large number of branches exist that connect all of the backbone molecules into a three-dimensional network, the material will not flow when heated, and it is considered a thermoset resin. Vulcanized rubber is an example where the sulfur linkages create a three-dimensional network, converting the precursor rubber into a solid thermoset material. Crosslinked backbone chains are shown in Fig. 2.8(e). When extruding many thermoplastics, the polymer can undergo chemical reactions to form small amounts of crosslinked material. Partial crosslinking is a problem with some PE resins that contain residual double bonds that are made using... 

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