Couplings elastomeric

Metallic-grid combination couplings Elastomeric flexible couplings... 

If a modest number of cross-links between the polymer backbone are introduced, the polymer Hquid crystal takes on elastomeric properties. The useflilness of these materials probably Hes in the coupling of mechanical and optical effects. 

On the bad side, many of the elastomeric types are highly nonlinear in their characteristics. The elastomeric compression-type couplings are very soft at small wind-ups under low loads, but once the elastomer has filled the available squeeze space, the coupling is effectively rigid. This makes prediction of system response difficult unless the load and coupling characteristics are well defined prior to installation. 

The elastomeric couplings generally do not have a life factor equivalent to a gear or flexible element coupling. This is further complicated by the fact liiat if the coupling is to provide damping, the dissipated vibrational energy is converted to heat, which can further shorten the life of the ele-... 

Figure 9-19. Elastomeric type coupling, commonly used tor torsional system tuning. (Courtesy of Kop-Pex Power Transmission ProductSi...

Applications of NBR adhesives are based on the excellent elastomeric properties of the polymer coupled with its polarity, which provides good solvent resistance... 

The material-flexing group includes laminated diskring, bellows, flexible shaft, diaphragm, and elastomeric couplings. 

Elastomeric couplings consist of two hubs connected by an elastomeric element. The couplings fall into two basic categories, one with the element placed in shear and the other with its element placed in compression. The coupling compensates for minor misalignments because of the flexing capability of the elastomer. These couplings... 

With the shear-type coupling, the elastomeric element may be clamped or bonded in place, or fitted securely to the hubs. The compression-type couplings may be fitted with projecting pins, bolts, or lugs to connect the components. Polyurethane, rubber, neoprene, or cloth and fiber materials are used in the manufacture of these elements. 

Spacing between the mating parts of the coupling must be within manufacturer s tolerances. For example, an elastomeric coupling must have a specific distance between the coupling faces. This distance determines the position of the rubber boot that provides transmission of power from the driver to the driven machine component. If this distance is not exact, the elastomer will attempt to return to its relaxed position, inducing excessive axial movement in both shafts. 

Elastomeric fibres based upon both polyester-urethane and polyether-urethane structures followed. The early work by Bayer led to the use of highly polar solvents such as dimethyl formamide. Formation of fibres by reactive spinning, where the isocyanate-ended polymer is extruded into an aqueous solution of a chain-coupling agent, was described in 1949 [75] and by dry-spinning a solution of the chain-coupled polymer in 1951 [76], However, Bayer did not immediately use their technology to produce commercial fibres [77],... 

According to O. Bayer, the latter procedure, which is used especially for the preparation of elastomeric polyurethanes, is carried out in two separate stages. First, a carefully dried, relatively low-molecular-weight, aliphatic polyester or polyether with hydroxy end groups is reacted with an excess of diisocyanate. A chain extension reaction occurs in which two to three linear diol molecules are coupled with diisocyanate, so as to yield a linear polymer with some in-chain urethane groups and with isocyanate end groups. 

The filler network break-down with increasing deformation amplitude and the decrease of moduli level with increasing temperature at constant deformation amplitude are sometimes referred to as a thixotropic change of the material. In order to represent the thixotropic effects in a continuum mechanical formulation of the material behavior the viscosities are assumed to depend on temperature and the deformation history [31]. The history-dependence is implied by an internal variable which is a measure for the deformation amplitude and has a relaxation property as realized in the constitutive theory of Lion [31]. More qualitatively, this relaxation property is sometimes termed viscous coupling1 [26] which means that the filler structure is viscously coupled to the elastomeric matrix, instead of being elastically coupled. This phenomenological picture has... 

AES (acrylonitrile-EPDM-styrene) is a blend of SAN and EPDM. SAN is a statistic copolymer of styrene and acrylonitrile. EPDM is an elastomeric terpo-lymer of ethylene, propylene and a nonconjugated diene. The diene studied here was 5-ethylidene-2-norbomene. The total content of EPDM was 34mole% [6]. The diene represented 8 mole% of the EPDM and the SAN phase was composed of 80 mole% of styrene and 20 mol% of acrylonitrile. The AES films were irradiated at / > 300 nm at 60 °C in the presence of oxygen. The photoproducts resulting from the photooxidation of each components of AES were identified by FTIR spectroscopy coupled with the same chemical and physical treatments as mentioned above for the previous studies. As pointed out in the literature [17], the EPDM component is more reactive than the copolymer SAN towards photooxidation. 

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