Mechanical and Viscoelastic Properties

Compatibilizers have a key role in improving the compatibility between the blend components and thereby enhancing the mechanical properties. Several reports are available in connection with improving the properties of NR/EPDM blends by compatibilization. George et al. (67) has reported on the improvement of mechanical properties of NR/EPDM blends by precuring EPDM prior to blending. Blends of 

NR/modified EPDM, in which EPDM was modified by pendant sulfur, exhibited improved endurance to repeated stress over that of covulcanized EPDM-NR mbber blends (68). The effects of ethylene and diene contents in EPDM, blend ratio, dicumyl peroxide curing system on the physical properties, interfacial adhesion force, and dynamic crack growth were examined (69). As the ethylene and diene contents in EPDM increased, the physical properties, such as dynamic cut growth, adhesion to other component were also increased. The mechanical properties of the blends are compared to those of the pure components in Table 15.3 (56). The ultimate tensile strength of noncompatibilized blends is lower than that of pure NR, as expected since these blends are incompatible. 

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To improve the thermal, mechanical, and viscoelastic properties of cellulose acetate butyrate, it was reinforced with nanocellulose crystals prepared from BC by acid hydrolysis. Using this nanosized cellulose (Sect. 1) a significant improvement in the properties of the composites was demonstrated [57]. 

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. 

Mechanical and viscoelastic properties depend strongly on the morphologies of the samples, which are defined by the proportion of the hard and soft segments as well as by the uniformity of the hard pMMA grafts, as illustrated in Fig.40 [301 ]. 

Lugassy, A. A. 1968. Mechanical and Viscoelastic Properties of Bone and Dentin in Compression, thesis. Metallurgy and Materials Science, University of Pennsylvania. 

Balachandran, M., Bhagawan, S.S. Studies on aerylonitrile—butadiene copolymer (NBR) layered silicate composites mechanical and viscoelastic properties. J. Compos. Mater. Sept. 45, 2011-2022 (2011)... 

Loos and co-workers [64] studied the effect of CNT on the mechanical and viscoelastic properties of epoxy matrices. Bisphenol A based epoxy resin nanocomposites were prepared with various small proportions of single-walled carbon nanotubes (SWCNT) and then investigated using acetone as a diluent to reduce the resin viscosity, and the products after removal of the solvent were characterised by FT-IR, Raman spectroscopy, thermogravimetric analysis (TGA), DSC, DMA, tensile, compression, flexural and impact testing, and SEM of the fracture surfaces. The effects of small amounts of SWCNT on mechanical and viscoelastic properties of the nanocomposites are discussed in terms of structural changes in the epoxy matrix. 

It was demonstrated that the grafting of St and MMA using a similar backbone is better controlled by applying the halogen exchange method (161,162). Mechanical and viscoelastic properties depend strongly on the morphologies of... 

Thermal analysis represents a broad spectrum of analytical techniques designed to assess the response of materials to thermal stimuli, typically temperature change. Various techniques evaluate changes in enthalpy, specific heat, thermal conductivity and diffusivity, linear and volumetric expansion, mechanical and viscoelastic properties with temperature. 

Mechanical and Viscoelastic Properties of Natural Rubber Based Blends and IPNs... 

Natural rubber based-blends and IPNs have been developed to improve the physical and chemical properties of conventional natural rubber for applications in many industrial products. They can provide different materials that express various improved properties by blending with several types of polymer such as thermoplastics, thermosets, synthetic rubbers, and biopolymers, and may also adding some compatibilizers. However, the level of these blends also directly affects their mechanical and viscoelastic properties. The mechanical properties of these polymer blended materials can be determined by several mechanical instruments such as tensile machine and Shore durometer. In addition, the viscoelastic properties can mostly be determined by some thermal analyser such as dynamic mechanical thermal analysis and dynamic mechanical analysis to provide the glass transition temperature values of polymer blends. For most of these natural rubber blends and IPNs, increasing the level of polymer and compatibilizer blends resulted in an increase of the mechanical properties until reached an optimum level, and then their values decreased. On the other hand, the viscoelastic behaviours mainly depended on the intermolecular forces of each material blend that can be used to investigate the miscibility of them. Therefore, the natural rubber blends and IPNs with different components should be specifically investigated in their mechanical and viscoelastic properties to obtain the optimum blended materials for use in several applications. 

FCS is a suitable technique to study polymer dynamics in solution, and the diffusional processes investigated by FCS provide important information about the local mechanical and viscoelastic properties of polymer solutions. Typically, a tiny amount of fluorescently labeled polymer chains or free dyes is added to the polymer solutions to be investigated or vice versa. This has not only the advantage of requiring minor amounts of fluorescent dyes or labeled polymers, but also minimizes the disturbance of the system by the introduced fluorophores. 

In a recent study (Nguyen et al. 2014), starting with the diffusive impedance of a conducting polymer actuator, electrical, mechanical, and viscoelastic properties of a tri-layer conjugated polymer actuator are combined into an advanced mafliematical model, which describes the relationship between the eurvature of the actuator and an applied voltage, expressed as... 

Haut, R.C. The mechanical and viscoelastic properties of the anterior craciate ligament and of ACL fascicles. In Jackson, D.W. (ed.) The Anterior Cruciate Ligament, p. 63. Raven... 

Ali R, larmace S and Nicolais L (2003), Effect of processing conditions on mechanical and viscoelastic properties of biocomposites , J Appl Polym Sci, 88, 1637-1642. Alvarez V A, Ruscekaite R A and Vazquez A (2003), Mechanical properties and water absorption behaviour of composites made from a biodegradable matrix and alkaline-treated sisal fibres , J Comp Mat, 37(17), 1575-1588. 

For the identification of space effects on polymers, numerous standard tests must be used, namely spectroscopy, thermal analysis, dielectric and conductivity measurements, mechanical and viscoelastic property determination, etc. In the late 1990s NASA decided to substitute polyurethane coatings (having carcinogenic) with another one. The 18 alternative candidates were subjected to 34 standard test procedures (Table 3.7). In the following report the number of candidates fell to eight, from which the best with the lowest cost-to-performance ratio will have to be selected. This procedure illustrates how involved the polymeric testing for space application is, even if the test procedures are quite standard. 

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