Mechanical properties of polymer blends

The low-speed mechanical properties of polymer blends have been frequently used to discriminate between different formulations or methods of preparation. These tests have been often described in the literature. Examples of the results can be found in the references listed in Table 12.9. Measurements of tensile stress-strain behavior of polymer blends is essential [Borders et al., 1946 Satake, 1970 Holden et al., 1969 Charrier and Ranchouse, 1971]. The mbber-modified polymer absorbs considerably more energy, thus higher extension to break can be achieved. By contrast, an addition of rigid resin to ductile polymer enhances the modulus and the heat deflection temperature. These effects are best determined measuring the stress-strain dependence. 

It is well known that the mechanical properties of polymer blends strongly depend on the raw materials and on their final morphologies, which are controlled by interfacial adhesion, properties of the neat materials, and processing conditions, among others [2, 37-39],... 

As reported above, the addition of plasticizers is considered a relatively simple route to modify the thermal and mechanical properties of polymers. Blending polymers with plasticizers may modify the physical properties of polymers and a decrease in processing temperature can be achieved. Thus, PHB is commonly blended with plasticizers and nucleation agents that lead to a lower glass temperature and lower crystallinity due to the formation of numerous, small, and imperfect crystallites. 

Heterogeneous epitaxy is a specific interfacial crystallization between different polymer pairs due to lattice matching. Heterogeneous epitaxy at interfaces may be an active way to improve the mechanical properties of polymer blends, especially for incompatible systems. The epitaxial growth of HDPE and LLDPE on the... 

Various composite models such as parallel model, series model, Halpin-Tsai equation, and Kerner s model can be used to predict and compare the mechanical properties of polymer blends [43-45]. For the theoretical prediction of the tensile behavior of PMMA/EMA blends, some of these models... 

Since the mechanical properties of polymer blends and composites are of major importance, some consideration of basic mechanical property terms is in order. In this appendix, such parameters are defined, and, where appropriate, interrelationships given. Common symbols are given in Table 1.4 it should be noted that in some cases several symbols are commonly cited for the same property. 

Many practical benefits can be obtained by blending polymers. Blending allows for the beneficial properties of two polymers to be combined in one material while shielding their mutual drawbacks. Deviations in the mle of mixing can lead to properties of the blend over and above those of its components. Thus, processibility, chemical and environmental resistance, adhesion, and mechanical properties of polymer blends are superior to those of their homopolymers. 

The relationship between microstructure and physical properties of ternary nanocomposites has been the subject of intense investigation due to their very complex nature. In this section, the mechanical properties of polymer blend nanocomposites are reviewed in the context of their microstructure. Following this, the various strategies that have been employed to obtain improved filler dispersion and interfacial interactions are mentioned. 

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