Polymer mechanical properties, predictions

Polymers mechanical properties are some from the most important, since even for polynners of different special purpose functions this properties certain level is required [199], However, polymiers structure complexity and due to this such structure quantitative model absence make it difficult to predict polymiers mechanical properties on the whole diagram stress-strain (o-e) length—fi-om elasticity section up to failure. Nevertheless, the development in the last years of fractal analysis methods in respect to polymeric materials [200] and the cluster model of polymers amorphous state structure [106, 107], operating by the local order notion, allows one to solve this problem with precision, sufficient for practical applications [201]. 

The mechanical responses (stress, strain, displacement, and strength) of fiber-reinforced polymer (FRP) composites under elevated and high temperatures are affected significantly by their thermal exposure. On the other hand, mechanical responses have almost no influence on the thermal responses of these materials. As a result, the mechanical and thermal responses can be decoupled. This can be done by, in a first step, estimating the thermal responses (as introduced in Chapter 6) and then, based on the modeHng of temperature-dependent mechanical properties, predicting the mechanical responses of the FRP composites. 

Shogenov, V. N., Kozlov, G. V, Mikitaev, A. K. (1989). Prediction of Rigid-Chain Polymers Mechanical Properties in Elasticity Region. Vysokomolek. Soed. B, 31(7), 553-557. 

Polymer mechanical properties are one from the most important ones, since even for polymers of different special-purpose function a definite level of these properties always requires [20]. Besides, in Ref [48] it has been shown, that in epoxy polymers curing process formation of chemical network with its nodes different density results to final polymer molecular characteristics change, namely, characteristic ratio C, which is a polymer chain statistical flexibility indicator [23]. If such effect actually exists, then it should be reflected in the value of cross-linked epoxy polymers deformation-strength characteristics. Therefore, the authors of Ref [49] offered limiting properties (properties at fracture) prediction techniques, based on a methods of fractal analysis and cluster model of polymers amorphous state structure in reference to series of sulfur-containing epoxy polymers [50]. 

The first synthetic polyglycoHc acid suture was introduced in 1970 with great success (21). This is because synthetic polymers are preferable to natural polymers since greater control over uniformity and mechanical properties are obtainable. The foreign body response to synthetic polymer absorption generally is quite predictable whereas catgut absorption is variable and usually produces a more intense inflammatory reaction (22). This greater tissue compatibihty is cmcial when the implant must serve as an inert, mechanical device prior to bioresorption. 

The modulus-time or modulus-frequency relationship (or, graphically, the corresponding curve) at a fixed Temperature is basic to an understanding of the mechanical properties of polymers. Either can be converted directly to the other. By combining one.of these relations (curves) with a second major response curve or description which gives the temperature dependence of these time-dependent curves, one can cither predict much of the response of a given polymer under widely varying conditions or make rather... 

Porter, D., Vollrath, F., and Shao, J. Z. (2005). Predicting the mechanical properties of spider silk as a model nanostructured polymer. Eur. Phys. J. E 16, 199-206. 

All this is true both for low molecular weight compounds and for polymers. However, relevant differences are found not only in specific structural features, but also in the different intent with which the analysis is carried out. In common otganic stereochemistry, attention is essentially on reactivity Many aspects of regio- or stereoselectivity, as weU as reaction rate, can be explained or predicted in terms of conformation. In contrast, in polymers, the focus of interest is almost always on the physical (or mechanical) properties. It should not be forgotten that polymers are principally used as materials (plastics, fibers, elastomers, etc.) and that their properties are sometimes modified during fabrication. The fabri-cation process may induce the formation of particular structures at the molecular and supetmolecular level, which can often be traced back to conformational factors. 

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