Polymeric materials structure

Ehrenstein, G. W. Polymeric Materials Structure-Properties-Applications, (2001) Hanser Gardner Publications, Cincinnati. 

Partridge I.K. Cartie D.D.R and Bonnington, T. (2003), Manufacture and performance of Z-pinned composites , Ch 3 in Advanced Polymeric Materials Structure-property relationships, Eds S.Advani and G. Shonaike, CRC Press (April 2003). 

Water vapor molecules selectively dissolve into the coating or membrane material, diffuse across it, and desorb into the environment, while organic vapor molecules are prevented from permeating through its polymeric material structure. 

Summerscales J. In-process monitoring for control of closed-mold techniques for the manufacture of thermosetting matrix composites. In Shonaike GO, Advani SG, editors. Advanced Polymeric Materials Structure-Property Relationships. Boca Raton, FL CRC Press 2003. p 57 ff. 

Shonaike, G.O. Advani, S.G.(2003). Advanced Polymeric Materials Structure Proprerty Relationships, CRC Pres, pp. 463-478, ISBN 1-58716-047-1, New York, USA... 

Thus, the structural model for polyethylene and nanocomposites on its basis creep process description is offered, taking into account the indicated polymeric materials structure heterogeneity. This treatment is given within the frameworks of the cluster model of polymers amorphous state structure and shown the good correspondence wit experiment [7]. 

As it was noted above, the value A is always larger or equal to zero. This means, according to the Eq. (14.6), solid-phase polymeric material structure fractal dimension increase at uniaxial drawing, which is confirmed experimentally [5, 7]. 

In the last three chapters we have examined the mechanical properties of bulk polymers. Although the structure of individual molecules has not been our primary concern, we have sought to understand the influence of molecular properties on the mechanical behavior of polymeric materials. We have seen, for example, how the viscosity of a liquid polymer depends on the substituents along the chain backbone, how the elasticity depends on crosslinking, and how the crystallinity depends on the stereoregularity of the polymer. In the preceding chapters we took the existence of these polymers for granted and focused attention on their bulk behavior. In the next three chapters these priorities are reversed Our main concern is some of the reactions which produce polymers and the structures of the products formed. 

In addition to plastics materials, many fibres, surface coatings and rubbers are also basically high polymers, whilst in nature itself there is an abundance of polymeric material. Proteins, cellulose, starch, lignin and natural rubber are high polymers. The detailed structures of these materials are complex and highly sophisticated in comparison the synthetic polymers produced by man are crude in the quality of their molecular architecture. 

Isotactic Type of polymeric molecular structure that contains sequences of regularly spaced asymmetric atoms that are arranged in similar configuration in the primary polymer chain. Materials having isotactic molecules are generally in a highly crystalline form. 

By far the majority of carbohydrate material in nature occurs in the form of polysaccharides. By our definition, polysaccharides include not only those substances composed only of glycosidically linked sugar residues but also molecules that contain polymeric saccharide structures linked via covalent bonds to amino acids, peptides, proteins, lipids, and other structures. 

The remainder of this chapter will deal with natural polymers. These are large molecules, produced by plants and animals, that carry out the many life-sustaining processes in a living cell. The cell membranes of plants and the woody structure of trees are composed in large part of cellulose, a polymeric carbohydrate. We will look at the structures of a variety of different carbohydrates in Section 23.3. Another class of natural polymers are the proteins. Section 23.4 deals with these polymeric materials that make up our tissues, bone, blood, and even hair. ... 

Vettegren VI, Dzyubenko PS et al. (1979) In Structure and properties of polymeric materials. Zinatne, Riga... 

According to Hosemann-Bonart s model8), an oriented polymeric material consists of plate-like more or less curved folded lamellae extended mostly in the direction normal to that of the sample orientation so that the chain orientation in these crystalline formations coincides with the stretching direction. These lamellae are connected with each other by some amount of tie chains, but most chains emerge from the crystal bend and return to the same crystal-forming folds. If this model adequately describes the structure of oriented systems, the mechanical properties in the longitudinal direction are expected to be mainly determined by the number and properties of tie chains in the amorphous regions that are the weak spots of the oriented system (as compared to the crystallite)9). 

After a temptative structure-based classification of different kinds of polymorphism, a description of possible crystallization and interconversion conditions is presented. The influence on the polymorphic behavior of comonomeric units and of a second polymeric component in miscible blends is described for some polymer systems. It is also shown that other characterization techniques, besides diffraction techniques, can be useful in the study of polymorphism in polymers. Finally, some effects of polymorphism on the properties of polymeric materials are discussed. 

In this article some literature studies together with studies conducted recently in our laboratories on the crystalline and molecular structure of polymorphic polymers are reviewed, also with the aim of showing possible influences of the polymorphism on the properties and, as a consequence, on the applications of polymeric materials. 

At one extreme, one has the structural models of perfect crystals, which have long-range positional order for all the atoms (apart thermal motion). A diffraction experiment on a set of such crystals oriented in one direction (corresponding, in most real cases of polymeric materials, to an oriented fiber) would result in a pattern of sharp reflections organized in layer lines. 

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