Lamellae chemical nature

Amorphous polymers, as the name implies, are structureless except at the molecular level where we shall propose a suitable RVE. Semicrystaliine polymers exhibit a wide variety of structures depending upon their chemical nature, the degree of polymerization, the form and size of crystals and their assembly into spherulites, lamellae, fibrils etc. 

Research on the chemical nature of hardwood xylem has revealed that the walls of fibers and ray cells contain lignin of one type, syringyl, while vessel walls together with the surrounding middle lamella are rich in lignin of a second type, guaiacyl, which is the same type found in softwood xylem (9, 10). This basic chemical difference between hardwoods and softwoods could, in some instances, potentially influence phenomena that depend on the chemical nature or reactivity of wood tissue at the cellular level. Further details on the nature and distribution of wood chemical constituents are found in Chapter 2. 

Azo BCs are one fascinating class of soft materials, showing a rich variety of microphase-separated nanostructures in films because the strongly bonded azo segments and the non-azo blocks are thermodynamically incompatible. As shown in Fig. 12.1, the microphase-separated morphologies can be controlled to be spheres, cylinders, or lamellae, depending on the length, chemical nature, architecture, and number of repeated units in each block (e.g., Thomas and Lescanec, 1994). 

The chemical nature of the carbohydrate matrix and the orientation of the cellulose microfibrils influence lignin deposition. In the middle lamella and the primary wall, lignin forms spherical structures, whereas in the secondary wall, lignin forms lamellae that follow the orientation of the microfibrils [20, 24, 94]. 

J.P. Thomber, J.C. Stewart, M.W.C. Hatton and J.L. Bailey, Studies on the nature of chloroplast lamellae, II, Chemical composition and further physical properties of two chlorophyll-protein complexes, Biochemistry 6 (1967) 2006-2014. 

Equipment types range from simple circular tanks, equipped with rake arms for large thickeners used in effluent treatment, through lamella type thickeners, which are fitted with inclined plates to increase the solids handling capacity, to flotation tanks where particles are caused to rise to the surface of the tank through natural low density or the use of gas bubbles or chemical flocculating agents. 

Role of Adsorbed Surfactant Layer. Foams, irrespective of the nature of liquid and gas involved, require a third component for stabilization of thin films (lamellae) of the liquid. In the familiar case of aqueous soap films, this third component is the soap, a surface-active chemical that adsorbs at the gas—liquid interface and lowers the surface tension of water. The two effects, adsorption at the liquid surface and the depression of surface tension, are intimately linked and occur concomitantly. The adsorption is defined as the excess moles of solute per unit area of the liquid surface. In a binary system, this surface excess can be directly related to the lowering of surface tension by Gibbs adsorption equation ... 

With regard to the mechanical reactirai of a polymer network to a stress applied, it is important that loose ends of macromolecules in a network structure are as shmrt as possible and/or their concentration is low. As these ends mostly extend out of the lamellas of crystallites then, while crossUnking is taking place in an amorphous phase and with the simultaneous presence of crystallites, a network with small loose ends should be formed. The crosslink junctions stabilize the natural molecular network (entanglements and crystallites), and every chain in the system is potentially elastically operative and can contribute to the stress in a tensile experiment [33]. The stabilization effect of chemical crosslinks on entanglements and crystallites may be the direct cause of observed differences in the determination of the amount of chemical crosslinks from mechanical property measurements and sol-gel analysis of the cross-linked polymer. 

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