Polymers fastness properties

Pigments have little real substantivity for textiles and therefore must be held onto the fabric surface by means of binders. These binders are low molecular weight polymers and copolymers at the time of application. Upon further polymerization, they cross-link and bond to the textile fiber and to the pigment. Thus, the fastness properties of pigment paddings depend upon the success of proper curing of the binders (8). While proper curing is imperative, it can be achieved by use of an efficient catalyst at lower temperatures and shorter cure times than those conventionally employed. 

Dibromanthrone red, PR 168, Cl No. 59300 is a bright, yellow-shade red with excellent fastness properties with no tendency to fade on prolonged outdoor exposure at all depths of shade. However, the pigment tends to bloom in flexible PVC and polyolefins and cannot be recommended for such polymer systems. 

Perylenes offer shades ranging from yellow-red to blue-red or maroon. They generally possess excellent fastness properties with respect to heat, light, and weather while offering colorants with a high color strength. Perylenes can be used to color most polymer systems, including PVC, LDPE, HD PE, and PP. 

The chemical shielding, dipole-dipole, spin-spin indirect coupling or J-coupling, spin-rotation, and hyperfine couplings represent the major internal magnetic interactions. The quadrupolar interaction has an electrostatic character. All these interactions have a tensorial character, ie, are function on the ori-entation of the principal axes of the tensor relative to the direction of Bq. They are relevant for solid polymers below and around the glass transition temperatures. For polymer in solution or for soft polymers fast molecular motions average these anisotropic interactions to isotropic or residual values which can be zero. Detailed description of the properties of these spin interactions can be found in References 1-9. 

Pigments and dyes are distinctly different types of colourants. A pigment is a finely-divided solid which is essentially insoluble in its polymeric application medium. Pigments are incorporated by a dispersion process into the polymer while it is in a liquid phase and, after the polymer solidifies, the dispersed pigment particles are retained physically within the solid polymer matrix. In contrast, a dye dissolves in the polymeric application medium and is usually retained as a result of an affinity between individual dye molecules and molecules of the polymer. Pigments are generally preferred to dyes for the coloration of plastics mainly because of their superior fastness properties, especially migration resistance. 

Similar observations apply to its coloristic and fastness properties in polymers. However, in plasticized PVC it has the advantage of being almost entirely fast to migration. Like Pigment Violet 23 it dissolves to some extent in polymers therefore much of its heat stability is lost as the white pigment concentration in a system is increased. 

Widely employed in the coloration of plastics. Pigment Violet 23 generally exhibits very good properties in terms of heat stability and lightfastness provided its concentration in the polymer is not too low (the fastness properties tend to dimin-... 

This book does not intend to cover the whole field of thermotropic liquid crystalline (TLC) materials as it is extremely difficult to cover within a single book. Instead it presents a collection of Chapters written by experts on various exciting topics in the field. Properties of recently developed TLCs (such as banana-type, thiophene-based, and columnar TLCs), phase biaxiaUty, and novel polymeric TLCs are discussed In detail. Solid-state NMR studies to obtain atomistic-level structural and geometrical information of TLCs are presented. Synthesis of liquid crystalUne conjugated polymers, fast switching of nematic materials by an electric field, and photoconducting discotic systems are also presented. 

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