Crystalline polymers See

They usually have a much wider range of solvents than crystalline polymers (see later). 

The model parameters q and ML can be estimated from experimental data for radius of gyration, intrinsic viscosity, sedimentation coefficient, diffusion coefficient and so on in dilute solutions. The typical methods are expounded in several recent articles and books [20-22], Here we refer only to the results of the application to representative liquid-crystalline polymers (See Table 1). 

E is also independent of chain stiffness and chain interactions, these factors play a role in the height of the glass-rubber transition temperature and the melting point. A stiffer chain, therefore, does not result in a stiffer polymer except, sometimes, in an indirect way, namely when stiff chains enable the formation of high orientation, such as in liquid-crystalline polymers (see 4.6). 

This remarkable scaling property, which is shared by some liquid crystalline polymers (see Section 11.3.4), by nematic surfactant solutions (Section 12.4.2), and by some particulate suspensions, is a consequence of the lack of an intrinsic relaxation time. In the case... 

This equation represents a generalization of the additivity of microhardnesses for high-crystallinity polymers, see eq. (4.3). However, Hsph and Ha, instead of describing the crystal and amorphous hardness, now represent the microhardnesses of the spherulites Hsph — 200 MPa) and interspherulitic regions Ha — 120 MPa), respectively. 

The liquid crystalline polymer (see Fig. 6.14) was filled and aligned in a cell consisting of rubbed polyimide surfaces. Making use of conventional intensity holography, they showed that rather high diffraction efficiency ( 50%) could be achieved with very low laser intensities (1 mW cm-2). 

An example with real experimental results is shown in Figure 23, obtained for a side-chain liquid-crystalline polymer (see more details in [177, 178]). In the global experiment, three peaks were clearly observed. Then, TS experiments were performed at different polarization temperatures, Tp, that enabled different curves to be extracted (Figure 23). The ensemble of such curves exhibits a contour consistent with the global spectra. 

There is considerable contraction of the moulding as it cools, and it is this that causes it to grip the male part. The volume contractions (from temperatiure of the liquid to 20°C) fell just below 10% for glassy polymers and between 10 and 20% for crystalline polymers (see Table 7.2). K the mould were filled at a pressure of one atmosphere, it would show voids and excessive sink marte after cooling, due to volume contraction. This formidable problem is overcome as follows see Figure 7.32. 

CRITICAL PHASE POLYMERIZATIONS. See Volume 2. CRYSTALLINE POLYMERS. See Semicrystalline polymers. 

The modern era (Table 14.13) includes the discovery of liquid crystalline polymers see Chapter 7. The newest major scientific development is polymer interface science. While a number of papers on polymer surfaces and interfaces date back into the classical era, the science itself dates from only 1989, when several key papers were published see Chapter 12. These described the shape of the polymer chain at interfaces, and their motion and entanglement across the interfaces. Other major advances in modern polymer science and engineering include biopolymers, conducting polymers, and nanotechnology. 

Starting from early publications [72] and in subsequent works, three relaxation regions have been observed in PE and similar flexible-chain polymers at low frequencies / (10 -1) Hz relaxation I at 150-200 K, relaxation II at 240-270 K, and relaxation III over the broad temperature range, for instance, of 300-370 K for PE or 300 20 K for POM. In addition, rather strong suppression of relaxation II may be observed in high-crystalline polymers (see, e.g., DMA curve presented for POMlnFig.il). 

Two principal approaches have been used to model the yield behaviour of polymers. The first approach addresses the temperature and strain-rate dependence of the yield stress in terms of the Eyring equation for thermally activated processes [39]. This approach has been applied to many amorphous and crystalline polymers (see Section 12.5.1) and links have been established with molecular relaxation processes determined by dynamic mechanical and dielectric measurements and with non-linear viscoelastic behaviour determined by creep and stress relaxation. The Eyring approach assumes that the yield process is velocity controlled, i.e. the yield process relates to existing thermally activated processes that are accelerated by the application of the yield stress to the point where the rate of plastic deformation reaches the applied macroscopic strain rate. This approach has... 

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