Amorphous matrix polymer

Materials. The amorphous matrix polymer was polyetherimide (Ultem 1000) sold by the General Electric Company. The semicrystalline matrices were PEEK and a high molecular weight polyphenylenesulfide (PPS) provided by ICI and Phillips Petroleum Co. (Barthesville, OK.), respectively. The reinforcing phase was one of several LCPs a liquid crystalline aromatic copolyester consisting of 73 %... 

Some recent examples demonstrating the molecular dispersion of rod polymer molecules in coil polymer matrices due to ionic interactions were given by Parker et al. (1996). These systems were based on three types of ionic PPTA s (Figure 5.4) and polar polymers, such as poly(4-vinylpyridine) (PVP), poly(vinyl chloride) (PVC), poly(ethylene oxide) (PEO), and poly(styrene-co-acrylonitrile) (S-AN). Due to the ionic-dipole interactions the rod-coil polymer pairs formed molecular composites as revealed by optical clarity, polarized microscopy, Tg measurements, as well as TEM observations. More significantly the molecular composites based on amorphous matrix polymers (e.g., PVP) were all transparent and showed no phase separation upon heating. Therefore they are melt-processible. As would expected, the mechanical properties of the molecular composites were... 

No polymer is ever 100% crystalline at best, patches of crystallinity are present in an otherwise amorphous matrix. In some ways, the presence of these domains of crystallinity is equivalent to cross-links, since different chains loop in and out of the same crystal. Although there are similarities in the mechanical behavior of chemically cross-linked and partially crystalline polymers, a significant difference is that the former are irreversibly bonded while the latter are reversible through changes of temperature. Materials in which chemical cross-linking is responsible for the mechanical properties are called thermosetting those in which this kind of physical cross-linking operates, thermoplastic. 

If dye molecules are embedded into an amorphous matrix, preferably transparent polymers, greatly and inbornogenously broadened spectral lines are observed. This broadening is caused by the energetic interaction of the dye molecules with the locally different environment in the polymer matrix. The ratio of the homogenous initial line width of the dye molecule T to the inhomogenous line width of the dye in the polymer T ranges from 1 10 to 1 10 . ... 

Figure 3.6. Two-dimensional representation of molecules in a crystalline polymer according to the fringed micelle theory showing ordered regions (crystallites) embedded in an amorphous matrix.

As Carfagna et al. [61] suggested, the addition of a mesophasic polymer to an amorphous matrix can lead to different results depending on the properties of the liquid crystalline polymer and its amount. If a small amount of the filler compatible with the matrix is added, only plasticization effect can be expected and the dimensional stability of the blend would be reduced. Addition of PET-PHB60 to polycarbonate reduced the dimensionality of the composite, i.e., it increased the shrinkage [42]. This behavior was ascribed to the very low... 

Usually, crystallization of flexible-chain polymers from undeformed solutions and melts involves chain folding. Spherulite structures without a preferred orientation are generally formed. The structure of the sample as a whole is isotropic it is a system with a large number of folded-chain crystals distributed in an amorphous matrix and connected by a small number of tie chains (and an even smaller number of strained chains called loaded chains). In this case, the mechanical properties of polymer materials are determined by the small number of these ties and, hence, the tensile strength and elastic moduli of these polymers are not high. 

Cement and Concrete Concrete is an aggregate of inert reinforcing particles in an amorphous matrix of hardened cement paste. Concrete made of portland cement has limited resistance to acids and bases and will fail mechanically following absorption of crystal-forming solutions such as brines and various organics. Concretes made of corrosion-resistant cements (such as calcium aluminate) or polymer resins can be selected for specific chemical exposures. 

The chains that make up a polymer can adopt several distinct physical phases the principal ones are rubbery amorphous, glassy amorphous, and crystalline. Polymers do not crystallize in the classic sense portions of adjacent chains organize to form small crystalline phases surrounded by an amorphous matrix. Thus, in many polymers the crystalline and amorphous phases co-exist in a semicrystalline state. 

For instance, crystalline lamellae in an amorphous matrix (semicrystalline polymer materials), hard domains in a soft matrix (thermoplastic elastomers)... 

Problem. Let a polymer fiber contain rod-shaped structural entities in an amorphous matrix with some preferential orientation. Let us assume that the rods are crystalline. Our interest is to study the crystalline structure of the rods. Instead of sharp hkl reflections we observe that each reflection is smeared over a spherical cap in solid angle. Thus the observed intensity is suitably expressed in polar coordinates... 

A decrease in the coefficient a with an increase in temperature as a result of the intensification of the molecular mobility in the polymer matrix with the increase in temperature. The increase in temperature decreases the energetic barrier Eor. In the amorphous-crystalline polymers all these processes occur in the amorphous phase of the polymer where reactants are dissolved. 

In most cases, however, polymers crystallize neither completely nor perfectly. Instead, they give semicrystalline materials, containing crystalline regions separated by adjacent amorphous phases. Moreover, the ordered crystalline regions may be disturbed to some extent by lattice defects. The crystalline regions thus embedded in an amorphous matrix typically extend over average distances of 10-40 nm. The fraction of crystalline material is termed the degree of crystallinity. This is an important parameter of semicrystalline materials. 

Where a melt-crystallized polymer has been processed by drawing, rolling or other means to produce an aligned structure in which lamellae as well as polymer chains have discernible order, a pseudocrystalline unit cell is present. Provided that this unit cell contains elements of the crystals as well as the boundaries between crystals and that it is entirely typical of the material as a whole then it could be considered as a RVE within the meaning defined above. The lamella crystal itself sometimes considered as embedded in an amorphous matrix would not seem to be an acceptable RVE for reasons similar to those advanced against the Takayanagi model, namely that its modulus is dependent upon the surface tractions. The boundaries between lamella crystals in the matrix must be included in an acceptable RVE. 

A second class of polarizers uses dichroism to produce linearly polarized light. Techniques to produce dichroic polarizing sheets were pioneered by Land [52], These are made by dissolving a strongly dichroic, small molecule into an amorphous, transparent polymer. The dichroic molecules are then oriented by a uniaxial stretching of the polymer matrix. Since this is accomplished below the polymers glass transition temperature, this ori-... 

Luminescence decay curves are also often used to verify that samples do not contain impurities. The absence of impurities can be established if the luminescence decay curve is exponential and if the spectrum does not change with time after pulsed excitation. However, in some cases, the luminescence decay curve can be nonexponential even if all of the luminescing solutes are chemically identical. This occurs for molecules with luminescence lifetimes that depend upon the local environment. In an amorphous matrix, there is a variation in solute luminescence lifetimes. Therefore, the luminescence decay curve can be used as a measure of the interaction of the solute with the solvent and as a probe of the micro-environment. Nag-Chaudhuri and Augenstein (10) used this technique in their studies of the phosphorescence of amino acids and proteins, and we have used it to study the effects of polymer matrices on the phosphorescence of aromatic hydrocarbons (ll). 

In some respects semi-crystalline polymers are similar to filled reinforced systems (crystallites, embedded in amorphous matrix) in the same way highly oriented semicrystalline polymers are similar to fibber-reinforced systems (micro-fibrils embedded in... 

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