Vitreous polymer

The hindrance of rotation of the macro-chain around bonds, which necessarily occurs in a vitreous polymer, accounts for the decrease in the real A value to A, according to the relationship [94] ... 

Relationship (11.45) actually holds (with a deviation of 20%) for epoxy polymers based on bisphenol A and cured by diamine (EP-1) or anhydride (EP-2) (Figure 11.9) [48]. This indicates that the fractality of the macromolecule section between chemical crosslinking points (entanglements) in a vitreous polymer is due to known mechanisms of the change in the statistical rigidity. 

Thus, the density of chemical crosslinking points cannot serve as an index for the cormectivity of the macromolecular skeleton of network polymers. This makes it impossible to use to characterise the structure of network polymers in a computer simulation, which follows from the results presented previously. The d value, which provides determination of elastic properties, may serve as a suitable parameter. However, to estimate other properties, one more parameter is required, which would characterise the degree of thermodynamic nonequilibrium of the structures of vitreous polymers. This role can be played by dfOr the density of the cluster network of physical entanglements [48], or by the proportion of clusters (p [140] For instance, the necessity to take into account d, V i or [Pg.334]

One interesting way to modify the mechanical properties and preserve the environmentally friendly aspect of polylactides is by introducing bio-based compounds within the PLA matrix. Furthermore, the use of non-edible biomass could constitute a wide source of additives, and could provide an economically viable way to get added-value from residues.Numerous studies to transform biomass by-products of the agriculture and food industries have been conducted recently and some eco-friendly products have been successfully used to plasticize vitreous polymers, such as PVC. ... 

It is known that macromolecules of polycarbonate (PC) are characterized by a great rigidity, limited by the rotation of aromatic nuclear and due to this reason they are weakly tend to crystallization. Industrial PC is a vitreous polymer which has both short and long range ordering areas. The degree of crystallity does not usually overcome 10-15 %, and it can reach 30-40% only after special treatment of specimens [2]. 

The linearisation of the creep curves, by representing in double logarithmic co-ordinates the variation of deformation with time can be done applying the method developed by B.W. Chery and D.F. Kindles [887], i.e. of overlapping of the stress vs. time, for the prediction of the polymers behaviour to creep for long periods of solicitation. In the case of the vitreous polymers, the creep rate can depend, in certain conditions, only by the applied stress and instantaneous deformation. 

Figure 9 Sketch of a craze preceding a crack in vitreous polymer. There are two regimes for the active zone a when AcX Rg, the active zone behaves like a rubber and can sustain load, whereas if A>X, Rg, the active zone behaves like a fluid and fails under stress. Adapted from (61).

TA1 Tager, A. A. and Popova, O., The effect of the molecular weight of vitreous polymers on the packing density of their chains. III. Triacetylcellulose (Russ.), Zh. Fiz. Khim., 33, 593, 1959. 

The sorption mechanism is more complicated for the porous vitreous polymers. In this case, the sorbet s surface and low molecular substances have true opening in the pol5nner. " ... 

The principal classes of high performance fibers are derived from rigid-rod polymers, gel spun fibers, modified carbon fibers, synthetic vitreous fibers, and poly(phenyiene sulfide) fibers. 

Elimination from the vitreous occurs by one of two pathways. This can be visualized by injecting fluorescent compounds and examining the concentration distribution in frozen sections obtained after a steady state has been established [230]. If the major route of elimination is by means of the re-tina/choroid, at steady state the lowest concentration would be in the vicinity of the retina. The contours observed in frozen sections of the rabbit eye obtained after intravitreal injection of fluorescein exhibit this pattern, with the highest concentration immediately behind the lens (Fig. 16A). Compounds not chiefly eliminated through the retina exit the vitreous by passive diffusion and enter the posterior aqueous, where they are eliminated by the natural production and outflow of aqueous humor. In such a situation, the contours would be perpendicular to the retina, with the highest concentration towards the rear of the vitreous cavity. This appears to be the case for fluorescently labeled dextran polymer, whose contours decrease in concentration toward the hyaloid membrane (Fig. 16B). 

Kirkpatrick, M.J., Finney, W.C. and Locke, B.R. (2003) Chlorinated organic compound removal by gas phase pulsed streamer corona electrical discharge with reticulated vitreous carbon electrodes, Plasmas and Polymers 8, 165-77. 

ABA-type triblock copolymerization of MMA/BuA/MMA should give rubberlike elastic polymers. The resulting copolymers should have two vitreous outer blocks, where the poly(MMA) moiety (hard segment) associates with the nodules, and the central soft poly(BuA) elastomeric block provides rubber elasticity. Ihara et al. [35] were the first to synthesize an AB-type block copolymer, with MMA (190 equivalents of initiator) first polymerized by... 

Several approaches have been undertaken to construct redox active polymermodified electrodes containing such rhodium complexes as mediators. Beley [70] and Cosnier [71] used the electropolymerization of pyrrole-linked rhodium complexes for their fixation at the electrode surface. An effective system for the formation of 1,4-NADH from NAD+ applied a poly-Rh(terpy-py)2 + (terpy = terpyridine py = pyrrole) modified reticulated vitreous carbon electrode [70]. In the presence of liver alcohol dehydrogenase as production enzyme, cyclohexanone was transformed to cyclohexanol with a turnover number of 113 in 31 h. However, the current efficiency was rather small. The films which are obtained by electropolymerization of the pyrrole-linked rhodium complexes do not swell. Therefore, the reaction between the substrate, for example NAD+, and the reduced redox catalyst mostly takes place at the film/solution interface. To obtain a water-swellable film, which allows the easy penetration of the substrate into the film and thus renders the reaction layer larger, we used a different approach. Water-soluble copolymers of substituted vinylbipyridine rhodium complexes with N-vinylpyrrolidone, like 11 and 12, were synthesized chemically and then fixed to the surface of a graphite electrode by /-irradiation. The polymer films obtained swell very well in aqueous... 

Intrinsically conducting polymers, 13 540 Intrinsic bioremediation, 3 767 defined, 3 759t Intrinsic detectors, 22 180 Intrinsic fiber-optic sensors, 11 148 Intrinsic magnetic properties, of M-type ferrites, 11 67-68 Intrinsic photoconductors, 19 138 Intrinsic rate expressions, 21 341 Intrinsic semiconductors, 22 235-236 energy gap at room temperature, 5 596t Intrinsic strength, of vitreous silica, 22 428 Intrinsic-type detectors, cooling, 19 136 Intrinsic viscosity (TV), of thermoplastics, 10 178... 

VDC polymer resistance to, 25 711 of vinyl chloride, 25 631 of vitreous silica, 22 422 in vitreous silica manufacture, 22 413 in wastewater treatment, 25 889t, 892t, 893, 910-911, 911-912 Oxidation and corrosion stability (OCS) tests, 75 235... 

---