Polycarbonates description

A rather crude, but nevertheless efficient and successful, approach is the bond fluctuation model with potentials constructed from atomistic input (Sect. 5). Despite the lattice structure, it has been demonstrated that a rather reasonable description of many static and dynamic properties of dense polymer melts (polyethylene, polycarbonate) can be obtained. If the effective potentials are known, the implementation of the simulation method is rather straightforward, and also the simulation data analysis presents no particular problems. Indeed, a wealth of results has already been obtained, as briefly reviewed in this section. However, even this conceptually rather simple approach of coarse-graining (which historically was also the first to be tried out among the methods described in this article) suffers from severe bottlenecks - the construction of the effective potential is neither unique nor easy, and still suffers from the important defect that it lacks an intermolecular part, thus allowing only simulations at a given constant density. 

A few years later, Baba reported a more comprehensive description of the coupling reaction of oxetane and C02 catalyzed by organotin iodides and Lewis bases as catalysts [60]. It was shown in this instance, that the choice of Lewis base which coordinated to the organotin iodides affected the catalytic activity and selectivity, that is, poly(TMC) and/or trimethylene carbonate. Whilst complexes with Bu3P yielded polycarbonate, the combination of Bu3SnI with Bu3P=0 yielded TMC exclusively in good yields. A reaction mechanism, as proposed by Baba and coworkers, is illustrated in Scheme 8.5. 

By combining both experimental techniques and atomistic modelling, the investigation into the motions involved in the ft transition of PMMA, CMIMx and MGIMx copolymers illustrates the detailed description that can be achieved (as for bisphenol A polycarbonate in Sect. 5). 

The approach developed in this paper, combining on the one side experimental techniques (dynamic mechanical analysis, dielectric relaxation, solid-state 1H, 2H and 13C NMR on nuclei at natural abundance or through specific labelling), and on the other side atomistic modelling, allows one to reach quite a detailed description of the motions involved in the solid-state transitions of amorphous polymers. Bisphenol A polycarbonate, poly(methyl methacrylate) and its maleimide and glutarimide copolymers give perfect illustrations of the level of detail that can be achieved. 

In Section I we introduce the gas-polymer-matrix model for gas sorption and transport in polymers (10, LI), which is based on the experimental evidence that even permanent gases interact with the polymeric chains, resulting in changes in the solubility and diffusion coefficients. Just as the dynamic properties of the matrix depend on gas-polymer-matrix composition, the matrix model predicts that the solubility and diffusion coefficients depend on gas concentration in the polymer. We present a mathematical description of the sorption and transport of gases in polymers (10, 11) that is based on the thermodynamic analysis of solubility (12), on the statistical mechanical model of diffusion (13), and on the theory of corresponding states (14). In Section II we use the matrix model to analyze the sorption, permeability and time-lag data for carbon dioxide in polycarbonate, and compare this analysis with the dual-mode model analysis (15). In Section III we comment on the physical implication of the gas-polymer-matrix model. 

In some studies, a statistical description of the nanotube dispersion state was obtained from TEM images. For example, Uchida et al. (56) measured the diameter distribution of SWNT bundles in poly(acrylonitrile), with and without a purification treatment involving sonication in methanol. The different bundle diameter distributions (especially the mean diameter) could explain the different composite tensile moduli. Fornes et al. (57) also determined the diameter distribution of SWNTs bundles in a polymer matrix (namely polycarbonate). To improve the contrast in the bright-field TEM images and better measure the bundle diameter, they dissolved the polymer in chloroform and studied the remaining SWNT network. 

Figure 102 Field dependence of the effective hole mobility in a number of polymeric samples for various concentrations (given in the by curve descriptions) of two molecular dopants [TPA (tripheny-lamine) and TPM (triphenylmethane)] in polycarbonate matrix. The experimental data for TPA (full circles) from Ref. 122 and for TPM (open circles) from Ref. 464, plotted in a semilogarithmic scale vs. the complex variable aF—b/F) with a and b resulting from the slopes of the high- and low-field range separate straight-line plots. After Ref. 319. Copyright 1992 Jpn. JAP, with permission.

The first measurements of Pb isotopes in Greenland snow were reported in 1993 (45). The samples were taken from a 10.7 m long, 10.5 cm diameter, snow core drilled at Summit, central Greenland, in 1989 (72°35 N, 37°38 W, mean annual accumulation rate 21.5 g cm year ). Cores were drilled with a polycarbonate auger to minimise the Pb contamination. The core contained snow deposited between the years 1967 and 1988. The 3.23 km elevation of the site provided representative samples of free tropospheric aerosols. An expanded data set and a more complete description and interpretation of these data were later reported by Rosman et al. (46). The latter included samples from the upper part of a 70 m snow core including snow deposited between 1960 and 1974. Data on all four Pb isotopes were given for these samples ( Pb/ Pb, ° Pb/ ° Pb and Pb/ °" Pb). Aliquots of these samples were also analysed for heavy metals by Boutron et al. (47) who showed there was a reduction in the Pb concentration in Greenland snow after 1970, which they attributed mainly to the reduction in the use of alkyl-leaded petrol. 

An empirical method for predicting the chemical compositions of random or partially ordered condensation copolymers which are capable of exhibiting mesophases (either in solution or in the melt) was devised by the author in 1989, while working on liquid crystal copolymer synthesis for BP Chemicals. A brief description of the method and its application to the chemical synthesis of amorphous thermotropic polyamides has been given in a previous paper [45] and a further more detailed description of the method is to be published shortly [46]. Subsequently, the method has been updated and applied to polycarbonates and polyimides. Thermotropic polyimides have also been synthesised by the author resulting from the use of the predictive method [43]. 

Presently, the amount of data on transport in uniaxially oriented amorphous polymers is small in comparison with that of semicrystalline materials. The transport properties of oriented natural rubber (22), polystyrene (i3.,ii), polycarbonate (22.), and polyvinyl chloride (22,22) among others have been reported. One of the more complete descriptions of the effects of uniaxial orientation on gas transport properties of an amorphous polymer is that by Wang and Porter (34) for polystyrene. 

Because of the toxicity of phosgene, research on nonphosgene routes to isocyanates and polycarbonates has intensified over the past decade. Eni-Chem of Italy has commercialized a process to manufacture dimethyl carbonate (DMC) by oxidative carbonylation of methanol. Dimethyl carbonate can be used as an intermediate for the production of polycarbonates. A description of the nonphosgenation chemistry for producing DMC and polycarbonates is included in Section II.A in this chapter. 

The description of applications is limited to those used in the manufacture of primary petrochemicals. It is also restricted to applications of major commercial significance and those practiced at multiple sites. The emphasis is strictly on commercial applications with a few exceptions, such as where commercialization will have an obvious and drastic effect on conventional technology (e.g., in the nonphosgene routes to isocyanates and polycarbonates). 

The fact, that macromolecular coil in diluted solution is a fractal object, allows to use the mathematical calculus of fractional differentiation and integration for its parameters description [72-74]. Within the framework of this formalism there is the possibility for exact accounting of such nonlinear phenomena as, for example, spatial correlations [74]. In the last years the methods of ftactional differentiation and integration are applied successfully for pol5mier properties description as well [75-77]. The authors [78-81] used this approach for average distance between polymer chain ends calculation of polycarbonate (PC) in two different solvents. 

General Description Ethylene vinyl alcohol (EVOH) copolymers are an important component of high-barrier, multilayered packaging materials. They can be easily coextruded with nylons, but coextrusion with polyolefins, polyesters, and polycarbonates requires use of adhesives in which the layers are structured as follows base film, adhesive, EVOH, adhesive, and heat sealant. 

The remaricable efficacy of the dual-mode sorption and transport rturdel for description of pure component data has been illustrated by plots of the linearized forms of Eq. (20.4-16) for a wide number of polymer-pen nt systems. " Typical examples of such data are shown in Fig. 20.4-10 for various gases in polycarbonate. These linearized plots are stringent tests of the ability of the proposed functional forms to describe the phenomenological data. Assink also has investigated the dual-mo model using a pulsed NMR technique and concluded the following ... 

Using the same multiparameter model as the one for the description of the specific volume under various temperature histories [4,6] we will examine and predict the creep behavior of a commercial polystyrene (Hostyren N 7000) [9-11] and a commercial polycarbonate (Makrolon 2800) [12] under various thermal histories. The theoretical calculations will be compared with experimental data. 

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