Polycarbonate, amorphous

Amorphous polycarbonate is transparent with light transmittance ranging from 80% up to 91%, a haze of roughly 0.7-1.5% and a refractive index of about 1.58-1.586. 

The density and n value of a polymer crystal are greater than those of an amorphous polymer. Many polymers are opaque because of the presence of ordered clusters of crystals called spherulites which have different n values. ptfe, which is highly crystalline, is opaque but amorphous polycarbonate (PC), PMMA, and PS are noncrystalline and clear. 

Lm,W., Kramer,E. J. Small-angle X-ray scattering from amorphous polycarbonate. J. Appl. Phys. 44,4288-4292 (1973). 

The density or its reciprocal, the specific volume, is a commonly used property for polymeric materials. The specific volume is often plotted as a function of pressure and temperature in what is known as a pvT diagram. A typical pvT diagram for an unfilled and filled amorphous polymer is shown, using polycarbonate as an example, in Figs. 2.10 and 2.11 The two slopes in the curves represent the specific volume of the melt and of the glassy amorphous polycarbonate, separated by the glass transition temperature. 

Kristiak, J., Bartos, J., Fristiakova, K., Sausa, O., Bandzuch, P. (1994) Free-volume microstructure of amorphous polycarbonate at low temperatures determined by positron-annihilation-lifetime spectrospcopy . Phys. Rev.B. 49(10), 6601. 

Computer) The Figure 4-2 data for amorphous polycarbonate is listed in file PC 4 OkDa. TXT in the CD. As explained in the footnote of Figure 4-2, these data are actually 1/7(10 s). Using the WLF constants for polycarbonate of C, = 16.4 and C2 = 54.3, with Tg = 150.8 °C, correct these data using the approximation of Problem 2-5. Plot on the same graph the modulus-temperature curves based on your G(10 s) and the original 1/7(10 s), and comment on the differences. 

In addition to solution measurements, several bulk measurements have been made on ferrocene chromophores incorporated into poled polymer films." These measurements have shown that there are no special problems associated with poling ferrocene chromophores. The best bulk performance achieved for a ferrocene-based polymer material was an EO coefficient, of 25pmV (1,300 nm) for a film of 18 incorporated at 20 wt.% into amorphous polycarbonate " this is not, however, competitive with the performance of state-of-the-art all-organic poled polymer systems. In some cases, the chromophores have been covalently linked to the polymer chain. Bulk SHG measurements have also been made on self-assembled Langmuir-Blodgett films incorporating ionic ferrocene-based chro-... 

Variation of thermal diffusivity with temperature, for amorphous polycarbonate and semi-crystalline polyethylene. 

Exceedingly large losses at low frequencies above 150°C are attributed to Maxwell-Wagner-Sillars (NWS) polarizations arising from conduction mismatches at the structural interfaces between a continuous matrix of amorphous polycarbonate and a crystalline or densified second phase. Provided that the discontinuous phase tends towards a two-dimensional aspect and has a conductivity less than that of the matrix, theory predicts substantial NWS losses even with a low concentration of the discontinous phase [37]. 

By chromophore-polymer composite materials, we refer to chromophores physically incorporated (dissolved) into commercially available polymer materials such as amorphous polycarbonate (APC) [58] finm Aldrich Chemicals. Chromophore and polymer are dissolved in a suitable spin-casting solvent, such as cyclopentanone. Spin-cast thin films are heated to near the glass transition temperature of the composite material (which will vary with chromophore concentration due to the plasticizing effect of the chromophore). Acentric chromophore order is induced by electric field poling. If one assumes that the presence of the polymer host does not stericaUy hinder the reorientation of the chromophores under the influence of the poling field, the order parameter can be readily calculated. We have already noted that if chromo-phore-chromophore intermolecular electrostatic interactions are neglected then (cos d) = fiF/5kT and the order parameter will be independent of chromophore concentration (or number density, N). Intermolecular electrostatic interactions can be treated at several levels of sophistication. 

Barto, R.R., Jr., P.V. Bedworth, C.W. Frank, S. Ermer, and R.E. Taylor. 2005. Near-infrared optical-absorption behavior in high-beta nonlinear optical chromophore-polymer guest-host materials. II. Dye spacer length effects in an amorphous polycarbonate copolymer host. J Chem Phys 122 234907 1-14. 

Figure 4.166 shows a DMA analysis of an amorphous polycarbonate, poly(4,4 -isopropylidenediphenylene carbonate). These data were taken with an instrument like that seen in Fig. 4.156. Measurements were made at seven frequencies between 0.01 and 1 Hz at varying temperatures. Again, the glass transition is obvious from the change in flexural storage modulus, as well as from the maximum of the loss modulus.

Thus the scattered low frequency intensity can be directly related to the specific heat calculation. Such calculations have been carried out satisfactorily for amorphous polycarbonate (58). 

C. G Sell and J. J. Jonas, Yield and Transient Effects During the plastic Deformation of Solid Polymers J. Mater. Sci. 16,1956-1974 (1981) C. G Sell, H. El Baril, J. Perez, J. Y. Cavaille and G. P. Johari, Cavailld and G.P Johari, Effect of Plastic Deformation on the Microstructure and Properties of Amorphous Polycarbonate Mater. Sci. Eng., Alio, 223-229(1989). 

Lin and coworkers [41] also investigated the static tensile strength and fatigue behavior of long glass-reinforced semicrystalline polyannide and amorphous polycarbonate composites. The static tensile measurement at various tanperatures and tension-tension fatigue loading tests at various levels of stress amplitudes were studied. 

The data in Fig. 2.84 indicate that an amorphous polycarbonate sample as small as 50 pg could be heated at 400 C/min and yield a glass transition that is as discernible as that shown in Fig. 2.84 for the 1-mg sample of polycarbonate scanned at 20 C/min. These results indicate that it is now possible to determine thermal properties on polymeric samples that were previously deemed too small to analyze. 

An amorphous polycarbonate (bisphenol A polycarbonate, Lexan ) film with a thickness of 30.5 pm was placed inside the lid of a WVT capsule. The lid had a 4.25-mm-diameter hole. The capsule was sealed with about 53 mg of water present. The TGA was held at 23 °C during the mass loss experiment. In this case the relative humidity inside the TGA was zero (i.e., p2 =0). The vapor pressure above the water drop inside the capsule (pi), was 21.1mm (2.11 cm) of mercury as found in a table of water vapor pressure values (Weast 1973). In Fig. 3.36 the mass loss of water in the sealed receptacle is plotted as a function of time. From these data it was determined that water vapor moved through the amorphous polycarbonate film at a constant rate of 0.062 0.001 mg/h for more than 275 min. This is equivalent to Ami At =0.44 mg/ (cm -h) in Eq. (3.33). 

Historically, guest-host systems have been the first polymeric NLO active materials to be developed. In these systems a high Per chromophore is physically dispersed in a suitable, amorphous polymeric matrix. The non centrosymmetry is induced by the usual poling procedure. Polymer matrices most frequently used include poly(methylmethacrylate), PMMA, because of its excellent optical properties, as well as other amorphous polymers with high Tg as amorphous polycarbonate (APC), polyquinoline, polyimides. Many reports have dealt initially with guest-host systems containing DRl or DANS as the dispersed chromophore. 

Very recently. Block et al. [133] reported on optical modulators with ring diameters smaller than 50 pm in a silicon nitride based waveguide system on silicon oxide with a top cladding of an electro-optic polymer, namely AJTB141 chromophore 28% wt into an amorphous polycarbonate polymer. Using Cu electrodes they attained a high frequency modulator with modulation up to 10 GHz with low drive voltage (2.7 Vpp). 

Fig. 14.14. Craze microstructure in a thin film of amorphous polycarbonate deformed in tension at -100°C.

Figure 1.1 Enthalpy (heat content) vs. temperature. Comparison of data for typical crystalline material (naphthalene) with those for crystalline (acetal copolymer) and amorphous (polycarbonate) plastics...

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