Polycarbonate

About: Polycarbonate is a(n) research topic. Over the lifetime, 14032 publication(s) have been published within this topic receiving 141740 citation(s). The topic is also known as: PC & Polycarbonate, PC.

A complex plane analysis of α‐dispersions in some polymer systems

Abstract: The α-dispersion in many polymer systems is the process to be associated with the glass transition temperature where many physical properties undergo drastic changes. We have measured and analyzed the complex dielectric behavior of the α-dispersions for five polymers [i.e., polycarbonate and polyisophthalate esters of bisphenol A, isotactic poly-(methyl methacrylate), poly(methyl acrylate), and a copolymer of phenyl methacrylate and acrylonitrile] and have found that the usual methods of analysis cannot be used to represent the data. However, it is possible to represent the relaxation process as the sum of two dispersions but there is no evidence to support this contention. An empirical expression is proposed to represent the data. This expression which takes the form of appears to be a general representation for the three known dispersions, i.e., Debye, circular arc, and skewed semicircle. The complex dielectric constants calculated with the aid of this expression and the parameters for each polymer system which was determined graphically were found to be in excellent agreement with the experimental complex dielectric constants. This method of representation was extended to sixteen α-dispersions reported in the literature always with excellent results.

Rheological and dielectrical characterization of melt mixed polycarbonate-multiwalled carbon nanotube composites

Abstract: A series of composites of polycarbonate (PC) with 23 different contents of multiwalled carbon nanotubes (MWNT) was produced by melt mixing using the masterbatch dilution method In dielectric measurements, AC conductivity and complex permittivity data obtained in the frequency range between 10 −3 and 10 7 Hz at room temperature indicated the electrical percolation threshold at about 10 wt% The dynamic mode melt rheological measurements for the same samples at eight temperatures between 170 and 280 °C showed a visible change in the frequency dependence of dynamic moduli and the absolute value of the complex viscosity | η *| particularly at low frequencies In literature these changes are sometimes related to so called ‘percolation threshold concentration’ Applying this picture to our experimental data we have to assume that the percolation threshold is strongly dependent on the measurement temperature It changes from about 5 to 05 wt% MWNT by increasing the measurement temperature from 170 to 280 °C, respectively This temperature dependence cannot be explained by a classical liquid-solid transition but may be related to the existence of a combined nanotube-polymer network

Processing-property relationships of polycarbonate/graphene composites

Abstract: Polycarbonate composites reinforced with graphite and functionalized graphene sheets (FGS) were produced using melt compounding. Composite samples with different degrees of graphite orientation were processed via injection, compression molding and long-term annealing. Electron microscopy and X-ray scattering revealed that FGS was nearly exfoliated. However, graphite remained multi-layer even after melt processing. Flow induced orientation of graphite was observed from both injection and compression molded samples. Graphite particles in samples after long-term annealing exhibited more random orientation. Composites with the exfoliated FGS required a smaller amount of reinforcement for rigidity and connectivity percolation, as determined by melt rheology and electrical conductivity measurements. FGS also showed better performance in suppressing gas permeability of polycarbonate. However, improvements by FGS dispersion in tensile modulus and dimensional stability were not as significant. This may be due to defects in the sheet structure formed during oxidation and pyrolysis used to exfoliate.

Copolymerization of carbon dioxide and epoxide with organometallic compounds

Abstract: Attempts to copolymerize carbon dioxide with epoxide led us to the first success in using carbon dioxide as a direct starting material for synthesizing high polymers. Some organometallic catalyst systems were found to catalyze the alternate copolymerization of carbon dioxide and epoxide, resulting in the formation of polycarbonates, the structures of which were confirmed with the aid of IR, NMR and elemental analysis. Diethylzinc-water system produced a methanol insoluble aliphatic polycarbonate of much higher molecular weight than that produced by polycondensation. Thermal properties of the methanol insoluble polycarbonate were studied by differential thermal analysis and thermogravimetric analysis.

Template synthesis of nanowires in porous polycarbonate membranes: electrochemistry and morphology

Abstract: The potentiostatic electrochemical template synthesis of nanowires (Ni, Co, Cu, Au, and polyporrole) in polycarbonate track-etched membranes with nominal pore diameters dN between 10 and 200 nm is ...