Polycarbonate Dynamic mechanical properties

The most extensive studies of the dynamic-mechanical properties of polycarbonates have been reported by Yee et al. 

W. S. Chow and S. S. Neoh, Dynamic mechanical, thermal, and morphological properties of silane-treated montmorillonite reinforced polycarbonate nanocomposites. Journal of Applied Polymer Science, 114 (2009), 3967-75. 

Multi-wall carbon nanotubes (MWNTs) were also used as the reinforcing phase in LCP nanocomposites prepared by means of melt blending technique in a twin-screw extruder equipped with an ultrasonic unit to facilitate MWCNT dispersion (Kumar and Isayev, 2010). The role of ultrasonication was positive and resulted in increased structural as well as rheological properties because of the better-dispersed nanofiller. MWCNT were also used in LCP blends with polycarbonate (PC) (Mukherjee et al., 2009) and PEI (Nayak, Rajasekar, and Das, 2010). In the first case, PC/LCP/MWNTs nanocomposites containing as-received or modified (COOH-MWNT) carbon nanotubes were prepared through the melt process in an extruder and then compression molded. The incorporation of functionalized MWCNTs improved thermal, structural, dynamic-mechanical, and electrical properties of the composites, in particular in blends with treated MWCNTs. MWCNTs were also used, both unmodified and surface treated with SiC particles, to improve dispersion in PEI/LCP blends prepared by melt blending. In the ternary systan, viscosity in the blend with modified MWCNTs was found to be lower than the ternary blend with pure MWCNTs, probably because modified MWCNTs improved the fibrillation of LCP compared to pure MWCNTs. Nanocomposite matrices have not been used to prepare foams yet. 

The most desirable property of polycarbonates is their high ductility on impact, relative to other engineering polymers in the unmodified state. There is no consensus on the mechanism of ductility researchers continue to explore this behavior through molecular dynamics studies of chain segment motion during the formation of crazes and propagation of the failure. 

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. 

To date, results have been obtained for minimum-energy type simulations of elastic deformations of a nearest-neighbor face-centered cubic (fee) crystal of argon [20] with different inclusion shapes (cubic, orthorhombic, spherical, and biaxially ellipsoidal). On bisphenol-A-polycarbonate, elastic constant calculations were also performed [20] as finite deformation simulations to plastic unit events (see [21]). The first molecular dynamics results on a nearest-neighbor fee crystal of argon have also become available [42]. The consistency of the method with thermodynamics and statistical mechanics has been tested to a satisfactory extent [20] e.g., the calculations with different inclusion shapes all yield identical results the results are independent of the method employed to calculate the elastic properties of the system and its constituents (constant-strain and constant-stress simulations give practically identical values). 

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