Polycarbonate mechanical constants

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). 

Requirements for CD-quality material are polycarbonate with low levels of chemical impurities, low particle levels, thermal stability, excellent mold release, excellent clarity, as well as constant flow and constant mechanical behavior (for reproducibility). There exists a time/cost balance. High molecular weight polycarbonate offers a little increase in physical property but the flow rate is slow, making rapid production of CDs difficult. The molecular weight where good mechanical strength and reasonable flow occurs, and that allows for short cycles, is in the range of 16,000-28,000 Da. 

Note Polymerization, like its handmaiden, catalysis, has long been one of the most complex and productive areas of chemical research from year to year new materials and reaction mechanisms are constantly being explored, sometimes with only marginal success. But it need only be recalled that such now commonplace materials as polyethylene, polycarbonate, nylon, neoprene, epoxies, acrylics, to mention only a few, as well as block, graft, and stereospecific polymers, have resulted from continuous and intensive research by many brilliant chemists over the last 60 years, and this research continues undiminished. 

The mechanical properties of the polyimide films (the sample size 10-mm length, 10-mm width) were examined at room temperature using a specially made machine with a constant drawing rate of 1 mm min"1. A profile of elongation vs. load for PI(BHDA+BBH) film is shown in Figure 4. The polyimide film possessed a tensile modulus of 2.1 GPa and a tensile strength of 52 MPa, and these values can compete in terms of strength with those of a commercial polycarbonate (PC).[8] The authors believe that this is the first example of a fully alicyclic polyimide for which the mechanical property was evaluated. 

This equation was found to be valid for a number of polymers (PVC, PC, PMMA, PS, CA) in more or less extended regions of temperature and strain rate [154,156,158]. The (temperature-dependent) activation volumes 7 had at room-temperature values between 1.4 (PMMA) and 17 nm (CA). This means that according to this concept polymer deformation at the yield point is due to the thermally activated displacement of molecular domains over volumes which are between 10 (PMMA) and 120 times (PVC) as large as a monomer unit. It has been indicated by several authors [155—158, 160] that the above criterion (Eq. 8.29) corresponds to the Coulomb yield criterion Tq + MP constant. The coefficient of friction ju is inversely proportional to 7. From an analysis of their experimental data on polycarbonate according to Eq. (8.29) Bauwens-Crowet et al. [158] conclude that two flow processes exist. They relate these to an a-process (jumps of segments of the backbone chains) and to the 3 mechanical relaxation mechanism. 

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