The peculiar rheo-optical behavior of bisphenol A-polycarbonate and polymethylmethacrylate

Wimberger-Friedl, R.

doi:10.1007/bf00404193

Cited by 21 publications

(16 citation statements)

References 42 publications

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“…As mentioned earlier, the value of

C_{σ}

above T g for PS is time‐ and temperature‐dependent being negative and positive below

T_{g}

. The stress‐optical coefficient

C_{σ}

of PMMA in melt state changes sign from negative to positive at high temperatures . Similar to the PS‐PC‐PS multilayered slabs freely quenched from the high initial temperature, the thermal birefringence distribution in freely quenched PS‐PMMA‐PS slabs is positive throughout the PMMA core layer with its value being very low in comparison with the value seen in the PC core layer in Fig.…”

Section: Simulated Results and Comparison With Experimentssupporting

confidence: 51%

Thermal birefringence in freely quenched multilayered slabs of amorphous polymers: Experiment and simulation

Kim

Isayev

2013

Polymer Engineering & Sci

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The simulation of the gapwise distribution of the thermally‐induced residual birefringence and stresses in freely‐quenched PS‐PC‐PS and PC‐PS‐PC multi‐layered slabs in water was carried out to calculate the gapwise distribution of the transient and residual birefringence. The modeling was based on the linear viscoelastic and photoviscoelastic constitutive equations combined with the first‐order rate equation for volume relaxation. The master curves for the Young's relaxation modulus and strain‐optical coefficient functions obtained earlier for PS and PC were used in the simulations. The obtained numerical results provided the evolution of the thermally‐induced stress and birefringence with time during and after quenching. The predicted gapwise residual birefringence distribution in these slabs was found to be in a fair agreement with the measured results. In addition, the gapwise distribution of the thermally‐induced residual birefringence in the multi‐layered PS‐PMMA‐PS, PMMA‐PS‐PMMA, PMMA‐PC‐PMMA, and PC‐PMMA‐PC slabs quenched from different initial temperatures was measured. Explanations were provided for the observed gapwise distribution of the thermal residual birefringence in each layer of these slabs including the effect of the initial temperature. POLYM. ENG. SCI., 54:2097–2111, 2014. © 2013 Society of Plastics Engineers

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“…As mentioned earlier, the value of

C_{σ}

above T g for PS is time‐ and temperature‐dependent being negative and positive below

T_{g}

. The stress‐optical coefficient

C_{σ}

Section: Simulated Results and Comparison With Experimentssupporting

confidence: 51%

Thermal birefringence in freely quenched multilayered slabs of amorphous polymers: Experiment and simulation

Kim

Isayev

2013

Polymer Engineering & Sci

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“…For the present geometry the shear stresses are proportional to the pressure gradient in flow direction. If we neglected normal stress contributions [34], this would lead to a birefringence in the cross-section of 1.6 × 10 -3 at maximum. The birefringence distribution in the cross-sections along the flow direction and transverse to it is shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…This material has been used in previous investigations [15,27,34], where mechanical and optical properties can be found.…”

Section: Methodsmentioning

confidence: 99%

Molecular Orientation in Polycarbonate Induced by Cooling Stresses

Wimberger-Friedl¹

1996

International Polymer Processing

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The origin of the maximum of the birefringence at the surface of injection-molded polymer products is discussed. By systematic variation of the molding conditions with polycarbonate, it is shown that the maximum at the surface not only depends on the filling, but even more so on the packing conditions. The birefringence at the surface is equal in the flow direction and transverse to it. The height scales with the cavity pressure during compression and packing. This cannot be explained by stresses due to the classical fountain flow at the flow front. Instead, the dominating contribution comes from transient deviatoric stresses induced by the compression of the vitrifying polymer in combination with wall adhesion. The pressure-induced stress history in the vitrifying polymer leads to molecular orientation and residual stresses giving a birefringence maximum at the surface.International Polymer Processing downloaded from www.hanser-elibrary.com by Kungliga Tekniska on August 22, 2015For personal use only.

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“…The thermally induced birefringence is not a linear function of the thermal stress because the stress‐ and strain‐optical coefficients show the photoviscoelastic behavior becoming a function of both time and temperature in the rubber‐to‐glass transition region. Therefore, the memory effect in the optical behavior of PMMA becomes significant, and a photoviscoelastic relation should be used in correlating the thermal birefringence with thermal stress . It should also be noted that the optical behavior of PMMA is more complicated than that of PS because the stress‐optical coefficient changes sign at 144°C with its value being negative below that temperature .…”

Section: Resultsmentioning

confidence: 99%

Birefringence and interface in sequential co‐injection molding of amorphous polymers: Simulation and experiment

Kim

Isayev

2014

Polymer Engineering & Sci

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Modelings of the interface distribution and flow-induced residual stresses and birefringence in the sequential coinjection molding (CIM) of a center-gated disk were carried out using a numerical scheme based on a hybrid finite element/finite difference/control volume method. A nonlinear viscoelastic constitutive equation and stressoptical rule were used to model the frozen-in flow stresses in disks. The compressibility of melts is included in modeling of the packing and cooling stages and not in the filling stage. The thermally induced residual birefringence was calculated using the linear viscoelastic and photoviscoelastic constitutive equations combined with the first-order rate equation for volume relaxation and the master curves for the relaxation modulus and strainoptical coefficient functions of each polymer. The influence of the processing variables including melt and mold temperatures and volume of skin melt on the birefringence and interface distribution was analyzed for multilayered PS-PC-PS, PS-PMMA-PS, and PMMA-PC-PMMA molded disks obtained by CIM. The interface distribution and residual birefringence in the molded disks were measured. The measured interface distributions and the gapwise birefringence distributions in CIM disks were found to be in a fair agreement with the predicted interface distributions and the total residual birefringence obtained by the summation of the predicted frozen-in flow and thermal birefringence. POLYM. ENG. SCI., 55:88-106, 2015.

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The peculiar rheo-optical behavior of bisphenol A-polycarbonate and polymethylmethacrylate

Cited by 21 publications

References 42 publications

Thermal birefringence in freely quenched multilayered slabs of amorphous polymers: Experiment and simulation

Thermal birefringence in freely quenched multilayered slabs of amorphous polymers: Experiment and simulation

Molecular Orientation in Polycarbonate Induced by Cooling Stresses

Birefringence and interface in sequential co‐injection molding of amorphous polymers: Simulation and experiment

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