Comparison of enthalpy relaxation between two different molecular masses of a bisphenol-A polycarbonate

Lee‐Sullivan, Pearl; Bettle, Mark

doi:10.1007/s10973-005-0763-x

Cited by 6 publications

(13 citation statements)

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“…However, their presence accelerates aging. It should be noted that the values obtained for Δ H / R , β , x , and ln A are in good agreement with the values published in literature for PC …”

Section: Resultssupporting

confidence: 55%

Physical aging in polycarbonate nanocomposites containing grafted nanosilica particles: A comparison between enthalpy and yield stress evolution

Ramakrishnan

Harsiny

Goossens

et al. 2016

J. Polym. Sci. Part B: Polym. Phys.

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Understanding and controlling physical aging below the glass transition temperature (Tg) is very important for the long‐term performance of plastic parts. In this article, the effect of grafted silica nanoparticles on the physical aging of polycarbonate (PC) below the Tg is studied by using the evolution of the enthalpy relaxation and the yield stress. The nanocomposites were found to reach a thermodynamic equilibrium faster than unfilled PC, implying that physical aging is accelerated in presence of grafted nanosilica particles. The Tool‐Narayanaswamy‐Moynihan model shows that the aging is accelerated by the grafted silica nanoparticles, but the molecular mechanism responsible for physical aging remains unaltered. Furthermore, dynamic mechanical analysis shows that the kinetics of physical aging can be related to a free volume distribution or a local attraction‐energy distribution as a result of the change in mobility of the polymer chain. Finally, a qualitative equivalence is observed in the physical aging followed by both the enthalpy relaxation and yield stress. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2069–2081

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Section: Resultssupporting

confidence: 55%

Physical aging in polycarbonate nanocomposites containing grafted nanosilica particles: A comparison between enthalpy and yield stress evolution

Ramakrishnan

Harsiny

Goossens

et al. 2016

J. Polym. Sci. Part B: Polym. Phys.

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“…Lastly, since the fictive temperature, T f , is a more accurate representation of aged state than the glass transition, the effects of aging on the T f is plotted in Figure 9. Consistent with enthalpic recover results found in Figure 6, T f decreases linearly with log t a , very similar to PC material 11, 65…”

Section: Resultssupporting

confidence: 89%

“…When Figures 5 and 6 are viewed together, they suggest that aging has a negligible effect on the ABS component's peak, even though the aging temperature is closer to the glass transition of ABS. It is clear that there is almost no change in the ABS endothermic peak but the PC aging peaks tend to decrease before increasing again, which is quite different from previously observed behavior 11, 12. This may be explained by the difference in aged states.…”

Section: Resultscontrasting

confidence: 71%

“…When Δ H a is plotted against log | t a | in Figure 6, the expected linear relationship of enthalpy recovered, Δ H a , with aging time is seen. Interestingly, however, the slope of the line or rate of change of $\mathop {\left( {{\textstyle{{\partial \Delta H_a } \over {\partial log|t_a |}}}} \right)}\nolimits_{q_1,T_a,q_2 } $ for the 75 : 25 PC/ABS blend is found to be 0.62 J/g per decade, which is almost identical to PC aged at a much higher temperature of 120°C 1, 11…”

Section: Resultsmentioning

confidence: 92%

“…The PC blend constituent has similar behavior to a poorly aged PC when aging at 80°C, while reported relationships in Refs. 11 and 12 are single PC polymers aged at much higher temperatures, e.g., 120°C.…”

Section: Resultsmentioning

confidence: 99%

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Observations of physical aging in a polycarbonate and acrylonitrile–butadiene–styrene blend

Tang

Lee‐Sullivan

2008

J of Applied Polymer Sci

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The effects of physical aging of a 75 : 25 PC/ABS blend have been studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). From DSC, two distinct peak endotherms at about 908C and 1108C, which are associated with the glass transition of ABS (T g,ABS ) and PC (T g,PC ) components, respectively, were observed. When progressive aging was monitored at 808C for over 1000 h, the changes in enthalpic relaxation, glass and fictive temperatures for the blend followed similar trends to those already seen in the literature for PC aged between 125 and 1308C. The rate of enthalpy relaxation was also comparable. The plot of peak endotherm against logarithmic aging time for the PC blend constituent, however, behaved quite differently from the linear relationship known for highly aged PC. The ABS peak component also appeared to be insensitive to aging. Both observations were confirmed to be statistically significant using analysis of variance methods. Using temperature modulated-DSC, there is evidence that aging increases the blend miscibility as the T g,PC shifts toward the stationary T g,ABS during aging. Parallel FTIR investigations found oxidation of butadiene during aging to be even at this relatively low temperature, forming hydroxyl and carbonyl degradation products. The presence of ABS in the blend also appeared to have prevented the shifting from the trans-cis to trans-trans arrangement of the carbonate linkage, which is a well-known phenomenon during elevated temperature aging of PC alone. Moreover, the carbonate linkage appears to have been at the lower energy, transtrans, arrangement prior to the aging process.

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Glass transition investigated by a combined protocol using thermostimulated depolarization currents and differential scanning calorimetry

Delbreilh

Negahban

Benzohra

et al. 2009

J Therm Anal Calorim

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Relaxation times of bisphenol A polycarbonate around the glass transition temperature are estimated using the combination of differential scanning calorimetry (DSC) and thermostimulated depolarization currents (TSDC). These measurements are performed using samples with different thermal histories below and above the vitrification transformation. This protocol enables the extension of the range of equilibrium relaxation times measured by dielectric spectroscopy. By this mean we may recalculate the values of the Kauzmann temperature and fragility index.

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Comparison of enthalpy relaxation between two different molecular masses of a bisphenol-A polycarbonate

Cited by 6 publications

References 0 publications

Physical aging in polycarbonate nanocomposites containing grafted nanosilica particles: A comparison between enthalpy and yield stress evolution

Physical aging in polycarbonate nanocomposites containing grafted nanosilica particles: A comparison between enthalpy and yield stress evolution

Observations of physical aging in a polycarbonate and acrylonitrile–butadiene–styrene blend

Glass transition investigated by a combined protocol using thermostimulated depolarization currents and differential scanning calorimetry

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