Table 1.
Exposure conditions.
Fig 1.
Cross panel figure for the change in YI with exposure time for each type of PET grade.
Note that the exposures are shown as columns and PET grades are shown as rows in the figure. Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. Regression lines are obtained through pathway equations from the netSEM analysis and represent the best fit for each relationship based on adjusted R2 values.
Fig 2.
Cross panel figure for the change in haze (%) with exposure time.
Note that the exposures are shown as columns and PET grades are shown as rows in the figure. Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. Regression lines are obtained through pathway equations from the netSEM analysis and represent the best fit for each relationship based on adjusted R2 values.
Fig 3.
UV-Vis Abs/cm spectra before and after degradation.
Fig 4.
Cross panel figure for the change in UV-Vis Abs/cm at 340 nm with exposure time.
Note that the exposures are shown as columns and PET grades are shown as rows in the figure. Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. Regression lines are obtained through pathway equations from the netSEM analysis and represent the best fit for each relationship based on adjusted R2 values.
Fig 5.
FTIR-ATR spectra before and after degradation.
Carbonyl and trans ethylene glycol regions and the normalization band are highlighted in rectangles. The inset spectra is the zoomed trans ethylene glycol region at 975 cm−1.
Fig 6.
Cross panel figure for the change in IR absorption at 1675 cm−1 with exposure time.
Note that the exposures are shown as columns and PET grades are shown as rows in the figure. Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. Regression lines are obtained through pathway equations from the netSEM analysis and represent the best fit for each relationship based on adjusted R2 values.
Fig 7.
Cross panel figure for the change in IR absorption at 975 cm−1 with exposure time.
Note that the exposures are shown as columns and PET grades are shown as rows in the figure. Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. Regression lines are obtained through pathway equations from the netSEM analysis and represent the best fit for each relationship based on adjusted R2 values.
Fig 8.
netSEM pathway diagram for the yellowing of UV stabilized grade under the HotQUV exposure.
The fitting models (Mod) and the adjusted R2 values (aR2) for each relationship are given along the connection lines. The models are SL (simple linear), SQuad (simple quadratic), Quad (quadratic), Exp (exponential), Log (logarithmic), CP (change point), and nls (non-linear least squares regression).
Fig 9.
netSEM pathway diagram for the yellowing of UV stabilized grade under the CyclicQUV exposure.
The fitting models (Mod) and the adjusted R2 values (aR2) for each relationship are given along the connection lines. The models are SL (simple linear), SQuad (simple quadratic), Quad (quadratic), Exp (exponential), Log (logarithmic), CP (change point), and nls (non-linear least squares regression).
Fig 10.
Direct and multi-step (mechanistic) pathway curves for the yellowing of UV stabilized grade.
Each exposure step (168 hours) corresponds to one week of exposure and the total exposure time (1176 hours) of seven steps corresponds to seven weeks of exposure. RMSE values are given for each pathway showing the predictive powers of the models.
Fig 11.
The change in YI as a function of photo-dose.