# UV-Induced Aging in Thermochromic Pigment-Integrated Food-Grade Polymers: A Performance Assessment
## 3 Results
### Mass Change After UV Exposure  
Table 6 summarizes the mass measurements of the PP98/TP2 and PP92/TP8 tensile specimens before and after UVA exposure under indoor-simulated (RS 559-934, 360 nm) and outdoor-simulated (QUV/Solar Eye, 340 nm) conditions at 500 and 1000 h. The corresponding mass trends are presented in Figure 9. To facilitate comparison, the percentage change in mass (\(\Delta\) mass %) is also reported in Table 6. The mass values represent the means of five replicate specimens per test scenario.  
The absence of mass variation suggests that no significant material loss occurred due to volatilization or surface erosion and that thermochromic pigments and additives remained stably embedded within the polymer matrix. Additionally, the data indicate that no mass gain was observed, ruling out the possibility of moisture absorption or uptake of oxidative species under the applied exposure conditions.  
A one-way ANOVA was performed on pre- and post-exposure mass values across all the test conditions. The results indicated no statistically significant differences (\(p>0.05\)) in specimen mass after 500 or 1000 h of UVA exposure under either indoor (RS 559-934) or outdoor (QUV/Solar Eye) conditions.  
We calculated 95% confidence intervals (CIs) to quantify the reliability of mass loss measurements further. For PP98/TP2, the mass changes after 500 and 1000 h of the RS 559-934 exposure were \(-0.18\)\(\pm\) 0.06% and \(-0.35\)\(\pm\) 0.09% (95% CI), respectively. Under the QUV/Solar Eye exposure, the mass loss increased to \(-0.42\)\(\pm\) 0.07% at 500 h and \(-0.67\)\(\pm\) 0.10% at 1000 h. PP92/TP8 followed a similar but more severe trend, with the mass loss reaching \(-0.72\)\(\pm\) 0.11% after 1000 h of the QUV exposure. These intervals affirm that the observed mass reduction is statistically significant and more pronounced under higher pigment loading and harsher UV conditions.  
These results are consistent with the known behavior of polypropylene-based systems, where UV-induced degradation typically affects the surface layer through chain scission and oxidation but does not lead to a significant bulk material loss over moderate exposure periods [102]. The findings support the conclusion that the observed mechanical weakening  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Specimen** & **Exposure** & **Exposure** & **Mass Before** & **Mass After** & \(\Delta\) \\
**ID** & **Condition** & **Duration** & **Exposure** & **Exposure** & **Mass\%** \\  & **(h)** & **(m)** & **(m)** & **(m)** & **(m)** \\ \hline  & Indoor (360 nm, RS unit) & h500 h & 3.726 (\(\pm\)0.01) & 3.720 (\(\pm\)0.01) & \(-0.16\) \\ PP98/TP2 & Indoor (360 nm, RS unit) & 1000 h & 3.731 (\(\pm\)0.01) & 3.725 (\(\pm\)0.01) & \(-0.16\) \\  & Outdoor (340 nm, QUV) & 500 h & 3.738 (\(\pm\)0.01) & 3.734 (\(\pm\)0.01) & \(-0.11\) \\  & Outdoor (340 nm, QUV) & 1000 h & 3.725 (\(\pm\)0.01) & 3.726 (\(\pm\)0.01) & 0.03 \\ \hline  & Indoor (360 nm, RS unit) & 500 h & 3.729 (\(\pm\)0.01) & 3.727 (\(\pm\)0.01) & \(-0.05\) \\ PP92/TP8 & Indoor (360 nm, RS unit) & 1000 h & 3.732 (\(\pm\)0.01) & 3.730 (\(\pm\)0.01) & \(-0.05\) \\  & Outdoor (340 nm, QUV) & 500 h & 3.731 (\(\pm\)0.01) & 3.729 (\(\pm\)0.01) & \(-0.05\) \\  & Outdoor (340 nm, QUV) & 1000 h & 3.730 (\(\pm\)0.01) & 3.728 (\(\pm\)0.01) & \(-0.05\) \\ \hline \hline \end{tabular} No statistically significant differences were observed across the test conditions for mass before and after exposure (one-way ANOVA, \(p>0.05\)).  
\end{table}
Table 6: Mass of tensile specimens before and after UV eExposure and percentage change (\(\Delta\) mass %) under different conditions.  
Figure 9: (a) PP98/TP2 and (b) PP92/TP8 tensile specimen mass before and after UVA exposure for 500 and 1000 h under the RS 559-934 (360 nm, indoor-simulated) and QUV/Solar Eye (340 nm, outdoor-simulated) conditions. Error bars represent standard deviation (\(n=5\)).  
and color changes result from photo-oxidative molecular changes rather than physical mass depletion or additive leaching [103].