# UV-Induced Aging in Thermochromic Pigment-Integrated Food-Grade Polymers: A Performance Assessment
## 4 Conclusions  
This study provides critical insights into the durability of thermochromic polypropylene blends under UVA exposure that are relevant to smart packaging applications. The effects of photodegradation on mechanical and optical properties were systematically assessed by simulating indoor and outdoor UV lighting environments over 500 and 1000 h. Colorimetric analysis revealed apparent time-dependent discoloration, with the pigment-rich PP92/TP8 blend undergoing the most severe fading. Mechanical testing showed that UV exposure led to pronounced embrittlement and strain and impact resistance reductions, particularly in QUV-exposed samples. However, there was no discernible mass change, suggesting that the deterioration was surface-confined rather than the consequence of bulk erosion or additive leaching. The results show how achieving thermochromic functionality and maintaining long-term material stability must be balanced. While increasing thermal responsiveness, higher pigment concentrations hasten mechanical deterioration and surface oxidation. These results imply that pigment concentration and UV stabilization techniques need to be adjusted to increase service life in practical food packaging applications. While the study provided meaningful insights through mechanical, colorimetric, and mass change analyses, it did not include molecular weight characterization (e.g., GPC). This was due to the surface-limited nature of UVA degradation in polypropylene and the complexity introduced by EVA-based thermochromic masterbatches. However, we acknowledge that GPC could offer valuable insights into bulk degradation mechanisms, particularly under more aggressive conditions, and recommend it as a valuable extension for future studies. Additionally, the study did not assess global or specific migration of thermochromic additives, which is essential for evaluating food contact. Although the absence of mass loss after UV exposure suggests stable pigment retention, this alone does not confirm the absence of low-level migration. Future work should incorporate migration testing using food simulants under conditions defined in relevant standards to assess the potential release of functional additives or their degradation products during typical use scenarios. The findings of this study are expected to inform the design and formulation of more robust thermochromic packaging systems that are capable of withstanding real-world environmental conditions. These insights will contribute to the advancement of innovative packaging solutions by guiding manufacturers, researchers, and regulatory bodies looking to incorporate intelligent materials into high-performance, environmentally friendly packaging systems. Together, these findings lay the groundwork for advancing thermochromic packaging from an experimental concept to a practical, market-ready solution. Notably, quantitative findings emphasize the severity of degradation: \(\Delta\)E\({}^{*}_{\text{ab}}\) values exceeded 34 in pigment-rich samples after 1000 h of outdoor UVA exposure, while the tensile strain at break and the notched impact strength declined by 48.67% and 44.15%, respectively. These measurable reductions directly affect the visual appeal and mechanical performance of packaging. Such losses can undermine consumer confidence. In addition, they can compromise protective functions for food-grade applications. Optimizing effective UV stabilization strategies and optimizing pigment levels are essential for maintaining packaging efficacy and safety across the product's shelf life. Conceptualization, C.B. ; methodology, C.B. ; writing--original draft preparation, C.B. ; writing--review and editing, C.B., D.M.C. and G.B. ; supervision, J.G. and L.M.G. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Data are contained within the article.