## 3 Results and Discussion
### Statistical Analysis of FTIR Data  
The statistical analysis of FTIR data (one-way ANOVA) related to the most significant results was obtained in this work using the trial version of OriginPro 2021 by OriginLab Co. The one-way statistical analysis of variance (ANOVA) was performed on the normalized spectral band intensities at 3145 and 3045 cm\({}^{-1}\) for the PLA samples (Table 4, Figures 8 and 9), and at 3132 and at 3045 cm\({}^{-1}\) for PHB samples (Table 5, Figures 10 and 11). These bands correspond to the largest changes in the spectra (-OH stretching vibrations of the carboxyl group), which suggests that the predominant scission of ester bonds occurs during the photodegradation process. Two pairs of practically unchanged UV irradiation bands (1379 cm\({}^{-1}\) and 1358 cm\({}^{-1}\) for PLA, as well as at 1379 cm\({}^{-1}\) and 980 cm\({}^{-1}\) for PHB) were chosen for comparison. The results of the ANOVA test show the difference between the means and their variations for two clusters with a coefficient of variation of 0.52473, while the F factor of more than 10 for a level of significance 0.05 indicates that the variance of the reflection power densities in two different spectral line clusters have a cardinal statistically significant difference and the hypothesis of their correlated deviation nature is insignificant. A significant difference between the means and their variations for two clusters in the PHB sample with a F factor of 10.22729 for a level of significance 0.05 supports our conclusion that the \"3132 and 3045 cm\({}^{-1}\)\" cluster's spectra density increase has to be attributed to \"chemical phenomena\" and not to the stochasticity of experimental results (Table 5). A similar ANOVA test performed for normalized power densities for the second sample (PLA) shows a noticeable difference between the means and their variations for two clusters with a coefficient of variation of 0.45. The F factor of 4.21955 for a level of significance 0.05 indicates that the variances in the reflection power densities in two different spectral line clusters also have a statistically significant difference with a probability of 97.767% (Table 4). The increase in the spectral density in the studied range of 3145-3045 cm\({}^{-1}\) similarly appears to be strongly attributed to the \"chemical phenomena\" of newly appeared spectra density peaks. Figure 7: Scheme of PLA (**a**) and PHB (**b**) destruction under the action of UV radiation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Descriptive Statistics** & & & & & \\ \hline  & **N Analysis** & **N Missing** & **Mean** & **Standard Deviation** & **SE of Mean** \\ \hline PLA 3045 & 5 & 0 & 0.49364 & 0.43882 & 0.19625 \\ PLA 3145 & 5 & 0 & 0.39137 & 0.44599 & 0.19945 \\ PLA 1379 & 5 & 0 & 0.91441 & 0.064 & 0.02862 \\ PLA 1458 & 5 & 0 & 0.9606 & 0.03875 & 0.01733 \\ \hline One Way ANOVA & & & & & \\ \hline Overall ANOVA & & & & & \\ \hline  & DF & Sum of Squares & Mean Square & F Value & Prob-F \\ \hline Model & 3 & 1.2566 & 0.41887 & 4.21955 & 0.02233 \\ Error & 16 & 1.58828 & 0.09927 & & \\ Total & 19 & 2.84488 & & & \\ \hline \hline \end{tabular}  
* Null Hypothesis: The means of all levels are equal
* Alternative Hypothesis: The means of one or more levels are different.
* At the \(0.05\) level, the population means are significantly different.
* Fit Statistics  
\begin{tabular}{c c c c} \hline \hline R-Square & Coeff Var & Root MSE & Data Mean \\ \hline
0.4417 & 0.45662 & 0.31507 & 0.69 \\ \hline \hline \end{tabular}  
* Mean  
\end{table} 
Table 4: One-way ANOVA for PLA samples under UV radiation at 0, 2, 5, 24, and 144 h.  
Figure 8: Bar chart. Figure 9: Means Plot SD (as error). Figure 11: Means Plot SD (as error).