## 3 Results and Discussion
### Multiple Regression Analyses of Tensile Strength
collinear influence, when VIF > 5, the independent variables are highly correlated. When VIF > 10, the accuracy of multiple regression analyses is low. The multiple regression model (1) is composed of correlations among the three designated independent variables and the tensile strength of recycled Kevlar(r)/PET/LPET nonwoven geotextiles that are immersed in H\({}_{2}\)O for 1, 2, 3, and 4 months. There is no statistically significant difference in their tensile strength when samples are immersed for different lengths of time or different solution  
Figure 8: Tensile strength and weight along the CD of recycled Kevlar®/PET/LPET nonwoven geotextiles of (**a**) H\({}_{2}\)O/23 \({}^{\circ}\)C, (**b**) H\({}_{2}\)O/50 \({}^{\circ}\)C, (**c**) CH\({}_{3}\)COOH/23 \({}^{\circ}\)C, (**d**) CH\({}_{3}\)COOH/50 \({}^{\circ}\)C, (**e**) NaOH/23 \({}^{\circ}\)C, and (**f**) NaOH/50 \({}^{\circ}\)C, as related to the implementation of thermal treatment. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Model**} & **Deposition** & \multirow{2}{*}{**NS**} & **Variable** & \multirow{2}{*}{**B**} & **Beta** & \multirow{2}{*}{**F**} & \multirow{2}{*}{**\(p\)**} & **Adjusted \(R^{2}\)** & **VIF** \\  & **Solution** & & & & & & & & & \\ \hline \multirow{3}{*}{1} & \multirow{3}{*}{H\({}_{2}\)O} & \multirow{3}{*}{231} & (Constant) & 106.21 & - & \multirow{3}{*}{65.76} & \multirow{3}{*}{0.00} & \multirow{3}{*}{0.22} & - \\  & & & Contents of & & & & & & & 1.00 \\  & & & Kevlar® fibers & & & & & & & \\ \hline \multirow{3}{*}{2} & \multirow{3}{*}{CH\({}_{3}\)COOH} & \multirow{3}{*}{196} & (Constant) & 113.81 & - & \multirow{3}{*}{69.98} & \multirow{3}{*}{0.58} & \multirow{3}{*}{0.00} & \multirow{3}{*}{0.48} \\  & & & & & & & & & \\ \cline{1-1}  & & & Period & & & & & & \\ \cline{1-1}  & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & \\ \hline \multirow{3}{*}{3} & \multirow{3}{*}{NaOH} & \multirow{3}{*}{117} & (Constant) & 96.82 & - & \multirow{3}{*}{217.58} & \multirow{3}{*}{0.00} & \multirow{3}{*}{0.65} & \multirow{3}{*}{1.00} \\  & & & Immersion & & & & & & \\ \cline{1-1}  & & & period & & & & & & \\ \cline{1-1}  & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Multiple regression analyses in the tensile strength of recycled Kevlar®/PET/LPET nonwoven geotextiles. temperatures. The statistical analyses indicate that contents of Kevlar(r) fibers is the only influential factor of a neutral environment (H\({}_{2}\)O) on the tensile strength of nonwoven geotextiles. The \(F\) test results demonstrate that this multiple regression analyses have statistical significance with (\(F\) (1,229) = 65.76, \(p\) = 0.00). The explanatory power is 22% without collinearity. The multiple regression model (2) is composed of correlations among the three designated independent variables and the tensile strength of recycled Kevlar(r)/PET/LPET nonwoven geotextiles that are immersed in CH\({}_{3}\)COOH for 1, 2, 3, and 4 months. The influential factors to the tensile strength of the nonwoven geotextiles that are immersed in CH\({}_{3}\)COOH are ranked as immersion periods, contents of Kevlar(r) fibers, and immersion temperatures. According to the results of one-way ANOVA analyses in section 3.2, there are statistically significant differences in the tensile strength of the nonwoven geotextiles that are immersed in an acid solution for 4 months, including the five combinations of 0 wt. % of Kevlar(r) fibers and 23 \({}^{\circ}\)C, as well as 0/5/10/15/20 wt. % of Kevlar(r) fibers and 50 \({}^{\circ}\)C. In addition, the tensile strength is proportional to the contents of Kevlar(r) fibers. In other words, the contents of Kevlar(r) fibers demonstrate an influence on the tensile strength. Immersion temperature is the last independent variable that is involved in the multiple regression model (2).