## 3 Results and Discussion  
### Mechanical Properties of Matrices  
Table 1 shows the mechanical properties along the machine direction (MD) and the cross machine direction (CD) of FR matrices and TI matrices. The optimal tensile force, tearing force, and bursting force for FR matrices occur when they are composed of a FI-to-LM ratio of 90:10. FR fiber has a high fineness, which means greater thickness and high strength. Therefore, more FR fibers provide the matrices with greater strengths. LM fiber, though it is finer, can still fill the pores formed between FR fibers and increases the overall strengths of FR matrices. However, an excessive content of 20 wt % LM fiber causes the tensile force to decrease, as more LM fiber means less FR fiber. The reinforcement primarily depends on FR fiber, and excessive LM fiber counteracts such reinforcement. Therefore, the optimal tensile force and bursting force of FR matrices (149.7 N and 507.3 N) occurs when the blending ratio is 90:10. For TI matrices, the optimal tensile force, tearing force, and bursting force occur when they are composed of a FI-to-LM ratio of 80:20. FI fibers are composed of a polymer solution and a far-infrared powder, and this manufacturing process leads to a weaker fiber structure. As a result, a relatively greater amount of LM fiber (20 wt %) endows TI matrices with an optimal tensile force of 70.8 N, an optimal tearing force of 121.6 N, and an optimal bursting force of 241.5 N.  
Compared with pure FR matrices (100/0), FR matrices (90/10) have a slightly lower LOL. LM fiber is not processed for its flame-retardant property, and it can be alight during combustion, which in turn affects the flame-retardant property of FR fiber. However, the LOI of FR matrices (90:10) is still 30, indicating a good flame-retardant property. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Matrices**} & \multirow{3}{*}{\begin{tabular}{c} **Blending** \\ **Ratio** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Fiber** \\ **Orientation** \\ \end{tabular} } & **Tensile** & **Tearing** & **Busting** \\  & & & **Force** & **Force** & **Force** & **Conductivity** & **Permeability** \\ \cline{3-8}  & & - & **N** & **N** & **N** & **-** & **W/m**- K & **cm\({}^{3}\)/cm\({}^{2}\)/s** \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} FR \\ **(FR/LM)** \\ \end{tabular} } & \multirow{3}{*}{**100/0**} & CD & \(143.4\pm 7.93\) & \(249.1\pm 19.92\) & \(463.5\pm 26.24\) & 32 & - & - \\ \cline{3-8}  & & MD & \(40.2\pm 4.15\) & \(141.2\pm 12.01\) & \(463.5\pm 26.24\) & 32 & - & - \\ \cline{2-8}  & \multirow{3}{*}{**90/10**} & CD & \(149.7\pm 14.9\) & \(226.3\pm 21.36\) & \multirow{3}{*}{507.3 \(\pm\) 24.23} & \multirow{3}{*}{30} & - & - \\ \cline{3-8}  & & MD & \(35.1\pm 4.89\) & \(124.5\pm 13.78\) & & & \\ \cline{3-8}  & & CD & \(133.3\pm 8.20\) & \(219.7\pm 27.73\) & & & \\ \cline{3-8}  & & MD & \(36.3\pm 2.26\) & \(124.5\pm 9.59\) & & & \\ \hline \multirow{3}{*}{
\begin{tabular}{c} TI \\ **(FI/LM)** \\ \end{tabular} } & \multirow{3}{*}{**100/0**} & CD & \(64.0\pm 6.32\) & \(95.8\pm 7.85\) & \multirow{3}{*}{232.3 \(\pm\) 21.44} & - & \(0.033\pm 0.0081\) & \(164.2\pm 7.38\) \\  & & MD & \(26.5\pm 3.26\) & \(76.3\pm 9.32\) & & & \\ \cline{3-8}  & & CD & \(65.9\pm 6.55\) & \(97.45\pm 8.47\) & & & \\ \cline{3-8}  & & MD & \(20.3\pm 1.68\) & \(81.5\pm 9.62\) & & & \\ \cline{3-8}  & & CD & \(70.8\pm 5.20\) & \(121.6\pm 10.91\) & & & \\ \cline{3-8}  & & MD & \(23.1\pm 2.16\) & \(94.5\pm 6.42\) & \(241.5\pm 23.73\) & - & \(0.045\pm 0.0166\) & \(146.7\pm 13.74\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mechanical properties of far-infrared (FR) and thermally insulating (TI) matrices in relation to the fiber orientation of the machine direction (MD) and the cross machine direction (CD). In addition, more LM fiber content results in high thermal conductivity and low air permeability in TI matrices. LM fiber has a low fineness, which means it is thin and fills the voids formed by FI fibers.