## 3 Results and Discussion
The capillary rise height of L-PCS solution was transformed from 12.0 mm to 16.0 mm after 40 wt.% introduction according to the capillary rise method. According to Equation (1), the calculated surface tension of PCS with 40 wt.% acetone was equal to \(25.4\times 10^{-3}\) N/m, almost 1.3 times higher than that of pure L-PCS (\(19.1\times 10^{-3}\) N/m). Moreover, the effects of the amount of acetone on the wetting angles for graphite were presented in Figure 6a. Obviously, it dropped by 37.7% from \(20.2^{\circ}\) for pure  
Figure 4: The variation in viscosity with different acetone content of liquid polycrystalline (L-PCS) solutions. Figure 5: PCS viscosity variation under 80 \(\upmu\)/min rates after 3 h under (**a**) heating treatment and (**b**) acetone introduction. L-PCS-0 sample to 12.6\({}^{\circ}\) for L-PCS-40 sample. Considering that the diameter of single carbon fiber is about 7 \(\upmu\)m, we set the graphite as the loaner, which had the same chemical property as carbon fibers. The value of wetting angles decreased with the increasing of acetone content, and the dipping height of PCS with 40 wt.% acetone was 18.9 mm according to the (Equation (2))-5.9 times higher than that of pure L-PCS (3.2 mm). The results mentioned above also confirm that acetone has the ability to improve the affinity between fibers and PCS and further to develop their wettability. Furthermore, carbon fibers are chemically stable and have strong corrosion resistance. As a result, acetone will not damage its properties at all. To sum up, the decrease in viscosity and improvement in PCS/graphite wettability were achieved by introducing acetone into L-PCS solutions, leading to an enhancement in impregnation efficiency of L-PCS. The density also presented the descending trend as acetone content increased, as shown in Figure 6b. To further explore the mechanism of viscosity reduction of L-PCS by adding acetone, GPC, Raman, XRD and FT-IR spectra were acquired. Figure 7 depicts the Raman and FT-IR spectra of L-PCS solutions with different acetone contents. The Si-H (2106 cm\({}^{-1}\)) and C-H (2897-2978 cm\({}^{-1}\)) peaks were obviously detected in Figure 7a, indicating that no effect of acetone on the chemical bonds occurred. Moreover, it was known that the introduction of acetone did not change the type and intensity of primary absorption bands except for the new absorption band of C = O (1716 cm\({}^{-1}\)), which existed in acetone (Figure 7b). Therefore, the introduction of acetone did not affect the type of the original chemical bonds, further indicating that acetone did not produce chemical reactions with PCS [35]. Figure 6: Curve of wetting angles between PCS/graphite and density of all mixtures with different acetone content, (**a**) wetting angles and (**b**) density. Figure 2:0 Raman and Fourier transform infrared spectroscopy (FT-IR) spectra of L-PCS solutions with different acetone content. (**a**) Raman spectra, (**b**) FT-IR spectra. The FT-IR spectra of all cured samples were shown in Figure 8a. The absorption bands of Si-H (2106 cm\({}^{-1}\)), C-H (2897-2978 cm\({}^{-1}\)), and Si-C (789, 1257 cm\({}^{-1}\)) could be detected. Also, a new absorption band of C = O (1716 cm\({}^{-1}\)) also appeared in pure L-PCS, which was due to the hydration reaction of C = C with water vapor in the air during curing [36]. Besides that, an alcoholic hydroxyl group was formed, which was in turn oxidized by oxygen in high temperature air to introduce a carbonyl group [35; 37].