surface morphology
Figure 1a is an SEM image of a hemp/wool nonwoven showing a fiber network with visible interfiber spaces, which is a characteristic of the nonwoven structure. This image reveals the fiber entanglement and bonding, which contributes to the mechanical stability of the material. The rough surface texture of hemp fibers contrasts with smoother wool fibers, increasing the overall surface area and potential adsorption properties of the fabric. The scale bar indicates the magnification level. Figure 1b shows a SEM image of the hemp/wool nonwoven fabric coated with banana sap-incorporated chitosan hydrogel, demonstrating the composite structure. The hydrogel layer is a continuous coating on the fibers, with visible adhesion points where the hydrogel tightly bonds to the fiber network. It is evident that the hydrogel is incorporated into the fabric structure, enhancing the mechanical and adsorption properties of the composite. Incorporation of banana sap is indicated by small inclusions within the hydrogel, contributing to its unique surface morphology and functionality.
Figure 1
SEM micrographs of (a) pure nonwoven fabric and (b) chitosan hydrogel composite.
chemical analysis
Figure 2 shows the FTIR spectra of all hydrogel composite samples of different concentrations of chitosan hydrogels on hemp/wool nonwoven fabrics. FTIR revealed characteristic peaks of hemp/wool nonwovens and chitosan hydrogels. The peak around 1550 cm-1 is due to NH bending vibrations of the wool protein backbone. Additionally, a broad peak exists around 2800–3000 cm-1 due to CH stretching vibrations in both cellulose (hemp) and keratin (wool). A broad peak around 3000–3600 cm−1 indicates the presence of hydroxyl (OH) groups, and another peak in the 2800–3000 cm−1 region indicates the stretching of CH within the chitosan molecule. The presence of carbonyl groups in the acetamide (COCH3) structure of chitosan is evident by the peak around 1640 cm-1. Finally, a peak around 1000–1150 cm-1 is expected due to the stretching of COC in the glycosidic bonds between the sugar units of chitosan. The peak intensities are lowest for samples 1–3, higher for samples 4–6, and highest for samples 7–9. This is because 0.5% chitosan was applied for samples 1–3, 1% for samples 4–6, and 1.5% for samples 7–9. As the concentration of the hydrogel increases, more molecules are present and the intensity of the peak increases. All these peaks confirm the presence of chitosan hydrogel on the surface of the wool/hemp nonwoven fabric.
Figure 2
FTIR analysis of hydrogel composite samples.
thermal analysis
Differential scanning calorimetry (DSC) was performed on various nonwoven hydrogel composite samples to investigate their thermal properties. The results are shown in Figure 3. The hemp/wool 70/30 sample showed a depth-endothermic peak at 130 °C. The exothermic peaks above 0.8 W/g and 350 °C (peak height 0.3 W/g) indicate water loss or phase transition and thermal degradation of the fibers, respectively. For the hemp/wool 70/30 composite with 1% chitosan hydrogel incorporating banana sap, the depth of the endothermic peak at 130 °C is -1.5 W/g and the exothermic peak is 320 W/g at the same peak height. shifted to °C. 0.3W/g. This suggests that the addition of chitosan and banana sap slightly decreases thermal stability while increasing energy absorption due to increased water content or enhanced interaction within the composite. When the chitosan concentration was increased to 1.5% in the same blend, the endothermic peak increased to 135 °C with a depth of -1.5 W/g, and the exothermic peak occurred at 330 °C with a peak height of 0.2 W/g. , showed robustness. Thermal stability was slightly improved due to reduced interactions and reduced energy release during decomposition. The hemp/wool 80/20 blend with 1.5% chitosan hydrogel showed an endothermic peak with a depth of -1.3 W/g at 130 °C and an exothermic peak with a peak height of 0.1 W/g at 330 °C, showing good results. The results have been reflected. High thermal stability and low energy release during deterioration. A hemp/wool 90/10 blend with 1.5% chitosan hydrogel exhibited an endothermic peak with a depth of -0.9 W/g at 125 °C and an exothermic peak with a peak height of 0.1 W/g at 330 °C, with increasing temperature. It shows that it is low. It has weak hygroscopicity and internal interactions, but high thermal stability and minimal energy release during degradation. The endothermic peak around 125–135 °C may be due to the loss of absorbed water or phase transition. Certain blends with higher chitosan content (e.g., chitosan and 70/30) exhibited greater depth, indicating that more energy was absorbed due to water loss or stronger internal interactions.
Figure 3
DSC thermogram (A: Hemp/Wool 70/30, B: Hemp/Wool 70/30 1% Chitosan, C: Hemp/Wool 70/30 1.5% Chitosan D: Hemp/Wool 80/20 1.5% Chitosan E: Hemp /wool 90/10 1.5% chitosan) hydrogel composite.
Mechanical properties
Figure 4 shows the tensile strength and elongation properties of hemp/wool nonwovens reinforced with different concentrations of chitosan hydrogel. The blend ratio of the nonwoven fabric was 70/30, 80/20, and 90/10. The tensile strength results show that application of 0.5% chitosan hydrogel resulted in the lowest tensile strength among all fabric types, with 70/30 blend showing the highest strength (7.15 N), followed by 80/20 Blend (4.95 N) was found to last. and 90/10 blend (3.77 N). When the chitosan concentration increases to 1%, the tensile strength increases significantly. The 70/30 blend shows the highest enhancement (18.98 N), but significant increases are also seen in the 80/20 and 90/10 blends (15.31 N and 14.11 N, respectively). At a chitosan concentration of 1.5%, the tensile strength reaches a peak, with the 70/30 blend exhibiting the highest strength (42.61 N), followed by the 90/10 blend (30.75 N), and the 80/20 blend (30.55 N). ). Overall, hemp fibers offer higher tensile strength compared to wool fibers, so increasing wool content generally decreases the tensile strength at each chitosan concentration.
In terms of elongation, chitosan hydrogel concentration 0.5% showed the highest elongation for all fabric types, 70/30 blend showed the highest elongation (48.39%), followed by 80/20 blend (43.45%), 90 Blend continues. /10 blend (42.51%). When the chitosan concentration increased to 1%, the elongation decreased slightly, with the 70/30 blend showing the highest elongation (45.32%), followed by the 80/20 blend (40.11%), and the 90/10 blend (40.1%). follows. At 1.5% chitosan concentration, the elongation decreased further, with 70/30 blend showing the highest elongation (45.76%), followed by 80/20 blend (38.33%) and 90/10 blend (36.45%). Because the elasticity of wool fibers is greater than that of hemp fibers, increasing the wool content increases the elongation, especially at low chitosan concentrations. However, increasing the chitosan concentration slightly decreases the elongation, probably due to the formation of a stiffer hydrogel matrix.
Figure 4
Mechanical properties of hydrogel composite samples.
Water absorption
The results of a systematic investigation of the water absorption properties of chitosan hydrogel composites reinforced with hemp/wool nonwovens and incorporating banana sap are shown in Figure 5. The concentration of chitosan hydrogel solution was varied in the study (0.5, 1, and 0.5, 1, and 2). 1.5) and the composition of the nonwovens (linen/wool ratios 70/30, 80/20, and 90/10). The results showed a clear trend of increasing the water absorption rate for all types of fabrics as the chitosan concentration increased. Specifically, at a chitosan concentration of 0.5, the water absorption was 483.838 for the 70/30 blend, 539.141 for the 80/20 blend, and 583.056 for the 90/10 blend. When the concentration increased to 1, the absorption values of 70/30, 80/20, and 90/10 blends increased to 538.23, 645.15, and 606.24, respectively. At the highest chitosan concentration of 1.5, absorption values of 615.64 for the 70/30 blend, 638.813 for the 80/20 blend, and 678.929 for the 90/10 blend were obtained. In particular, nonwovens with higher hemp content consistently showed greater water absorption capacity. This was particularly noticeable for the 90/10 hemp/wool blend, which achieved a maximum absorption rate of 678.929 at the highest chitosan concentration of 1.5. These findings suggest that both chitosan concentration and hemp content in the nonwovens significantly improve the water absorption capacity of the composites. This study highlights the importance of optimizing both polymer matrix concentration and fabric composition to achieve the desired water absorption properties of hydrogel composites. This is essential for applications in areas where high moisture retention is required.
Figure 5
Water absorption of hydrogel composite samples.
Flame retardancy test
Table 3 shows the results of vertical flame retardancy tests for all composite and control samples. The results show that increasing the chitosan concentration generally reduces the combustion time, especially at the 1.5% concentration, which has the shortest combustion time (less than 10 seconds). It can be seen that when the chitosan concentration increases, the carbonization length is significantly shortened, and the flame retardance is improved due to more effective carbonization. At lower chitosan concentrations (0.5% and 1%), the composition of the nonwovens did not significantly affect the char length, and all samples showed a char length of 30 cm. However, at a concentration of 1.5%, the char length decreased significantly across all fabric compositions, suggesting that higher chitosan content enhances flame retardancy. Interestingly, the afterglow time increases with 1% chitosan concentration, especially for 80/20 and 90/10 fabric compositions. This may be due to a more pronounced smoldering effect as the hydrogel may release more water vapor and other non-flammable gases during combustion. Conversely, chitosan at 1.5% significantly reduced the afterglow time for all fabric types compared to 1%, indicating that the hydrogel effectively extinguished the flame and prevented long-term smoldering. Masu.
Table 3 Vertical flammability test results.
From Figure 6, the control sample (0% chitosan) shows a very short combustion duration (3 seconds) but a relatively long afterglow time and char length (30 cm). This indicates that although the initial combustion is short, the material continues to burn slowly during the afterglow stage and does not effectively form a protective char layer. Since chitosan is a polysaccharide, it forms a char layer when heated, which acts as a barrier to heat and mass transfer. This char layer helps reduce the spread of flame and protect the underlying material. Incorporation of banana sap may improve flame retardancy by accelerating carbonization and forming a protective layer. The ratio of hemp to wool in a nonwoven fabric affects the material's inherent flammability, with wool having natural flame retardancy and linen being less so. The observed results indicate that the higher the chitosan concentration, the more pronounced the overall flame retardant properties are improved, regardless of the fabric composition. In conclusion, the concentration of chitosan hydrogels significantly influences the flame retardant properties, and generally higher concentrations lead to better flame retardancy and shorter char length. The combination of chitosan hydrogel, banana sap, and hemp/wool nonwoven fabric provides effective flame retardant properties, especially at high chitosan concentrations.
Figure 6
Results of vertical flammability test after sample combustion.
