3. Results and discussion
3.1. Grafting of CNT on the ramie fabric
The schematic representation for the mechanism of ramie fiber surface treatments is shown in Fig. 2. For the alkali treatment of ramie fiber, the NaOH reacts with the hydroxyl groups of the ramie fiber as shown in Fig. 2(a). During silane treatment, the hydrolysis of silane takes place initially (Fig. 2(b)) which then reacts with the active hydroxyl functionalities in ramie fiber (Fig. 2(c)). Each silane molecule has three silanol (Si-OH) groups. For CNT treatment, first the silanised CNT is produced by the chemical reaction between silanol groups and the hydroxyl functional groups present in MWCNT (Fig. 2 (d)). The silanized CNT is then grafted on the surface of ramie fiber through silane as shown in Fig. 2(e). A portion of silanol groups present in KH 560 molecule reacts with -OH groups of MWCNT and the other silanol groups react with -OH groups present in cellulose of ramie fiber forming the structural network of Si-O-C of CNT and Si-O-cellulose. a. …show more content…
SEM
The SEM images of ramie fiber before and after chemical treatment are shown in Fig. 3. The surfaces of untreated and the alkali treated ramie fiber were smooth (Fig. 3(a) and (b)) whereas the surfaces of silane treated (Fig. 3(c)) and the CNT treated fiber (Fig. 3(d)) showed roughness which is attributed to the chemical reactions of the ramie fiber with the silanol functional groups. The clear evidence of CNT on the ramie fiber is observed on the CNT treated fiber. However, the grafting is not uniform and some agglomerates were observed on ramie fiber. b. FTIR Infrared radiation refers broadly to the part of the electromagnetic spectrum between the visible and microwave regions. Of great practical use is the wavenumber region between 4000 and 400 cm-1. FTIR is an important tool in investigating the polymer composite structure. The IR spectra of these materials vary according to their compositions and may be able to show the occurrence of interaction between various constituents . The control fiber and the treated fibers (alkali, silane coupling agent, and CNT) are characterized by FTIR spectroscopy to confirm the chemical reaction between the silane and the ramie fiber, and the spectra are shown in Fig. 4. The absorption peaks and the bond characteristics are shown in Table 2. All the characteristic peaks of cellulose structure were observed in all the fibers. The absorption peaks at 834 cm-1 and 852 cm-1 in silane- and the CNT-treated fibers are assigned to the cellulose-Si bonding. The small peaks at 933 cm-1 and 920 cm-1 designate the Si-O-C or Si-O-cellulose bonding . These observations reveal some chemical reaction between the silane and the ramie fiber through direct condensation reaction between the silanol and the hydroxyl groups of CNT and cellulose present in ramie fiber. Moreover, the decrease in intensity of peaks corresponding to the -OH stretching and bending vibrations also suggests the grafting of CNT onto the surface of ramie fiber. The peaks seen at 1543 cm-1 and 1566 cm-1 in CNT-treated fiber corresponds to the carbon skeleton vibrations of CNT. X-ray photoelectron spectroscopy (XPS) provides an understanding of both the quality of interfacial bond and the performance of bond during service. XPS spectra give the chemical composition of the cellulose surface. For lignocellulosic materials, oxygen and carbon are the predominant species, as is evident …show more content…
… The storage modulus is closely related to the load bearing capacity of the material. The storage modulus of CNT-grafted ramie fiber composite is high compared to the untreated, alkali-treated and silane-treated fiber composites. This indicates that the fiber/matrix adhesion is high in CNT-grafted fiber composite, and grafting with CNT is best method for improving the interfacial adhesion compared to alkali and silane treatments.
The loss modulus reflects the amount of energy dissipated during the strain process. The untreated ramie fiber composite has poor interfacial bonding and the surface treatments improve the enhance the interfacial bonding as seen in Fig. … The maximum heat dissipation occurs at the temperature where loss modulus is maximum indicating the glass transition temperature (Tg) of the system. The increase of Tg is associated with the decreased mobility of the matrix chains, which is an indication of improved interfacial adhesion between the fiber and the
3.1. Grafting of CNT on the ramie fabric
The schematic representation for the mechanism of ramie fiber surface treatments is shown in Fig. 2. For the alkali treatment of ramie fiber, the NaOH reacts with the hydroxyl groups of the ramie fiber as shown in Fig. 2(a). During silane treatment, the hydrolysis of silane takes place initially (Fig. 2(b)) which then reacts with the active hydroxyl functionalities in ramie fiber (Fig. 2(c)). Each silane molecule has three silanol (Si-OH) groups. For CNT treatment, first the silanised CNT is produced by the chemical reaction between silanol groups and the hydroxyl functional groups present in MWCNT (Fig. 2 (d)). The silanized CNT is then grafted on the surface of ramie fiber through silane as shown in Fig. 2(e). A portion of silanol groups present in KH 560 molecule reacts with -OH groups of MWCNT and the other silanol groups react with -OH groups present in cellulose of ramie fiber forming the structural network of Si-O-C of CNT and Si-O-cellulose. a. …show more content…
SEM
The SEM images of ramie fiber before and after chemical treatment are shown in Fig. 3. The surfaces of untreated and the alkali treated ramie fiber were smooth (Fig. 3(a) and (b)) whereas the surfaces of silane treated (Fig. 3(c)) and the CNT treated fiber (Fig. 3(d)) showed roughness which is attributed to the chemical reactions of the ramie fiber with the silanol functional groups. The clear evidence of CNT on the ramie fiber is observed on the CNT treated fiber. However, the grafting is not uniform and some agglomerates were observed on ramie fiber. b. FTIR Infrared radiation refers broadly to the part of the electromagnetic spectrum between the visible and microwave regions. Of great practical use is the wavenumber region between 4000 and 400 cm-1. FTIR is an important tool in investigating the polymer composite structure. The IR spectra of these materials vary according to their compositions and may be able to show the occurrence of interaction between various constituents . The control fiber and the treated fibers (alkali, silane coupling agent, and CNT) are characterized by FTIR spectroscopy to confirm the chemical reaction between the silane and the ramie fiber, and the spectra are shown in Fig. 4. The absorption peaks and the bond characteristics are shown in Table 2. All the characteristic peaks of cellulose structure were observed in all the fibers. The absorption peaks at 834 cm-1 and 852 cm-1 in silane- and the CNT-treated fibers are assigned to the cellulose-Si bonding. The small peaks at 933 cm-1 and 920 cm-1 designate the Si-O-C or Si-O-cellulose bonding . These observations reveal some chemical reaction between the silane and the ramie fiber through direct condensation reaction between the silanol and the hydroxyl groups of CNT and cellulose present in ramie fiber. Moreover, the decrease in intensity of peaks corresponding to the -OH stretching and bending vibrations also suggests the grafting of CNT onto the surface of ramie fiber. The peaks seen at 1543 cm-1 and 1566 cm-1 in CNT-treated fiber corresponds to the carbon skeleton vibrations of CNT. X-ray photoelectron spectroscopy (XPS) provides an understanding of both the quality of interfacial bond and the performance of bond during service. XPS spectra give the chemical composition of the cellulose surface. For lignocellulosic materials, oxygen and carbon are the predominant species, as is evident …show more content…
… The storage modulus is closely related to the load bearing capacity of the material. The storage modulus of CNT-grafted ramie fiber composite is high compared to the untreated, alkali-treated and silane-treated fiber composites. This indicates that the fiber/matrix adhesion is high in CNT-grafted fiber composite, and grafting with CNT is best method for improving the interfacial adhesion compared to alkali and silane treatments.
The loss modulus reflects the amount of energy dissipated during the strain process. The untreated ramie fiber composite has poor interfacial bonding and the surface treatments improve the enhance the interfacial bonding as seen in Fig. … The maximum heat dissipation occurs at the temperature where loss modulus is maximum indicating the glass transition temperature (Tg) of the system. The increase of Tg is associated with the decreased mobility of the matrix chains, which is an indication of improved interfacial adhesion between the fiber and the