Study On Bagasse Cellulose Microfiber

Bagasse is a by-product of sucrose extraction from sugarcane, and its cellulose content is very high.

Lignin and hemicellulose can be separated by pulping, and bagasse cellulose fibers can be obtained.

Bagasse fiber can be used as a source of cellulose nanoparticles.

Under certain acid hydrolysis conditions, it can be dispersed into rod like microcrystalline fibers.

This study demonstrated the possibility of separation of bagasse microfiber and nano enhanced filler.

Scanning electron microscopy (SEM), atomic force microscopy (AFM) and solid-state nuclear magnetic resonance (NMR) spectroscopy were used to study the morphological changes of fibers in microfibrils.

1 experimental materials and methods

1.1 experimental materials bagasse, sodium hydroxide, glacial acetic acid and sulfuric acid.

1.2 purification of bagasse cellulose

The dried cane sugar can be ground to 40 mesh.

According to the data, bagasse contains about 50% cellulose, 25% lignin and 25% hemicellulose.

The dried bagasse was immersed in 4% sodium hydroxide solution and reacted with 4 h at 80 C, which could remove most lignin and hemicellulose.

Due to the uneven color of fibers, bleaching fibers with sodium chlorite / glacial acetic acid mixed solution to eliminate residual lignin and hemicellulose.

After bleaching, the fiber is washed with 5% sodium hydroxide, and then the deionized water is rinsed repeatedly to make the pH value neutral and the dry cane slag fiber can be obtained.

Preparation and dispersion of 1.3 cellulose microfibrils

5% of bagasse fiber suspension was heated to 75 degrees centigrade and stir in 10 min.

Then uniform pump was used to homogenate the fibers, and the fibers were broken into homogeneous particles.

After the homogeneous fibers were hydrolyzed in 2.5 sulfuric acid at 60 C and 60% (w/v) for 2.5 h, the non crystalline region was removed and the dispersed microfibers were obtained.

Add cold water to stop the reaction.

After washing, the microfiber was dispersed by ultrasonic breaker for 5 min.

First use water as dispersing medium and then substitute butanol.

Finally, the microfiber was removed and freeze-dried.

1.4 morphological structure analysis

Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to observe the effects of hydrolysis and mechanical shear on the supermolecular structure of cellulose.

The cellulose microfibrils were placed on glass slides after ultrasonic treatment, and the dispersion of cellulose microfibrils was observed by Universal microscope.

A droplet of acid treated microfiber was suspended on the graphite plate, and the microstructure of the microfiber was analyzed by scanning electron microscopy.

The surface morphology and structure of microfibrils can be seen through the surface image obtained by AFM, and can also be used to analyze the surface morphology and crystallization direction of fibers.

1.5 solid NMR studies of hydrogen bonds in cellulose supramolecular structure reduce its solubility in most NMR solutions. Therefore, NMR spectroscopy of cellulose microfibrils can be obtained by solid state detectors.

Solid phase cross polarization / magic angle rotation (CP/MAS) nuclear magnetic resonance measurements were performed at 75.01 MH with a Brook 300 MH spectrometer.

The dried cellulose samples (before hydrolysis and after hydrolysis) were packed in a 7 mm wide zirconia rotator and measured by CP pulse program.

The rotation rate is (5 + 0.1) kH.

The external calibration of carbonyl carbonyl acid to 176ppm.

2 results and discussion

2.1 scanning electron microscope (SEM)

Scanning electron microscope (SEM) showed that the morphology of the fibers changed greatly after acid hydrolysis.

Fig. 1 is an image of cellulose fiber before the acid hydrolysis. It can be seen that the length of most fibers is 2mm.

After the acid hydrolysis, the electron microscope image of the fiber (shown in Fig. 2) shows that the size of most microfibrils is in the sub micron range with the aspect ratio of 50~120.

Cellulose microfiber was separated from fiber bundles after acid treatment, ultrasonic treatment and homogenization treatment.

It can be seen from Fig. 2 that the cross-sectional area of fiber is different.

It may be that some of the microfibrils are not completely dispersed after being processed, or they are reassembled when scanning electron microscopy and atomic force microscopy are used.

The different size of sugarcane will also affect the cross-sectional size of cellulose microfiber.

The cross-section size of cellulose microfibrils is between 20~200 nm, and the cross section dimension of single microfiber is between 3~20 nm.

Under the same hydrolysis conditions, the degree of aggregation of bagasse micro cellulose was more obvious than that of other cellulose fibers, such as Cladpho-ra and oak bowl.

2.2 atomic force microscope

The morphological characteristics of bagasse cellulose microfibrils can be seen from the images generated by atomic force microscopy (figures 3 and 4).

The nanoscale (30nm) structure of cellulose microfibrils can be seen in Fig. 3.

In Fig. 4, the width (60~100 nm) in the region (bright area) represents the crystalline region, and the amorphous region (dark area) is along the direction of the fiber axis.

Because it is a semi crystalline polymer, the brighter region is the crystalline region and the dark area is amorphous.

2.3 solid state NMR study

Cross polarization / magic angle spinning (CP/MAS) technique was used to study the morphological changes of cellulose during acid hydrolysis.

The NMR spectra of cellulose microfibrils and hydrolyzed cellulose microfibrils before hydrolysis were shown in figures 5A and B respectively.

The 6 carbon atoms are dominant in the two spectrograms, and the peaks are located between 105~60 ppm.

The peak formed by C1 is about 105 ppm.

Next comes the peak formed by C4 between 82~89 ppm, and the peak between 72~79 ppm is generated by C2, C4 and C5.

The peak at 64 ppm is due to the chemical shift produced by C6.

There is no aromatic peak between 110~140 ppm, indicating that lignin in bagasse has been removed after alkali treatment and bleaching.

In the NMR spectra of cellulose, the two peak between 80~92 ppm is generated by C4 atoms.

The relatively sharp peaks correspond to crystalline regions, and relatively gentle peaks correspond to microcrystalline surfaces or disordered regions.

An unobvious peak formed between C6 and 63~65 ppm is generated by amorphous and disordered regions in cellulose.

The NMR spectra of cellulose before and after acid hydrolysis are quite different: the peaks formed by C4 and the peak profiles of crystalline and amorphous regions in 80~92 ppm have changed greatly.

Cellulose fibers without acid hydrolysis have roughly the same crystalline region and amorphous region (Fig. 6A slightly).

The peaks of cellulose fibers at acid hydrolysis were more sharp at 89 ppm (Figure 6B slightly).

The ratio of the peak strength to the amorphous region increases, indicating that the C4 peak in the crystalline region is enhanced, indicating that the disordered and amorphous regions have been successfully removed, leaving a high crystallinity of cellulose microfibers.

At 63 ppm, the peak of C6 formation is due to the amorphous zone in bagasse cellulose.

After the hydrolysis of bagasse cellulose, the peaks produced by C6 were more sharp. However, the number of dislocations represented by C6 was greatly reduced, and cellulose was further degraded by acid hydrolysis and mechanically dispersed fibers.

3 conclusion

In the process of bagasse cellulose separation from bagasse, it depends on certain acid hydrolysis conditions and mechanical functions.

The best process is to use 60% (W/V) sulfuric acid to hydrolyse cellulose fiber 2.5 h at 60 degrees Celsius.

Under these conditions, the amorphous region is successfully removed and there is no great damage to the crystalline region.

The above conditions do not separate all single cellulose microfibrils from cellulose bundles.

It is not advisable to separate the single cellulose microfiber from the fiber bundle under the improved reaction conditions, but it destroys the crystalline region.

The NMR spectra of the fibers showed that lignin was completely removed in the process of pulping.

Nuclear magnetic resonance spectroscopy showed that large area of amorphous region in microfiber was removed after acid hydrolysis and mechanical action.

The amorphous region is widespread in fibers without acid hydrolysis.