Crystalline cellulose was extracted from jute by hydrolysis with 40% H2SO4 to get mixture of micro/nanocrystals. Scanning electron microscope (SEM) showed the microcrystalline structure of cellulose and XRD indicated the I
Considering the huge benefits of environmentally friendly materials, the use of natural/biofiber reinforced composites has rapidly expanded due to the availability of such renewable resources, for use as reinforcing composites with other synthetic and biodegradable polymer matrices (biocomposite) [
Crystalline cellulose (CC), where the amorphous regions are removed by acid hydrolysis, can be a very promising cellulosic reinforcement for polymers. Native cellulose is one of the strongest and stiffest natural fibers available; the theoretical modulus is estimated at 167.5 GPa [
Preparation of composites has been considered a promising method to increase the softening temperature of biopolymers. Therefore, it is interesting to study if the incorporation of reinforcements can improve the toughness and thermal stability. Oksman et al. [
Although there was significant work already done for the preparation of crystalline cellulose-PLA from different sources such as wood, cotton, and sisal, there was no report in the literature which addresses the application of jute cellulose crystals for biocomposite preparation with PLA. In all literature the composites were characterized by conventional techniques such as thermal, morphological, flexural, and hardness, but no biological properties are addressed. In the present study, micro- and nanocrystalline cellulose are prepared from jute by sulfuric acid hydrolysis of mercerized and bleached jute fiber. The cellulose crystals will be used to reinforce biocomposite with PLA by extrusion and heat press molding. The extensive mechanical, thermal, morphological, and bioactive characteristics of the composites are evaluated to determine its suitability for biomedical applications.
Jute-white
Jute fibers were subjected to a washing pretreatment to remove impurities and waxy substances covering the external surface of fiber cell walls. The fibers were milled into fine size (
Preparation of cellulose reinforced poly(lactic acid) composite consists of two steps: extrusion and hot press. The composition of the CC reinforced PLA composites are shown in Table
Composition of PLA/cellulose composites.
Film | Amount of CC, g | Amount of PLA, g |
---|---|---|
Film with 0% cellulose | 0.00 | 5.00 |
Film with 3% cellulose | 0.15 | 4.85 |
Film with 6% cellulose | 0.30 | 4.70 |
Film with 12% cellulose | 0.60 | 4.40 |
Film with 15% cellulose | 0.75 | 4.25 |
After extrusion, the cylindrical rod-like samples were cut into small size (1.5 cm long) and arranged on an in-lab made dye, which has a ring of inside diameter 8 cm and outside diameter of 12 cm and has two discs on each side each of 1.5 cm in thickness. Then the samples in the dye were hot pressed in between two plates of a hot press (Weber Pressen Hydraulic Press) for 2-3 min after reaching process temperature of 165°C.
The dried CC sample and the composites were analyzed by an ATR-FTIR spectrophotometer (Model-01831, SHIMADZU Corp., Japan). Crystal’s structure was monitored by a D8 Advance X-ray diffractometer, employing Cu radiation of wavelength
Thermal properties were monitored by thermogravimetric analysis (TGA) and differential thermal analyses (DTA) of cellulose and the composites were performed by using a TG/DTA EXTAR 6000 STATION, Seiko Instrument Inc., Japan. Thermomechanical analysis (TMA) of the scaffold film was carried out by using a Shimadzu TMA-50 analyzer, Japan. The sample (
The composites prepared from PLA and CC by extrusion and hot press method are highly brittle, and it is difficult to measure their tensile properties and in that cause surface hardness and yield strength were determined. Microhardness testing was done according to ASTM E-384 method, which gives an allowable range of loads for testing with a diamond indenter; the resulting indentation is measured and converted to a hardness value. The result for Vickers' microhardness was reported in kg/
Identification of sensitivity of bacteria (
Cellulose crystals can be prepared from delignified cellulose by acid hydrolysis [
Alkali treatment can remove natural and artificial impurities and produce rough surface topography as shown in Figure
SEM images of CCs and biocomposite. (a) Mercerized jute, (b) bleached jute, (c) and (d) acid hydrolyzed jute, (e) picture of composite, and (f) image of PLA/CC biocomposite with 15% CC.
The images of the CC and the composites as obtained by SEM are shown in Figure
FTIR spectra of CCs and CC-PLA composites are given in Figure
FTIR spectra of (a) jute cellulose crystals and (b) CC-PLA biocomposite.
XRD patterns of (a) cellulose, (b) PLA, and (c) PLA crystalline cellulose biocomposite.
Pure PLA showed a strong absorption band at 1751
The XRD analysis of the raw materials and the biocomposites was done to obtain further insight into the materials' crystallinity. The XRD patterns of PLA, CC and composite are shown in Figure
The results from the TGA, DTG, and DTA are presented in Figure
Comparison of TG/DTA and DTG value of (a) cellulose crystals (red), (b) PLA (black), and (c) biocomposite (blue).
Thermomechanical analysis (TMA) microgram of pure PLA and its composite with 15% cellulose are shown in Figure S1 in the supporting information. Figure S1(a) for PLA showed total contraction and it showed two peaks at 60.7°C and at 157.8°C which indicated the softening point and melting point of PLA, respectively. Figure S1(b) showed two peaks at 52.2°C and 154.1°C which indicate the softening point and melting point, respectively, indicating that CC has less effect on softening and melting of the composite.
DSC analysis was performed to investigate the crystallinity of the PLA and composite samples. Figure
DSC thermogram of (a) jute CC, (b) PLA, (c) composite with 6% CC, and (d) composite with 15% CC.
As the PLA film and its composites were very fragile in nature Vickers hardness (VH) test and yield strength (YS) measurement were carried out. From the experiment, it was found that both the hardness and yield strength of PLA composites increase in the incorporation of reinforcing agent (cellulose) in the PLA matrix. However, it was observed that no significant change occurred for increasing cellulose concentration from 3 to 15%. It may be defined in the way that the test of indentation is a surface phenomenon; it is not affected much by the reinforcing agent that agglomerates in the lower portion. Figure
Variation of VH and YS at different cellulose contents.
After incubation it was found that only the same 10 (as shown in Figure
Mortality of brine shrimp (
Sample no. | Sample name | Dose (mg/L) | Number of nauplii present after incubation | Mortality (%) |
---|---|---|---|---|
1 | Positive control (vincristine sulfate) | 0.5 | 0 | 100 |
2 | Negative control (artificial sea water) | — | 10 | 0 |
3 | Film with 0% cellulose | 0.2 | 10 | 0 |
4 | Film with 3% cellulose | 0.2 | 8 | 20 |
5 | Film with 6% cellulose | 0.2 | 9 | 10 |
6 | Film with 15% cellulose | 0.2 | 8 | 20 |
The increasing demand of the bioabsorbable composites for the biomedical purposes leads to the responsibility and obligation of researchers to develop products with better properties compared with those of existing materials. In this research work, we have extracted nano- and microcrystalline cellulose from jute and various reaction parameters were optimized in a view to obtain high extraction yield. The crystalline cellulose was used to fabricate composite with PLA. It was observed that hydrogen bonding exists between CC and PLA when the composite was fabricated by extrusion or hot press. The thermal stability and the crystallinity of the composites have increased when composite was prepared from CC and PLA. Vickers hardness test cellulose/PLA composite prepared from 15% CC showed maximum hardness and also that showed better antimicrobial properties. All these properties suggest that the composite can be used in biomedical purposes such as regenerative bone tissue.
The authors declare that there is no conflict of interests regarding the publication of this paper.