Optimization of microcrystalline cellulose (MCC) isolated from rice husk (RH) as reinforcement filler in polylactic acid (PLA) biocomposite / Nur Hanani Abu Seman

In this study, microcrystalline cellulose (MCC) was isolated from rice husk (RH)
cellulose via acid hydrolysis process using nitric acid (HNO3) in comparison with
sulphuric acid (H2SO4) and hydrochloric acid (HCl). The parameters used to isolate MCC
from RH were extensively studied by using 0.5M and 1.0M of different acid
concentration at 30 min, 60 min and 120 min reaction time. The optimum condition of
acid hydrolysis process was undergone with 0.5M of HNO3 and 30 min reaction time
successfully produced the highest percentage yield of MCC-RH at 83.5% as compared to
H2SO4 and HCl at 80.6% and 81.8% respectively. Besides, the analysis of Fourier

Transform Infrared (FTIR) spectroscopy affirmed the successive elimination of non-
cellulosic material from RH cellulose resulting highly purified MCC-RH. X-ray

Diffraction (XRD) analysis showed MCC-RH treated with HCl produced the highest
crystallinity index value of 54.2% while HNO3 and H2SO4 produced comparable results
of 52.4% and 49.7% respectively. TGA analysis showed the thermal stability of the
MCC-RH treated with 0.5M HNO3 was enhanced as the degradation temperature at Ton,
T20 and T50 increased compared with the untreated RH. The highest MCC-RH yielded by
0.5M of HNO3 was further analyzed as reinforcement filler in polylactic acid (PLA)
biocomposite preparation through solvent casting technique. The incorporation of 1%,
3%, 5%, 7% and 9% of MCC-RH filler in the prepared PLA/MCC-RH biocomposite
were successfully enhanced the physical and mechanical properties of PLA.
Thermogravimetric analysis (TGA) has proved 3% MCC loading has the highest thermal
stability as it degraded at higher temperature, 380 °C compared with pure PLA and 9%
MCC loading which degraded at 365 °C and 350 °C respectively due to good interaction
of MCC filler and PLA matrix. The good incorporation of 3% MCC loading with PLA
matrix of the prepared PLA/MCC-RH biocomposite was further proved by SEM analysis
with no agglomeration, filler pulled-out and void observed. In addition, PLA/MCC-RH
biocomposite with 3% MCC loading has the highest tensile strength at 25.08 MPa with
56.6% increment compared with pure PLA which only produced tensile strength at 16.02
MPa due to good dispersion between MCC filler and PLA matrix that produced a good
filler and matrix interaction. Whilst the addition of 5%, 7% and 9% of MCC loading
caused declination in tensile strength and Young’s modulus due to agglomeration of
MCC, filler pull-out and voids observed during SEM analysis. PLA/MCC-RH
biocomposite with minimal water absorption properties is favorable to prolong the
lifetime of the prepared PLA/MCC-RH biocomposite. Hence, water immersion test was
done on the prepared biocomposites to determine its water absorption properties.
PLA/MCC-RH bioomposite with 3% MCC loading was observed with minimal water
absorption and thickness swelling recorded at 1.59% and 5.65% respectively compared
with 9% MCC loading resulted 5.28% water absorption and 7.40% thickness swelling.