Structure and Properties of Polylactic Acid Biocomposite Films Reinforced with Cellulose Nanofibrils

Abstract

Polylactic acid (PLA) is one of the most promising biodegradable and recyclable thermoplastic biopolymer derived from renewable feedstock. Nanocellulose reinforced PLA biocomposites have received increasing attention in academic and industrial communities. In the present study, cellulose nanofibrils (CNFs) was liberated by combined enzymatic pretreatment and high-pressure homogenization, and then subsequently incorporated into the PLA matrix to synthesize PLA/CNF biocomposite films via solution casting and melt compression. The prepared PLA/CNF biocomposite films were characterized in terms of transparency (UV-Vis spectroscopy), chemical structure (attenuated total reflectance-Fourier transform infrared, ATR-FTIR; X-ray powder diffraction, XRD), thermal (thermogravimetric analyzer, TGA; differential scanning calorimetry, DSC), and tensile properties. With 1.0–5.0 wt % additions of CNF to the PLA matrix, noticeable improvements in thermal and physical properties were observed for the resulting PLA/CNF biocomposites. The 2.5 wt % addition of CNF increased the tensile strength by 8.8%. The Tonset (initial degradation temperature) and Tmax (maximum degradation temperature) after adding 5.0 wt % CNF was increased by 20 °C, and 10 °C, respectively in the nitrogen atmosphere. These improvements were attributed to the good dispersibility and improved interfacial interaction of CNF in the PLA matrix.

The role of cellulose nanofibrillated fibers produced with combined supercritical carbon dioxide and high‐pressure homogenization process as reinforcement material in biodegradable polymer

“…CNF has been previously reported to affect not only on the mechanical properties of the polymer matrix but also the thermal properties. [ 46, 54 ] The result of the DTG confirmed the earlier reported literature. [ 23, 55 ] Figure 8(A)‐(D) showed the differential scanning calorimetry of the neat PLA and the composite with increased CNF loading.…”

“…The dispersion of CNF resulted in no agglomeration and therefore result in inter-facial and intra-facial interaction of the polymer mix as seen in the surface morphology ( Figure 3) and the schematic drawing ( Figure 5) of the PLA and CNF interaction. [46] The values of the tensile strength in this study are similar to those reported by Abdul Khani et al [47] on PLA/modified CNF. However, Their study solves the agglomeration challenge between PLA and CNF with chemical acetylation of CNF as against this present study on supercritical preparation of CNF.…”

“…This observation in the fractured surface morphology corroborates those indicated by the surface morphology as earlier reported. [ 46, 49 ]…”

“…This observation in the fractured surface morphology corroborates those indicated by the surface morphology as earlier reported. [46,49] Figure 6 showed the AFM images of the neat PLA and the composite with increased loading of cellulose nanofabrillated fiber. The AFM images further confirm the morphological properties result of the scanning electron microscope.…”

“…This means that the degradable properties of PLA are not affected by CNF addition. [46] Figure 7(B) showed the derivative thermogravimetric analysis (DTG) of the neat PLA and the composites with increased loading of cellulose nanofibrillated fiber. The DTA curve exhibited the first initial drop, which is due to the evaporation of the solvents (chloroform and water content) and a major single peak between 400 C and 450 C. The peak temperature for each of the composite ranges from 411 C, 415 C, 419 C, and 421 C for PLA, PLA + 1% CNF, PLA + 3% CNF, and PLA + 5%.…”