Functionality of Cellulose Nanofiber as Bio-Based Nucleating Agent and Nano-Reinforcement Material to Enhance Crystallization and Mechanical Properties of Polylactic Acid Nanocomposite

Abstract

Polylactic acid (PLA), a potential alternative material for single use plastics, generally portrays a slow crystallization rate during melt-processing. The use of a nanomaterial such as cellulose nanofibers (CNF) may affect the crystallization rate by acting as a nucleating agent. CNF at a certain wt.% has been evidenced as a good reinforcement material for PLA; nevertheless, there is a lack of information on the correlation between the amount of CNF in PLA that promotes its functionality as reinforcement material, and its effect on PLA nucleation for improving the crystallization rate. This work investigated the nucleation effect of PLA incorporated with CNF at different fiber loading (1–6 wt.%) through an isothermal and non-isothermal crystallization kinetics study using differential scanning calorimetry (DSC) analysis. Mechanical properties of the PLA/CNF nanocomposites were also investigated. PLA/CNF3 exhibited the highest crystallization onset temperature and enthalpy among all the PLA/CNF nanocomposites. PLA/CNF3 also had the highest crystallinity of 44.2% with an almost 95% increment compared to neat PLA. The highest crystallization rate of 0.716 min–1 was achieved when PLA/CNF3 was isothermally melt crystallized at 100 °C. The crystallization rate was 65-fold higher as compared to the neat PLA (0.011 min–1). At CNF content higher than 3 wt.%, the crystallization rate decreased, suggesting the occurrence of agglomeration at higher CNF loading as evidenced by the FESEM micrographs. In contrast to the tensile properties, the highest tensile strength and Young’s modulus were recorded by PLA/CNF4 at 76.1 MPa and 3.3 GPa, respectively. These values were, however, not much different compared to PLA/CNF3 (74.1 MPa and 3.3 GPa), suggesting that CNF at 3 wt.% can be used to improve both the crystallization rate and the mechanical properties. Results obtained from this study revealed the dual function of CNF in PLA nanocomposite, namely as nucleating agent and reinforcement material. Being an organic and biodegradable material, CNF has an increased advantage for use in PLA as compared to non-biodegradable material and is foreseen to enhance the potential use of PLA in single use plastics applications.

Combined Effects of Cellulose Nanofiber Nucleation and Maleated Polylactic Acid Compatibilization on the Crystallization Kinetic and Mechanical Properties of Polylactic Acid Nanocomposite

“…Among the T c investigated, more distinct nucleation effects with a minimum t 1/2 value can be seen at T c = 100 • C for all nanocomposites. This temperature corresponds to the optimum temperature of isothermal crystallization of the nanocomposites similar in PLA/CNF study previously conducted [45]. A similar trend can be seen for crystallization rate as shown in Figure 7b, which shows that the highest crystallization rate was observed for PLA/PLA-g-MA0/CNF3 nanocomposites.…”

“…Nanocomposites neat PLA, PLA/PLA- g -MA3/CNF0 and PLA/PLA- g -MA/CNF3 with different PLA- g -MA loading were prepared using the same method as described in our previous study Shazleen et al [ 45 ]. Prior to mixing, moisture from PLA pellets was removed by drying at 60 °C for 24 h under vacuum condition to minimize hydrolytic degradation during the melt compounding at high temperature.…”

“…In the previous research, we investigated the optimal PLA and CNF blending ratio to achieve the maximal crystallization rate and mechanical properties for PLA nanocomposites [ 45 ]. In this article, we study the PLA nanocomposites blended with 3 wt.% of CNF with the addition of PLA- g -MA as a compatibilizer.…”

Chain Extension of Poly(Lactic Acid) (PLA)–Based Blends and Composites Containing Bran with Biobased Compounds for Controlling Their Processability and Recyclability

“…The c composite showed ( Figure 10 ) the highest X c value (6.9, always poor) suggesting that bran fibers, being natural fibers, could act as a nucleating agent. This effect is known in literature because they act as sites of heterogeneous nucleation [ 55 , 56 , 57 ]. This result was reduced in cESO due to ESO plasticizing action which increases the free volume between the amorphous part and the crystals [ 58 ].…”

Compatibilization and Toughening of Biodegradable Polylactic Acid/Cellulose Acetate Films by Polyamide Amine Dendrimers

“…3 shows the POM images of PLA / CA blends isothermal crystallized at 120 °C for 30 minutes. In PLA / CA blends, CA could promote the crystallization rate of PLA as a nucleating agent, but the agglomeration phenomenon inhibited the nucleation effect of CA [31]. From Fig.…”