Development of cellulose nanocrystal‐reinforced polylactide: A comparative study on different preparation methods

Abstract

A masterbatch of polylactide (PLA) containing cellulose nanocrystals (CNCs) prepared via a solution-cast method was further diluted with neat PLA in the melt state using either a twin-screw extruder or an internal batch mixer to reach a final CNC content of 4 wt%. For the sake of comparison, a direct melt mixing method was employed to prepare PLA-CNC composites. Then, the efficiency of the preparation methods was assessed by comparing the morphological, rheological and thermomechanical properties of the compounded samples. Scanning electron microscopy showed the disappearance of large agglomerates when using the PLA-CNC masterbatch. Transmission electron microscopy revealed the existence of well-dispersed CNCs within the PLA matrix at a nanoscale for masterbatch-based nanocomposites. The rheological properties of the nanocomposites containing the PLA-CNC masterbatch were significantly increased for both steady and small-amplitude oscillatory shear flow fields, compared to the composites prepared via direct melt mixing. In addition, the masterbatch-based nanocomposites exhibited pronounced overshoots in the transient start-up viscosity. The crystalline content of the PLA in the nanocomposites and the crystallization temperature increased when the CNCs were well dispersed, which showed the nucleating effect of the CNCs. In dynamic mechanical thermal analysis, the storage modulus of the nanocomposites increased up to 41 and 128% in the glassy and rubbery regions, respectively. These results show that hydrophilic CNCs can be well dispersed and reinforce PLA using efficient preparation methods. POLYM. COMPOS., 00:000-000,

Effect of preparation method on the properties of polylactide/cellulose nanocrystal nanocomposites

“…In other words, as there was no CNC surface treatment or compatibilizer, the dispersed CNC nanoparticles dramatically tended to reagglomerate during the melt process. [ 31 ] Although this may not be favorable but still the viscoelastic properties showed enhancements when compared to those samples that directly melt mixed (the results are not shown).…”

“…This is due to the hydrophilic structure of CNC, which causes the formation of CNC agglomerates in the matrix. [ 25,31 ] Besides the high surface energy of CNC, the presence of strong hydrogen bonding among these nanoparticles prevents their dispersion in PLA. Various studies have been reported on improving of CNC dispersion in PLA matrix by using surface‐modified CNCs, [ 32,33 ] compatibilizer, [ 34,35 ] or different CNC preparation techniques.…”

“…Combining solution casting and melt mixing methods, Bagheriasl et al [ 31 ] compared the rheological properties of PLA with 4 wt% CNC when prepared through solution casting, direct melt mixing, and dilution of solution‐casted PLA/CNC masterbatch through melt mixing. They reported that the CNC dispersion and hence the rheological properties of nanocomposites were significantly improved in the solution‐casted nanocomposites.…”

Preparation and characterization of reinforced poly (ε‐caprolactone) nanocomposites by cellulose nanowhiskers

“…It has attracted a great deal of scientific consideration for high‐performance applications . Therefore, CNCs can be used in many applications such as reinforcing agents in polymer nanocomposites due to their incredible properties …”

An overview of the recent advances in polylactide‐based sustainable nanocomposites

“…Solvent casting of PLA/CNC nanocomposites results in the development of a strong CNC percolation network without the problem of thermal degradation of PLA, a problem associated with melt mixing. [172] Bagheriasl et al [191,192] achieved superior dispersion of CNC nanoparticles in PLA/CNC nanocomposites produced by solvent casting with DMF. They also observed that compared melt mixing in TSE, solvent casting led to a better dispersion of nanoparticles in PLA nanocomposites containing 4 wt% CNC.…”