Dispersão de celulose nanocristalina em blenda da PBAT/PLA sob fluxo elongacional em canal hiperbólico

Abstract

The effect of the elongational deformation mixture on the dispersion evolution of nanocrystalline cellulose (CNC) in a biodegradable polymer matrix was evaluated. The polymer matrix used was commercial blend of polyolefin poly(butylene adipateco-terephthalate) (PBAT) with polylactide (PLA) BASF ecovio® F2224, and as reinforcement, the CNC sold by CelluForce®. For the production of nanocomposites, two CNC mass proportions were selected: 2% and 5%. Two rates of uniaxial elongational deformation were evaluated: 3.47 and 17.34 s-1. The analyzes were carried out from data collected during the production of nanocomposites and from thermal, rheological and morphological characterization. The data obtained from the production of the nanocomposites demonstrated the reliability of the constructed device, perceptible in the reproducibility of the pressures developed in the piston during the processing. The nanocomposite production conditions did not result in thermo-oxidative degradation of the CNC, but there was a thermal degradation of the PLA, identified during the thermal evaluation. Thermal evaluations also indicated the formation of oriented domains in the amorphous regions of PLA, apparent in the form of enthalpic relaxations. The rheological results showed increase of the complex viscosity 𝜂∗(𝛾̇) with the increase of the CNC fraction present in the nanocomposite. No significant changes were found in the storage modulus (G ') and in the loss modulus (G'') with the incorporation of CNC in ecovio. The results found for the morphological evaluations showed the additive effect of convergent and divergent hyperbolic sections arranged in sequence, in the exfoliation and dispersion of CNC agglomerates in the molten matrix, for the 4 studied conditions. From the results obtained for the area ratio, number of agglomerates per unit area and average size of CNC agglomerates, it was observed that, for the same mass ratio, the higher the pressure developed during processing, the better the dispersion obtained.