Abstract
Poly(hydroxybutyrate) (PHB)-based films, reinforced with bacterial cellulose (BC) or cellulose nanocrystals (CNC) and plasticized using a molecular (tributyrin) or a polymeric plasticizer (poly(adipate diethylene)), were produced by solvent casting. Their morphological, thermal, wettability, and chemical properties were investigated. Furthermore, the effect of adding both plasticizers (20 wt % respect to the PHB content) and biobased selected nanofillers added at different contents (2 and 4 wt %) on disintegrability in composting conditions was studied. Results of contact angle measurements and calorimetric analysis validated the observed behavior during composting experiments, indicating how CNC aggregation, due to the hydrophilic nature of the filler, slows down the degradation rate but accelerates it in case of increasing content. In contrast, nanocomposites with BC presented an evolution in composting similar to neat PHB, possibly due to the lower hydrophilic character of this material. The addition of the two plasticizers contributed to a better dispersion of the nanoparticles by increasing the interaction between the cellulosic reinforcements and the matrix, whereas the increased crystallinity of the incubated samples in a second stage in composting provoked a reduction in the disintegration rate.
Highlights
Biodegradable polymers have attracted great scientific and technological interest worldwide, due to their important role in the reduction of plastic waste problem
These bands became broader due to the hydrogen bond interactions between hydroxyl groups of nanocellulose and PHB and TB carbonyl groups, as proposed by Arrieta et al [28]. These results of nanocellulose and PHB and TB carbonyl groups, as proposed by Arrieta et al [28]. These results indicate that only cellulose nanocrystals (CNC) composites present superficial –OH groups and this promotes the hydrophilic indicate that only CNC composites present superficial –OH groups and this promotes the hydrophilic character of the films
Films exhibited a marked acceleration in disintegration, since the addition of the plasticizer increases the wettability of the cellulosic-based nanoreinforcements was tested
Summary
Biodegradable polymers have attracted great scientific and technological interest worldwide, due to their important role in the reduction of plastic waste problem In this sense, several biodegradable polymers have been investigated during the past as possible replacement options to non-degradable polymers currently used in film production [1]. PHB melting temperature can be lowered, avoiding the thermal degradation of the polymer, by considering chemical or physical modifications [6], by introducing structural units into the PHB backbone or blending with other biopolymers, as in the case of PLA (polylactic acid)/PHB blends [4] Other than these possibilities, the application of biopolymers can be extended by considering the addition of modifiers/plasticizers, by copolymerization or blending.
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