Cellulose nanofibrils reinforced PBAT/TPS blends: Mechanical and rheological properties.

Poly(butylene adipate-Co-terephthalate)/thermoplasticized starch PBAT/TPS blends are among the most produced biodegradable plastic for wide application packaging, sharing more than 20% of the global production capacity of bioplastics. However, this class of material suffers from poor mechanical strength in comparison of neat PBAT, especially when the TPS content exceeds 30 wt%. Aiming at enhancing the mechanical performance of PBAT/TPS blends while maintaining relatively high TPS content, cellulose nanofibrils (CNFs) was incorporated into the TPS phase using twin screw extrusion. The effects of CNFs content on the microstructure, mechanical properties, melt-rheology and humidity absorption were investigated. An enhancement in the tensile strength and modulus was noted with the inclusion of CNFs, with optimal performance attained at 8 wt% of CNFs. A narrowing in the distribution of the TPS nodules within the PBAT matrix was also observed with the addition of CNFs, which is expected to be on the origin of the main evolution in the mechanical, rheological and humidity observed. Because of the availability of CNFs, biodegradability and facile processability, the ternary PBAT-TPS-CNFs blends might contribute to improve the performance of this class of biodegradable bioplastic.

One-step processing of plasticized starch/cellulose nanofibrils nanocomposites via twin-screw extrusion of starch and cellulose fibers.

Nanocomposites based on thermoplasticized starch filled with cellulose nanofibrils (CNFs) were produced in a single step by twin-screw extrusion of corn starch granules, glycerol as a plasticizer, and oxidized cellulose fibers. The objective was to demonstrate the possibility to produce CNFs in situ during the processing of the nanocomposite when a hydrophilic polymer matrix was used. For comparison purpose, nanocomposites were also prepared by extrusion of a previously prepared CNF suspension, corn starch granules and glycerol. The nanocomposites were characterized in terms of mechanical properties, morphology, crystallinity, and transparency. The nanocomposites prepared via in situ fibrillation displayed a higher strength than those produced by incorporating readily prepared CNFs. In addition, the transparency degree up to a 15 wt% CNF content was similar for the two processing routes, confirming the effective breakdown of pretreated cellulose fibers into CNFs during the extrusion process.

PBAT/thermoplastic starch blends: Effect of compatibilizers on the rheological, mechanical and morphological properties.

The effect of maleic anhydride (MA), citric acid (CA) and maleated poly(butylene adipate-Co-terephthalate) PBAT (PBATg-MA), as compatibilizer, on properties of blends of plasticized starch/PBAT in a weight ratio of 60/40 were investigated using rheological measurements, tensile tests, SEM observations and mechanical dynamic analyses. A strong evolution in the mechanical, morphological and rheological properties of the blend was observed according to the type of additives used. The type of compatibilizer was shown to control the morphology and continuity development of the TPS/PBAT 60/40 wt% blend. In the absence of the compatibilizer and in presence of PBATg-MA, the PBAT was the continuous phase, while the TPS became the continuous one in presence of MA and CA. These evolutions were explained by the change in the melt rheological properties of TPS in the presence of the compatibilizer and its aptitude to promote interfacial adhesion between TPS and PBAT phases. A huge evolution in the tensile strength and strain at break were also observed according to the structure of the compatibilizer.