Abstract
Compression molded biodegradable films based on poly(butylene succinate) (PBS) and poly(butylene adipate-co-terephthalate) (PBAT) at varying weights were prepared, and their relevant properties for packaging applications are here reported. The melt rheology of the blends was first studied, and the binary PBS/PBAT blends exhibited marked shear thinning and complex thermoreological behavior, due to the formation of a co-continuous morphology in the 50 wt% blend. The films were characterized by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), mechanical tensile tests, scanning electron microscopy (SEM), and oxygen and water vapor permeability. PBS crystallization was inhibited in the blends with higher contents of PBAT, and FTIR and SEM analysis suggested that limited interactions occur between the two polymer phases. The films showed increasing stiffness as the PBS percentage increased; further, a sharp decrease in elongation at break was noticed for the films containing percentages of PBS greater than 25 wt%. Gas permeability decreased with increasing PBS content, indicating that the barrier properties of PBS can be tuned by blending with PBAT. The results obtained point out that the blend containing 25 wt% PBS is a good compromise between elastic modulus (135 MPa) and deformation at break (390%) values. Overall, PBS/PBAT blends represent an alternative for packaging films, as they combine biodegradability, good barrier properties and reasonable mechanical behavior.
Highlights
The quest for the development of biobased and biodegradable polymer formulations is ever increasing due to environmental pollution, global heating and the foreseen shortage of oil supplies
The blend with the highest content of poly(butylene adipate-co-terephthalate) (PBAT) (PBS25/PBAT75) displayed slightly higher values in the lower frequency region compared to PBAT, while the curves of the other blends cPoPonolylcymmeerrensrs2e20d022,00,i,1t122,is,223w3117o7 rth highlighting that the poly(butylene succinate) (PBS)/PBAT blends showed multimodal crystalliza7t7ioooffn1178 profiles, corresponding to the different types of crystal lamellae formed during cooling from melt
For PO, its values in the PBS/PBAT blends decreased with PBS content, and the values obtained for all blends were smaller than those predicted by the rule of mixtures
Summary
The quest for the development of biobased and biodegradable polymer formulations is ever increasing due to environmental pollution, global heating and the foreseen shortage of oil supplies In this respect, biodegradable and partially biobased polyesters, such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS) and aliphatic-aromatic copolyesters, are considered as suitable replacements for traditional oil-based commodity polymers, such as polyolefins or poly(ethylene terephthalate) (PET) [1,2,3,4,5]. Concerning gas barrier properties, among biodegradable polymers PBAT shows slightly higher PO and water vapor permeability (PWV) compared to PLA and PBS [5]. The permeability values were converted to SI units, (mol/m·s·Pa), considering the molar mass of water, 18.02 g/mol, and the normal molar volume of ideal gases, 22,414 cm (STP)/mol
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