Abstract
Biopolymers with universal accessibility and inherent biodegradability can offer an appealing sustainable platform to supersede petroleum-based polymers. In this research, a hybrid system derived from cellulose nanocrystals (CNCs) and zinc oxide (ZnO) nanoparticles was added into poly (lactic acid) (PLA) to improve its mechanical, thermal, and flame resistance properties. The ZnO-overlaid CNCs were prepared via the solvent casting method and added to PLA through the melt-blending extrusion process. The composite properties were evaluated using SEM, a dynamic mechanical analyzer (DMA), FTIR TGA, and horizontal burning tests. The results demonstrated that the incorporation of 1.5% nano-CNC-overlaid ZnO nanoparticles into PLA enhanced the mechanical and thermal characteristics and the flame resistance of the PLA matrix. Oxidative combustion of CNC-ZnO promoted char formation and flame reduction. The shielding effect from the ZnO-CNC blend served as an insulator and resulted in noncontinuous burning, which increased the fire retardancy of nanocomposites. By contrast, the addition of ZnO into PLA accelerated the polymer degradation at higher temperature and shifted the maximum degradation to lower temperature in comparison with pure PLA. For PLA composites reinforced by ZnO, the storage modulus decreased with ZnO content possibly due to the scissoring effect of ZnO in the PLA matrix, which resulted in lower molecular weight.
Highlights
The global concern over reducing the environmental impact caused by petroleumbased polymers has accelerated research aimed at developing biopolymer materials from sustainable resources [1]
Among different types of biopolymers, poly(lactic acid) (PLA) as the most commercially available biopolymer is a reliable alternative for petroleum-based polymers in different industries
In addition to the application of cellulose nanocrystals (CNCs), the shielding effect from zinc oxide (ZnO) serves as an insulator and results in noncontinuous burning, which increases the fire retardancy of nanocomposites
Summary
The global concern over reducing the environmental impact caused by petroleumbased polymers has accelerated research aimed at developing biopolymer materials from sustainable resources [1]. Biopolymers with universal accessibility and inherent biodegradability can offer an appealing sustainable platform to supersede petroleum-based polymers. Among different types of biopolymers, poly(lactic acid) (PLA) as the most commercially available biopolymer is a reliable alternative for petroleum-based polymers in different industries. PLA is used in diverse applications by different industries ranging from medical devices, packaging, and consumer products to automobile composites due to its superior transparency, easy processability, and high mechanical properties [2,3]. PLA-based nanocomposites are known for improved properties such as stiffness, thermal stability, biodegradability, and lower permeability [4]. The inherent limitations of PLA such as low thermal properties and high flammability need to be addressed to extend the potential applications of PLA [5,6]
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