Improved Weathering Performance of Poly(Lactic Acid) through Carbon Nanotubes Addition: Thermal, Microstructural, and Nanomechanical Analyses

Abstract

To understand the interrelationship between the microstructure and degradation behavior of poly(lactic acid) (PLA), single-walled carbon nanotubes (CNTs) were introduced into PLA as nucleating agents. The degradation behavior of PLA-CNT nanocomposites was examined under accelerated weathering conditions with exposure to UV light, heat, and moisture. The degradation mechanism proceeded via the Norrish type II mechanism of carbonyl polyester. Differential scanning calorimetry (DSC) studies showed an increase in glass transition temperature, melting temperature, and crystallinity as a result of the degradation. However, pure PLA showed higher degradation as evidenced by increased crystallinity, lower onset decomposition temperature, embrittlement, and a higher number of micro-voids which became broader and deeper during degradation. In the PLA-CNT nanocomposites, CNTs created a tortuous pathway which inhibits the penetration of water molecules deeper into the polymer matrix, making PLA thermally stable by increasing the initial temperature of mass loss. CNTs appear to retard PLA degradation by impeding mass transfer. Our study will facilitate designing environmentally friendly packaging materials that display greater resistance to degradation in the presence of moisture and UV light.

Fabrication of a packaging film based on PLA blends: The evolution of physical, mechanical, and rheological properties

“…12 Extensive research has been done for improving as well as tuning the physical and mechanical properties of PLA, which usually involves the addition of nanoparticles or blending with another polymer. [13][14][15][16][17][18] In a research conducted by Kim et al, they found that upon adding a small amount of carbon nanotubes/graphene oxide hybrid nanoparticle system, the permeability of oxygen into PLA film would be greatly reduced. 5 Urquijo et al observed that the percentage of gas penetration into a blend of PLA and poly (ε-caprolactone) could significantly be reduced by adding an appropriate amount of nanoclay.…”

“…Extensive research has been done for improving as well as tuning the physical and mechanical properties of PLA, which usually involves the addition of nanoparticles or blending with another polymer 13–18 . In a research conducted by Kim et al, they found that upon adding a small amount of carbon nanotubes/graphene oxide hybrid nanoparticle system, the permeability of oxygen into PLA film would be greatly reduced 5 .…”

Effects of photodegradation performance with PLA‐containing samples on double injection molding

“…Due to its biodegradable nature, PLA undergoes degradation under the influence of environmental factors, leading to a significant decline in its performance, thereby failing to meet usage requirements. 8,9 PLA is susceptible to aging degradation when exposed to conditions such as light during the usage process, 4,10 undergoing photodegradation from the surface to the interior upon direct irradiation. Under light excitation conditions, the carbonyl and hydroxyl groups in PLA molecules react with oxygen, forming intermediate ions and generating a large number of free radicals, gradually breaking down the PLA molecules into small molecules.…”

Oil-Soluble Ultraviolet-Absorbing Carbon Dots Dispersed in Polyethylene Films as Antiaging Materials

“…Depan et al demonstrated that carbon nanotubes could act as nucleating agents to increase the nucleation density and form smaller spherulites. The poly­(lactic acid) and carbon nanotube composite changed the microstructure and improved the crystallinity compared with pure poly­(lactic acid), resulting in better stability against weathering . Koumoulos et al showed that carbon fibers added into poly­(methacrylic acid) (PMAA) reinforced the interphasial properties.…”

“…The poly(lactic acid) and carbon nanotube composite changed the microstructure and improved the crystallinity compared with pure poly(lactic acid), resulting in better stability against weathering. 10 Koumoulos et al showed that carbon fibers added into poly(methacrylic acid) (PMAA) reinforced the interphasial properties. The modified PMAA had the unique molecular weight of grafted macromolecules and different chain-length brushlike structures, which enabled the composite to maintain better mechanical properties after weathering.…”