Retarding hydrolytic degradation of polylactic acid: Effect of induced crystallinity and graphene addition

Abstract

The combination of elevated temperature and humidity leads to rapid degradation of polylactic acid (PLA) because of hydrolysis. Consequently, PLA, which is a bio-derived and biodegradable polymer, is not currently used for durable applications since properties cannot always be maintained over time. In this work, the ability of polymer crystals to reduce the rate of degradation during accelerated aging tests was studied. Also examined was the influence of addition of 2 wt % graphene nanoplatelets to act as moisture transport barriers in the polymer. PLA samples were immersed in aqueous media of different pH or exposed to 100% relative humidity at 50 8C for different lengths of time to study the hydrolytic degradation behavior. In addition to monitoring the loss in mass of the samples, the values of crystallinity, melt viscosity, and mechanical properties, among others, were measured as functions of aging time using techniques such as DSC and rheometry. It was found that both crystallization and graphene addition are able to slow down the rate of degradation at short times, but significant degradation of PLA still occurs at long times. This is because PLA crystallites and graphene nanoplatelets can only reduce, but not eliminate, moisture diffusion into the polymer sample. Between the use of nanoplatelets and crystals, though, the former approach may be the better choice since enhanced crystallization tends to make PLA brittle.

Retardation effect of nanohydroxyapatite on the hydrolytic degradation of poly (lactic acid)

“…Without degradation water barrier and reduced the mobility of the amorphous phase and hindering water diffusion into the sample. Finniss et al [26] observed that the incorporation of 2 wt% of graphene nanoplatelets in PLA acted as water transport barriers, retarding hydrolytic degradation of PLA. Peponi et al [27] observed that PLA/PCL blend reinforced with 0.5 wt%, 1 wt% or 3 wt% hydroxyapatite presented lower disintegration rates than the unmodified blend under compost conditions.…”

Preparation and Characterization of Bio-Based PLA/PBAT and Cinnamon Essential Oil Polymer Fibers and Life-Cycle Assessment from Hydrolytic Degradation

“…This is controlled by the rate constant, absorbed water, diffusion coefficient of chain fragments, and solubility of degradation products [4]. Many authors have studied hydrolytic degradation of PLA [28][29][30]. However, few studies have been conducted to study hydrolytic degradation of PBAT and PLA/PBAT blends with CEO.…”

Hydrolytic Degradation and Mechanical Stability of Poly(ε-Caprolactone)/Reduced Graphene Oxide Membranes as Scaffolds for In Vitro Neural Tissue Regeneration

“…Similar behavior was observed by Zhao et al [ 19 ], who developed nanocomposites of PLLA with multiwalled carbon nanotubes (MWNTs). Nevertheless, the literature also provides studies showing that the incorporation of graphene nanoplatelets into the polymer matrix produced the opposite effect, i.e., a reduction of the biodegradation rate of the material, due to the hydrophobic constitution of graphene [ 20 , 21 ]. Recently, Murray et al [ 21 ] reported the enzymatic degradation of PCL/rGO mixtures and composites.…”