(763a) Non-Isothermal Degradation Studies of Poly (lactic acid)/Sucrose Ester Nanocomposites

Efforts towards the exploration of novel bio-reinforcement material for synthesizing poly (lactic acid) (PLA) based composites for food packaging applications are increased in recent years.¹ Apart from exploration of novel fillers, understanding the influence of these reinforcements on the thermal degradation behavior of the PLA composites becomes a pre-requisite factor in order to render these materials suitable for food packaging applications.² Investigating the thermal degradation behavior of PLA composites is important in determining how molten PLA should be processed without causing serious thermal decomposition.³ In the current work, we used thermogravimetric analysis (TGA) as a tool to study the solid-state thermal degradation kinetics of novel biofiller based PLA composites. Overall kinetics of the PLA composites is obtained by measuring the change in mass of a composite material with time based on non-isothermal decomposition profile of TGA analysis.

An approach based on model-free isoconversional method is employed to determine kinetic triplets i.e., activation energy (E_a), pre-exponential factor (A), and reaction order (n).⁴ In the current study, the two well-known representatives of model-free approaches i.e., Flynn-Wall-Ozawa (F-W-O) and Kissinger methods are used to investigate the thermal degradation behavior of PLA and its composites.⁵ The DTG analysis revealed that there is no change in the T_max (Temperature at which maximum rate of degradation)for pure PLA and its composites (up to 5 wt% of bio-filler loading). In the case of 10 wt% of the filler incorporated in the PLA matrix, T_max suddenly shifted to lower temperature (324 ⁰C). This downturn in T_max at higher loading of the filler is possibly due to the increase in reactive sites which could enhance the rate of degradation. The activation energy for thermal degradation of both PLA and its composites was evaluated as a function of conversion throughout the degradation process by F-W-O method. The variation in activation energy obtained with respect to conversion suggested that thermal degradation of both PLA and composites occurs through complex mechanism. The activation energy values obtained for PLA and its composites by both the methods were found to be in good agreement.  In addition to this, based on the thermal degradation profile of PLA composites, hypothetical mechanism for the degradation of the same is proposed.

AUTHOR INFORMATION

*Corresponding author.

Email: pugal@iitg.ernet.in & vkatiyar@iitg.ernet.in

References

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