Abstract:
Poly(lactic acid) (PLA) is an attractive candidate for replacing petrochemical polymers
because it is fully biodegradable. This study investigated the potential of PLA as a sustainable
and environmentally friendly alternative material that can be developed into commercially viable
wearable mosquito repellent devices with desirable characteristics. PLA strands containing DEET
and IR3535 were prepared by twin screw extrusion compounding and simultaneously functioned
as plasticizers for the polymer. The plasticizing effect was investigated by thermal and rheological
studies. DSC studies showed that the addition of DEET and IR3535 into PLA strands reduced the
glass transition temperature consistent with predictions of the Fox equation, thus proving their
efficiency as plasticizers. The rheology of molten samples of neat PLA and PLA/repellents blends,
evaluated at 200 C, was consistent with shear-thinning pseudoplastic behaviour. Raman studies
revealed a nonlinear concentration gradient for DEET in the PLA strand, indicating non-Fickian Type
II transport controlling the desorption process. Release data obtained at 50 C showed initial rapid
release followed by a slower, near constant rate at longer times. The release rate data were fitted to a
novel modification of the Peppas-Sahlin desorption model.
