Preparation and Properties of Immiscible Poly(lactic acid)/Ethyl Cellulose Bioplastic Blends with Good Transparency and Optical Control by Drawing

AbstractIn this study we prepared a poly(lactic acid)/ethyl cellulose (PLA/EC) bioplastic blend film by melt pressing after solvent casting and investigated the optical, thermal, and mechanical properties in relation to the structural changes revealed by various microscopies and scattering measurements. Despite the immiscibility of PLA and EC, the blend film exhibited good optical transparency due to the close match in their refractive indices. A second run of differential scanning calorimetry during heating revealed a decrease in the glass transition temperature ( TgPLA) and melting point ( TmPLA) of PLA with EC although EC had the higher values. Thermomechanical analysis suggested that these decreases were due to the negative pressure generated due to the suppression of PLA shrinkage below TgEC and above TgPLA during cooling. Furthermore, ductile drawing of the blend film (70/30) at an optimal temperature of 70 °C above TgPLA resulted in a uniform whitening near 100 % strain. Delamination at the interface between the PLA matrix and EC domain led to the formation of micrometer-sized oriented voids, which enhanced the refractive index difference in the phase-separated structure, thereby scattering light and achieving the uniform and oriented white blend film.Keywords: Poly(lactic acid)Ethyl celluloseImmiscible bioplastic blendOptical transparencynegative pressureDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also.