Solid and microcellular injection molded polylactic acid/polyvinyl alcohol (PLA/PVA) biodegradable blends: Morphology and property characterization

Targeted for tissue engineering scaffold applications, highly porous and interconnected polylactic acid (PLA) scaffolds were produced using two approaches. The first approach involved melt compounding of biodegradable polylactic acid (PLA) and water-soluble polyvinyl alcohol (PVA) resins using a thermokinetic mixer (K-mixer) to first produce miscible blends prior to leaching out the sacrificial material (PVA in this case). Different volume fractions of PLA and PVA were melt mixed. The second method employed microcellular injection molding of PLA/PVA resins blended in the machine hopper with supercritical fluid (SCF) gas (nitrogen) as the physical blowing agent. Water leaching (extraction) was used to remove the sacrificial PVA domains in the solid or microcellular PLA/PVA samples. Co-continuous morphology development of the blends was investigated via scanning electron microscopy (SEM). The phase inversion point (forming co-continuous diphase morphology) of microcellular samples was found to be at a ratio of 65/35 PLA/PVA, whereas for solid counterparts the corresponding ratio was 55/45 PLA/PVA. The dimensions of the voids originally occupied by PVA in the blends were measured using an image analysis tool. Microcellular injection molding technology is known to facilitate high porosity and interconnected channels in the PLA matrix. In addition, the miscibility of these blends was evaluated by solubility parameter calculations and thermal characteristic measurements using a differential scanning calorimeter (DSC). It was found that the continuity development and microstructure features of the PLA/PVA blends were dependent on component composition and miscibility.