Experimentally Determined Hansen Solubility Parameters of Biobased and Biodegradable Polyesters.

Hansen solubility parameters (HSP) of 15 commercially relevant biobased and biodegradable polyesters were experimentally determined by applying a novel approach to the classic solubility study method. In this approach, the extent of swelling in polymer films was determined using a simple equation based on the mass difference between swollen and nonswollen film samples to obtain normalized solvent uptake (N). Using N and HSPiP software, highly accurate HSP values were obtained for all 15 polyesters. Qualitative evaluation of the HSP values was conducted by predicting the miscibility of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-co-HHx, 7 mol % HHx) and poly(lactic acid) (PLA) with a novel lignin-based plasticizer (ethyl 3-(4-ethoxy-3-methoxyphenyl)propanoate, EP) with a relative energy difference (RED) less than 0.4. Additionally, an HSP-predicted plasticizer (di(2-ethylhexyl) adipate, DA) with a larger RED (>0.7) was used to demonstrate the effects of less-miscible additives. Plasticized samples were analyzed by differential scanning calorimetry and polarized optical microscopy (POM) to determine the Tg depression, with EP showing linear Tg depression up to 50% plasticizer loading, whereas DA shows minimal Tg depression past 10% loading. Further analysis by POM reveals that the DA phase separates from both polymers at loadings as low as 2.5% (PHB-co-HHx, 7 mol % HHx) and 5% (PLA), while the EP phase separates at a much higher loading of 50% (PHB-co-HHx, 7 mol% HHx) and 30% (PLA).

A Biologically Degradable and BioseniaticTM Feedstock for the High-Quality 3D Printing of Anatomical Models.

A Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) -based filament was evaluated as an alternative feedstock for Fused Deposition Modeling (FDM) of instructional and clinical medical specimens. PHBHHx-based prints of domestic cat vertebrae, skull bone, and an aortic arch cast were found comparable to conventional materials. PHBHHx-based filament and extrudate samples were evaluated for biological degradability, to meet the BioseniaticTM standard, defined by the University of Georgia New Materials Institute. Both samples achieved more than 90% mineralization within 32 days in industrial composting conditions.