Experimentally Determined Hansen Solubility Parameters of Biobased and Biodegradable Polyesters
Kush G. Patel, Ryan K. Maynard, Lawrence S. Ferguson, Michael L. Broich, Joshua C. Bledsoe, Caitlin C. Wood, Grant Crane, Jessica A. Bramhall, Jonathan M. Rust, Amanda M. Williams-Rhaesa, Jason Locklin
Abstract
High Resolution Image Download MS PowerPoint Slide 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 T g depression, with EP showing linear T g depression up to 50% plasticizer loading, whereas DA shows minimal T g 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).