X-ray Tomographic Reconstruction for Understanding Lignin-Induced Changes in the Microstructure and Properties of Polyurethane Insulation Foam

Lignin,the most abundant aromatic biopolymer, is explored as arenewable polyol substituent and functional additive in rigid polyurethanefoam (RPUF) for structural and insulation applications. The understandingof the complex microstructural changes in the RPUF caused by ligninmicro-nanoparticles has been limited by traditional two-dimensionalcross-sectional imaging methods (typically limited to the averagecell diameters). This study reports the microstructural changes inducedby the dispersion of kraft lignin (0-2% w/w) in RPUF as monitoredusing X-ray computed microtomographic (X-ray & mu;CT) analysis.The reconstruction and quantification analysis provide greater insightinto the changes induced by lignin on the microstructure of the RPUF,allowing rationalization of the microstructure with physical properties.In comparison to scanning electron microscopy, the magnitude of differencesobserved in spatial parameters (cell volume, cell surface area, cellellipticity, and distribution) and skeletal parameters (thickness,length, and the distribution of cell walls and struts) is significantand the presented methodology can be applied to the in-depth analysisof other cellular plastics.