High-resolution X-ray computed tomography for 3D microstructure characterization of a cellulose particle filled polymer foam

Abstract

Due to the excellent strength/weight ratio, good energy absorbing ability, superior thermal, and acoustic insulation properties together with reasonable costs, polymer foams are the material of choice for many applications. The incorporation of particulate or fibrous fillers can even improve the properties. In this article, we investigate an opencell polyurethane foam filled with cellulose particles. This is a new moisture-absorbing wood-plastic composite used for special mattresses. The foam was characterized by high-resolution cone-beam X-ray computed tomography (XCT) with voxel sizes between 0.7 mm 3 and 2.2 mm 3 . The XCT measurements were performed with a tube voltage of 50 kV to obtain enough contrast. The XCT data were processed by various algorithmic steps (e.g., smoothing, thresholding, watershed transformation, erosion, dilation, and feature extraction) to ascertain the three-dimensional open-cell structure together with particle distribution, size, and position. Quantitative data for the cells (mean diameter, shape, volume, and position), for the cellulose particles (mean diameter, shape, volume, and position), for the polymer vertices (shape and position) and for combinations of them (e.g., distance between particles and vertices) were derived from the XCT data. 15.2 cells/mm 3 , 41 cellulose particles/mm 3 , and 88.7 polymer vertices/mm 3 were found. The average diameter value for the mostly globular cells was found to be 465 mm with a Gaussian-like distribution function. The cellulose particles are globular and elongated and the distribution resembles an exponential function where 95% of the particles have diameters below 60 mm. The particles are situated within the polymer walls and close to the surface. The function for the distance of the particles from the Downloaded from closest vertices corresponds to a Weibull distribution function with a scale parameter of 53 mm and a shape parameter of 1.7.

Effect of mixing conditions on the morphology and performance of fiber-reinforced polyurethane foam

“…Kastner et al. 48 observed regenerated cellulose particles embedded in PU foam cell struts using CT tomographs. They were able to isolate the cellulose using a series of image processing steps.…”

“…47 Three-dimensional stereo microscopy and high-resolution X-ray computed tomography (CT) have been used to observe the fiber dispersion and cell morphology in fiber-reinforced foams. Kastner et al 48 observed regenerated cellulose particles embedded in PU foam cell struts using CT tomographs. They were able to isolate the cellulose using a series of image processing steps.…”

Development and investigation of the applicability of computed tomography data-based modelling technique for polymeric high-density foams

“…These parameters are determined in the same way as described in Kastner et al (2011). 29 For the separation of the air and polymer phase, a global threshold method is utilized.…”

“…These parameters are determined in the same way as described in Kastner et al (2011). 29 For the separation of the air and polymer phase, a global threshold method is utilized. A threshold is chosen in this way that the air to polymer ratio equals the measured material density.…”

Morphological Analysis of Foamed HDPE/LLDPE Blends by X-ray Micro-Tomography: Effect of Blending, Mixing Intensity and Foaming Temperature

“…To characterize the foam morphology, surface microscopy techniques are usually employed including scanning electron microscopy (SEM) and optical microscopy. In these methods, cell size distribution and population density measurements are limited to specific 2D cross-section images, while the whole three-dimensional structure could be more complicated [10][11][12]. Therefore the cell morphology interpreted using 2D images might not be accurate.…”