Evaluation of sectioning techniques for electron microscopic analyses of low-density polyethylene foams

Cell sizes of low-density polythylene foams in the range of 0.5 to 5 ..mu..m are most conveniently measured by SEM analyses. Unfortunately, the cell walls are relatively weak and fragile membranes that either collapse or are severely distorted by conventional surface preparation and sectioning techniques. Sectioning damage can be circumvented to some extent by freeze fracturing. However, fractures tend to propagate through the weakest structural features, they can be associated with severe deformation, even at liquid nitrogen temperatures, and they frequently do not yield planar surfaces for reliable statistical measurements. Therefore, alternate sectioning techniques were evalated. The most promising techniques are vibrotome sectioning and ultramicrotomy. These techniques are compared with freeze fracturing using SEM examinations of carbon-coated specimens prepared from the same batch of foam. 3 refs., 4 figs.