The photographic light scattering technique permits a measurement of the size, anisotropy, radial periodicity, packing, and internal structure of polymer spherulites. The theory of some of these effects is described, and experiments are presented showing changes occurring in the melting and growth of spherulites.

The scattering patterns are calculated from anisotropic rods having an arbitrary angle of the polarizability axis with respect to the rod axis. The effect of a distribution of orientation of the rods is explored. This leads to a change in scattering patterns produced by orienting the rods upon stretching the sample. The scattering patterns are affected by the relationship between the refractive indexes of the rods and that of the surroundings. The influence of the optic axis orientation angle changing upon orienting the rods is explored. Theoretical patterns are compared with experimental ones obtained upon stretching polytetrafluoroethylene (PTFE) films.

The compressive behavior of a rigid polyurethane foam reflects its geometric structure and the physical properties of the matrix polymer. Foam properties may be modified by the inclusion of silica particles in the polymer matrix. These silica particles alter the mechanical properties of the base polymer as well as the geometrical structure of the foam. The yield stress and the modulus of the foam decrease with the initial introduction of the silica filler after which the mechanical properties of the foam increase with increasing filler content. A model is presented expressing the foam yeild stress and the modulus as a function of the polymer modulus and the cell parameters. These parameters are I, a cell edge length, and d, a characteristic strut thickness. This results in the expressions, E f = C' Ep(d 11)4 and (T y = C"E p (dll)". This model is applicable to either filled or unfilled foams and accommodates changes in the properties of the solid phase, through the use of Ep, as well as changes induced in the cell geometry through the dll relationship.

The basic concepts of quantitative stereology are introduced and how stereology relates morphology to a statistical characterization of foams is described. The stereological parameters for the foam system are obtained with a computer-interfaced optical microscope and are calculated by traditional methods for either static or dynamic systems and for either polymeric or nonpolymeric foams. These foam parameters are used either individually or in combination to provide an additional perspective on the mechanism of foam formation and stability. Finally, they serve to generate correlations with physical test values associated with the bulk foam behavior.

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