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A general method is described to take into account the multiple scattering effect in a small-angle light scattering from thin polymer films. It is seen that multiple scattering tends to make the scattering envelope more diffuse, reducing the intensity in the high intensity regions and increasing it in the low intensity regions. The method is applied here to a spherulitic system, but it is valid for any other system where the principal scattering is in the forward direction.

A procedure is described to include the effect of depolarization of the originally plane-polarized incident light beam as it passes through a thin polymer sample on the intensity of multiple light scattering. The multiple scattering gives rise to “polarization scrambling” in which, for example, Hv scattering measurements involve multiple scattered rays which may have undergone some Vv scattering. These phenomena reduce the angular dependence of scattering since large intensities originally occurring at small values of θ are rescattered so as to enhance intensities at other angles. Correction factors for both Hv and Vv scattering are presented.

The rate at which PTFE transforms from the triclinic to the hexagonal phase has been measured under isothermal conditions. Samples in a series of decreasing density and crystallinity show increased isothermal rates of transformation. Observed kinetic data are interpreted on the basis of a modified Avrami-Johnson-Mehl treatment. A model for the transformation in which planes of helix-hand reversal propagate through the lattice is shown to fit the experimental results. The transformation rate is observed to be proportional to the total (001) surface area in the polytetrafluoroethylene specimens, suggesting that nucleation of the transformation takes place at grain boundaries.