Session D40 - Poster Session I.
POSTER session, Monday afternoon, March 12
Exhibit Hall, Washington State Convention Center
Semicrystalline polymers melt over a temperature interval of ca. 10-40 ^oC, an effect attributed to crystals of increasing stability (thickness) melting at higher temperatures. Small-angle X-ray scattering (SAXS) has long been used to follow this melting process. We model the scattering I(\its) of an isotropic assembly of lamellar stacks in which the crystals are melted sequentially according to thickness. Average crystal thickness, average amorphous layer thickness and the average long period all increase as melting proceeds. As expected, the maximum of the SAXS pattern first shifts to smaller \its, then converts to single particle scattering from the unmelted, thickest crystals in the initial distribution. The transition from discrete scattering from spatially correlated lamellae to continuous scattering from isolated lamellae occurs when the crystalline fraction has been reduced to ca. 0.1. Correlation function g(\itr) and interface distribution function \gamma (r) are analyzed to provide average phase dimensions and apparent crystalline fraction during the melting process. Model results are compared to experiments