Correlating Structure and Crystallization Conditions for Ethylene Copolymers by Real-Time SALS
Abstract
The melting behavior of a homogeneous ethylene-butene copolymer (Mw = 70,000 g/mol; ρ = 0.90 g/cm^3; 6.4 mol % comonomer) is studied by the simultaneous measurement of transmitted light and small angle light scattering (SALS) under cross polarized (H_V) and parallel polarized (V_V) optical alignments. Measurements were performed on samples crystallized at several temperatures ranging from room temperature to 110 ^oC (16 ^oC above the peak melting temperature (94 ^oC) of quenched samples) for various crystallization times (1 hr to 72 hrs). We show that the final melting temperature (T_m^f) can be determined from our SALS measurements. T_m^f values we obtain from HV and VV SALS measurements are in good agreement with values from differential scanning calorimetry (DSC) and small angle x-ray scattering (SAXS) for samples with the same thermal history. From SALS we are able to evaluate how the crystallization conditions determine the segregation between the first forming and latter forming crystals and, the number of crystal populations observed by DSC. We are also able to determine the time and temperature dependence of the fraction of the first forming crystals. We discuss the implications of our results for understanding how chain microstructure and crystallization conditions affect the structure of copolymers of ethylene and α-olefins.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2003
- Bibcode:
- 2003APS..MAR.R1230A