A temperature rising elution fractionation study of ultra low density polyethylene.

摘要

Temperature rising elution fractionation (TREF) is a very powerful polymer characterization technique used in separating polyolefins. Microstructural features such as short chain branching, tacticity, and copolymer distribution are readily determined using TREF. Branching distribution is of importance as polymer physical properties are dependent on this parameter.;The objectives of this work were many. First, an experimental TREF apparatus was constructed. In order, to test the system a number of experimental variables were examined using a 50%/50% blend by weight of polyethylene/polypropylene. Variables examined included concentration, crystallization rate, heating rate, supports, etc. Second, ultra low density polyethylene was examined in detail using both analytical and preparative TREF. Fractions collected using preparative TREF, were subjected to further testing using DSC, DMTA, GPC, mechanical, ;Third, differential scanning calorimetry was used as an alternative probe of crystallizability, comparing both melt and solution crystallized samples. Solution crystallized specimens were found to generate curves which were very similar to TREF curves. A method for generating DSC curves from TREF data is presented.