Melting behavior of ethylene copolymers and branched polyethylenes

✍ Scribed by Griskey, Richard G. ;Foster, George N.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1970
• Tongue: English
• Weight: 491 KB
• Volume: 8
• Category: Article
• ISSN: 0449-296X
• DOI: 10.1002/pol.1970.150080702

✦ Synopsis

Abstract

Prior research on the melting behavior of ethylene copolymers and branched polyethylenes could not be effectively evaluated since there were large differences in the levels of comonomer contents. The present research was undertaken to determine additional data so that an overall evaluation could be made. A consideration of the experimental data of the present work and earlier research data showed that methyl side groups caused less diffuse melting and less melting point depression than either ethyl groups or polyethylene branches. In addition, it was found that the Flory equation can be used to describe the relation of melting point depression to foreign group concentration for propylene copolymers. The equation did not hold for 1‐butene‐ethylene copolymers or branched polyethylenes. For these materials the Wunderlich modification of the Flory equation applied. Activity values for both 1‐butene‐ethylene copolymers and branched polyethylenes gave a common correlation with foreign groups. Enthalpy and entropy fusion data for ethylene copolymers and branched polyethylenes were also determined. It was also shown that good agreement was found between crystallinities for these materials determined independently by differential thermal analysis and x‐ray analysis.