Elution fractionation of atactic and isotactic polypropylene

✍ Scribed by Shyluk, Shirley

• Publisher: John Wiley and Sons
• Year: 1962
• Weight: 555 KB
• Volume: 62
• Category: Article
• ISSN: 0022-3832
• DOI: 10.1002/pol.1962.1206217405

✦ Synopsis

Abstract

Procedures and an apparatus for the elution fractionation of polypropylenes are described. The isotactic polymer is precipitated onto a sand column from p‐xylene solution by cooling slowly from 126°C. to room temperature. After removal of the solvent and the atactic fraction soluble at room temperature, the column is heated to 156°C. Fractions are eluted with mixtures of a high boiling hydrocarbon fraction as solvent and 10% ethylene glycol in 2‐butoxyethanol as nonsolvent. The dissolving power of the eluents is periodically increased to fractionate the polymer. Upward solvent flow is used. Recovery is usually quantitative, and good reproducibility is demonstrated. Polymer degradation during fractionation has been reduced to generally less than 5% by suitable techniques. Molecular weight distribution curves for three samples are shown. Good selectivity is established by the fact that the ratio of the molecular weight of the highest to that of the lowest fraction is usually in the range of 50 to 200. A description of the fractionation of atactic polypropylene is given also. The atactic material was used to show the effect of depositing the polymer selectively or randomly on the surface of the support as well as the effect of diffusion on fractionation efficiency.