The determination of the relative isotactic content of polypropylene by extraction

Abstract

Abstract Attention is called to the variables effecting the extraction of polypropylene. Under controlled conditions, the extraction of polypropylene with first diethyl ether and then n ‐heptane will give reproducible results. It is necessary to extract with heptane in an atmosphere of nitrogen. The values obtained by the extraction procedure described are regarded as relative measures of the amounts of isotactic, stereoblock and atactic material present in a sample. Extraction with n ‐heptane alone by this procedure also gives the same value of relative isotacticity. Infrared studies showed that the ether soluble fractions were essentially atactic, while the n ‐heptane‐soluble or stereoblock material possessed a degree of order corresponding to 20–40% isotactic polypropylene.