Inter‐ and intramolecular polymerization in heat‐bodied linseed oil

Abstract

Summary 1. Linseed oil has been polymerized at 300° for 1.5, 3, and 6 hours. The polymeric glycerides have been separated from the monomeric glycerides, and the derived methyl esters of each fraction have been analyzed for monomer, dimer, and trimer. 2. The monomeric glycerides show very little intradimerization, ranging from 1.3 to 6% of their acid groups, or 3 to 4% of the total polymeric acid groups in the whole oil. 3. The polymeric glycerides show appreciable intradimerization, from 10 to 20% of their total polymeric acid groups. 4. There is no evidence that a shift from intra‐ to interdimerization is the major cause of the sudden increase in viscosity in the later stages of thermal polymerization. 5. The rapid rise in viscosity is due to the nature of the relationship of viscosity to molecular weight and of molecular weight to extent of reaction in the difunctional polymerization system present.