Growth of needle‐like crystals of polyoxymethylene during polymerisation

Abstract

Abstract Needle‐like crystals of polyoxymethylene, 5 to 20 μm long, have been obtained in the course of the polymerisation of trioxane in cyclohexane. It has been found that such crystal growth is favoured at large BF 3 .OEt 2 /H 2 O or BF 3 /H 2 O ratios, when the nucleation takes place fast. The needle is considered to consist of fully extended chains oriented parallel with the direction of the length. The mechanism of the needle‐type growth is briefly discussed with reference to the plate‐like growth previously found.