On the morphology of blends of linear and branched polyethylene

A blend of linear and branched polyethylene was examined in view of establishing conditions of cocrystallization and/or segregation. Two members of the SCLAIR series were used in 1∶1 proportions. Conditions of segregation on crystallization were first explored by DSC, which was followed by morphological examination of selected samples. This involved optical and electron microscopy, the latter using the permanganate etching technique of Bassett and Hodge. Dependent upon crystallization temperature and time, crystal segregation on different scales was observed revealing that the final product can be regarded as a morphological composite where the ratio and nature of the constituents are determined by the conditions of solidification. The particulars should be relevant to the presently evolving practice of blending different polyethylenes. Examples of the different morphologies will be demonstrated. The individuality of the lamellae of the more readily crystallizable species can become strikingly apparent which incidentally reveals details in the edge on view, such as have not been seen before, and may have relevance to the fundamentals of the structure of lamellar crystals in general.