Polyethylene ionomers. The effect of annealing

The effect of annealing on the morphological structure and properties of a poly(ethylene‐co‐methacrylic acid) ionomer is discussed. The density of samples annealed at different temperatures was measured and compared with densities calculated from calorimetry measurements assuming additivity of component volumes. At intermediate annealing temperatures, densities calculated from calorimetry are higher than densities experimentally measured. Also, at intermediate annealing conditions the X‐ray scattering associated with separation of ionic groups changes, and the multiple DSC melting endotherms merge into a single endotherm. These effects are thought to be caused by a thickening of polyethylene lamellae to a uniformly large fold distance which causes strain of the non crystallizable polymer segments and void formation.