Permeability of water and oleic acid in composite films of phase separated polypropylene and cellulose stearate blends

• Immiscible blends of CS and PP could be prepared by hot melt extrusion compounding.
• Due to significant difference in melting temperatures of components CS particles form flake-shaped structures.
• Introduction of cellulose stearate into polypropylene changes crystallization processes by decreasing spherulite size of PP.
• Change in spherulite size effects permeability of PP to water and oleic oil.

Cellulose esters with long carbon side chains (e.g. stearate) were produced via a homogenous reaction in ionic liquids. The degree of substitution was calculated to approximately 2. The melt rheology was studied for the pure cellulose esters but also combinations of the esters and polypropylene to study the processability of a blended composite material. It was shown that the compatibility between the two components was weak, which resulted in a phase-separated composite material. The morphology and permeability of water and oleic acid of the composite films were studied and it was shown that the water permeability decreased upon addition of the cellulose ester to the polymer. The permeability of oleic acid was however unchanged, which is most probable a result of high solubility in the cellulose ester rich domains of the composites. Also, the following hypothesis is stated: cellulose stearate influence the polypropylene crystallization process by decreasing the size of spherulites.