Influence of Carboxylic Acid Additives on the Flow Behavior of Molten Thermoplastics
Sungtae Ahn, James L. White
The University of Akron
USA

Keywords: carboxylic acid additives, capillary experiments, cone-plate experiments

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Following the suggestions of the behavior of carboxylic acid lubricants between steel surfaces, we have considered their influence as an additive in polymer melts. An experimental study of the influence of carboxylic acid additive in various thermoplastics in rheometers is described. Capillary and cone-plate experiments are reported. A series of polymers of varying polarity including polyethylene, polypropylene, polystyrene, poly methyl methacrylate and polyamide-12 are compared. Both aliphatic fatty acids and aromatic carboxylic acids are used as additives. The aliphatic fatty acids include propionic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid and commercial stearic acid (mixture of tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid). The aromatic carboxylic acids include benzoic acid, p-toluic acid, and 3-phenylpropionic acid. The greatest effects were found in polyethylene and polypropylene. Little or no effects are found with the other polymers. Aliphatic fatty acids were more effective than aromatic carboxylic acids. Mechanisms for this behavior are discussed.