Encapsulation of a pressure sensitive adhesive by spray-cooling: Optimum formulation and processing conditions

An industrial pressure sensitive adhesive (PSA) was encapsulated by spray-cooling using hydrogenated palm oil. A screening design methodology was used to evaluate the impact of some formulation and process variables on the particle properties. Six operating factors were retained and the results considered were the production yield, the particle volume-surface average diameter D-32, the residual humidity, the ratio of the fusion enthalpies of the polymorphs alpha and beta'/beta and the normalized peeling force. The statistical analysis of the results showed a negligible impact of the parameters related to the process. The heating temperature, the PSA and surfactant ratios were the most significant factors. It was possible to produce spherical particles with a mean size of 17.7 mu m and a normalized peeling force of 0.218 N m(2)/g. The production yield was 70%. A duplicate test confirmed the results. Mechanical tests on unitary particles showed an increase of the rupture and adhesion forces with particle size. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.