Polyurethane encapsulant

Wang, Z. Y., Feng, Z.Q., Liu, Y., and Wang, Q. 2007. Flame retarding glass fibers reinforced polyamide 6 by melamine polyphosphate/polyurethane-encapsulated solid acid. J. Appl. Polym. Sci. 105 3317-3322. 

Figure 1. Dynamic mechanical properties of linear polyurethane encapsulants at 11 Hz. Formulation nomenclature the first number refers to the weight ratio of polyether (ET) in the soft segment and the remainder is assumed to be the polyester the second number designates the overall weight percent of the diisocyanate.

Figure 2. Creep compliance vs. time for linear polyurethane encapsulants at constant load. See Figure 1 for nomenclature.

Polyurethanes offer a combination of properties which make them ideal as coating materials for electrical and electronic applications. With the correct formulation they are capable of giving films that exhibit excellent adhesion, high gloss, water and solvent resistances, low gas and moisture permeabilities and outstanding electrical properties. Formulations are also available which produce solvent removable linear polyurethane encapsulants allowing a rework capability for expensive electronic packages. 

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