▎ 摘　　要

NOVELTY - Two-part coating composition, comprises: (a1) part A comprising (a) a polyol component comprising at least one of a difunctional polyol, a trifunctional polyol, and a tetra functional polyol, (b) a foam catalyst, (c) optionally, a gel catalyst, (d) optionally, at least one flame retardant, and (e) water; and (b1) part B comprising (1a) an isocyanate functional material, where the isocyanate functionality is 2, preferably where the isocyanate functional material is an isocyanate prepolymer with a functionality of 2-3, and (1b) optionally, at least one flame retardant, where the flame retardant must be present in at least one of part A and part B. USE - The composition is useful: for applying a protective coating to at least one surface of a substrate; in an electronic substrate assembly (all claimed); and in various applications to provide resistance to thermal shock, high temperature, and relative humidity and to protect against condensation and immersion. ADVANTAGE - The composition: produces an expanded closed-cell foam coating that provides protection for electronic substrates operating in harsh environments; is an improved protective coating composition; is a protective coating composition that provides superior coating of features mounted on an electronic substrate; provides coating or encapsulating features on an electronic substrate; produces a protective coating i.e. low stress; provides a coating that provides a weight savings; provides a coating i.e. electrically insulating; provides a coating i.e. resistant to thermal shock, high temperature, and relative humidity; provides a coating that, protects against condensation and immersion, provides flame retardancy, can be coupled to a topcoat layer to provide additional protection, and has low viscosity; and provides a coating i.e. aesthetically pleasing. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: applying a protective coating to at least one surface of a substrate, comprising (c) mixing a two-part coating composition comprising (i) part A comprising (1A) a polyol component comprising at least one of a difunctional polyol, a trifunctional polyol, and a tetra functional polyol, (1B) a foam catalyst, (1C) optionally, a gel catalyst, (1D) optionally, at least one flame retardant, and (1E) water, and (ii) part B comprising an isocyanate functional material, where the isocyanate functionality is 2, preferably where the isocyanate functional material is an isocyanate prepolymer with a functionality of 2-3, and optionally, at least one flame retardant, where the flame retardant must be present in at least one of Part A and Part B, to prepare a liquid coating composition, and (d) applying the liquid coating composition to a substrate and allowing the liquid coating composition to expand into a closed-cell foam coating; and electronic substrate assembly comprising a printed circuit board, where the printed circuit board comprises a base support and a plurality of electrical circuit components extending outwardly from the surface of the base support attached to its and electrically connected to the electrical circuitry, and a closed-cell foam protective coating is applied to at least a portion of the surface of the electronic substrate assembly comprising many electrical circuit components, where the closed-cell protective coating comprises the two-part coating composition, where Parts A and B are in a mixed form in the closed-cell protective coating, and/or the closed-cell protective coating is applied by the method.