Compositions and foam compositions containing composite particles, articles, composite particles, and methods

A composite particle comprising:

• a chemical blowing agent particle encapsulated within a shell including an uncrosslinked thermoplastic material;
• and a co-encapsulated metal salt of the form MX or M (X)2,
• wherein M is zinc, calcium, cadmium, potassium, barium, strontium, magnesium, mercury, titanium, tin, lead, sodium, lithium, or cesium,
• wherein X is an organic ligand or an inorganic ligand containing a nitrate, phosphate, phosphite, sulfate, carbonate, oxalic acid, halide, para-toluenesulfonate, tetrafluoroborate, perchlorate, hydroxide, cyanide moiety, or hydrates thereof,
• wherein the uncrosslinked thermoplastic material exhibits a complex viscosity of 3,700 Pascal seconds (Pa·s) or greater at a decomposition temperature of the chemical blowing agent particle,
• wherein the chemical blowing agent is selected from a diazocompound, a sulfonyl hydrazide, a tetrazole, a nitrosocompound, an acyl sulfonyl hydrazide, hydrazones, thiatriazoles, azides, sulfonyl azides, oxalates, thiatrizene dioxides, isatoic anhydride, or combinations thereof, and
• wherein the composite particle is free of liquid hydrocarbon physical blowing agents.