A process of producing a polymer foam, the process comprising: dispersing an organic nucleating agent in a dispersing medium to obtain an additive dispersion; contacting the additive dispersion with a mineral nucleating agent to obtain a hybrid nucleating agent comprising the organic nucleating agent localized on at least a portion of a surface of the mineral nucleating agent; and contacting the hybrid nucleating agent with a polymer in the presence of a foaming agent to obtain a polymer foam; wherein the organic nucleating agent is at least one selected from the group consisting of aluminum dibenzoate, barium benzoate, barium stearate, benzylidene sorbitol, a derivative of benzylidene sorbitol, calcium benzoate, calcium montanate, calcium myristate, calcium octacosanoate, calcium oxalate, calcium stearate, erucic acid amide, ethylene bis-lauric acid amide, hydroxystearic acid amide, lithium benzoate, lithium dibenzoate, lithium stearate, lithium terephthalate, magnesium benzoate, magnesium stearate, 2,2-methylbis(4,6-di-t-butylphenyl)sodium, palmitic acid amide, potassium benzoate, potassium dibenzoate, potassium laurate, potassium myristate, potassium salicylate, potassium stearate, potassium terephthalate, sodium benzoate, sodium cyclohexane carboxylate, sodium laurate, sodium-2,2'-methylenebis(4,6-di-t-butylphenyl) phosphate, sodium montanate, sodium myristate, sodium β-naphthalate, sodium octacosanoate, sodium salicylate, sodium sulfoisophthalate, sodium stearate, sodium terephthalate, sodium p-toluene sulfonate, sodium toluoylate, stearic acid amide, tris(t-butylamide) trimesate and zinc salicylate. dispersing an organic nucleating agent in a dispersing medium to obtain an additive dispersion; contacting the additive dispersion with a mineral nucleating agent to obtain a hybrid nucleating agent comprising the organic nucleating agent localized on at least a portion of a surface of the mineral nucleating agent; and contacting the hybrid nucleating agent with a polymer in the presence of a foaming agent to obtain a polymer foam; wherein the organic nucleating agent is at least one selected from the group consisting of aluminum dibenzoate, barium benzoate, barium stearate, benzylidene sorbitol, a derivative of benzylidene sorbitol, calcium benzoate, calcium montanate, calcium myristate, calcium octacosanoate, calcium oxalate, calcium stearate, erucic acid amide, ethylene bis-lauric acid amide, hydroxystearic acid amide, lithium benzoate, lithium dibenzoate, lithium stearate, lithium terephthalate, magnesium benzoate, magnesium stearate, 2,2-methylbis(4,6-di-t-butylphenyl)sodium, palmitic acid amide, potassium benzoate, potassium dibenzoate, potassium laurate, potassium myristate, potassium salicylate, potassium stearate, potassium terephthalate, sodium benzoate, sodium cyclohexane carboxylate, sodium laurate, sodium-2,2'-methylenebis(4,6-di-t-butylphenyl) phosphate, sodium montanate, sodium myristate, sodium β-naphthalate, sodium octacosanoate, sodium salicylate, sodium sulfoisophthalate, sodium stearate, sodium terephthalate, sodium p-toluene sulfonate, sodium toluoylate, stearic acid amide, tris(t-butylamide) trimesate and zinc salicylate. <EOS>