Low temperature cure coating compositions

A film-forming thermoset coating composition, comprising:

• (a) an aqueous medium;
• and
• option 1 and/or option 2 as follows:
• option 1:
• (b1) polyurethane-acrylate core-shell particles comprising a polymeric acrylic core at least partially encapsulated by a polymeric shell comprising urethane linkages, wherein the polymeric shell comprises an acid functional group and two or more hydrazide functional groups, wherein the polymeric shell is covalently bonded to at least a portion of the polymeric core;
• (c1) (i) formaldehyde;
• (ii) polyformaldehyde;
• and/or (iii) a compound that generates formaldehyde, wherein the total amount of formaldehyde present and/or generated in (c1) is in the range of 0.1 to 3 weight %, based on total resin solids of the coating composition;
• and
• a crosslinker separate from (b1) and (c1), wherein the crosslinker is reactive with functional groups of (b1), (c1), and/or a reaction product of (b1) and (c1);
• option 2:
• (b2) polyurethane-acrylate core-shell particles comprising a polymeric acrylic core at least partially encapsulated by a polymeric shell comprising urethane linkages, wherein the polymeric shell comprises an acid functional group and two or more N-methylolated hydrazide functional groups, wherein the polymeric shell is covalently bonded to at least a portion of the polymeric core;
• and
• wherein the coating composition includes less than 5 weight percent, based on total resin solids, of polyurethane-acrylate core-shell particles that include keto and/or aldo functional groups.