Expanded and extruded polyolefin foams made with methyl formate-based blowing agents

A dimensionally stable polyolefin foam structure prepared by a process including:

• preparing expandable beads, the beads including a polyolefin and a blowing agent, the blowing agent comprising about 5 to about 80 weight percent of methyl formate and about 20 to about 95 weight percent of one or more C2 to C5 hydrocarbons;
• and
• expanding the expandable beads to form the polyolefin foam structure,
• wherein the blowing agent is substantially miscible with the polyolefin, and wherein the polyolefin foam structure has an absolute percent gauge change less than about 15 percent after aging up to 7 days.

A dimensionally stable polyolefin foam board or plank prepared by a process including:

• melting a polyolefin;
• dissolving an effective amount of a blowing agent in the polyolefin to define a mixture, the blowing agent comprising about 5 to about 80 weight percent of methyl formate and about 20 to about 95 weight percent of one or more C2-C5 hydrocarbons;
• forming an extrudate from the mixture;
• and
• expanding the extrudate to form the polyolefin foam board or plank, wherein the blowing agent is substantially miscible with the polymer, and wherein the polyolefin foam board or plank has an absolute percent gauge change less than about 15 percent after aging up to 7 days.

A process for making a dimensionally stable polyolefin foam board or plank comprising:

• melting a polyolefin;
• dissolving an effective amount of a blowing agent in the polyolefin to define a mixture, the blowing agent comprising about 5 to about 80 weight percent of methyl formate and about 20 to about 95 weight percent of one or more C2-C5 hydrocarbons;
• forming an extrudate from the mixture;
• and
• expanding the extrudate to form the polyolefin foam board or plank, wherein the blowing agent is substantially miscible with the polymer, and wherein the polyolefin foam board or plank has an absolute percent gauge change less than about 15 percent after aging up to 7 days.