Foamable composition using recycled or offgrade polypropylene

A process for preparing a polymeric foam, the process comprising:

• (a) melting a conventional linear polypropylene, a high melt strength polypropylene and a rheology modifier resin to form a polymeric composition, the polymeric composition comprising from about 1 to 25 weight percent of conventional linear polypropylene, from about 51 to about 85 weight percent of high melt strength polypropylene and from about 5 to about 30 weight percent of the rheology modifier resin, the composition being Dynamic Mechanical Spectroscopy using a frequency of 1.00 radians/sec and 25 mm diameter parallel plates with a 1.00 mm gap to have complex viscosity (η*) in the range of 1.6×104 to 6.0×104 poise, tan δ in the range of 0.7 to 1.8, and a power-law relation between tan δ and η* where the exponent is within the range between −0.35 and −0.01
• (b) adding a stability control agent to the polymeric composition;
• (c) dissolving an effective amount of blowing agent;
• (d) transferring the mixture of step (c) to an expansion zone;
• and
• (e) permitting the mixture of step (d) to expand in the expansion zone to produce the polymeric foam.