ZnO reduced both the decomposition temperature of AC and the amount of gas yielded. The average cell size became smaller as the content of the foaming agent increased. Larger cells were observed at 0.5 wt.% of modified azodicarbonamide (mAC), they were about 2–4 times the size of cells created by mAC at 3.0 wt.%. Fine cells were observed when mAC was applied at 2.0 and 3.0 wt.%. For the range of particle sizes studied, the 22 lm mAC created the largest average cell size while the 5 lm mAC provided the smallest ones, all cells did not pack closely.