Polyamide 6 (PA 6) is known for its mechanical strength, thermal stability, and good abrasion performance. In this study, the foaming ability of PA 6 was studied by batch foaming using CO2 as the blowing agent. PA 6 was blended with its own copolymer to create two melting peaks for bead foam applications. The results showed that the expansion ratio of PA 6 foam was significantly improved due to the decrease of crystallinity of the blends. The effect of CO2 saturation, foaming, and cooling rate to the melting behavior were investigated using DSC. It was found that the cooling rate would significantly affect the melting behavior of PA 6 blends. Double melting peaks disappeared as the cooling rate increased. This result may provide information for bead foam processing.