The melt strength of polyolefin materials could be enhanced by graft modification, since the introduction of long side chains could result in entanglement among the chains and thus improve the foaming properties. Herein, polybutylene (PB) with the improved foaming property was produced by melt grafting of octadecyl methacrylate (SMA) as long side chains. It was found that the chain entanglement was increased and the foaming behavior was improved. The structure was characterized by infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Compared with un-modified PB, the tensile strength of the modified PB decreased, whereas its impact strength firstly increased and then decreased when increasing the amount of SMA. DSC curves showed that the crystallinity of PB decreased when increasing the grafting dosage. The SEM images showed that all the parameters including the average cell size, cell size distribution, and cell density of foam beads were improved after introducing the longside chains. When the weight ratio of SMA/PB was 3/100, the average cell diameter of PB was 12.3 mu m, the cell density was 38 x 10(7) cells/cm(3), and the expansion ratio was 12. The cell density and expansion ratio of PB with longside chains were 9.2 times and 1.6 times respectively as many as those of un-grafted PB produced with the same foaming method. Additionally, the grafted PB exhibited a wider foaming temperature range. 

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