The two-dimensional multifractal detrended fluctuation analysis is applied to reveal the multifractal properties of the fracture surfaces of foamed polypropylene/polyethylene (PP/PE) blends at different temperatures. Nice power-law scaling relationship between the detrended fluctuation function F-q and the scale s is observed for different orders q and the scaling exponent h(q) is found to be a nonlinear function of q, confirming the presence of multifractality in the fracture surfaces. The multifractal spectra f (alpha) are obtained numerically through Legendre transform. The shape of the multifractal spectrum of singularities can be well captured by the width of spectrum Delta alpha and the difference of dimension Delta f. With the increase of the PE content, the fracture surface becomes more irregular and complex, as is manifested by the facts that Delta alpha increases and Delta f decreases from positive to negative. A qualitative interpretation is provided based on the foaming process. (C) 2008 Elsevier B.V. All rights reserved.