The XRD patterns of PB/HDPE composites with different contents of PB are shown in Fig. 2. All the XRD curves shown in Fig. 2 have a similar trend, and two main characteristic peaks of the four PB/HDPE composites could be observed at 2θ ¼21.6� and 24�, which were assigned to the (110) and (200) crystal planes, consistent with neat HDPE. It meant that the diffraction peak positions of HDPE did not shift with the addition of PB, and the PB/HDPE composites were also partly crystalline. For all composites, it can be observed that all the main diffraction peaks appearing in the composites are contributed by HDPE rather than PB, which revealed that PB was amorphous in nature. In addition, it should be noted that with the loading of PB, the intensity of the two main diffraction peaks reduced, and the two narrow and sharp diffraction peaks gradually got wider and even disappeared, which indicated that the increase of PB may have a negative effect on the crystallinity of HDPE. The reason was that the lack of crystalline HDPE in the composites with a high loading of amorphous PB caused the decrease of XRD peak intensities [33].