AbstractThe structure and properties of high‐density polyethylene (HDPE) ultraviolet irradiated in ozone atmosphere were studied by FTIR, XPS, GPC, XRD, DSC, TG, gel, and contact angle test. The oxygen‐containing groups such as CO, CO, and C(O)O were quickly introduced onto HDPE chains through ultraviolet irradiation in ozone atmosphere; their content increased with increase in the time of ultraviolet irradiation. Compared with those of HDPE, the molecular weight of the irradiated HDPE decreased and its distribution became wider. There was no gel in the HDPE irradiated in ozone atmosphere. After ultraviolet irradiation for short times in ozone atmosphere, the water contact angle of the irradiated HDPE decreased and its hydrophilicity was improved. The crystal shape of the irradiated HDPE was still an orthorhombic structure; its cell parameter and the face space did not alter, but its melting temperature decreased slightly. Compared with that of HDPE, the temperature of initial weight loss for irradiated HDPE decreased. The irradiated HDPE/sericite‐tridymite‐cristobalite (STC) blends were prepared. The dispersion and compatibility of the irradiated HDPE/STC blends were improved compared with those of HDPE/STC blends; thus its mechanical properties increased. Copyright © 2008 John Wiley & Sons, Ltd.