Nucleating agents for high-density polyethylene-A review

Abstract

A review of nucleating agent (NA) types and their effect on crystallization in high-density polyethylene (HDPE) is presented. The focus is on methods to improve the physical properties of HDPE due to its widespread use in commercial applications and high volume use in typical industrial processes including extrusion, injection molding, and blow molding. The crystallization process in HDPE significantly affects its final optical, mechanical, and thermal properties. The addition of NAs affects the physical properties of HDPE by controlling the crystallization from the melt state. Specific NAs improve properties such as clarity, cycle time, and modulus. NAs are more widely developed for polypropylene (PP) than HDPE as its slower crystallization rate allows greater control in achieving property improvements. While certain NAs are effective in improving property characteristics in HDPE, greater control over the crystallization process would achieve further improvements in specific properties. Research has progressed in identifying effective NAs for HDPE, though the magnitude of the effects remains lower than those generally observed in PP. Inorganic and organic NAs are reviewed with an emphasis on the mechanisms by which they function. Fundamentals of polymer crystallization and modeling kinetics during both isothermal and nonisothermal studies provide the necessary framework for characterizing the effects of a NA in HDPE. Finally, the interactions between HDPE, NA, and industrial processing conditions as related to practical applications are discussed. POLYM. ENG. SCI., 56:541–554, 2016. © 2016 Society of Plastics Engineers