The effect of inorganic and organic nucleating agents on the electrical breakdown strength of polyethylene

ABSTRACT Altering the morphology of polyethylene affects physical and electrical properties with reduced spherulite size correlating with higher electrical breakdown strength. Nucleating agents in polyethylene influence the final crystal morphology by increasing the number of spherulites and reducing spherulite size. Few studies are available that relate the nucleating activity to improved electrical breakdown strength. Although nanosilica is known to improve electrical breakdown strength of polyethylene in addition to serving as a nucleating agent, previous studies have not fully addressed the relationship between the improved breakdown strength and nucleating activity. In this article, direct current electrical breakdown strength and nucleation effects on morphology are assessed on a single set of controlled polyethylene compositions containing two types of surface treated nanosilica particles. The results are compared to composites with two types of organic nucleating agents 1,3:2,4‐bis(3,4‐dimethylbenzylidene) sorbitol or calcium 1,2‐cyclohexanedicarboxylate (CDA). CDA was the most effective organic nucleating agent and the hexamethyldisilizane treated nanosilica was the most effective inorganic nucleating agent in reducing spherulite sizes in low density polyethylene (LDPE). Reduced spherulite sizes in nucleated samples correlated with increased breakdown strength and lower conduction current compared to the neat LDPE. The LDPE sample with CDA also had the highest increase in crystallization temperature indicating stronger nucleating agent performance than the nanosilica and 1,3:2,4‐bis(3,4‐dimethylbenzylidene) sorbitol composite samples. The addition of these inorganic and organic nucleating agents all resulted in improvements in electrical breakdown strength. The results show that nucleation deserves more attention as a potential cause for improved breakdown strength observed with silica and organic nucleating agents. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46325.