Among the different types of polyethylene used in household and molding applications, high density polyethylene (HDPE) is primarily used for blow molding. Generally, a distinction is made between small-part (< 5 liters) and large-part (> 5 liters) blow molded articles. Typical small-part blow molded articles are bottles and household and industrial containers, whereas drums, pails, tanks and intermediate bulk containers are considered large-part blow molded items.

Processing and Thermal Stability

Typically, HDPE grades for blow molding are pelletized  under high shear and high temperatures (often above 260 °C). Furthermore, during the blow molding process a significant amount of polymer is recycled in order to economize cost and to minimize polymer waste. Severe pelletization conditions and high recycling rates require an optimum processing stability and thermal stability to ensure high melt flow stability and color control of the HDPE. The recommended stabilizer solution depends on the type of catalyst and type of production process. Typically, chromium catalyst-based Phillips-type polyethylene (Cr-HDPE) requires higher levels of stabilizers than titanium-based Ziegler/Natta-type polyethylene (Ti-HDPE).

Light Stability

For large-part blow molded articles in outdoor applications Ciba®CHIMASSORB® 944 or Ciba® TINUVIN® 783 are recommended to prevent light-induced polymer degradation.

Ciba® IRGASTAT® permanent antistat and Ciba® IRGAGUARD® antimicrobials offer further value to the polyethylene in blow molding applications.

To incorporate additives efficiently, we offer Customer Specific Blends in various product forms. For more information, please, contact us.