The encapsulation of metal boss components within rotomoulded liners for type IV H₂ tanks

Polymer liners are a critical component in Type IV hydrogen storage tanks, providing a barrier layer to prevent gas from escaping out of the vessel. These liners must have metal components embedded within them, providing an opening for connection to a gas management system. The rotational molding process is one of the methods capable of producing the tank liners. Metal components, known as mold inserts, may be molded into the typical moldings produced using the process. However, these are typically small metal inserts to allow for bolting components together and are, therefore, not subjected to demanding mechanical conditions. By comparison, the metal components used in gaseous hydrogen tank polymer liners are considerably larger, making their encapsulation more challenging, more costly, and with the final molding placed under more demanding conditions. A study was conducted to explore how the design of the boss effects the encapsulation of the component within rotomoulded H2 tank liners. Rapid prototyping methods were employed, providing a low-cost high-speed method of manufacturing the parts. The bosses were molded into tank liners using a state-of the-art electronically heated robotically controlled rotational molding machine, and visually inspection of the encapsulation around the design features completed.