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 can have metal components embedded within them, providing an opening for filling and draining, and to provide a means of support during the manufacturing and installation of the tank. The rotational moulding process is an established method for producing tank liners. Metal components, known as mould inserts, may be moulded into the typical mouldings 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 rotationally moulded tank liners are considerably larger, making their encapsulation more challenging, more costly, and with the final moulding placed under more demanding conditions. A series of studies was conducted to explore how the encapsulation of the metal components within rotomoulded H2 tank liners could be optimised analysing the boss design, boss and liner material, and moulding process parameters. Rapid prototyping methods were employed to explore the effects of the parameters on the part encapsulation, using a state-ofthe-art electronically heated robotically controlled rotational moulding machine.