Selection of rotational molding process for plastic inner liner of type Ⅳ hydrogen storage bottles
The dimensional precision of plastic liners has a significant influence on the service performance of type Ⅳ hydro-gen storage tanks.Poor uniformity of wall thickness can directly lead to deformation and reduced straightness of the inner liner,resulting in poor winding process,cracking of hydrogen storage bottles,and decreased pressure resistance.Rotational molding,as an important liner molding method,has challenges in controlling the wall thickness uniformity of the liner,due to the missing mecha-nism of the effect of rotational molding process on the dimensional accuracy of the liner.There is relatively little research in the industry on the impact of process factors on wall thickness in detail.In this work,the effect of eight common rotational molding processes on the wall thickness uniformity type was analyzed by using ROTOSIM software.The results show that when producing typical-sized hydrogen storage tank liners,the uniformity of wall thickness improves with the increase of rotation speed,but too fast can cause powder scattering to affect the uniformity of wall thickness.The rotation speed ratio should be avoided as an integer or half integer to prevent duplicate powder trajectories.The use of the swing machine or rotary machine L-arm liner vertical placement mode is superior to the rotary machine L-arm liner horizontal placement mode and the rotary machine straight-arm mode.More importantly,whether the rotation center coincides with the inner liner axis has a relatively small impact on the uniformity of wall thickness,providing a theoretical basis for the one machine multi mode production method.As an optimization plan for this study,when the rotation speed of the rocking machine is 1 r/min and the rocking speed is 6.5 times/min,the coefficient of variation of the plastic inner liner wall thickness is 9％,which is the minimum value within the research range.
rotational moldinguniformity of wall thicknessplastic inner liner of hydrogen storage bottlerotating tech-nologyspeed ratio
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