Research On The Integrated Molding Process And Equipment Of Type Ⅳ Hydrogen Storage Tank Liner

In the context of global carbon peaking and carbon neutrality,hydrogen energy is attracting attention as a clean energy source without carbon emission.High-pressure gaseous hydrogen storage is currently the main way of hydrogen energy storage and transportation link,and the type IV hydrogen storage tank with plastic liner combined with carbon fiber full winding has become one of the research hotspots.However,the existing plastic liner injection-welding molding method cannot avoid the occurrence of weld defects,which will easily lead to the failure of highpressure hydrogen storage cylinders.In order to solve this problem,the integrated liner molding process has become one of the key technologies,but the existing process and equipment need urgent research and technological innovation in terms of molding efficiency,liner quality and energy utilization,in order to improve the capability level in the field of hydrogen energy storage and transportation.This paper focuses on the integrated molding process and equipment for type IV hydrogen storage tank.The innovative development of type IV hydrogen storage tank liner integrated molding equipment with mold in-situ temperature control technology as the core has improved the accuracy and balance of temperature control in the molding process.The mechanism of typical defects such as air bubbles in the liner was studied by visualization method,and the solution of molding process was proposed;in terms of material,the toughening modification of high barrier nylon was carried out to improve the mechanical properties and gas barrier performance of the liner material.The main research results achieved are shown as follows:(1)The innovative method of mould zoning in-situ temperature control process for forming liner is proposed,and the type IV hydrogen storage tank liner integrated molding equipment is developed.The results of finite element simulation analysis show that the in-situ temperature control mold has better temperature uniformity,which effectively solves the molding problems such as low temperature control accuracy and uneven wall thickness of traditional rotational molding process.Based on this,the developed type IV hydrogen storage bottle liner integrated molding equipment has the functions of high precision temperature control and rotational oscillation of the mold with infinitely adjustable speed,and its advantages of high energy utilization,good temperature uniformity of the mold,zonal temperature control and high automation are verified through testing,which can fully meet the high requirements of integrated liner molding.(2)The innovative visualization method was used to study and reveal the typical defect generation mechanism of integrated liner molding and propose corresponding solution measures.The study shows that the plastic powder gradually forms the wall thickness of the liner product after adhering and accumulating inside the rotational molding mold and melting.The powder flow and temperature field caused by the mold rotation affect the heat transfer process between the plastic powder and the surface of the mold,and become the key factor affecting the wall thickness uniformity of the liner products.In this study,a mold partitioning in-situ temperature control process with high temperature control accuracy was used to regulate the wall thickness of the product,and the uniform control of the wall thickness of the liner and the elimination of molding defects were successfully achieved.At the same time,the visualization experiment shows that the plastic powder adhesion melting process leads to bubble defects in the product due to the partial gas residue in the melt.By using the mold temperature control process,the air bubbles can be gradually dissolved in the melt and achieve the elimination of air bubble defects in the liner products.In addition,the experimental study of different cooling methods on the crystallinity and mechanical properties of the liner material shows that forced air cooling can improve the mechanical properties and processing efficiency of the liner products.(3)A nylon 6 modification preparation scheme using nano-fillers(OMMT)and elastomeric tougheners(POE-g-MAH)was investigated for the high barrier and impact resistant use requirements of type IV hydrogen storage tank liners.The results showed that the addition of10wt% of POE-g-MAH could improve the impact resistance of nylon 6by 102.9% because the elastomeric toughening agent could consume more energy in the transfer of stress between the two phases.Since the flake OMMT filler can significantly extend the gas penetration path in the composite matrix,the addition of 3wt% OMMT composite improves the barrier performance by 43.9% and exhibits a synergistic effect for enhancing the impact performance.Using integrated molding equipment to try out the liner,the results show that the modified nylon can improve the impact performance by 50% relative to the original nylon 6 liner product while maintaining the uniformity of the liner wall thickness.The results of the study can provide material solutions for integrated molding of high barrier and impact resistant liners.