Stuay On Barrier Properties Of HDPE/GO As Liner Material For Type Ⅳ Hydrogen Storage Vessel

Hydrogen energy has the advantages of no pollution and wide source of raw materials.And it is one of the most potential clean energy in the 21 st century.The storage and transportation of hydrogen energy can be realized through hydrogen storage vessels.At present,there are four types of hydrogen storage vessels.Type IV hydrogen storage vessel(non-metallic liner fiber fully wound vessel)is one of them.It is widely used in new energy vehicles because of its light weight,high hydrogen storage density and low energy consumption.However,the inner liner of type IV hydrogen storage vessel is usually made of polymeric materials,and its gas barrier performance is relatively poor.Hydrogen is easy to penetrate under high pressure,which has great potential safety hazards.Therefore,it is very necessary to modify the polymer material used in the inner liner of type IV hydrogen storage vessel.In this paper,HDPE/GO composites were prepared by melt blending with high density polyethylene(HDPE)as the matrix material and graphene oxide(GO)as the filler.The effects of coupling agent type,coupling agent content and GO content on the crystallization,barrier properties and mechanical properties of the composites were investigated by single factor experiment.The possible interaction between formulas was further explored by using the orthogonal test with interaction,and the relatively best horizontal collocation was determined.The flow domain under different feeding rates and host screw speeds was simulated by POLYFLOW software,and the effects of each feeding rate and host screw speed on dispersive mixing performance,distributive mixing performance and comprehensive mixing performance were analyzed.The extrusion process was experimentally explored by using the orthogonal test of three factors and three levels.The conclusions are as follows:Firstly,the single factor experiment of the formulation was carried out,and the results showed that: With the increase of the content of silane coupling agent KH570,the crystallinity,tensile strength and impact strength of the composites increased first and then decreased,the oxygen permeability coefficient of the composites decreased first and then increased,and so did the effect of GO content on the properties of the composites.When the type of coupling agent was silane coupling agent KH570,the content of coupling agent was 1.5wt% of GO and the content of GO was 0.5wt% of HDPE,HDPE/GO composites had relatively best crystallization properties,barrier properties and mechanical properties.Secondly,the orthogonal experiment with interaction was carried out on the formulation,and the results showed that: When the crystallinity and oxygen permeability coefficient was taken as the test index,the content of coupling agent and the content of GO had a highly significant impact,and there was a strong interaction between them.When the tensile strength was taken as the test index,the type of coupling agent had the most significant influence,and there was a significant interaction with the content of coupling agent.When the impact strength was taken as the test index,the content of coupling agent had the greatest influence,and there was an obvious interaction with the type of coupling agent.When the type of coupling agent was KH570,the content of coupling agent was 1.5wt% of GO and the content of GO was 20 g,the composites had the relatively best crystallization properties,barrier properties and mechanical properties.Thirdly,the extrusion process was numerically simulated,and the results showed that: When the host screw speed was constant,with the increase of feeding rate,the inlet and outlet differential pressure,weighted average shear stress,backflow coefficient,cumulative residence time and cumulative maximum shear stress showed a decreasing trend.When the feeding rate was constant,with the increase of host screw speed,the inlet and outlet differential pressure,weighted average shear stress,backflow coefficient and cumulative maximum shear stress increased,and the cumulative residence time increased first and then decreased.The dispersive mixing coefficient,distributive mixing coefficient and comprehensive mixing coefficient decreased with the increase of feeding rate,and increased with the increase of host screw speed.After comparing the simulation results with the experimental results under the same process,it was found that the larger the comprehensive mixing coefficient,the smaller the oxygen permeability coefficient and the better the barrier performance of HDPE/GO composites.Finally,three factors and three levels orthogonal experiments were carried out on the extrusion process: In terms of crystallinity and oxygen permeability coefficient,the influence of extrusion temperature was particularly significant,and the influence of host screw speed was significant.The optimal level combination of various factors was that the optimal extrusion temperature of each zone and die-head along the extrusion direction was 200℃,200℃,200℃,215℃,220℃,225℃,225℃,225℃,230℃,230℃,230℃,230℃,220℃(diehead temperature),the optimal host screw speed was 200r/min,and the optimal feeding rate was 7.5kg/h.The tensile strength and impact strength of HDPE/GO composites were also improved under this extrusion process.