Study On The Preparation Of Uhmwpe Microporous Materials By Non-dense Injection Molding

Microporous materials are widely used in the field of filtration,such as foodstuffs industry,medical treatment,water treatment,etc.because of their uniform and stable micropore structure.They are the key points in the process of filtration and separation.Ultrahigh molecular weight polyethylene(UHMWPE)is a very prominent thermoplastic.Microporous materials prepared by them tend to be more superior performance,to better meet the filtration requirements.However,there are many problems in the preparation methods of UHMWPE microporous materials in the current,and a new method of high automation and high productivity for forming UHMWPE microporous filter materials needs to be studied.In this paper,aiming at the shortcomings in the existing methods for preparing UHMWPE microporous materials,UHMWPE microporous materials are molded by a new,more efficient and environmentally friendly called non-dense injection molding method.The characteristics of the forming process and the basic forming principle are studied.The effects of injection volume,injection pressure,injection speed,and molecular weight on the UHMWPE injection molding,and by adjusting the process parameters to prepare different microporous structure and performance requirements of microporous materials.The main conclusions are as follows:(1)The non-dense injection molding of UHMWPE microporous material is formed by the "jet flow" powder produced during the high-speed injection process,mutual bonding and piling with non-dense compression in the cavity.SEM observation showed that the microstructure was similar to the powder sintering method.The performance and structure of microporous materials depend on the "jet flow" powder produced by the new injection.The feasibility of non-dense injection moulding of UHMWPE microporous material was verified,which is the new process completely different from any existing process.(2)It was found that when the injection direction is perpendicular to the "jet flow" direction,along the "jet" flow direction the micropore structure varied in gradient.It is easy to become dense at the end of the gate,and it is easy to form the micropores at the end of the gate.The pore diameter distribution is more uniform,the average pore diameter is larger,and the porosity is higher.(3)The new method of "jet flow" powder combined with "injection compression" technology was tried,and it was preliminarily determined that the products with more uniform and stable micropore distribution could be easily obtained by this method.(4)The effects of UHMWPE with different molecular weights on the structure and properties of microporous materials were studied.With the increase of molecular weight of UHMWPE,microporous materials were more easily formed,the regularity of microstructure was improved,the pore diameter distribution was more uniform and the compressive strength of the products increased.(5)The effects of injection molding parameters,such as injection volume,injection pressure,and injection speed,on the structure and properties of UHMWPE microporous materials were studied.The optimum injection molding parameters were as follows:injection volume 60%,injection pressure 63.8MPa,injection speed 100%.At this time,the UHMWPE microporous material has the better comprehensive properties,the average pore diameter and porosity are 38.92?m and 38.34%,the bulk density is 0.599g·cm-3 and the compressive strength is 9.28MPa,which is very close to the sintered filter material.It is proved that the performance of commercial sintered filter products is very similar to the products by non-dense injection.