Flow Characteristics And Mechanical Behavior Of Low-dose Electron Beam Irradiation Of Polyethylene

Crosslinking of Molecular chain can improve Polyethylene's mechanical strength and broaden its application range.High dose irradiation can produce high crosslinking degree,which can significantly improve the mechanical strength of polyethylene,but the possibility of recovery and reproduction is lost;However,low dose irradiation can improve the properties of polyethylene while retaining its recycling and reproduction properties.Because of the different molecular structure of different kinds of polyethylene,the effect of low dose electron beam irradiation on its flow characteristics and mechanical behavior is different.In this paper,the effects of low energy electron beam on the properties of different kinds of polyethylene are summarized in detail.The main work and results are as follows:(1)The effect of low dose irradiation on linear low density polyethylene(LLDPE)was analyzed.The results of infrared spectrum and polarizing microscope show that the LLDPE particles are mainly long chain branched,short chain branched and small crystal particles when the irradiation dose is 5kGy.With the increase of irradiation dose,the LLDPE particles are mainly irradiation crosslinked,the methyl content decreases,the long chain increases,and the crystal structure gradually forms a network structure;The results show that the melt strength of LLDPE can be improved by the capillary rheological test.When the irradiation dose is 10kGy and 15kgy,the shark skin ripple on the extruded material surface is reduced or even disappeared,and the extrusion increases.However,with the increase of irradiation dose,the shear viscosity of LLDPE increases and the rheological property decreases;The tensile test results show that the tensile strength of LLDPE increases with the increase of irradiation dose,and the yield strength also increases with the increase of irradiation dose.The change rule of elongation at break has a turning point.With the increase of irradiation dose,the tensile strength first increases and then decreases.The impact test shows that the impact strength of LLDPE increases with the increase of irradiation dose;The results of DSC and XRD show that the crystallinity XC of LLDPE first increases and then decreases with the increase of irradiation dose;TGA results showed that the thermal decomposition temperature of LLDPE was decreased by long chain branching,and the thermal decomposition temperature of LLDPE was increased by increasing the short peak of micro crosslinking content;The results of TMA test show that the viscosity fluidization transition temperature and thermal deformation degree of LLDPE increase with the increase of micro content.(2)The effect of low dose irradiation on the properties of low density polyethylene(LDPE)was analyzed.The results of infrared spectrum showed that the molecular structure and molecular weight distribution of LDPE were not affected by low dose irradiation.LDPE itself contained a large number of long and short branched chains,which made it easier to cross link;The results show that the shear viscosity of LDPE increases and the fluidity of LDPE deteriorates after low dose irradiation.The mechanical test shows that with the increase of irradiation dose,the tensile strength and yield strength of LDPE increase,the toughness decreases,and the impact strength increases slightly;DSC test results show that low dose irradiation can promote the crystallization of LDPE,but the influence regularity is not strong;TGA test shows that micro crosslinking can increase the thermal decomposition temperature of LDPE;The results of TMA test show that the viscosity fluidization transition temperature and thermal deformation degree of LLDPE increase with the increase of micro content.The effect of low dose irradiation on the properties of medium density polyethylene(MDPE)is similar to that of LDPE.With the increase of irradiation dose,the content of micro crosslinking increases,the shear viscosity of MDPE increases,the rheological properties of capillary become worse,and the elongation at break decreases;The difference is that the impact strength of MDPE is increased,while the tensile strength and yield strength are almost unchanged.(3)The effect of low dose irradiation on the properties of high density polyethylene(HDPE)was analyzed.Through the red spectrum test results,there are two different long chain branching.When the irradiation dose is 5kGy,the long chain branching of HDPE forms more long chain branching.With the increase of irradiation dose,the second branching of long chain forms more short chain branching.The rheological properties of HDPE are affected by the formation of long and short branched chains and micro crosslinking;The results of capillary rheology test show that with the increase of irradiation dose,the shear viscosity increases,the fluidity of HDPE becomes worse,and the melt fracture phenomenon occurs;The tensile test shows that the tensile strength and yield strength of HDPE show three changes with the increase of irradiation dose.When the irradiation dose is less than 15kgy,they almost remain unchanged.When the irradiation dose is 15kgy-40kgy,they show an upward trend.When the irradiation dose is more than 40kgy,they show a downward trend.The elongation at break decreases with the increase of irradiation dose,The results show that the impact strength of HDPE first increases and then decreases with the increase of irradiation dose,and reaches the peak value when the irradiation dose is 10-15kgy;The DSC results show that the crystallization properties of hdpe8007 change with the increase of irradiation dose,reaching the peak at 5kGy and 40kgy respectively;TGA test showed that the thermal decomposition temperature of LLDPE was decreased by long chain branching,and the thermal decomposition temperature of HDPE was increased by increasing the short peak of micro crosslinking content;The results of TMA test show that the viscosity fluidization transition temperature and thermal deformation degree of HDPE increase with the increase of micro content.The effect of low dose irradiation on ultra high molecular weight polyethylene(UHMWPE)is similar to that of HDPE.The shear viscosity of UHMWPE increases and the rheological properties of UHMWPE capillary become worse.However,when the irradiation dose is less than 20kgy,the melt strength of UHMWPE increases.(4)The effect of low dose irradiation on Toughening of LDPE/POE and HDPE/POE blends was analyzed.Compared with LDPE and HDPE,the tensile strength of non irradiated LDPE/POE and HDPE/POE decreased to some extent,and the elongation at break increased to some extent;After electron beam irradiation,LDPE/POE and HDPE/POE show different changing rules.The decreasing curve of elongation at break of LDPE/POE is similar to that of LDPE,almost parallel to that of LDPE.The elongation at break of HDPE/POE decreases like a cliff,and the toughening effect of Poe is almost No.