Electron Radiation Preparation And Properties Characterization Of EMMA/EPDM Heat Shrinkable Materials

This paper is aiming to synthesize a new heat-shrinkable material. Two kinds ofpolymers of EMMA (ethylene-methyl methacrylate) and EPDM(Ethylene-Propylene-Diene Monomer) are selected as raw materials, of which are usedto prepare EMMA/EPDM heat-shrinkable material by means of1.2MeV high-energyelectron beam radiation inducing crosslink. The blending process and the mode andmechanism of radiation induced crosslinking were investigated. The shape memory,vacuum outgassing and mechanical property at low temperature were evaluated.The analysis on mechanical performance of EMMA and EPDM blends withvarious formulations shows that the elongation as well as the compatibility is reducedwhen the proportions of two blending elements are close. In order to ensure the highmechanical properties and low temperature resistance of heat shrinkable material, theEPDM should be a major element in the blend formulation. The electron irradiation canimprove the compatibility of blend to a certain extent, aiding to modify the materialusing EMMA.The crosslinking degree of the EMMA/EPDM blends is increased with increasingirradiation dose. The analyses from EPR, FTIR, DSC et al for the blends before andafter irradiation show that, the reaction of free radicals is the main mechanism ofradiation induced crosslinking. The unsaturated functional group of EPDM molecularstructure has a sensitization effect in the irradiation process, which can promote thecrosslinking of blend system.On the basis of the analysis and research, an EMMA/EPDM heat shrinkablematerial was prepared using EMMA/EPDM blends under the mix ratio of3:7and theirradiation crosslinking with30-40kGy dose, followed by processes of stretching,cooling and shaping. The results of performance evaluation of the material are asfollows. The thermal shrinkage response temperature is ranged in60-90℃under the200%deformation. The shape fixed ratio is93%, while the shape recovery ratio reaches97%, indicating a good shape memory performance. After storage in vacuum at125℃for24h, the total mass loss rate and the condensable volatile content of the materials isabout0.48%and0.08%, respectively, which meet the requirements by the criterionQJ1558-88. Under the condition of-70℃, the material presents breaking strength of50MPa and elongation of400%, showing good mechanical properties at low temperature.Research results indicate that the heat shrinkable material of EMMA/EPDMmanufactured by using electron beam radiation crosslinking shows excellent propertiesof shape memory, and high resistance to low temperature and vacuum, which isqualified the basic conditions for application in high cold and/or space environment.