Study On Preparation And Properties Of EPDM/HDPE Thermoplastic Elastomer

Thermoplastic vulcanizate(TPV)is a recyclable and environmentally friendly material prepared by blending rubber and plastic.Because of the high elasticity of rubber and the processability of plastics,it can be used as a substitute for cross-linked rubber materials,which has attracted widespread attention.In addition to the properties of rubber and plastic,the performance of TPV is also affected by the microscopic distribution of the rubber in the plastic.The microscopic morphology of TPV is mainly determined by the processing conditions.However,the processing technology of dynamically vulcanized thermoplastic elastomer is complicated,the processing conditions are difficult to control,and it is easy to cause TPV performance unstable.Therefore,in order to obtain a TPV with excellent performances,it is of great significance to explore the processing technology and analyze its relationship with the micro morphology for controlling the micro-morphology,which also has important scientific research significance and industrial value.EPDM and HDPE were used to prepare EPDM/HDPE TPV with cross-linking agent1,4-bis(tert-butylperoxyisopropyl)benzene(BIBP)and auxiliary cross-linking agent triallyl isocyanurate(TAIC)dynamic vulcanization.The influences of addition amount of BIBP and TAIC,processing temperature,processing time,rheometer speed and preparation method on the processing performance of EPDM/HDPE blends were investigated,and the mechanical properties of EPDM/HDPE TPV were also analyzed.EPDM was mixed with 0.3 wt%BIBP and 0.3 wt%TAIC for 4 min at 120?and 60 rpm to prepare EPDM masterbatch,then the masterbatch and HDPE dynamic vulcanizated at 180?and 50 rpm for 10 minutes to obtain EPDM/HDPE TPV.The obtained TPV-0.3-0.3 had excellent mechanical properties,tensile strength reached 14.2MPa,the elongation at break reached 675%,the hardness was 85A.The influence of the dynamic vulcanization reaction between EPDM and HDPE on the bonding of the two-phase interface was studied.The interfacial tension between EPDM and HDPE was 7.59 m J/m~2,while the interfacial tension between vulcanization EPDM and HDPE was 9.99 m J/m~2.After crosslinking,the interfacial tension between EPDM and HDPE increased,and the tendency of binding between the two phases decreased.On the other hand,through the analysis of the cross-linking mechanism,it was found that during the dynamic vulcanization process,EPDM and HDPE and the cross-linking system may cause partial co-crosslinking reaction,which promoted the improvement of the compatibility between two phases.And the formation of micron-sized rubber particles increased the interface area between the rubber and plastic,and compensated for the damage to the mechanical properties caused by the decrease in the bonding force between the cross-linked EPDM and HDPE.It could be indirectly reflected in the SEM photograph of TPV-0.3-0.3 with no phase separation of brittle surface and rough tensile section.The changes of the rubber network structure in EPDM/HDPE blends with different processing times were explored.When the mass ratio of EPDM/HDPE was 65/35,the EPDM phase,which accounted for most of the total mass,was the continuous phase at the beginning of dynamic vulcanization.Under the action of BIBP and TAIC,EPDM undergone a crosslinking reaction while being sheared.EPDM was sheared while undergoing a cross-linking reaction.When the processing time was 5 minutes,the TPV could not be dissolved and broken in the hot xylene,indicated that the cross-linked EPDM was still a continuous phase,and the phase inversion had not occurred.When the processing time was 7minutes,TPV could be broken in hot xylene,but the cross-linked EPDM particles obtained by breaking were larger,indicating that the reverse was taking place.After 7 minutes,since the reverse rotation had already occurred,the samples obtained after that time disintegrated when soaked in hot xylene.When the processing time was 10 minutes,The SEM photograph of the sample at this time showed that there were many cross-linked rubber particles with particle size of about 3?m?5?m on the etched cross-section.Compared with EPDM/HDPE blending directly,the rubber crosslinking network formed by dynamic vulcanization of EPDM and HDPE increased the storage modulus and apparent viscosity of the rubber-plastic blend,exhibited shear thinning behavior.The apparent viscosity at high frequencies was similar to that of pure HDPE,indicating that dynamic vulcanization contributed to the improvement of processing performance.In addition,the formation of rubber cross-linking network was harm to the regular arrangement of molecular chains in TPV.Compared with the EPDM/HDPE simple blend,the crystallinity and crystallization temperature of TPV-0.3-0.3 were reduced to 60.8%and 109.4?,respectively.