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Study On Silane Grafting And Crosslinking Reaction Of Polyethylene And Its Application To Thick Product

Posted on:2002-12-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:N B YeFull Text:PDF
GTID:1101360032457359Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
The grail reactions of polyethylene by silane (SGPE) and its crosslinking reaction were studied systematically and the reaction kinetics were characteized. The effects of concentration of different polyethylene, initiators and silanes and their mechanism on reaction were investigated. The reaction process in single screw extruder was simulated based on mathematical model. The structure changes of the molecular and aggregate state in the grafting and cmsslinking reaction and the relationship between the structure and properties were inspected in detail. The effects of antioxidants and scorch retardant additives and their mechanism in reaction were investigated. The structure and properties of SGPEIPA(~polyaniide) blends and crosslinked materials were studied to extend the application of SGPE for thick samples. The main conclusions are as followings.1.The reaction of SGPE follows first order reaction kinetics. The reaction activation energy (Ea) of HDPE and LLDPE gralled by vinyl tiiethoxysilane (VTEOS) initiated by dicumyi peroxide (DCP) are 190 and 6OKJ/mol respectively. The reaction activation energy of HDPE grafted by vinyl tiimethoxysilane (VIMOS) is I 75KJ/mol. The temperature range and ongoing time of grafting reaction depend on decomposition character of initiators, reaction activity of silanes, and melting character and reaction capability of PEs. The grafting reaction velocity and its temperature and time-dependent behavior are controlled by their Ea and the above characters of components.2.The simulation of reaction process in single screw extruder based on mathematical model can effectively predict the variations of DCP and silane concentration, degree of grafting and crosslinking along three zones of extruder and it can also predict the influence of DCP and silane contents, barrel temperature profiles on the grafting reactioit It is useful to the control of the reaction extrusion of SGPE.3.The crossIinkin~ reaction of SGPE hydrolyzed water decomposition follows first order reaction kinetics on the content of initiator and water and its activation energy is 40KJ/mol. The catalytic efficiency relationship DBTDL>DMTBL>HStII>E-AA exists between the different catalyst. The major structure changes of HDPE during the grafting and crosslinking reaction are the grafting and netting of linear macromolewlar, the decrease of the degree of ciystallization and the thinning of crystal. There are two melt temperature corresponding to the structure of sol and.gel The properties of crosslinked materials depend on these structure changes.4.The antioxidant(10 10, RD) can retard the appearance of precrosslinking and decrease the degree of gel. The scorch retardant additive (CA) can promote the grafting reaction and retard the precrosslinking reaction and it has no effect on the degree of crosslinking due to its join the grafting reaction5.The uniform crosslinking in the skin and core of thick sample could be obtained by the assimilation character of PA and the formation of routeway.6.The properties of cmsslinked polyethylene by silane is in agreement with modem industrial standard.
Keywords/Search Tags:sllane, initiator, polyethylene, grafting reaction, cwssiinking reaction, kinetics, reactive extrusion, computer simulation, stnzcture/properties, control of precrosslinking, crosslinking of thick product
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