Effects Of Iron Ions On Aging Properties Of SBS And Their Characterization

The thermoplastic elastomer SBS is a triblock copolymer prepared by reactive anionic polymerization initiated by RLi as the initiator,styrene and butadiene as the monomer.The SBS product produced by the coupling process,the coupling agent and the water contact is easy to produce acid,It can produce free metal ions when contact with the reactor and piping.Because of the presence of unsaturated double bonds in the polybutadiene segment(PB)in the SBS molecular chain,it is very sensitive to light and oxygen,especially under the catalysis of metal ions,which is more pro ne to photocatalysis and thermal oxygen aging,Causing molecular chain oxidation crosslinking or oxidative degradation,it will greatly reduce its using performance and resulting in its shortened service life.Therefore,the study of trace iron on the cata lytic oxidation of SBS has a very important application value.Using the method of phenanthroline spectrophotometric to determine the iron content in SBS and iron neodecanoate as the basis for the preparation of Fe/SBS materials.The results show that the dry ashing method can pre-treat the organic samples and burn into ash.When the mass concentration of Fe2+ is in the range of 0~0.5mg/L,the absorption value is linear with the iron content,and conform to Beer's law;This method can be used to determine the trace iron in polymer materials.In this paper,the effects of iron content on the hot air aging of SBS samples were studied.The evolution of molecular structure during hot air aging was investigated by fourier transform infrared spectroscopy(FTIR)and UV spectroscopy,and explored mechanism of aging.The heat crosslinking and thermal degradation kinetic parameters was investigated by thermal analysis methods such as DSC and TGA and so on.The gel content in the process of hot air aging was measured quickly by mea ns of Soxhlet extraction method.Using the method of GPC and RPA to research the change rule of performance in the materials ageing process.The results of DSC measurement show that the temperature of thermal crosslinking decrease gradually with the increase of iron content,thermal crosslinking peak intensity increases gradually,and the isothermal oxidation induction time of the system decrease with the increase of iron content.Indicating that iron ions can obviously catalyze the aging reaction of SBS materials.The researches of TGA show that the activation energy of pure SBS is less than activation energy of 0.5?g/gFe-SBS system.It may because that catalytic oxidation of iron SBS and generate crosslinked structure in high temperature conditions,and increase the activation energy required.The rapid determination of gel content by GPC analysis and Soxhlet extraction show that the gel content of the material increased with the increase of iron content and the increase of aging time,and the crosslinked structure increased,and there was a certain degree of degradation.The evolution of molecular structure during the hot air aging of SBS and Fe / SBS system was analyzed by IR technique.The experimental results show that the carbonyl structure and ether bond are produced during the aging process of SBS and Fe / SBS system,and the growth trend is "S" type with the aging time,and the carbonyl group takes precedence over the ether bond.The ?-H and C=C double bond of the molecular structure are reduced in varying degrees,methylene was first attack ed,and then cause a series of chemical reactions.Iron ion catalytic only accelerates the process o f oxidizing reaction materials,prompt the SBS molecular structure oxidization crosslinking and degradation in the process of aging,did not produce new structural unit.