Study on the Preparing Technology and Properties of Rubber by Using Molten Iron Desulphurization Slag as Functional Filler

Author:Gu Heng Xing

Supervisor:xu de long li hui

Database:Doctor

Degree Year:2017

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Pages:147

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To enhance the added value of steel slag utilization,the basic properties of different kinds of steel slag were investigated,and molten iron desulphurization slag(MIDS)was selected as the raw meal for preparing rubber filler.The preparation process and the properties of rubber functional filler prepared were studied,including the effect of MIDS as filler on the rubber properties,the reinforcing mechanism of MIDS on the styrene butadiene rubber,modification of MIDS and the properties of styrene butadiene rubber prepared by modified MIDS.New process for preparation of flame retardant conveyor belt coating added with MIDSas different fillers were developed.According to the preparation requirements of rubber filler,the basic properties(chemical composition,density,grindability,free calcium content,mineral composition,activity index)of steel slags discharged from Baosteel’s different production and treatment processes and other properties used as rubber filler were systematically studied.The conclusions were as follow:(1)the chemical composition of steel slag discharged from Baosteel’s different production and treatment processes(MIDS,cast slag,poured converter slag,converter roller slag,poured electric furnace slag and electric furnace roller slag)were similar to the calcium silicate component of traditional rubber filler,among them MIDS had the minimum density,best grindability,highest content of free calcium oxide,more composition of reinforcing mineral and higher activity than other steel slag,which was suitable for preparation of rubber filler material.(2)the 45μm washing sieve residue content,oil absorption,water soluble material content,105℃volatiles mass fraction of MIDS met the standard requirements as rubber filler,and the pH of the aqueous suspension was alkaline,which had a role in promoting rubber curing.The effects of MIDS on the properties of rubber were studied.The effects of the ratio of MIDS and carbon black,fineness of MIDS,curing time,the ratio of curing accelerator on the properties of natural rubber(NR)and styrene butadiene rubber(SBR)were analyzed.It was found that:(1)the overall performance of SBR added with MIDS was better than NR added with MIDS.When the ratio of MIDS and carbon black was20:30,the fineness of MIDS was 1000 mesh with specific surface area of 1165.10 m2/kg,the curing time was 25min,the ratio of curing accelerator(NS:sulfur)was 1(phr,weight parts):1.75(phr,weight parts),the tensile strength of the styrene butadiene rubber added with MIDS was more than 20MPa,and SBR had the best overall performance.(2)The excessive or too little fineness of MIDS would result in worse dispersion and compatibility of tailings in NR and SBR,which would lead to the decrease of mechanical properties of rubber.The particle size distribution evaluation model of MIDS was established by using the fuzzy group theory,and the reinforcing mechanism of MIDS on SBR was studied.It was found that:(1)the evaluation model of particle size distribution of MIDS based on fuzzy group theory(y/(1-y)(28)K1((10)r1x/(1-x))/(1(10)r21(-x)/x))and the variation of non-linear fitting results r1/r2 were consistent with the change of tensile strength of SBR material added with different fineness of MIDS.(2)The curing process of SBR added with MIDS could be divided into scorch period,thermal curing period and curing flat period.In the scorch period,the MIDS could provide alkali environment which was beneficial to improving the flowability of SBR,the porous structure was helpful to physically adsorb rubber molecular chain.In the scorch period and thermal curing period,the Ca2SiO4 contained in MIDS could continuously hydrated to form C-S-H gel,which increased the viscosity of SBR to achieve the effect of reinforcing SBR.A uniform test scheme was designed taking account of the amounts of stearic acid,anhydrous ethanol and silane K550,the stirring speed and the reacting temperature as the factors.The modified MIDS was prepared by semi-dry process.The mechanical properties of SBR added with modified MIDS were studied.On this basis,two theoretical optimization methods,nonlinear regression and BP neural network,were used to further improve the mechanical properties of SBR,and the validity and guidance accuracy of these two methods on optimizing the mechanical properties of SBR were compared.The results revealed that:(1)The optimal process parameters determined by nonlinear regression(stearic acid content was 4.4%,anhydrous ethanol was 21.7%,silane K550 was 3.5%,stirring speed was 638 r/min and reaction temperature was 72°C were very close to the predicted optimal process parameters by BP neural network model(4.5%for stearic acid,22.1%for anhydrous ethanol,3.4%for silane K550,606 r/min for stirring,and 70°C for reaction temperature),and the measured mechanical properties of the prepared SBR materials were in good agreement with the predicted values.(2)Both nonlinear regression and BP neural network model had higher validity and guidance accuracy when they were used to direct the modification of MIDS and the mechanical properties improvement of SBR.For revealing the modification mechanism of MIDS,the changes of structure,composition and repose angle of MIDS were measured before and after modification.The mineral composition of the modified MIDS,SBR without filler,SBR added with modified MIDS were tested.The microstructure of original MIDS,modified MIDS,SBR added with original MIDS,SBR added with modified MIDS were observed.It was found that:(1)After modification,silane K550 and stearic acid were adsorbed on the surface of MIDS,that changed the surface composition of MIDS by chemical reaction,and reduced the repose angle of MIDS which could improve its flow properties in SBR.(2)The modified MIDS were effectively wrapped by SBR,the addition of KH550 and stearic acid improved the dispersion of MIDS in SBR,and improved the interface fusion between MIDS and SBR.Industrial application test of flame retardant conveyor belt coating(FRCBC)prepared by adding with MIDS as filler was completed.FCBCs were prepared by added with 6001000 mesh original or modified MIDS for replacing carbon black,silicon aluminum carbon black,aluminum hydroxide and other fillers,as well as low halogen flame retardant,the performance of FRCBC under different curing conditions were tested.It was found that:(1)For the mixing process,when the curing temperature was145℃and the curing time was 10 minutes,the mechanical properties,abrasion and flame retardant performance of FRCBC prepared by adding with 30 phr(weight parts)MIDS met the standard requirements,and this process can be used with less than 10 phr of carbon black,15 phr of aluminium hydroxide and 4 phr of vulcanizing accelerators.(2)When the curing temeperature was 145℃and the curing time was 45min,the mechanical properties,flame-retardant properties and abrasion of the low-halogen FRCBC added with 15 phr of MIDS as low halogen flame retardant met the standard requirements also.