Study On Preparation Of Graphite/sericite Polystyrene Composite Thermal Insulation Material By Suspension Polymerization With Dispersed Phase Pre-increase Viscosity Method

Since its introduction,expandable polystyrene foam has become popular worldwide for its excellent performance in sound insulation,water resistance,low density and low thermal conductivity,especially for its excellent thermal insulation performance,which makes it a leader in the field of insulation.As an insulation material,it is challenging to reduce thermal conductivity.In this thesis,the in situ pre-polymerization and in situ dissolution methods were used to prepare polystyrene(PS)composite beads and its foam(EPS)with low thermal conductivity,and the feasibility of the methods was verified,based on which sericite/polystyrene composite beads and graphite/polystyrene composite beads were prepared using the in situ pre-polymerization and in situ dissolution methods.The in-situ dissolution method has been shown to utilize waste polystyrene or polystyrene scrap(w EPS),enabling the use of scrap and increasing benefits in industrial production.The in situ pre-polymerization and in situ dissolution methods facilitate the doping of inorganic non-metallic materials in the polystyrene matrix to achieve diverse and versatile polystyrene bead preparation with a stable process and no sticky kettle phenomenon.The main work carried out in the thesis is as follows:1.Verification of the feasibility of in situ dissolution method and in situ pre-polymerization methodPrior to suspension polymerization,a high-viscosity homogeneous system of styrene-polystyrene(ST-PS)is formed by the native polymerization of styrene(ST)or by dissolving w EPS in styrene.When the viscosity meets the polymerization conditions,the continuous phase is added to the homogeneous polymer system for suspension polymerization to obtain polystyrene beads.Subsequent immersion into the blowing agent can be obtained from the EPS beads,pre-foaming,molding and molding to obtain EPS foam board.The prepared polystyrene bead pellets were characterized by FT-IR,SEM,TGA-DSC and XRD,and the thermal conductivity and apparent density of the obtained EPS foam sheets were determined.The comparison of commercial polystyrene beads and commercial EPS foam sheets showed that there was no significant difference between the polystyrene beads and EPS foam sheets prepared by in situ dissolution and in situ pre-polymerization methods,which also proved the feasibility of this method.2.Preparation of polystyrene composite beads doped with sericite and graphite using in situ pre-polymerization and in situ dissolution methodsThe sericite doped polystyrene(S-PS)composite beads and graphite doped polystyrene(G-PS)composite beads were prepared using in situ pre-polymerization and in situ dissolution,which were characterized by FT-IR,TGA-DSC,XRD and SEM.The foaming agent was dipped into S-PS and G-PS composite beads to obtain sericite EPS(SEPS)beads and graphite EPS(GEPS),respectively.SEPS composite foam board and GEPS composite foam board were prepared by using SEPS and GEPS composite beads,and their thermal conductivity and apparent density were tested.The following conclusions were obtained:(1)Sericite and graphite did not produce chemical changes when combined with polystyrene,and the structure was not destroyed.(2)The doping of sericite and graphite improved the thermal properties of the composite beads,and the thermal stability and glass transition temperature of S-PS composite beads and G-PS composite beads were improved.(3)SEPS composite foam board and GEPS composite foam board thermal conductivity than commercial EPS foam board is lower,respectively,0.038 W/(m-K),0.031 W/(m-K)and 0.034 W/(m-K),sericite,graphite can be added to significantly improve the thermal insulation performance of EPS foam board.3.The mechanism and relevant process parameters of in situ dissolution method for suspension polymerization of S-PS composite beads were discussedThe effects of suspension polymerization conditions(sericite mass fraction,initiator mass fraction,w EPS dissolution mass fraction,dispersant mass fraction,surfactant mass fraction,stirring rate and volume ratio of continuous and dispersed phases)on the success rate of suspension polymerization,polystyrene bead size and bead sphericity were investigated by in situ dissolution method using S-PS composite beads as the target.It was concluded that the bead size and sphericity of the S-PS composite beads prepared using the optimum process parameters(benzoyl peroxide 1w%,sericite 5 w%,w EPS 22 w%,dispersant 0.09 w%,surfactant 0.9 w%,stirring rate 500 r/min,continuous phase volume 100 m L)met the requirements for use.In addition,the amount of w EPS that can be dissolved using the in-situ dissolution method can be up to 30 w% of the ST-PS system,much higher than the 5 w% of the producer,which allows the producer to effectively use w EPS to reduce the scrap rate.