Study On Graphene/PMMA Composites By In-situ Polymerization And Supercritical CO₂ Assisted With Ultrasound

Due to its cost-effective,general,aesthetic speciosity advantages and so on,the polymer materials obtains the widespread application more and more in the industrial production.However,the poorer thermodynamic performance and mechanical properties of PMMA,especially the lower impact strength,and the electrostatic effect,restrict its application in many industrial fields with high-quality.Graphene,large specific surface area,high electron transfer rate,good chemical properties,good thermal conductivity,high elastic modulus and mechanical strength to make it in the field of polymer materials has great application value and research value.This dissertation used ultrasonic assisted supercritical carbon dioxide method to produce graphene.This method can produce high-quality product with a simple,mild,harmless,reaction conditions and simple post-processing.The Graphene/PMMA Composite Materials by in situ polymerization:Graphene/PMMA was prepared in situ polymerization with initiator,after graphene and MMA were blended with ultrasonic.The morphologies of these composites were characterized by TEM,AFM,SEM,FTIR and XRD.The electrical and mechanical properties of the composites were characterized by materials testing machine and four point probe instrument.The results showed that graphene were homogeneous dispersed throughout Graphene/PMMA composites.When compared with PMMA,the mechanical properties,including modulus of elasticity and maximum tensile strain,of the composites have a great improvement.With higher thermodynamic stability,the thermal decomposition peak temperature of graphene/PMMA was improved from 396?to 420?with incorporation of only 5 wt.%graphene into PMMA.The electrical conductivity of the composites increases from 10^-14 S/cm to 8.89×10^-2 S/cm with incorporation of only 1 wt.%graphene into PMMA.In this study,PMMA was successfully prepared using ultrasound in SC-CO₂ atmosphere.The effects of the ultrasound power and time on the molecular weight?MW?and the yeilds of the product were investigated,and the mechanism behind was discussed.The results shown that under SC-CO₂conditions,the ultrasound power had a threshold value?150 W/cm²?to induce the polymerization and an optimized value?225 W/cm²?,according to both the yields and the energy cost.The ultrasound time also had a optimized value of 2 h.Under the optimized conditions,the wight-everage and the number-average MWs of the PMMA synthesized were 103511 and179732,respectively,and the Mw dispersity index was 1.74.Basing on Ultrasonic synthesis of PMMA experiments,the preparation of Graphene/PMMA composites by ultrasonic were researched.The SEM,IR,XRD graph of Graphene/PMMA composites prepared by Ultrasonic-initiated fall in line with composites in situ polymerization.The TG and DTG curves of composites prepared by Ultrasonic-initiated are not closely representative of composites in situ polymerization:compared with those produced by BPO,the distribution of free radicals produced by Ultrasonic-initiated is more homogeneous to prevent unsaturated polymer.The electrical conductivity of the composites increases from 10^-14 S/cm to1.13×10^-1 S/cm with incorporation of only 1 wt.%graphene into PMMA The results show that graphene distributed in the composite would be better when the ultrasonic and supercritical carbon dioxide fluid were injected.