Preparation And Properties Of Epoxy Resin Dielectric Composites

During the working process of the laser printer,the organic photoconductor drum(OPC drum)can convert optical signals into electrical signals and is an indispensable photosensitive element in printers;The UCL is one of the important coatings on the OPC drum.It is a dielectric material that can enhance the charge storage capacity of the OPC drum.At present,the common commercial UCL matrix material is nylon.Because nylon has a high water absorption rate,the dielectric properties and resistivity of such UCL materials are prone to change during long-term operation in a humid and hot environment,which affects the stability of printing.Therefore,the development of UCL materials with low water absorption and stable resistivity and dielectric properties under humid and hot conditions is an important way to improve the performance of OPC drums.Epoxy resin(EP)has excellent mechanical properties,low curing shrinkage,corrosion resistance,and low water absorption.The low water absorption rate enables it to maintain stable performance in long-term hot and humid environments.However,EP has a low dielectric constant,which cannot meet the requirements of OPC drum UCL materials for dielectric constant.Based on the demand of OPC drum UCL for high-performance polymer materials,this paper optimizes the curing agent and curing process of epoxy resin,and investigates the influence of different dielectric fillers on the dielectric properties,resistivity and performance stability of EP under humid and hot conditions.In-depth explore the influence of silicone modification on the properties of EP composites.Using the co-precipitation of chitosan(CS),titanium dioxide(Ti O₂)and carbon nanotubes(CNTs)were used to prepare T/M mixed fillers,the effect of the mixed filler on the dielectric properties,mechanical properties,resistivity and water absorption of epoxy resin composites was studied.Firstly,the dielectric properties and resistivity of common commercial OPC drum UCL materials were measured,and it was found that the dielectric constant was 19.4 and the dielectric loss was 0.23 at an electric field frequency of 10² Hz,the dielectric constant is 6.6and the dielectric loss is 0.05 at 10⁷ Hz,and the volume resistivity was 2.25×10¹⁵?·cm.Use80?deionized water to simulate the humid and hot conditions to test the stability of the dielectric properties and resistance performance of the composite material in the humid and hot environment.The test results show that the common commercial OPC drum UCL material has a water absorption rate of 5.2%after being immersed in deionized water at 80?for 5 hours,The dielectric constant becomes 324.8 at 10² Hz and 15.7 at 10⁷ Hz;the volume resistivity becomes 5.1×10⁹?·cm,down six orders of magnitude.Choose bisphenol A glycidyl ether type epoxy resin as the matrix,three common amine curing agents:imidazole,curing agent 593,curing agent W93 are used to cure EP,the effect of the type and amount of curing agent on the gelation time,mechanical properties and resistivity of EP was explored to optimize the curing temperature and curing time suitable for the industrial production of OPC drum UCL materials.The dielectric filler titanium dioxide(Ti O₂),silicon dioxide(Si O₂),barium titanate(Ba Ti O₃),and aluminum oxide(Al₂O₃)were compounded with EP to obtain a dielectric composite material,the test results show that Ti O₂ has the most obvious effect on improving the dielectric constant of EP.When the content of Ti O₂ is 120phr,the dielectric constant of EP dielectric material is 7.9 at an electric field frequency of 10² Hz and6.8 at 10⁷ Hz,and the dielectric loss is below 0.041.After being immersed in deionized water at 80?for 5 h,the water absorption rate of EP dielectric material is 1.3%,the dielectric constant under the electric field frequency of 10²Hz is changed from 7.9 to 10.4,the dielectric loss is now 0.12,and the volume resistivity is changed from 1.30×10¹⁵?·cm to 2.75×10¹³?·cm.Compared with commercialization nylon-based OPC drum UCL materials,it exhibits lower water absorption under humid and hot conditions,and the stability of volume resistivity and dielectric constant has been improved.The EP matrix is modified with phenyltrimethoxysilane(PTMS)and?-glycidoxypropyltrimethoxysilane(GPTMS),and the modified EP is compounded with 120 phr of Ti O₂ to prepare a dielectric composite material.The impact strength of the composite material with a mass ratio of GPTMS to EP of 10:90 is increased to 14.8 k J/m²,and the bending strength is increased to 145.4 MPa.When the mass ratio of PTMS to EP is 10:90,the modified dielectric composite material has an impact strength of 13.5 k J/m² and a flexural strength of133.0 MPa,after the modified dielectric composite material is immersed in deionized water at80°C for 5 hours,the volume resistivity of EP dielectric material changed from 5.34×10¹⁵?·cm to 3.75×10¹⁴?·cm;the dielectric constant of the EP dielectric material at an electric field frequency of 10²Hz changes from 7.6 to 8.4,10⁷Hz changes from 6.7 to 8.4,and the dielectric loss can be kept below 0.071.Titanium dioxide(Ti O₂)and carbon nanotubes(MWCNTs)are co-precipitated by the co-precipitation of chitosan(CS)to prepare a mixed filler titanium dioxide/carbon nanotube(T/M),the influence of the content of MWCNTs in the mixed filler T/M on the dielectric properties,mechanical properties,electrical resistivity and water absorption of EP was studied.It was found that the content of MWCNTs has little effect on the mechanics and water absorption of the composite material,but it can change the dielectric properties and volume resistivity of the composite material.The results show that when the content of MWCNTs is 1.2 phr,the volume resistivity of the epoxy resin composite is 1.46×10¹⁴?·cm,the dielectric constant is 11.5 and the dielectric loss is 0.024 at 10² Hz.When the content of MWCNTs is 3phr,the volume resistivity of the epoxy resin composite is 5.71×10¹¹?·cm,the dielectric constant is 46.6 and the dielectric loss is 0.245 at 102 Hz.The dielectric constant of the epoxy resin composite material can be adjusted in a larger range under the lower content of the filler,and the dielectric loss can be kept low.