Curing Kinetics Of Epoxy Resin/Alumina Insulation Composites For Ultra High Voltage Electrical Equipment

Epoxy resin is a kind of synthetic resin with excellent performance.It has good adhesion,high insulation and strong heat resistance.It is unmatched by other synthetic resins and has an irreplaceable role in industry.The UHV large-size basin-type insulators in China are prepared using an epoxy resin/alumina composite system.The formula composition,physical and chemical properties and curing process of the system have a significant impact on the quality of the insulator.Epoxy resin as the base material of the basin insulator has excellent insulation properties,but it has poor compatibility with the filler alumina,its segments contain hydroxyl groups,ether bonds and other polarities,and the group with strong activity leads to curing The molecular segment of the compound has poor flexibility,and there are problems such as large internal stress and brittleness,which may cause the insulator to break down and damage under high pressure.This is a technical bottleneck restricting the development of UHV insulation equipment.Important practical value.Differential scanning calorimetry(DSC)method studies the curing kinetics through the change of thermal enthalpy.It is easy to operate,requires few samples,has a wide temperature test range,and can easily control the temperature change rate.It can obtain the curing behavior of the composite system and can be quantitatively described.The conversion rate,so the relationship between the heat flow rate,conversion rate and temperature of the composite system is explored through the DSC method through isothermal and non-isothermal curing,and the change of the thermal enthalpy and structure of the composite system during the curing process is revealed to optimize the process of the actual production process Provide theoretical guidance.In this paper,the non-isothermal method is first used to study the curing reaction process of epoxy resin/alumina composite system with different alumina content and different curing agent content,and then the isothermal test is used to supplement the curing kinetics of the system.Under non-isothermal test,the system curing has the characteristics of double peaks,and the curve is divided into peak curing to divide it into front curing and rear curing.The increase of alumina content reduces the apparent activation energy E_a of the epoxy resin in the first stage of curing,and the apparent activation energy E_a of the later stage of curing decreases slightly and then rises rapidly.The increase in the content of the curing agent changes the DSC curve from a double peak to a single peak.The apparent activation energy E_a of the front curing of the sample is basically unchanged,and the E_a of the rear curing of the sample with low curing agent content decreases significantly as the content of the curing agent increases.The enthalpy change of the isothermal test increases slightly as the curing temperature rises.The analysis results show that the surface of the filler alumina has a small amount of amino groups,and reaction control dominates in the front-end process,but diffusion control and reaction control have a synergistic effect in the back-end process.The actual curing process conforms to the SB(m,n)model,and the autocatalytic reaction plays a leading role in the curing reaction.