| Epoxy resin,as an important thermosetting polymer,has excellent dielectric properties,low shrinkage,strong adhesion,good flexibility and stability.At present,the main epoxy resin on the market was bisphenol A epoxy resin（DGEBA）.Since bisphenol A was a reprotoxic R2 substance,some countries had banned bisphenol A as a raw material for the production of polymers or polymer products.Therefore,it was necessary to develop a kind of excellent performance epoxy resin.In this paper,acrylopimaric-based epoxy resin（APA-ER）and maleopimaric-based epoxy resin（MPA-ER）were prepared from rosin.Then the curing kinetics and curing process of APA-ER and MPA-ER were studied.Finally,the multiwalled carbon nanotubes（MWCNTs）and cork powders（Corks）were mixed with two rosin-based epoxy resins respectively.The influence of MWCNTs and cork powders on the mechanical properties and thermal properties of rosin-based epoxy resin were studied,and the toughening and flame retardant mechanism of MWCNTs and cork powders were explored.The main results were presented as follows:1.Using methyl nadic anhydride（NMA）as curing agent,APA-ER/NMA and MPA-ER/NMA prepolymers were prepared.The results showed that the total enthalpy changes were 109.0 and 150.4 J/g,average activation energy were 48.81 and 58.25kJ/mol,reaction series were 0.96 and 0.93,pre-exponential factor were 1.52×106and1.44×107min-1,respectively,of curing reaction of APA-ER/NMA and MPA-ER/NMA.The first-order kinetics equations of curing systems of APA-ER/NMA and MPA-ER/NMA were established,respectively.It could be used to simulate the curing process and process conditions of rosin-based epoxy system.2.Using NMA as curing agent,APA-ER and MPA-ER as matrix after heating and curing by stages.The research of mechanical properties showed that the impact strength,young’s modulus and bending modulus of MPA-ER were 5.84 kJ/m2,233.78and 2851 MPa and increased by 100%,163%and 182%,respectively,compared to APA-ER.Further research on the thermal properties showed that the storage modulus,glass-transition temperature and initial decomposition temperature of MPA-ER were slightly higher than those of APA-ER.The peak heat release rate（PHRR）and carbon residue rate were 376 k W/m2 and 5.45%,respectively.The PHRR of MPA-ER decreased by 28%,while carbon residue rate increased by 343%,respectively,compared to APA-ER.It also showed that the highly cross-linked structure of tri-functionality MPA-ER with good mechanical strength,thermal stability and flame retardancy.3.Using NMA as curing agent,the MWCNTs with different contents were added into APA-ER and MPA-ER,and cured by heating in stages.The mechanical properties of MPA-ER/MWCNTs were higher than those of APA-ER/MWCNTs.When the content of MWCNTs was 1.2%,the mechanical properties of MPA-ER/MWCNTs（1.2）were the optimal,and the impact strength,young’s modulus and bending modulus were15.11 kJ/m2,333.21 and 4087 MPa,respectively.The research on the thermal properties showed the addition of MWCNTs increased the thermal stability of APA-ER and MPA-ER.The PHRR and carbon residue rate of APA-ER/MWCNTs（1.5）and MPA-ER/MWCNTs（1.2）were 389 kW/m2,2.23%and 324 kW/m2,9.18%,respectively.Compared with APA-ER and MPA-ER,the PHRR decreased by 25%and 14%,respectively,while the carbon residue rate increased by 81%and 68%,respectively.Moreover,the MPA-ER/MWCNTs（1.2）had better thermal stability and flame retardance than APA-ER/MWCNTs（1.5）.4.Using NMA as curing agent,the cork powders with different particle sizes were added into APA-ER and MPA-ER,and cured by heating in stages.The mechanical properties of MPA-ER/Corks were better than those of APA-ER/Corks.Moreover,when the cork particle size was 200-300 mesh,the mechanical properties of MPA-ER/Corks（200-300）were the optimal,and the impact strength,young’s modulus and bending modulus were 10.16 kJ/m2,428.05 and 2252 MPa,respectively.The research on the thermal properties demonstrated that the addition of cork particles improved the thermal stability of APA-ER and MPA-ER significantly,and MPA-ER/Cork（200-300）had the best flame retardant effect.The PHRR and carbon residue rate were 287 kW/m2and 11.39%respectively.Compared with MPA-ER,the PHRR decreased by 24%,and the carbon residue increased by 109%.And the fire combustion index was the lowest,which was 0.83 kW·m-2·s-1.The flame retardant effect of cork powder on rosin-based epoxy resin was remarkable,the main reason was that the flame retardant of cork particles on rosin-based epoxy resin was synergistic effect of solid flame retardant and gas phase flame retardant. |
