Preparation Of Branched Cardanol–based Epoxy Resin Containing A Cyclotriphosphazene Core And Properties Of Its Crosslinking Polymers

Cardanol-based epoxy resin has good mechanical properties and thermal stability,excellent chemical resistance,high binding property,low shrinkage and biodegradability and other advantages,which have been widely used in industrial applications.The cyclotriphosphazene derivatives not only have the properties of high heat resistance and halogen-free flame retardancy,but also have the hydrolytic resistance.Therefore,functionalized epoxy cardanol derivatives are prepared through the organic combination of cardanol and ring three polyphosphazene in this article which has excellent thermal stability,flame retardancy and biodegradability.The preparation method and properties of the cured product were also studied.First,a new cyclotriphosphazene derivatives with six-armed cardanol was prepared by using bio-based cardanol and hexachlorocyclotriphosphazene,and the based-cardanol epoxy resin(EHCPP)was synthesized by the epoxidation of HCPP using the H2O2/HCOOH system,epoxy value is 6.5;its structure was characterized by NMR and FT-IR spectrum methods,which were in accord with the expected structure.Low molecular polyamide(P651)and cardanol modified amine(CA)as curing agent of epoxy resin for heat curing,with the help of FT-IR and rotational rheometer to detecte the polymer curing behavior,and predict their curing operation window;Then,the thermal properties of the cured material were studied.The research results show that the introduction of phosphazene ring into bio-based epoxy resin significantly improves the thermal stability and flame retardancy of its crosslinkink polymers.Compared with P1,the crosslinking density of P2 and P3 has been improved with the introduction of the curing agent while P2 and P3 maintaining its good thermal stability,mechanical properties at the same time,tensile properties of P2 and P3 are respectively increased to 981 KPa,1091 KPa from 46.7 Kpa,The contact angles of polymers is range from 90? to 103?,showing certain hydrophobicity.The copolymer of epoxy resin and two kinds of amine curing agent has better performance,taking P2-2(40% P651)as an example,the 5% weight loss temperature of of P2-2 is 311.5 ?,char yield Yc is10.4% at 850 ?,the glass transition temperature Tg is 18.6 ?,the tensile strength and elongation was 0.83 MPa and 52.9 %,respectively.Secondly,a new type of bio-based UV-curing acrylic resin(AEHCPP)was synthesized by acrylic modified EHCPP,and the structure was characterized by NMR and FT-IR spectrum methods.The UV curings was prepared with three propylene glycol diacrylate TPGDA and Trimethylolpropane triacrylate(TMPTA)as the diluent.Photopolymerization kinetics of different curing system were studied using P-DSC analysis method,and the maximum polymerization rate and final conversion rate of C=C in different UV-curing systems were successful calculated.At the same time,the curing process of the UV-curing system was determined by FT-IR,and the curing time is 10 min;and the thermo properties of the cured films were also investigated.The results showed that the heat stability and flame retardancy of the cured AEHCPP were higher than that of the conventional bio-base acrylic resin,while the addition of diluent TPGDA and TMPTA did not significantly discrease the thermal stability of polymer.The calculated limit oxygen index LOI of polymer without adding any diluent was 28.7,the addition of 10wt% TPGDA and 40wt% TMPTA polymer LOI were 26.7 and 29.6,respectively.It can be found that the addition of diluent TMPTA can keep flame retardant properties of polymers.With the addition of diluent,the crosslinking density and the glass transition temperature of UV cured films were improved to a certain extent,and the mechanical properties of the polymer were improved obviously.The tensile strength of the polymer was improved while the addition of diluent decreased the elongation at break,such as the addition of 30wt% TPGDA and 40wt% TMPTA polymers respectively show the maximum tensile strength of 5.3 MPa,13.9 MPa,at the same time,their elongation is respectively 11.3%,1.9%.In addition,the refractive index measurement results show that the UV cured film had good optical properties and their refractive index in the range of 1.5544 to 1.6020.