Synthesis And Performance Of Degradable And Self-curable Hyperbranched Epoxy Resins

Hyperbranched epoxy resins(HEP)have been widely used to modify traditional bisphenol A epoxy resins(DGEBA)due to their low viscosity,high branching degree,high activity and good processability.However,the crosslinking networks of cured HEP are difficult to be degraded and recycled.In this work,a kind of degradable and self-curable epoxy-ended hyperbranched polymers(DSEHP-n)was synthesized by molecular design,and the mechanism of self-curing and degradation of DSEHP-n were invesitagced.The strengthing and toughening mechanism and degraded properties of DSEHP-n/DGEBA composites were also studied.The results in detail are shown as follows:(1)Synthesis and characterization of DSEHP-n.Here we have prepared a series of degradable and self-curable thermosetting epoxy-ended hyperbranched polymers(DSEHP-n,n=3,5,7 and 11)by a reaction between glycidol and isocyanate-ended hyperbranched polymers(IHP-n).The IHP-n were synthesized by a click reaction between 2,2',2"-(1,3,5-hexahydro-s-triazine-1,3,5-triyl)benzyl mercaptan(HT-BM)and toluene-2,4-diisocyanate(TDI).The structures of HT-BM,IHP-n and DSEHP-n were characterized by ~1H-NMR,FT-IR and matrix-assisted laser desorption-ionization time-of-flight mass.At 110?~200?,the carbamates in DSEHP-n are broken to amino groups,then amino groups reacted with epoxixes resulting the self-curing.The self-cured DSEHP-n films showed high adhesion strength(Class 1)and very strong pencil hardness(6H)and wear resistance increased with the increase of molecular weight of DSEHP-n.It is interesting that the self-cured films could be degraded completely in comfortable condition into some renewable monomers.(2)Performances and mechanism of degration of DSEHP-n/DGEBA composites.The mechanical performances of DSEHP-n/DGEBA composites increased firsty and then decreased with the increase of content and molecular weight of DSEHP-n.The best results are shown by 12wt%DSEHP-5/DGEBA.Compared with pure DGEBA,the tensile,bending and impact strength of 12wt%DSEHP-5/DGEBA composites were improved by 64.8%,38.1%and 93.7%.DSEHP-n has obvious effect on DGEBA which was consistent with the in situ strengthing and toughening mechanism.The degradation degree of DSEHP-n/DGEBA was significantly improved with the increase of DSEHP-n content,and the degradation degree of 12wt%DSEHP-n/DGEBA reached 100%.The degradation products and degradation mechanism have been studied.