Synthesis And Properties Of Novel Degradable Cycloaliphatic Epoxy Resins

The insolubility and infusibility of highly crosslinked three-dimensional network endow the cured cycloaliphatic epoxy resins with excellent mechanical strength,thermal stability,chemical-heat resistance and adhesion property,which confer on epoxy resins long-term service stability under harsh operating conditions.Nevertheless,the insoluble and infusible nature hinders the after-treatment of the products cured by conventional epoxy resins.At the same time,large amounts of wastes generated from epoxy resins also give rise to increasing pressure on ernvironment.As a consequence,the research and development of epoxy resins with controllable degradability play an important role in the disassembly of discarded products,the recovery of precious components and metal as well as environmental protection.Furthermore,because of fossil resources shorage and environmental pollution,biobased epoxy resins derived from renewable resources draw more and more attentions compared with conventional epoxy resins based upon fossil feedstocks.In this thesis,several novel cycloaliphatic epoxy resins with degradable property were designed and synthesized through incorporating chemically or thermally labile groups from some raw materials including biobased furfural and ?-terpineol into the backbone of epoxy resins.The degradation behaviors and mechanism of the cured products were emphatically investigated.The main contents and results are summarized as follows:A novel cycloaliphatic epoxy resin(Epoxide-S)containing sulfite linkage was synthesized from thionyl chloride and cyclohex-3-enyl-l-methanol.The homopolymers of Epoxide-S and the commercial cycloaliphatic epoxy resin ERL-4221 as well as their copolymers were prepared by thermo-initiated cationic ring-opening polymerization in the presence of KWM-753.The results show that,due to the thermally liable sulfite groups in the epoxy network,the cation-cured Epoxide-S starts to decompose at 185?,which is significantly lower than that of the cation-cured ERL-4221(323?).Moreover,after co-curing between Epoxide-S and ERL-4221,the thermal degradation temperatures of the copolymers are tunable in the range from 185 to 323? by varying the ratio of two monomers.A novel cycloaliphatic epoxy resin(Epoxide-TE)containing tertiary ether linkage was synthesized from diphenyldichlorosilane and biobased raw material ?-terpineol.After curing with HMPA,the intrinsic tertiary ether linkages and the tertiary ester linkages generated at the crosslinked sites are both introduced into the network,endowing the anhydride-cured Epoxide-TE with lower onset decomposition temperature(269?)than that of the anhydride-cured ERL-4221(323?).Morever,in comparison with the anhydride-cured ERL-4221,the anhydride-cured Epoxide-TE has increased storage modulus below T%from 2.19 to 2.41 GPa.In addition,through varying the Epoxide-TE content of the copolymers,crosslinking density,glass transition temperatoe and thermal degradation temperature of the crosslinked networks are adjustable.A novel cycloaliphatic epoxy resin(Epoxide-P1)containing phosphonate linkage was synthesized from phenylphosphonic dichloride and cyclohex-3-enyl-1-methanol.The cured products of Epoxide-P1 were prepared through anhydride curing and thermo-initiated cationic ring-opening polymerization,respectively.For the anhydride-and cation-cured Epoxide-P1,storage modulus in glassy region,Tg-DMA and crosslinking density are 2.43 and 2.42 GPa,171 and 113?,0.53 and 1.06×10-3 mol cm-3,respectively.Due to the introduction of phosphonate linkage,the anhydride-and cation-cured Epoxide-P1 show a lower onset decomposition temperature of 283 and 228?,respectively,which can meet the temperature requirement as degradable epoxy rcsins.Purthcrmore,the anhydridc-cured Epoxide-P1 has a LOI value of 24.2,increasing by 33%than that of the anhydride-cured ERL-4221(18.2).The shear strength of cation-cured Epoxide-P1 at room temperature is 6.65 MPa^ and decreases rapidly when heating temperature rises to 210?,indicating that the products cured by Epoxide-P1 can be conveniently disassembled over 210?.A novel cycloaliphatic epoxy resin(Epoxide-A)containing acetal linkage was synthesized from bio-based raw material furfural and commercial cyclohex-3-enyl-1-methanol.Compared with ERL-4221,the product after curing with HMPA exhibits a similar glass transition temperature(186?)and onset decomposition temperature(over 300?)but significantly higher mechanical modulus(2.51 GPa),crosslinking density(1.35×10-3 mol cm-3),shear strength(4.70 MPa)and lower coefficient of thermal expansion(64.2 ppm K-1).Acid degradation tests show that the anhydride-cured Epoxide-A can readily degrade in an acidic aqueous solution due to the labile acetal linkages distributed within the cross-linked network,and the degradation apparently accelerates with the increase of the solution acidity.After acid hydrolysis for 60 min and 120 min in MSA solution with the strongest acidity,the sample losses about 48%and 83%weight,respectively.