Biobased High Performance Thermosetting Resins

Since the first synthetic resin was successfully synthesized in 1872,polymer materials have become indispensable for human life and prduction.However,as the preparation of polymer materials relies heavily on petrochemical resources,nowadays,the crisis of petrochemical resources poses a great threat on it.Therefore,using renewable biobased raw materials to replace petrochemical resources for prqparing polymer materials has become the most effective way for its sustainable development.Thermosetting resins are a kind of materials which are insoluble and infusible after molding,so they are difficult to be recycled and depend on petrochemical resources more heavily.Therefore,research on biobased thermosetting resins has far-reaching significance.At the same time,the rapid developments of cutting-edge fields such as aerospace,electronic information and new energy also demand more on the performance of thermosetting resins.However,the renewable carbon contents of existing biobased thermosetting are low,and their integrated performances including thermal properties,mechanical properties,flame retardancy,etc.,are need to be further improved.This thesis focuses on using biomass as raw material to prepare high-performance thermosetting resins with high renewable carbon content and excellent integrated performances.Firstly,a trifunctional allyl compound,tris(4-allyl-2-methoxyphenyl)phosphate(TEUP)with 100%renewable carbon content was synthesized from renewable eugenol through one-step method using water as the solvent.TEUP was then used to prepare flexible and transparent thiol-ene polymer networks TEUP-SH via solvent-free thiol-ene "click" photopolymerization with various multifunctional thiols.The influences of the thiol functionality from 2 to 4 on structure and integrated performances were systematically researched.Among them,TEUP-SH4 shows the best thermal and mechanical properties;specifically,its glass transition temperature(Tg)is as high as 35℃,and its tensile strength and modulus are as high as 19.8±0.6MPa and 601.6±22.4MPa,respectively;at the same time,it still maintains a high flexibility.The nature behind these outstanding integrated performances is attributed to the unique structure of TEUP which is rich in aromatic structure and the very high crosslinking density of TEUP-SH4 network.Secondly,a new epoxy monomer with a precise structure,bis(2-methoxy-4-(oxiran-2-ylmethyl)phenyl)furan-2,5-dicarboxylate(EUFU-EP),was synthesized from two biobased green and low toxic compounds(2,5-furandicarboxylic acid and eugenol),and the renewable carbon content of EUFU-EP is as large as 100%.In addition,a new biobased epoxy resin,EUFU-EP/MHHPA,was prepared by using methyl hexahydrophthalic anhydride(MHHPA)as the curing agent and 2-ethyl-4-methylimidazole as the curing accelerator.The curing reactivity and integrated performances including thermal and mechanical properties as well as flame retardancy of the cured resin were systematically researched,and compared with those of epoxy resin(DGEBA/MHHPA)based on petrochemical resources consisting of commercial diglycidyl ether of bisphenol A(DGEBA),MHHPA and 2-ethyl-4-methylimidazole.Results show that EUFU-EP/MHHPA and DGEBA/MHHPA have similar curing reactivity,but cured EUFU-EP/MHHPA resin shows better thermal properties,rigidity and flame retardancy than cured DGEBA/MHHPA resin.Specifically,Tg of EUFU-EP/MHHPA resin is as high as 153.4℃,the storage modulus at 50℃ increases by 19.8%,meanwhile both peak heat release rate and total heat release reduce by 19.0%.The nature behind these outstanding integrated performances is attributed to the unique structure of EUFU-EP,which is not only rich in aromatic structure,but also has furan ring.Thirdly,a biobased epoxy monomer,tris(2-methoxy-4-(oxiran-2-ylmethyl)phenyl)phosphate(TEUP-EP),with high renewable carbon content(100%)was synthesized from renewable eugnol with a sustainable process,TEUP-EP was then blended with 4,4’-diaminodiphenylmethane(DDM)to develop a new biobased epoxy resin(TEUP-EP/DDM).The integrated performances of TEUP-EP/DDM resin were studied and compared with those of petroleum-based diglycidyl ether of bisphenol A(DGEBA)/DDM resin.Compared with DGEBA/DDM resin,TEUP-EP/DDM resin has much better integrated performances,which not only exhibits about 26℃ higher Tg,24.4%or 57%increased flexural strength or modulus,but also shows outstanding flame retardancy.Specifically,the limiting oxygen index(LOI)increases from 26.5%to 31.4%,UL-94 grade improves from no rating to V-0 level;moreover,the peak heat release rate and total heat release reduced by 63.1%and 57.4%,respectively.These excellent integrated properties are resulted from the trifunctional structure of TEUP-EP which is rich in aromatic structure.Forthly,TEUP was then used to replace petroleum-based 2,2’-diallylbisphenol A(DBA)partly or totally to modify 4,4’-bismaleimidodiphenylmethane(BDM),and thus four kinds of bismaleimide(BMI)resins(BDTP or BTP)were developed.The influence of the TEUP content on structure and integrated performances of BMI resins was systematically researched.Among them,BTP resin,which was prepared by only TEUP and BDM shows the best integrated properties.Compared with traditional DBA modified BDM resin(BD),BTP not only has a higher renewable carbon content(45%),but also shows an about 70℃ higher Tg(>380℃),the combined advantage of which is the best one among biomass-modified bismaleimide resins ever reported so far.Meanwhile,BTP resin exhibits excellent flame retardancy,LOI increases from 30.7%of BD to 39.6%;the peak heat release rate,total heat release and total smoke production decrease by 63.1%,72.9%,and 77.2%,respectively.In addition,BTP resin has excellent mechanical and dielectric properties.These excellent integrated properties indicate that TEUP is a multifunctional modifier of BMI,which not only overcomes the poor processability and brittleness of BDM,but also imparts BDM resins with excellent flame retardancy,heat resistance,mechanical and dielectric properties This is because of the unique T-type trifunctional chemical structure of TEUP and its effect on the cross-linking structure of BDM.