Preparation And Properties Of Non-isocyanate Polyurethane Based On Five-membered Cyclic Carbonate

Polyurethane(PU)is a widely used synthetic polymer material and plays an important role in many fields such as national defense,transportation,medicine,and construction in the form of plastic,foam,coatings,elastomers,fibers,adhesives,and sealants.However,the traditional polyurethane raw material isocyanate is toxic and does not conform to the concept of green chemistry.Therefore,non-isocyanate polyurethane(NIPU)prepared from cyclic carbonate and amine has become a new research direction.In this paper,the route of preparing glycerol carbonate(GC),then synthesizing cyclic carbonate(CC),and finally the synthesis of non-isocyanate polyurethane(NIPU)was adopted.The investigation results indicated that the catalyst prepared from natural waste eggshells as raw material adding dolomite and talcum powder by calcined at 1250°C for 4h showed high catalytic ability.The prepared catalyst can be used in the synthesis of glycerol carbonate and had a good activity.The optimal conditions for the synthesis of glycerol carbonate were obtained: both the conversion rate of glycerol and the purity of GC about 95% was achieved at5 wt.% of the amount of catalyst,3:1 of the molar ratio of DMC to glycerol and 80°C of 2h reaction.Bicyclic carbonates(CC)were prepared from sebacic acid and glycerol carbonate in the presence of and 4-dimethylaminopyridine(DMAP)as catalyst,1-(3-dimethylaminopropyl)-3-ethylcarbodiimide(EDC)as corresponding agent and dichloromethane(DCM)as solvent.The optimum reaction conditions of bicyclic carbonate were as follows: the molar ratio of GC to sebacic acid was 3:1,the molar ratio of EDC to sebacic acid was 3:1,the molar ratio of DMAP to sebacic acid was 1:2,and the reaction time was 16 hours under the protection of N2 at room temperature.Under the optimum conditions,the yield and purity of bicyclic carbonate were 84.81% and 90.59%,respectively.Non-isocyanate polyurethane(NIPU)was synthesized from bicyclic carbonate(CC)and1,6-hexanediamine(HMDA)with 1,5,7-triazadiracyclic[4,4,0]decane-5-ene(TBD)as catalyst and N,N-dimethylformamide(DMF)as solvent.The optimum reaction conditions of NIPU were as follows: the molar ratio CC to HMDA was 1:1,the amount of catalyst TBD was 3% of the total mass of the reactant,the amount of DMF was 3m L and the reaction time was 24 hours under the protection of N2 at 140?.NIPUs with different molecular weights were prepared through the reaction of different kinds of amines with CC.The addition of TBD increased the molecular weight of NIPU and the Mn of tetraethylenepentamine(TEPA)reached 8371 g/mol.All NIPUs had good thermal stability and need to be enhanced in mechanical properties.Introducing epoxy resin E51 into NIPU to obtain hybrid NIPU(HNIPU)effectively improved its strength.The tensile strength of HNIPU obtained by using4,4-Methylenebis(cyclohexylamine)(MBCHA)reached 16.4 MPa and the strength of HNIPU prepared from TEPA was 14.2 MPa,and the elongation at break was 102%.