Preparation And Properties Of Polyurethane And Graphene Oxide/Polyurethane Materials

In this paper,4,4-diphenylmethane diisocyanate(MDI),polytetramethylene ether glycol(PTMG)and 1,3-propanediol(PDO)were used as raw materials to synthesize thermoplastic polyurethane(TPU)with a prepolymer method.90 min was determined as the best reaction time of the prepolymer at 80?.Under the nitrogen atmosphere at room temperature,the prepolymer would not present a significant decrease in isocyanate(-NCO)content for 24 h.At the same time,the effect of hard segment content on TPU performance was explored by FTIR,DSC,mechanical performance testing and other means.The results showed that when hard segment content increased,the degree of hydrogen bonding of TPU,glass transition temperature,hard segment melting temperature,tensile strength,tear strength,hardness,the modulus increased and the crystalline melting temperature and elongation at break of the soft segment decreased.In the range of 33%-45% of the hard segment content,the TPU exhibited a "sea-island" structure,and increased with the hard segment content.The degree of microphase separation gradually increased.In order to study the influence of small changes in the structure of the chain extender on the degree of hydrogen bonding,thermal and mechanical properties of the TPU,the prepolymer was synthesized with MDI and PTMG.Under the condition that the prepolymer had the same-NCO content,ethylene glycol(EG),1,3-propanediol,1,4-butanediol(BDO),1,6-hexanediol(HDO),1,2-propanediol(PG)were used to synthesize TPU,after FTIR,DSC and mechanical performance test,the result showed that as the length of the molecular chain of the even-numbered carbon chain extender increased,the degree of hydrogen bonding of the synthesized TPU decreased gradually;The hydrogen bonding degree of TPU synthesized by chain extender of odd carbon atoms was lower than that of TPU synthesized by adjacent even carbon atoms.;the structural regularity of the hard segment of the TPU synthesized by the chain extender with pendant groups was broken,and the degree of hydrogen bonding was the lowest.TPU with 1,4-butanediol as the chain extender had the lowest glass transition temperature of-44.4 ?,while TPU with 1,6-hexanediol as the chain extender had the highest tensile strength of 36.9 MPa.For the same prepolymer,EG and BDO were mixed in different proportions for chain extension,and FTIR,DSC and mechanical properties were also analyzed.The results showed that the degree of hydrogen bonding of the TPU prepared after mixing the two was lower than that as a chain extender alone,and the closer to 1: 1 the molar ratio between the two was,the lower the degree of hydrogen bonding was.After EG and BDO were mixed,the melting temperature of hard segment,tensile strength,tear strength,hardness,and modulus of the TPU were reduced,and the glass temperature and elongation at break increased.In particular,when the mixing ratio n(EG): n(BDO)= 1: 2,the tensile strength was increased to 29.2 MPa,and the elongation at break was reduced to 353%.In this paper,graphene oxide(GO)was grafted with isophorone diisocyanate(IPDI)to obtain modified graphene oxide(iGO).MDI,PTMG,BDO,iGO were used to prepare graphene oxide/Polyurethane composites(iGO/PU)by in-situ polymerization.Tested for iGO and iGO/PU by FTIR,Raman,XRD,TGA,electronic tensile machine,etc.The results showed that the grafting rate at 24 hours at 60 ? was higher than that at 12 hours.Freeze-drying method is more favorable to retain the unreacted-NCO on iGO than nitrogen drying at 60?.With the increase of iGO addition,modulus and hardness of iGO/PU increased,elongation at break decreased,tensile strength and tear strength increased first and then decreased.When the amount of iGO added was 0.6wt%,the tensile strength of iGO/PU increased from 9.5 MPa to 14.7 MPa for pure PU.