Çok kısımlı poliüre kopolimerlerinde diizosiyanat yapısının ve yumuşak kısmı oluşturan oligomerin zincir uzunluğunun yapıya ve fiziksel ve mekanik özelliklere etkisinin incelenmesi

: Bora İNCİName of the Student: Material Science and EngineeringProgram of Study: Investigation of the effect of diisocyanate symmetryThesis Titleand soft segment molecular weight on thestructure-property behavior of non-chain extended,segmented polyureas.AbstractThe effect of diisocyanate structure and soft segment molecular weight on thestructure-property behavior of novel, non-chain extended, segmented polyureaswere investigated. These novel polyureas were synthesized by the stoichiometricreactions of diisocyanates and amino functional oligomers. Amine terminatedpoly(tetramethylene oxide) (PTMO) and poly(ethylene/butylene) (PEB) oligomerswere synthesized by using a two step process from commercially availablehydroxyl terminated PTMO and PEB with number average molecular weights of2000 and 3340 g/mol, respectively. The diisocyanates used in the preparation ofpolyureas were 1,6-hexamethylene diisocyanate (HDI), 1,4-phenylenediisocyanate (pPDI), 1,4-trans-cyclohexyl diisocyanate (CHDI) and 4,4?-dicyclohexylmethane diisocyanate (HMDI). All polymerization reactions wereconducted at room temperature, by the dropwise addition of oligomer solutiononto the diisocyanate solution under strong agitation. Hard segment contentswere varied around 6.0 wt% for PTMO based polyureas and 4.5 wt% for PEBbased polyureas calculated from the reaction stoichiometry. Atomic ForceMicroscopy (AFM) images of all PTMO based polyureas possessed microphaseseparated morphology with thread-like hard domains in the soft segment matrix.PTMO based polyurea films had a tensile strength of approximately 30 MPa andelongation at break of ~1000 %, which are comparable to the commercial chainextended thermoplastic elastomers with much higher hard segment contents.DMA scans of PEB based polyurea films also indicated microphase separation,in spite of only 4.5% hard segment content. It also displayed a fairly long rubberyplateau extending between -25 ºC and 150 ºC.