Study On The Correlation Among Structure, Properties And Temperature Of Polyurethane Based On Htbn

The properties of polyurethane are affected by the multistep architecture. Studyon the correlation among structure, properties and temperature of polyurethane plays avery important role in preparing the heat-resistance PU elastomers. In this dissertationfor academic degree, the structure and properties of PU based on the liquid hydroxylterminated polybutadine-acrylonitrile copolymer glycol(HTBN) were studied, and thecorrelation among structure, properties and temperature of polyurethane was alsofurther discussed.The effect of hard segment contents, the diisocyanate type, the chain extender type,the type of polydiols and their molecular weight on structure and properties of PUUwas investigated in detail by FTIR, DSC, TGA and strain-stress machines. The resultsshowed that under the fixed hard segment contents , with an increase in the content ofhard segment, the degrees of hydrogen bonding of PUU increased; the degrees ofmicrophase separation between hard and soft segments decreased; thermostability ofPUU degraded. The degrees of microphase separation of PUU based on TDImaintained high level; tensile strength of PUU based on IPDI reached 17.83MPa; thehighest thermal decomposition temperature of PUU based on TDI came up to 458.8℃.The glass transition temperature(Tg) of soft segment of PUU extended by DMTDAwas -55.2℃, and tensile strength reached 21.92MPa. The first decompostiontemperature of PU extended by BDO was 332. 8℃. Tg of PU extended by PDO was-48.2℃and the tensile strength of PU extended by DEG came up to 12.82MPa. Tg ofPU based on HTPB was -48.2℃; thermostability of PU based on HTBN of differentCN content was similar. Tg of PUU synthesized by PTMG(M=2000) was verylow-down to -74.9℃; the Tg of polyether soft segment was higher than of polyester orHTBN soft segment; with increase of molecular weight, Tg of soft segment is higher;the PUU based on HTBN showed outstanding heat resistance.The paper took PUU based on the soft segment(HTBN) and hard segment(DMTDA and TDI) as the research object, and the correlation among structure, properties andtemperature of polyurethane-ureas was investigated by means oftemperature-dependent FT-IR spectroscopy. The results showed that with temperatureincreased, the absorption of stretching vibration of NH hydrogen bonded gradualydecreased; the band site of NH hydrogen bonded shifted to higher wave numbers andhalf width of absorption band was significantly expanded. The absorption of bendingvibration of NH hydrogen bonded decreased too and the band site of NH hydrogenbonded shifted to lower wave numbers. The C=C in aromatic ring shifted to lowerwave numbers. The absorption of stretching vibration of urea C=O hydrogen bondedgradualy decreased; the band site of urea C=O hydrogen bonded had hardly anychange at all. The result of curve fitting for carbonyl region of PUU showed that withthe temperature increased, the contents of ordered hydrogen bonded carbonyl groupgradually decreased while the contents of disordered hydrogen bonded carbonyl groupfirst increased and then decreased gradually higher than 150℃; the degree ofmicro-phase separation decreased. At the same time, the hard domain of PUU wasdissociated under heating, and tensile strength of material was decreased quickly withthe temperature improving;but decreasing tendency of tensile strength became gentlybeyond 100℃. The mechanical properties under high-temperature environmentmainly depended on the physicochemical reaction of soft domain of PUU.