Microphase-Separated Structure And MechanicalProperties Of Novel Poly(carbonate)-Based Polyurethanes

摘要

The aliphatic copolymerized poly (carbonate) glycols (PCGs), which have the different number of methylene unit, were prepared and their crystallinities were investigated with wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC). Also, WAXD, DSC and mechanical properties of the polyurethane elastomers (PUEs) prepared from the PCGs, 4,4'-diphenylmethane diisocyanate, and 1,4-butanediol were investigated. The used PCGs had hexamethylene (C6) and trimethylene (C3), tetramthylene (C4), or pentamethylene (C5) unit between carbonate groups in various composition ratio (C4/C6, C5/C6, C3/C4=0/100, 50/50, 100/0). The number average molecular weighs of these PCGs were 2000. The glass transition temperature of the homo-PCG decreased from - 31.5 °C to -55.6 °C with increasing methylene unit length from C3 to C6. The glass transition temperature of the copolymerized PCGs decreased with increasing content of the component with long methylene unit. C3-homo-PCG was amorphous, while C4- and C6-homo- PCGs exhibited strong crystalline peaks. C5-homo-PCG also did crystalline peaks, but its peak intensity was weaker than for C5- or C6-PCG. However, randomly copolymerized PCGs C4/C6, C5/C6, and C3/C4=50/50 were amorphous. The PUEs were prepared with 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD). In the all WAXD profiles of the PUEs, no particular crystalline peaks were observed. The glass transition temperature of the homo-PCG based PUEs decreased from - 7.0 °C to —21.1 °C with increasing methylene unit length from C3 to C6. The glass transition temperature of the copolymerized PCGs was between that of each homo-PCG based PEU. In stress-strain curves steep increases in the stress related to the elongation-induced crystallization of the PCG were observed for the 4002-PUE and 6002-PUE. On the other hand, the 5002-PUE gave relatively lower stress increase than for the 4002-PUE or 6002-PUE, and no steep increase in the stress was observed for the 3002-PUE. The behaviors in the copolymerized PCG based PUEs were not observed. These results were indicate that an odd number of the unit length of homo-PCG based PUEs and the copolymerized PCG based PUEs were more amorphous than an even number of the unit length of homo-PCG based PUEs.