Abstract:

The friction properties of polyurethane elastomers are of great significance in areas such as marine, automotive, and biomedical applications. However, the fine design of friction properties of such materials through chemical modification strategies still has urgent needs in research and application prospects. In this work, p-phenylene diisocyanate(PPDI) and polytetramethylene ether glycol(PTMG) were used, and the PPDI-based polyurethane elastomers with different degrees of cross-linking were synthesized through varing the molar ratio of two chain extenders of 1,4-butanediol and trimethylolpropane. Results of the Fourier transform attenuated total reflection spectra(FTIR-ATR), wide-angle X-ray diffraction(WAXD) and differential scanning calorimetry(DSC) indicate that the crystallinity of both hard segment and soft segment in polyurethane elastomer is inhibited with the increase of cross-linking degree. Meanwhile, the results of mechanical test show that the elastic modulus of the material decreases, while the friction coefficient of PPDI-based polyurethane elastomer increases. In addition, the hysteresis loop curve shows that the change in the degree of cross-linking also affects the damping properties of the PPDI-based polyurethane elastomer, and the difference in the damping of the polyurethane elastomer is also reflected in the dependence of the friction performance on the rate. This work therefore proposes that by using different degrees of crossl-inking, the crystallinity of hard and soft segments in PPDI-based polyurethane can be changed, which leads to the difference in the elastic and the loss modulus of the material, and the friction properties can thus be controlled, which provides a simple-to-achieve and effective way for the regulation of frictional properties of PPDI-based polyurethane elastomers.

Key words: polyurethane elastomers, degree of cross-linking, tribology, micro-phase separation, elastic modulus