Polyurethane (PU) sheets were fabricated by the reaction of polypropylene glycol (PPG) and liquid diphenyl methane diisocyanate (L-MDI) with various trimethylol propane (TMP) contents. The Tg value was varied from 34.8 ℃ to 49.9 ℃ according to the TMP content. As the content of TMP was increased from 4 to 12 wt%, the modulus of the PU sheet was increased from 322 MPa to 423 MPa, its tensile strength was increased from 10.6 MPa to 14.8 MPa, and its elongation was decreased from 62.8% to 49%. In case of acoustic properties, the sound speed of PU sheet was increased while its attenuation coefficient was decreased as the content of TMP was increased. The fabricated PU sheet was stable in water bath for 4 weeks.

가교제인 trimethylol propane(TMP)의 함량변화에 따라 다양한 폴리우레탄(PU) 평판을 제작하였다. DMA 측정을 통하여 TMP 함량에 따라서 PU의 Tg는 34.8 ℃에서 49.9 ℃로 증가를 확인하였다. TMP의 함량이 4%에서 12%까지 증가함에 따라 탄성률은 322 MPa에서 423 MPa로 증가하였고, 인장강도는 10.6 MPa에서 14.8 MPa로 다소 증가하였으며, 신율은 62.8%에서 49%로 감소하였다. 음향특성의 경우, TMP의 함량이 증가함에 따라 가교 정도가 높아지며, 음속은 증가하였으나 음향감쇠계수는 감소하였다. 제작한 PU 평판은 4주간 수중에서 안정적임을 보여 주었다.

Keywords: PU sheet; crosslinking; acoustic window; attenuation coefficient