Preparation and properties of transparent rigid polyurethane

Transparent rigid polyurethanes with different hard segment (HS) contents were prepared using 4,4'-dicyclohexylmethane diisocyanate, polytetrahydrofuran polyether, high hydroxyl-value polyether polyol, and trimethylolpropane as raw materials. The mechanical properties, optical and dynamic mechanical properties, and the thermal resistance of the transparent rigid polyurethanes with different HS contents were studied using an electronic universal testing machine, a hardness tester, a light transmittance and haze tester, a dynamic mechanical analyzer, and a thermogravimetric analyzer, respectively. The results showed that as the HS content increased, the tensile strength and hardness of the polyurethane gradually increased. The maximum tensile strength reached 62.0 MPa and the Shore D hardness at 20 ℃ had a maximum value of 84. The visible light transmittance ranged from 91.06% to 92.08%, and the haze ranged from 1.62% to 1.71%. The glass transition temperature increased gradually, reaching a maximum value of 92.5 ℃. The temperature range with tan δ ≥ 0.5 shifted toward higher temperatures and broadened. The temperature at 5% weight loss exhibited an initial decreasing trend followed by an increase, reaching a minimum of 286.6 ℃. As the HS content increased from 80% to 85%, the thermal decomposition process of the HS shifted from two stages to a single one.