Synthesis and characterization of hydroxyl-terminated polybutadiene modified low temperature adaptive self-matting waterborne polyurethane

Hydroxyl-terminated polybutadiene (HTPB) is a flexible telechelic compound with a main chain containing a slightly cross-linked activated carbon-carbon double bond and a hydroxyl group at the end. Therefore, in this paper, HTPB was used as a terminal diol prepolymer, and sulfonate AAS and carboxylic acid DMPA were used as hydrophilic chain extenders to prepare low-temperature adaptive self-matting waterborne polyurethane (WPU). Due to the fact that the non-polar butene chain in the HTPB prepolymer cannot form a hydrogen bond with the urethane group, and the solubility parameter difference between the hard segment formed by the urethane group is large, the gap of T_g between the soft and hard segments of the WPU increases by nearly 10 °C, with more obvious microphase separation. At the same time, by adjusting the HTPB content, WPU emulsions with different particle sizes can be obtained, thereby obtaining WPU emulsions with good extinction properties and mechanical properties. The results show that HTPB-based WPU with a certain degree of microphase separation and roughness obtained by introducing a large number of non-polar carbon chains has good extinction ability, and the 60° glossiness can be as low as 0.4 GU. Meanwhile, the introduction of HTPB can improve the mechanical properties and low temperature flexibility of WPU. The T_g,s (the glass transition temperature of soft segment) of WPU modified by the HTPB block decreased by 5.82 °C, and the ΔT_g increased by 21.04 °C, indicating that the degree of microphase separation increased. At −50 °C, the elongation at break and tensile strength of WPU modified by HTPB can still maintain 785.2% and 76.7 MPa, which are 1.82 times and 2.91 times those of WPU with only PTMG as soft segment, respectively. The self-matting WPU coating prepared in this paper can meet the requirements of severe cold weather and has potential application prospects in the field of finishing.