There are some special characteristics for the PU foam used as the core material to meet the stringent
requirements for VIPs, such as a low thermal conductivity, a high open-cell content, a high compressive strength,
ect. The foam used in the study was prepared by a blend polyol, which is a mixture of two types of polyethers with
different OH value, combined with appropriate amount of surfactant, open-cell agent, multiple catalysis, blowing
agent and foam stabilising agent[26]. The reactants were mixed at room temperature, and the mixing speed and
times were 1500 r/min and 8