The thermoplastic panel surface has extremely high tensile, bending strength and impact toughness, and does not deform. It has excellent chemical stability against the atmosphere, rainwater, and media such as general concentrations of acids, alkalis and salts. The surface is smooth, UV-resistant, maintains its shine, does not discolor, is easy to clean, and is especially suitable for various vehicle compartment advertisements. The thermal conductivity of the thermoplastic panel is about 0.23 W/m.K while the rigid polyurethane foam has a thermal conductivity of 0.018-0.028 W/m.K, and the overall heat transfer coefficient K can be lower than 0.3 W/m.K. Water resistance: both sides of the thermoplastic panel are impermeable, having excellent water resistance, ensuring no leakage in the entire vehicle compartment. After repair, no obvious repair marks remain, which is incomparable with steel or aluminium panels. Environmental performance: the thermoplastic panel surface contains no volatile or corrosive substances, and the sandwich insulation panels are filled with polyurethane foam material, making it green and environmentally friendly.