PU (polyurethane) and PET (polyethylene terephthalate) foams exhibit significant differences in multiple aspects:
Chemical Structure and Composition
PU foam is a polymer material synthesized through the reaction between isocyanates and polyols. Its molecular structure contains carbamate groups, endowing it with high design flexibility. By adjusting the proportions and types of raw materials, PU foams with diverse performance characteristics can be produced. In contrast, PET foam is based on polyethylene terephthalate, which is obtained via the esterification and polycondensation of terephthalic acid and ethylene glycol. As a thermoplastic polyester - based foam, it features a regular molecular chain structure, ensuring high stability.
Physical Properties
Density and Hardness：PU foam has a broad density range, spanning from a few kilograms per cubic meter to several hundred kilograms per cubic meter, and can be fabricated into soft, semi - rigid, and rigid forms. Soft PU foam, characterized by excellent elasticity and flexibility, is commonly applied in sofas, mattresses, and other cushioning products. Rigid PU foam, with its high hardness and strength, is well - suited for thermal insulation applications. PET foam, on the other hand, has a relatively low density, typically ranging from 30 to 150 kg/m³. It offers high hardness and strong rigidity, providing reliable structural support while maintaining a lightweight nature.
Thermal Insulation and Flame Retardancy：PU foam, especially the rigid variety, demonstrates excellent thermal insulation properties due to its low thermal conductivity, making it a popular choice for building and industrial insulation. However, conventional PU foam is flammable and requires the addition of flame retardants to enhance its fire resistance. PET foam also possesses certain thermal insulation capabilities and inherently exhibits good flame retardancy. Notably, it does not readily produce drips when burning, enhancing overall safety.
Chemical Resistance and Weather Resistance：PU foam shows good oil resistance but may degrade when exposed to strong acids, alkalis, and other aggressive chemicals. Prolonged exposure to ultraviolet radiation, high temperatures, and humidity can also lead to performance deterioration. In contrast, PET foam boasts exceptional chemical corrosion resistance, effectively withstanding common acids, alkalis, and organic solvents. Its superior weather resistance enables it to maintain stable performance across various climatic conditions.
Processing Technology
PU foam is typically manufactured using the foaming process. This involves mixing raw materials and incorporating a foaming agent, allowing the mixture to react and expand within a mold or designated space. Process parameters can be fine - tuned to control the foam's structure and properties. PET foam, conversely, is mainly produced through extrusion or compression molding. The PET raw material is first heated to a molten state and then shaped into foam sheets or products via molds. This process demands precise control over temperature and pressure.
Application Fields
PU foam enjoys extensive applications. Soft PU foam is utilized for cushioning and filling in furniture, automotive interiors, and similar products. Rigid PU foam finds use in building wall insulation, refrigerator cold storage insulation, and other thermal insulation scenarios. PET foam, by contrast, is predominantly employed in sectors with stringent requirements for material strength, dimensional stability, and flame retardancy, such as the production of wind turbine blades, aerospace composite structural components, and high - speed train interior panels. It enables weight reduction while ensuring structural integrity and safety.