What's the disadvantages of casting polyurethane prepolymers ?
Polyurethane (Polyurethane) is an important polymer material that can be used to prepare foams, elastomers, coatings, adhesives and other products.
However, polyurethane prepolymers also have some disadvantages. Here are some possible problems:
Odor generated during the production process: During the preparation process of polyurethane prepolymer, some volatile organic compounds (VOCs) may be released, causing the generation of odor. These odors may have a negative impact on the production environment and usage environment.
Sensitive to moisture: Polyurethane prepolymer is sensitive to moisture and easily absorbs moisture. Moisture may cause the decomposition of the prepolymer and affect its performance and stability, so appropriate moisture-proof measures need to be taken during production and storage.
Flammability: Polyurethane materials may exhibit elevated flammability under some circumstances. Although there are flame retardants that can be used to improve its flame retardant properties, in some specific applications, this is still an issue that needs to be considered.
Poor photostability: When exposed to UV rays for a long time, polyurethane prepolymers may photodegrade, resulting in color changes, surface cracks, and reduction in mechanical properties. Therefore, in applications requiring UV resistance, appropriate additives are required to improve its photostability.
Higher price: The preparation process of polyurethane prepolymer is more complicated and the cost of related raw materials is higher. Therefore, polyurethane products may have a higher price than some other materials.
A drawback of polyurethane prepolymers is that their resistance to high temperatures can be improved by adding calcium carbonate and silica. However, casting-type polyurethane prepolymers are not perfect. Their main disadvantages include:
1. High internal heat generation, with a normal operating temperature range of -40 to 120°C for heat resistance. If long-term action is required under conditions of high-frequency oscillation or high temperature, corresponding modifications must be made in structural design or formulations.
2. At certain temperatures, alcohols, acids, and ketones can cause swelling and degradation of polyurethane prepolymers, while solvents such as chloroform, methylene chloride, dimethylformamide, and trichloroethylene can cause swelling of polyurethane prepolymers at room temperature.
3. Recycling waste is an international challenge and a major environmental issue.