Mondur® 501

Mondur 501 prepolymer must be stored in tightly closed containers and protected from contamination with moisture and foreign materials, which can adversely affect processing. It will react slowly with water to form ureas and carbon dioxide gas, which may cause sealed containers to expand and rupture. Partially filled containers should be blanketed with dry nitrogen. Storage temperatures should be maintained between 24° to 35°C (75° to 95°F). Within this range, lower storage temperatures will maximize the storage life.
Mondur 501 prepolymer must not be allowed to freeze. Exposure to temperatures less than the recommended storage conditions, even for short periods of time, can result in the formation of solid material. Appropriate precautions must be taken during shipment and storage. Prolonged storage of solid or partially solid Mondur 501 prepolymer may result in the formation of MDI dimer in amounts which exceed its solubility in the prepolymer at normal storage temperatures. This can make the product unusable.
If solids should form because of exposure of Mondur 501 prepolymer to low temperatures, it may be possible to reliquify the product by reheating. Use a well-ventilated oven for the minimum time necessary to render it clear. The temperature of the product should not exceed 60°C (140°F). Agitation or drum rollers are recommended to avoid excessive local heating, which will degrade the product. Significant amounts of MDI dimer may form during the heating process. As a result, the remelted prepolymer may be cloudy, and the processing behavior and/or properties of the final product may be affected.
The shelf life is six months after receipt of material by customer, when stored in sealed original containers under conditions stated above.