What is the envelope of a hot air balloon typically made of?

The envelope of a hot air balloon is typically made of nylon due to its favorable properties. Nylon is lightweight, strong, and has good tear resistance, which is essential for the durability and safety of the balloon during flight. Additionally, nylon can withstand the high temperatures of the heated air inside the envelope, which is crucial for maintaining lift. Its ability to be coated or treated for improved performance against ultraviolet light also makes it suitable for outdoor use, thus extending the life of the balloon.

Other materials like plastic may not possess the necessary heat resistance and strength required for a hot air balloon envelope. Rubber, although elastic, does not provide the structural integrity needed, and canvas, while durable, is heavier and has less ability to withstand high temperatures and is not commonly used in modern hot air balloon construction.