Rubber is commonly used as a gasket material in pressure cookers due to several advantageous properties, but it's not the only material that can be used. Other materials may not be as prevalent for various reasons, which I'll outline below:
Non-conductivity: Rubber is an excellent electrical insulator, which is essential in preventing any electrical hazards in a pressure cooker that utilizes electricity for heating. Using conductive materials could pose a safety risk if they come into contact with electrical components.
Heat resistance: Rubber can withstand high temperatures without degrading or melting. This property is crucial in pressure cookers, where temperatures can reach and exceed boiling points of water (around 100°C or 212°F). Not all materials can handle such high temperatures without losing their integrity or releasing harmful substances.
Sealing properties: Rubber gaskets can form a tight seal between the lid and the pot of a pressure cooker. This ensures that pressure builds up inside the cooker, enabling efficient cooking and preventing steam from escaping, which could lead to slower cooking times or an ineffective pressure cooking process. Not all materials possess the required elasticity and sealing capabilities.
Food safety: Rubber materials used in pressure cookers are typically food-grade and non-toxic, ensuring they won't leach harmful substances into the food during the cooking process. Alternative materials may not meet the same food safety standards or may not be suitable for contact with food.
Durability and longevity: Rubber gaskets are often durable and can withstand repeated use, exposure to moisture, and high cooking temperatures without significant wear and tear. Some other materials might degrade more quickly under these conditions, leading to a shorter lifespan for the gasket.
While rubber is a common and effective material for pressure cooker gaskets, some modern pressure cookers may use other materials, such as silicone or synthetic rubber compounds, that offer similar advantages. These alternatives might provide better temperature resistance or improved sealing properties while maintaining the necessary non-conductive and food-safe characteristics. The choice of material ultimately depends on the specific requirements of the pressure cooker design and the manufacturer's preference for performance, safety, and cost considerations.