No, it is generally not safe to put plastic in a microwave oven unless it is specifically labeled as microwave-safe. Heating plastic in a microwave can cause it to melt, warp, or release harmful chemicals into your food. When exposed to high temperatures, certain types of plastic can leach chemicals into the food, which can be hazardous to your health.
If you need to heat or reheat food in the microwave, it is best to use microwave-safe containers made of glass, ceramic, or microwave-safe plastic specifically designed for microwave use. These materials are less likely to warp or release harmful substances when exposed to microwave radiation.
Always check the packaging or labels of containers to ensure they are safe for use in the microwave. It's important to prioritize safety and follow the manufacturer's instructions to avoid any potential hazards.