The melting points of various plastics vary greatly, so some, like polyvinyl chloride plastics, can melt at as little as 165 degrees Fahrenheit while others, like the plastic used in Teflon cookware, can only melt at temperatures of about 600 degrees or more. The majority of durable polymers liquefy before 500 degrees.
Polymers, which make up plastics, come in a wide range of chemical compositions. Because of this, some polymers melt incredibly easily while others are nearly hard to melt. Boiling water has a temperature of 212 degrees Fahrenheit, and while sturdy plastics can normally withstand this temperature, soft polymers, such as plastic bags, would melt in the presence of boiling water.