What is the term for those plastics that will melt under fire conditions?

The term that describes plastics that will melt under fire conditions is thermoplastic. Thermoplastics are a category of polymers that become pliable or moldable at high temperatures and solidify upon cooling. This characteristic means they can be reshaped multiple times upon heating, but it also implies that they will lose structural integrity and potentially melt in a fire. This behavior can lead to hazards in a fire situation, as they can drip, run, or emit toxic fumes when burned.

The other options do not accurately describe this property. For example, thermodynamic refers to the branch of physics that deals with heat and temperature, and their relation to energy and work; it is not specific to plastic behavior. Thermosupple is not a recognized term in this context and does not pertain to the properties of materials under fire conditions. Similarly, isothermal refers to processes or reactions that occur at a constant temperature and is not relevant to the melting characteristics of plastics in fire situations. Understanding the properties of different materials, such as thermoplastics, is essential for firefighters in assessing and managing the risks associated with fires.