Final answer:
Pipe joint materials must be insoluble in water, nontoxic, and applicable to ensure a secure connection. They should also have properties like nonflammability, electrical conductivity in aqueous solutions, and ionic bonding, depending on the application.
Step-by-step explanation:
The requirements for the material used in pipe joints are that the material must be insoluble in water, nontoxic, and can be applied to the pipe joints to ensure a secure and durable connection. Materials that are soluble in water would not provide a reliable seal as they could dissolve over time. Toxic materials cannot be used in piping systems that carry potable water or other sensitive substances due to potential health hazards. Moreover, the material should have properties such as nonflammability and the ability to conduct electricity if aqueous solutions pass through it, plus it should form an ionic bond to maintain a strong joint. Other properties like high melting points and high boiling points may also be important depending on the specific application of the pipe.