The glass we use is heat resistant BOROSILICATE GLASS. Typically, the glass composition is about 81% silica, 13% boric oxide, 4% sodium oxide/potassium oxide, and 2% aluminium oxide by weight and meets all specifications of Type 3.3 expansion. The glass begins to soften around 821 °C, and annealing point is 565 °C.
It is a synthetic fluoropolymer commonly known as teflon. Its melting point is 327 °C, but its properties degrade above 260 °C. PTFE has very low friction and high heat resistance, chemically inert.
It is a thermoplastic polymer, is rugged, has good resistance to fatigue and resistant to many chemical solvents, bases and acids. PP has a melting point of 320 degrees Fahrenheit (160 degrees Celsius).