n-Octadecane, also known as PCM28, is a straight-chain alkane with the chemical formula C18H38. It is a colorless, odorless solid at room temperature, melting at around 28°C. n-Octadecane is part of the paraffin hydrocarbon family and is typically obtained from petroleum. This compound is notable for its thermal stability and low volatility, which make it useful in various applications, including as a phase change material (PCM) for thermal energy storage. Its high latent heat of fusion allows it to absorb and release significant amounts of heat, making it ideal for temperature regulation.