Thermal Decomposition Products of Expanded Polystyrene Pattern in Evaporative Pattern Casting of Cast Iron

Thermal decomposition products collected from a thermal decomposition gas layer at various positions in a columnar pattern were evaluated by gas chromatography to clarify the formation process of the products. Cast iron melt was poured into an expanded polystyrene pattern, and the amount of thermal decomposition products in liquefied resin and gas were evaluated. Fractions of styrene monomer and molecules larger than the monomer were measured. The amount of thermal decomposition gas did not change even if the position of collection changed. Large amounts of liquefied resin were collected from the middle of the columnar pattern. With decreasing distance of the collection position from the gate, the larger was the styrene monomer fraction. Liquefied resin collected around the final part of melt filling was difficult to evaporate due to the large fraction of molecules larger than the monomer. Such liquefied resins have the potential to develop carbon defects in the EPC process.