Characteristics of copolymer sheet
The copolymer sheets include STMMA and STMMA-FD copolymer sheets (FD sheets for short). STMMA copolymer sheets are mainly used for the casting of ductile iron and steel castings, and the FD sheets are mainly used for the casting of gray cast iron. The copolymer sheets do not contain any flame-retardant ingredients and have the characteristics of low carbon and fewer slags, sufficient combustion, high gas evolution rate, and easy decomposition. Recarburization and carbon defects can be significantly reduced. Compared with EPS sheets, STMMA casting-specific sheets have the following advantages:
(1)Low carbon content, easy decomposition and less recarbonization EPS has a relatively high carbon content (92%), and its molecular structure is a relatively stable benzene ring structure (as shown in Figure 1.3(a)). It is not easy to decompose when heated, EPS is broken and decomposed in a disordered manner, it is not easy to gasify instantly, and residues that are not easy to decompose are generated. STMMA has a small carbon-to-hydrogen ratio (shown in Figure 1.3(b)) and low carbon content (63%)and is broken and decomposed in a zipper-like manner at high temperatures, having more honeycombs inside, which increases the contact area between the material and the air and accelerates the burning rate of the material. The molecular structure contains oxygen atoms. During heating and combustion, oxygen atoms react with carbon atoms to generate gas, so few residues are generated.
(2)Good gasification, few residues, and fewer carbon defects STMMA casting-specific sheets are well gasified, and most foam models are decomposed into products such as CO, CO2, water, and carbides during the casting process. Low molecular gases can escape through the coating layer, so few residues are generated in the foam pattern, Experimental data shows that for EPS and STMMA copolymer sheets of the same density, the residues on the STMMA copolymer sheets under high-temperature casting conditions are about one-tenth of that of the EPS sheets.
(3) Reducing the amount of patching, eliminating secondary processing of castings, and improving the quality of castings. Since STMMA casting-specific sheets have excellent casting properties such as low carbon content, easy decomposition, less recarbonization, good gasification, and fewer residues and carbon defects, castings made of STMMA casting-specific sheets have a high surface finish and less recarbonization and carbon defects, and the machined surface is smooth and flat, and the quality of castings is greatly improved. Only then can casting companies reduce the amount of patching, eliminate secondary processing of castings, and thereby reduce the total production costs of castings. Moreover, the production cycle of castings has also been shortened, thereby achieving the goals of rapid production and delivery. The appearance of the sheets is shown in Figure 1.4, and the sheet production site is shown in Figure 1.5.