PMMA Supercritical Foaming Granule

Lost foam casting (also known as full mold casting) is one of the most advanced casting processes in the world at present. It is to paint the foam model similar in size and shape to the casting with refractory coating, bury it in dry sand and pour it with molten metal to vaporize the model , a new casting method that forms castings after the molten metal solidifies.  This casting process is more environmentally friendly and efficient, and is called the green casting process of the 21st century.  The existing lost foam model materials mainly include the following three types:

1.Expandable polystyrene (EPS) has many carbon slag defects, significantly increased carbon content, and many toxic gases. It is mainly used for low-end products such as gray iron castings.

 2. Copolymer (STMMA) is obtained by copolymerization of styrene and MMA. Compared with EPS, the carbon slag defects are reduced, but there are still certain effects, especially for low carbon steel, mainly used for ductile iron and ordinary cast steel  and other low-end products;

 3. EPMMA is only produced by Chung’s Chemical in Japan. It is used in the high-end precision alloy casting product market, such as military industry, aerospace and other fields, but has not entered Chinese market due to technical blockade and high price. 

With the development of lost foam casting technology, EPS and STMMA are prone to defects such as bright carbon and surface carburization when they are applied to cast steel, especially low-carbon alloys, making them unable to fully meet the development needs of lost foam casting.  On the contrary, the third material EPMMA has lower total carbon content and more complete thermal decomposition because there is no benzene ring structure in the molecule, which can well solve the defects of bright carbon and surface carburization during lost foam casting, 

In addition, its decomposition product is mainly gas, making the poured sand very clean, with good fluidity, and can be reused.Therefore, in the near future, EPMMA will replace EPS and STMMA as the main model materials for lost foam casting. However, all three materials mentioned above have a fatal drawback, which is that the foaming process uses volatile alkanes as foaming agents. These alkanes have a flammable and explosive risk, and have a certain impact on the environment, producing carbon dioxide greenhouse gases.To solve the above problems, GMF adopts the supercritical carbon dioxide physical microcellular foaming process to prepare PMMA foaming granules. The foaming process is not only safe and environmentally friendly,and also uses organic small molecule acrylates without benzene ring structure as  the basic unit of the new material for lost foam casting, so the carbon content is lower, and the decomposition is more complete at high temperature, which greatly reduces the generation of carbon slag and benzene poisonous gases in the thermal decomposition products, and is more suitable as the shape material of lost foam casting  , especially high-end casting products such as low-carbon alloys.