Copolymer beads for lost foam casting are polymer bead materials specifically developed for the lost foam casting process. The core material is STMMA (styrene–methyl methacrylate copolymer resin) and its derivative grades, including EPS–EPMMA composite modified materials. These materials are advanced alternatives to conventional EPS (expanded polystyrene).

Main Types of Copolymer Beads and Their Characteristics:

1. STMMA Base Grade

This grade is based on the copolymerization of styrene (ST) and methyl methacrylate (MMA). It features low residual carbon content (approximately 63%), moderate gas generation, and excellent moldability. The material effectively suppresses carbon-related defects and delivers smooth casting surfaces.

Typical Applications:

Low-carbon steel, ductile iron, alloy steel, and complex foam pattern geometries.

2. STMMA-FD Grade

The STMMA-FD grade features a carbon content of approximately 82% and a foaming temperature range of 85–95 °C. It offers stable foaming behavior, effectively reducing metal back-spray and gas-related defects such as porosity during pouring.

Typical Applications:

Cast iron components and general mechanical parts

3. STMMA-FC Grade

The STMMA-FC grade offers high strength and excellent moldability, making it well-suited for complex foam pattern structures while ensuring dimensional accuracy of the final casting.

Typical Applications:

Valves, pipe fittings, and automotive components.

4. EPS–EPMMA Composite Modified Material

This composite material combines EPS and EPMMA, offering a balance between the two. It is more cost-effective than pure EPMMA, has moldability close to EPS, and features lower residual carbon than EPS.

Typical Applications:

Castings with moderate surface quality requirements and limited budget considerations.