The processing technology of EPP molded products mainly focuses on material foaming and molding. The core processes and characteristics are as follows:

Raw Material Pretreatment

1. Raw Material Selection

Use polypropylene (PP) as the base material, add blowing agents (such as butane, pentane), nucleating agents (talcum powder, etc.), and additives (antioxidants, flame retardants, etc.), and mix uniformly to form special EPP particles.

2. Particle Drying

Remove moisture from raw materials through hot air drying (water content ≤ 0.1%) to avoid bubble defects during foaming.

Pre-foaming Process

1. Physical Foaming Method

Feed raw material particles into a pre-foaming machine, and pass steam (temperature 100-150℃) or hot air to vaporize the blowing agent, forming micro-porous structures inside the particles. The volume expands to 5-50 times the original.

2. Key Controls

Temperature, pressure, and time must be precisely regulated (e.g., steam pressure 0.3-0.5MPa, processing time 30-120 seconds) to obtain pre-foamed particles with uniform density (20-200g/L).

Aging Treatment

Pre-foamed particles need to stand at room temperature for 8-24 hours (aging) to balance the air pressure inside the pores with the external environment, stabilize the pore structure, and prevent cracking during molding.

Molding Processing

1. Compression Molding (Mainstream Process)

Mold Design: Customize metal molds (e.g., aluminum alloy) according to product shapes. The molds must have air holes (diameter 0.2-0.5mm) to discharge steam and air.

Molding Process:

Fill the aged particles into the mold, close the mold, and pass high-pressure steam (0.5-0.8MPa, temperature 110-130℃) to soften the particles and fuse them to fill the mold cavity.

Pass cooling water (10-25℃) for shaping, and demold to obtain molded products.

Advantages: High dimensional accuracy (±0.5mm), suitable for mass-producing structural parts such as cushioning liners and insulation boxes.

2. Extrusion Molding

Heat and melt the raw materials through an extruder, extrude them through a die, and rapidly cool them to form EPP sheets or boards, which can be further cut and thermo-pressed into packaging trays, partitions, etc.

Features: High production efficiency, suitable for preparing large-area and regular-shaped products.

3. Injection Molding

Less used for EPP. Special equipment is required to inject raw materials into the mold, and complex small parts (such as cushioning parts for precision instruments) are directly molded by controlling temperature and pressure, but the cost is high.

Post-treatment

1. Surface Treatment

Carry out anti-static spraying, flame-retardant coating, or paste protective films to improve wear resistance as needed.

2. Cutting Processing

Mill, punch, or laser-cut the compression-molded or extruded parts into specific shapes (such as special-shaped liners, folding box boards).

3. Assembly Integration

Assemble multiple EPP components through hot-melting, gluing, or snap structures to form composite functional products (such as insulated boxes with hinges).

Process Advantages and Application Adaptation

1. Advantages

Customizable density and structure to balance cushioning, thermal insulation, and lightweight requirements.

No harmful substances are released during production, meeting environmental protection requirements.

Waste can be crushed and re-granulated for high recycling efficiency.

2. Typical Applications

Compression molding: Cold chain insulation boxes, cushioning liners for electronic products.

Extrusion molding: Logistics pallets, shelf buffer strips.

Special processes: Carbon fiber-reinforced EPP for high-end air cargo packaging.

Technical Trends

1. Micro-foaming Technology

Improve pore uniformity and reduce density to below 15g/L for lightweight components in drones.

2. Composite Molding

Co-mold with plastics, metals, and other materials to enhance structural strength (e.g., battery pack brackets for automotive logistics).

3. Intelligent Production

Introduce AI to control foaming parameters, improving yield and reducing energy consumption (steam utilization increased by over 20%).