Polystyrene (PS) is a type of thermoplastic formed from the polymerization of styrene.

Characteristics of PS Plastic

  • Form: Virgin PS plastic is hard, transparent, and odorless.
  • Color: Naturally, PS plastic is clear white, but it can be easily colored to meet specific needs.
  • Properties: PS plastic has good electrical insulation, water resistance, high mechanical strength, and is easy to process.

General-purpose PS is primarily used for low-value products due to its relatively low durability. Packaging constitutes the majority of its applications: cups, bowls, and trays are produced through molding and thermoforming methods. The low melting point and high flowability of PS allow for the high-speed production of thin-walled parts with good dimensional accuracy. However, in many cases, PS has been replaced by Polypropylene (PP), Polyethylene (PE), and Polyethylene Terephthalate (PET, polyester). These plastics offer superior mechanical performance in thin-walled packaging.

Polystyrene (PS), also known as plastic number 6

Types of PS Plastic

  1. HIPS (High-Impact Polystyrene)
    HIPS is a tougher version of PS plastic, created by adding approximately 15% polybutadiene during production. This makes the plastic more flexible and impact-resistant, but reduces its tensile strength. HIPS is transparent and easy to dye. Applications of HIPS include products such as razors, office supplies, disposable items, promotional gifts, toys, and laboratory equipment. This plastic is suitable for injection molding, reproduces surface details well, and avoids the need for complex printing.
  2. EPS (Expanded Polystyrene)
    EPS is expanded PS plastic, containing about 5% PS and the rest is air. EPS is lightweight and has a closed-cell structure, providing insulation and product protection in packaging. Common densities of EPS are 16, 32, and 48 kg/m³. Applications of EPS include food containers, insulation and soundproofing materials in construction, and buoyant materials in floating nets and rafts. EPS is also used for making helmets and in composite panels.
  3. XPS (Extruded Polystyrene)
    XPS is PS plastic that is foamed during extrusion, creating sections of closed-cell foam. XPS has a higher density and better compressive strength than EPS, and is commonly used in construction applications. XPS typically comes in colors such as blue, pink, and green.

Recycling and Reuse

PS plastic can be recycled and is often marked with recycling code number 6. However, recycling PS and EPS presents challenges due to transportation costs and complex processing procedures. Compression systems are used to make the transportation of EPS more efficient. Recycled materials are commonly used to produce new products such as packaging, office supplies, and plant pots. Although EPS is lightweight, which helps reduce the energy required for transportation, it is not always the most efficient option.