Injection Moulding Polystyrene (PS)

Material Description

Polystyrene (PS) is a versatile and widely used thermoplastic polymer characterized by its transparent or translucent appearance, low cost, and lightweight nature. It is composed of a linear chain of styrene monomers and can be produced in various forms, including solid, foamed, and expanded varieties. PS exhibits excellent electrical insulating properties, making it suitable for applications in electronics and packaging. Its low thermal conductivity, however, makes it less suited for high-temperature environments. PS boasts a good combination of mechanical properties, with high tensile strength and impact resistance, while maintaining ease of processing, such as injection molding and extrusion. Its glass transition temperature is around 100°C, and it exhibits a relatively low melting point of approximately 240°C. PS is susceptible to UV degradation, which may lead to brittleness and yellowing over time, thus necessitating the addition of stabilizers for outdoor applications. Moreover, PS is highly recyclable, contributing to its sustainability in the plastics industry. Overall, Polystyrene’s unique combination of properties makes it a valuable material in a wide range of consumer and industrial applications, from food packaging and disposable utensils to insulation and consumer electronics casings.

Tensile Yield
Modulus (MPa)
Point (°C)
Coefficient of
(x 10^-6 /°C)
Absorption (%)
1020 - 108030 - 502.5 - 3.5100-1200.13 - 0.351.3 - 1.575 - 1150.01 - 0.2

Design Recommendation

Polystyrene is sensitive to cooling rates, so ensure the mold has sufficient cooling channels to maintain a uniform cooling rate across the part. This helps prevent differential shrinkage and ensures dimensional stability. Adequate cooling also reduces the likelihood of part distortion and warpage. Additionally, when designing parts with PS, consider using ribs and gussets to increase stiffness and reduce the risk of flexing or bending. Uniform wall thickness is also essential to maintain part quality and prevent sink marks.

Cost Saving Tip

One effective cost-saving strategy for Polystyrene (PS) in injection molding involves optimizing the design of molds and part geometry. By employing advanced mold design techniques, such as incorporating uniform wall thickness, minimizing undercuts, and reducing the number of intricate features, manufacturers can significantly lower material consumption, cycle times, and overall production costs. Streamlining part designs to eliminate unnecessary details and ensuring uniform wall thickness not only reduces the amount of PS required but also results in shorter cooling times, faster cycle rates, and improved part quality. Additionally, utilizing materials with higher flow rates and incorporating efficient gating and runner systems can further enhance production efficiency, ultimately leading to substantial savings in PS usage and operational expenses.