Injection Moulding Polypropylene (PP)

Material Description

Polypropylene (PP) is a versatile thermoplastic polymer renowned for its exceptional combination of physical, chemical, and mechanical properties. PP possesses a high melting point, typically around 160-166°C, making it suitable for various industrial applications. This material exhibits excellent chemical resistance, remaining unaffected by most acids, bases, and solvents. Its low moisture absorption rate ensures dimensional stability, even in high-humidity environments. PP is characterized by remarkable tensile strength, typically ranging from 30 to 45 MPa, and a relatively low density, making it both lightweight and durable. Additionally, it displays good electrical insulating properties and a low coefficient of friction. It is worth noting that PP is susceptible to UV degradation, which may limit its outdoor use unless it is appropriately stabilized. In summary, Polypropylene is a cost-effective, readily processable material with a diverse range of properties, making it suitable for applications in industries such as packaging, automotive, textiles, and medical devices.

Tensile Yield
Modulus (MPa)
Point (°C)
Coefficient of
(x 10^-6 /°C)
Absorption (%)
900 - 92025 - 401.0 - 2.5130-1710.10 - 0.222.380 - 1800.01 - 0.1

Design Recommendation

In the case of Polypropylene, a key design consideration is maintaining a proper melt temperature. PP is sensitive to heat, and excessive temperatures during processing can lead to thermal degradation, resulting in material properties degradation. It’s important to carefully control the barrel temperature of the injection molding machine to avoid overheating the material. Additionally, when designing parts for injection molding with PP, aim for a simple and uniform geometry. Avoid sharp corners and intricate features that can lead to stress concentrations. Ensure that the wall thickness is uniform to prevent sink marks and warpage, which can be common issues with PP.

Cost Saving Tip

One effective cost-saving tip for Polypropylene (PP) in injection molding is to optimize the design of the injection mold to reduce cycle times and minimize material waste. This can be achieved by employing techniques such as conformal cooling, which involves designing cooling channels that closely follow the contours of the mold to enhance heat dissipation. Additionally, implementing multi-cavity molds can increase production efficiency by allowing multiple parts to be produced in a single molding cycle, thereby reducing energy consumption and labor costs. By refining the mold design to improve cooling efficiency and maximize production throughput, manufacturers can substantially lower operational expenses associated with Polypropylene injection molding.