Polycarbonate, or PC, is a transparent, durable, and heat-resistant material widely used in industries like automotive, electronics, and healthcare. In this post, we will explore Polycarbonate’s significance and practical applications in injection molding highlighting its process, advantages, common issues, and design principles.
What is Polycarbonate?
Polycarbonate, often referred to as PC, is a thermoplastic polymer known for its exceptional characteristics. It has gained widespread recognition in various industries due to its impressive combination of physical and chemical properties.
Polycarbonate comes in several types or grades, each tailored to specific applications and requirements. Here are some common types of Polycarbonate:
General-Purpose Polycarbonate (GPC):
This type of PC is suitable for a wide range of applications and is known for its balance of properties, including strength, clarity, and heat resistance. It is often used in consumer goods, automotive parts, and electrical components.
Optical-grade PC is designed for applications where exceptional optical clarity and minimal distortion are essential. It is used in products like eyewear lenses, optical discs, and camera components.
Flame-retardant PC is formulated to meet strict fire safety regulations. It is commonly used in applications where fire resistance is critical, such as electrical enclosures and aerospace components.
This type of PC is formulated to resist ultraviolet (UV) radiation, making it suitable for outdoor applications. It is often used in products like greenhouse panels, outdoor signage, and automotive exterior components.
High-impact Polycarbonate is reinforced to provide even greater impact resistance. It is commonly used in safety equipment, including helmets, face shields, and safety glasses.
A PC that meets medical-grade standards is used in healthcare applications, such as medical devices, IV components, and surgical instruments. It is formulated to be biocompatible and withstand sterilization processes.
Designed for use in the food industry, this type of PC is compliant with food safety regulations. It is used in applications like food containers, kitchenware, and equipment for food processing.
Some PC materials are made from recycled sources, contributing to sustainability efforts. These types of PCs are used in various applications, including eco-friendly consumer products.
Manufacturers can create custom formulations of PCs to meet specific performance requirements. Custom formulations may involve modifications to enhance properties like UV resistance, flame resistance, or chemical resistance.
Properties of Polycarbonate
1.2 – 1.22
Shrinkage Rate (%)
0.4 – 0.7
M75 – M110
Tensile Strength at Yield (MPa)
55 – 75
Elongation at Break (%)
80 – 150
Flexural Modulus (GPa)
2.2 – 2.4
Flexural Strength (MPa)
75 – 100
Drying Temperature (°C)
80 – 100
Drying Time (hrs)
2 – 4
Melt Temperature (°C)
220 – 260
Mold Temperature (°C)
70 – 100
Advantages of Polycarbonate Injection Molding
Exceptional Impact Resistance
PC is known for its exceptional impact resistance. Compared with other plastic materials, It can withstand significant forces without breaking, making it suitable for applications where durability is crucial.
PC is highly transparent, with optical clarity close to that of glass. This transparency is advantageous for products like lenses, windows, and displays. Many other plastics are not as transparent or may require additional processes to achieve clarity.
High Heat Resistance
PC retains its properties at elevated temperatures, making it suitable for components exposed to heat and thermal stress. This advantage is particularly valuable in applications like automotive lighting and electronics, where heat resistance is required.
PC exhibits resistance to various chemicals, which makes it suitable for applications in chemically challenging environments. Not all plastics offer the same level of chemical resistance.
PC serves as an excellent electrical insulator, making it suitable for electrical and electronic components. Some other plastics may not provide the same level of electrical insulation.
Common Issues in Polycarbonate Injection Molding
Polycarbonate can experience significant shrinkage as it cools after injection. This can lead to dimensional inaccuracies in the final part. To mitigate shrinkage, adjust mold design for compensation, lower melt temperature to reduce cooling rate, and apply proper packing and holding pressure during molding.
Warping, or deformation of the part after molding, can occur due to uneven cooling rates or internal stresses. Prevent warping by ensuring uniform cooling, using mold design features like cooling channels, and implementing post-molding annealing processes.
Polycarbonate parts may develop surface defects like blemishes, streaks, or surface haze during molding. Achieve a flawless surface finish by maintaining clean mold surfaces, optimizing processing conditions, and using mold release agents and venting as needed.
Hydrolysis and Degradation
Polycarbonate can be sensitive to moisture and high temperatures, potentially leading to hydrolysis and material degradation. Prevent hydrolysis and degradation by thoroughly drying the material, maintaining temperature control, and considering additives or stabilizers to enhance resistance.
Polycarbonate Injection Molding Process
Polycarbonate injection molding is a manufacturing process used to create various plastic parts and components from Polycarbonate resin. The process typically includes steps such as material preparation, mold design, machine setup, injection of the molten Polycarbonate, cooling, ejection, quality control, and the repetition of these steps for mass production. Proper control of temperature settings, injection parameters, cooling, and cycle times is essential to achieve consistent and reliable results in PC injection molding.
Considerations During Polycarbonate Injection Molding Process
Compared with other plastic injection molding, the polycarbonate injection molding process requires special attention.
Material Drying: Polycarbonate is sensitive to moisture, so proper material drying is critical before processing. Ensure that the polycarbonate pellets are adequately dried to prevent moisture-related defects like bubbles or splay marks.
Precise Mold Temperature Control: Polycarbonate’s high shrinkage rate and sensitivity to cooling can result in warping or dimensional inaccuracies. Therefore, precise mold temperature control is essential to achieve uniform cooling and minimize part stress.
Longer Cooling Time: Polycarbonate parts require adequate cooling time to solidify and maintain their shape. Longer cooling times may be needed compared to some other plastics.
Parameters for PC Injection Molding Process
Here are the typical ranges for some key PC injection molding process parameters for reference. The specifications parameters number need to be adjusted depending on PC types and grade.
Injection Molding Temperature:
Generally, the recommended melt temperature for PC falls within the range of 260°C to 320°C (500°F to 608°F).
The Temperature of the Screw Barrel:
The temperature of the screw barrel is typically set within the range of 260°C to 320°C (500°F to 608°F) to match the melt temperature of the PC material.
Polycarbonate Melt Temperature:
The melt temperature, as mentioned earlier, should be in the range of 260°C to 320°C (500°F to 608°F).
A Constant Temperature of the Barrel:
Maintain a consistent barrel temperature within the same range, typically around 260°C to 320°C (500°F to 608°F).
Mold temperature can vary depending on the specific application, but it is generally set in the range of 70°C to 95°C (158°F to 203°F) for Polycarbonate.
Injection pressure is typically set between 70 MPa and 140 MPa (10,000 psi to 20,000 psi) to ensure proper material flow and filling.
Back pressure can vary but is often set between 2 MPa and 10 MPa (300 psi to 1500 psi) to assist in plasticizing the PC material.
Holding pressure, applied after injection, is typically set between 50% and 80% of the injection pressure to prevent part shrinkage.
Injection speed can vary based on part design and size but is often set in the range of 50 mm/s to 200 mm/s (2 in/s to 8 in/s).
Screw speed varies depending on the machine and material, but it typically ranges from 50 RPM to 200 RPM.
Polycarbonate Injection Molding Design Guidelines
When designing PC injection molding parts, these guidelines help ensure that PC parts meet end-use requirements and maintain high quality.
Aim for a minimum wall thickness of 0.040 inches (1 mm) and a maximum of 0.150 inches (3.8 mm) for PC parts. This range supports thin walls and complex geometries.
Click here to learn about wall thickness design guidelines.
When using ribs for additional strength or support, make the rib thickness between 0.5 and 0.6 times the thickness of the adjoining wall. Avoid using rib heights more than three times the thickness.
Prevent stress concentrations by avoiding sharp corners. Use a corner radius of at least 0.125 inches (3 mm) in PC parts.
Incorporate a draft angle, typically ranging from 0.5° to 1° per side, to assist with part ejection from the mold. Adjust the draft angle as needed based on part shape and mold design.
Optimize gate locations to minimize stress. A mold flow analysis can help determine the most suitable gate location for the specific part and geometry.
Polycarbonate supports a variety of surface finishes, including gloss and high-gloss finishes. Matte finishes can reduce glare, making them suitable for control panel overlays. Non-glossy finishes may be preferred for certain applications like screw caps.
Applications of Polycarbonate Injection Molding
Polycarbonate injection molding finds applications in various industries. Especially due to its excellent optical clarity, it is used for eyewear lenses, optical discs, and components in the optical industry. Here are some of the applications.
Polycarbonate is used for automotive components such as headlamp lenses, interior trim, and window glazing due to its impact resistance and lightweight properties.
It is used in electronic enclosures, connectors, and components due to its electrical insulating properties and heat resistance.
Polycarbonate is employed in medical equipment and devices, including IV connectors, housings, and surgical instruments.
It is used for eyewear lenses, optical discs, and components in the optical industry due to its excellent optical clarity.
Polycarbonate finds applications in aircraft interiors, including windows, panels, and interior components, where lightweight and high strength are essential.
Polycarbonate is used in lighting fixtures, including diffusers and lenses, due to its optical properties and resistance to UV radiation.
In summary, Polycarbonate injection molding is a versatile and widely used manufacturing process known for its ability to produce high-quality parts with exceptional properties. If you have a project that could benefit from Polycarbonate injection molding, don’t hesitate to explore its potential. Whether you’re in the automotive, medical, or any other industry, Polycarbonate could be the solution you need. For reliable Polycarbonate injection molding services, consider reaching out to Zhongde, your trusted partner in manufacturing excellence.
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