Polycarbonate (PC) Material Guide

Introduction

Polycarbonate (PC) is a high-performance engineering thermoplastic known for its exceptional impact resistance, optical clarity, dimensional stability, and heat resistance.

Compared with general-purpose plastics such as ABS or polypropylene, polycarbonate offers superior mechanical performance, making it widely used in demanding applications including medical devices, electronics, automotive components, and industrial equipment.

For injection molded parts requiring strength, transparency, and reliability, PC is one of the most commonly selected engineering plastics.

Key Properties of Polycarbonate Material

Polycarbonate combines several properties that make it suitable for precision injection molding applications.

1. Excellent Impact Resistance

One of the most important advantages of PC is its outstanding impact strength.

Compared with many common plastics:

PC components can withstand sudden impacts and mechanical stress without cracking easily.

Common applications:

• Protective covers
• Safety components
• Electronic housings
• Automotive parts

2. High Heat Resistance

Polycarbonate maintains its mechanical properties at elevated temperatures.

Typical characteristics:

• Glass transition temperature: approximately 147°C
• Continuous service temperature: around 115–130°C depending on grade

This makes PC suitable for applications exposed to:

• Heat cycles
• Electrical components
• Automotive environments
• Industrial equipment

3. Optical Transparency

Transparent PC grades provide excellent light transmission while maintaining much higher impact resistance than acrylic.

Compared with acrylic:

Property	PC	Acrylic
Impact Resistance	Excellent	Moderate
Transparency	High	Excellent
Heat Resistance	Higher	Lower
Scratch Resistance	Lower	Higher

Because of this balance, PC is often selected when durability is more important than maximum optical clarity.

4. Dimensional Stability

Polycarbonate provides good dimensional accuracy after molding.

Advantages include:

• Low shrinkage variation
• Good stiffness
• Stable performance under temperature changes

This makes PC suitable for precision components with tight tolerances.

Polycarbonate Material Advantages and Limitations

Advantages of PC

1. High Strength-to-Weight Ratio

PC provides strong mechanical performance while remaining lightweight.

2. Excellent Electrical Insulation

PC is commonly used for:

• Electrical housings
• Connectors
• Insulation components

3. Good Chemical Resistance

PC performs well against many oils, greases, and mild chemicals.

Limitations of PC

Despite its advantages, PC also has several design considerations.

1. Lower Chemical Resistance Compared with Some Engineering Plastics

PC can be affected by:

• Strong alkalis
• Some solvents
• Hydrocarbons

Material compatibility should always be verified for chemical exposure applications.

2. Higher Processing Requirements

PC requires more careful molding control compared with commodity plastics.

Important factors include:

• Drying temperature
• Melt temperature
• Mold temperature
• Injection speed
• Cooling control

Improper processing may cause:

• Silver streaks
• Internal stress
• Cracking
• Surface defects

Polycarbonate Injection Molding Considerations

1. Material Drying

Polycarbonate is hygroscopic and absorbs moisture from the environment.

Before molding, PC resin typically requires drying to prevent:

• Hydrolysis
• Reduced mechanical strength
• Surface defects

Typical drying conditions:

• Temperature: 120°C
• Time: 3–5 hours

(Actual parameters depend on resin grade and supplier recommendations.)

2. Recommended Mold Temperature

PC generally requires higher mold temperatures compared with materials such as ABS.

Typical range:

80–120°C

Higher mold temperatures can improve:

• Surface finish
• Flow performance
• Internal stress reduction

3. Melt Temperature

Typical processing range:

280–320°C

Too low:

• Poor filling
• Weld line weakness
• High residual stress

Too high:

• Material degradation
• Discoloration

4. Gate Design Considerations

Gate design is critical for PC injection molding.

Recommended practices:

• Avoid sharp transitions
• Use sufficient gate size
• Minimize flow restrictions
• Consider stress-sensitive areas

Poor gate design can create:

• Flow marks
• High residual stress
• Optical defects

5. Wall Thickness Design

Uniform wall thickness is important for PC parts.

Recommended:

• Avoid sudden thickness changes
• Use ribs instead of thick sections
• Maintain consistent cooling conditions

Common issues from uneven thickness:

• Sink marks
• Warpage
• Internal stress

Common Polycarbonate Injection Molding Defects

1. Stress Cracking

Cause:

• Chemical exposure
• Excessive residual stress
• Poor processing conditions

Solutions:

• Optimize mold temperature
• Reduce shear stress
• Improve part design

2. Sink Marks

Cause:

• Thick sections
• Insufficient cooling

Solutions:

• Optimize wall thickness
• Add ribs
• Improve cooling design

3. Flow Marks

Cause:

• Incorrect injection parameters
• Low melt temperature

Solutions:

• Adjust injection speed
• Increase mold temperature

4. Bubbles and Voids

Cause:

• Moisture
• Poor packing
• Improper drying

Solutions:

• Improve drying process
• Optimize holding pressure

Polycarbonate Applications

1. Medical Devices

PC is widely used in medical applications because of:

• Transparency
• Impact resistance
• Sterilization compatibility (depending on grade)

Examples:

• Diagnostic equipment housings
• Medical instrument components
• Protective covers

2. Electronics

Applications include:

• Device housings
• Optical components
• Connectors
• Protective covers

3. Automotive

PC is commonly found in:

• Lighting components
• Interior components
• Sensor housings

4. Industrial Equipment

Examples:

• Machine guards
• Control panels
• Safety covers

PC vs ABS: Which Material Should You Choose?

Property	PC	ABS
Impact Resistance	Excellent	Good
Heat Resistance	Higher	Moderate
Cost	Higher	Lower
Surface Finish	Good	Excellent
Processing Difficulty	Higher	Easier

Choose PC when:

• High impact strength is required
  
• Temperature resistance matters
  
• Transparency is needed

Choose ABS when:

• Lower cost is important
  
• Easy processing is preferred
  
• Moderate performance is acceptable

Design Tips for PC Injection Molded Parts

For successful PC injection molding:

Recommended:

• Maintain uniform wall thickness
  
• Add proper draft angles
  
• Reduce sharp corners
  
• Optimize rib thickness
  
• Consider residual stress during design

Avoid:

• Extremely thin sections without flow analysis
  
• Sharp internal corners
  
• Poor gate locations
  
• Excessive molding stress

How AccuMolds Supports Polycarbonate Injection Molding Projects

Polycarbonate parts require careful coordination between:

• Material selection
• Mold design
• Injection parameters
• Quality control

At AccuMolds, we support customers with:

• Precision injection mold design
• DFM analysis
• Mold design optimization and engineering support
• Prototype validation
• High-volume production molding

Our engineering team helps optimize PC parts for manufacturability, performance, and long-term reliability.

Conclusion

Polycarbonate remains one of the most versatile engineering plastics for applications requiring strength, transparency, and heat resistance.

However, successful PC injection molding depends on proper material selection, part design, mold engineering, and process optimization.

Working with an experienced injection molding partner can significantly reduce manufacturing risks and improve final product performance.
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