Polycarbonate and ABS are two of the most widely used engineering thermoplastics for injection molding consumer products, electronics, medical devices, automotive components, and more. But despite their popularity, these two materials have distinct differences when it comes to their properties, molding behaviors, and performance.
This guide provides a detailed comparison of polycarbonate vs. ABS injection molding. We’ll examine the advantages and limitations of each material and process considerations for successfully molding them. With this breakdown of polycarbonate and ABS injection molding properties and capabilities, you can determine which material is optimal for your application requirements.
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Overview of Polycarbonate Injection Molding
Polycarbonate (PC) is an amorphous, transparent thermoplastic known for its unbeatable combination of toughness, temperature resistance, and optical clarity. Key traits include:
- Extreme impact strength and ductility
- Heat resistance up to 130°C
- Transparency and glossy finish
- Dimensional stability
- Flame retardant grades available
Polycarbonate is molded using conventional injection molding with the following process guidelines:
- Melt Temperature: 280-320°C
- Mold Temperature: 80-120°C
- Injection Pressure: 10,000-15,000 psi
- Cycle Time: 45-60 seconds
Polycarbonate molds well and flows easily into thin wall sections. Parts have good replication of mold details with smooth finishes. The material does require proper drying prior to molding to prevent defects.
Common applications of polycarbonate injection molding include automotive lenses, medical devices, transparent components, safety gear, and more.
Overview of ABS Injection Molding
ABS (acrylonitrile butadiene styrene) is an inexpensive engineering thermoplastic known for its strength, rigidity, and impact resistance. Key characteristics include:
- Good tensile and flexural strength
- Heat resistance up to 80°C
- Chemically resistant
- Dimensionally stable
- Various aesthetic finishes
ABS injection molding follows these general processing guidelines:
- Melt Temperature: 220-260°C
- Mold Temperature: 40-80°C
- Injection Pressure: 10,000-15,000 psi
- Cycle Time: 25-50 seconds
ABS flows very well into thin sections but has only moderate replication of fine mold details. Proper drying is critical to prevent defects. The material is also prone to stress cracking.
Common uses include automotive trim, enclosures, toys, appliance housings, pipe fittings, and consumer electronics.
Comparing Polycarbonate vs. ABS Material Properties
Polycarbonate and ABS have distinct differences in their material properties:
| Property | Polycarbonate | ABS |
|---|---|---|
| Tensile Strength | 9,500 psi | 5,300 psi |
| Flexural Modulus | 340,000 psi | 330,000 psi |
| Izod Impact Strength | 12-24 ft-lb/in | 3-5 ft-lb/in |
| Heat Deflection Temperature | 270-290°F | 190-210°F |
| Chemical Resistance | Poor | Good |
| UV Resistance | Poor | Fair |
In summary, polycarbonate exhibits superior impact strength, heat resistance, and ductility compared to ABS but has worse chemical and UV resistance.
Key Considerations for Polycarbonate vs. ABS Injection Molding
There are some important process differences to factor in when injection molding polycarbonate versus ABS:
- Mold Surface Finish: Polycarbonate requires highly polished mold surfaces (SPI A-1 finish) to replicate gloss and clarity while ABS can use textured finishes.
- Dimensional Tolerances: ABS can hold tighter tolerances than polycarbonate.
- Cycle Times: ABS generally allows faster cycle times due to its lower molding temperature and faster solidification.
- Shrinkage: Polycarbonate has around 0.5-0.7% shrinkage versus 0.3-0.6% for ABS.
- Mold Venting: Polycarbonate needs generous vent depths and locations to allow gas escape whereas ABS vents more easily.
- Fillers/Additives: ABS compounds commonly include fillers like glass fiber which can cause tool wear.
Determining Ideal Applications for Each Material
When selecting polycarbonate or ABS for a product, consider factors like:
Polycarbonate is ideal when:
- Extreme impact strength is needed
- End use temperatures exceed 100°C
- Flame retardance is required
- Optical clarity and glossy finish are desired
ABS is preferable when:
- Dimensional stability is critical
- Chemical resistance is needed
- Lower material cost is important
- Textured finishes or colors are specified
By understanding their unique injection molding behaviors and performance traits, you can choose the right material for your application requirements between polycarbonate and ABS.
Conclusion: Key Takeaways on Polycarbonate vs. ABS Injection Molding
- Polycarbonate offers unmatched impact resistance and heat tolerance but lower chemical/UV resistance compared to ABS
- ABS flows easily into thin walls but cannot achieve the same optical properties as polycarbonate
- Polycarbonate molding requires higher temperatures, pressures, highly polished tools, and longer cycles than ABS
- Polycarbonate suits applications demanding strength, heat resistance, clarity while ABS fits needs for precision, aesthetics, cost
- Matching material characteristics to part functions and end-use conditions is crucial when selecting between these two versatile engineering thermoplastics.
