Brief Introduction of PC/ABS And Its Common Injection Problem And Solutions

PC/ABS is an alloy material composed of polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS). It combines the excellent properties of both materials: the moldability of ABS and the mechanical properties, impact strength, heat resistance, and UV resistance of PC. The material is colorless transparent granules and is widely used in automotive interior parts, business machines, communication equipment, household appliances, and lighting equipment.

Application Fields

1. Automotive Interiors and Exteriors:

• Dashboard

• Pillar trims

• Instrument panel covers

• Grilles

• Interior and exterior trim parts

2. Business Equipment Casings and Internal Parts:

• Laptops and desktops

• Copiers

• Printers

• Plotters

• Monitors

3. Telecommunications:

• Mobile phone housings

• Accessories

• Smart cards (SIM cards)

4. Electrical and Electronic Products:

• Electronic device housings

• Meter covers and housings

• Household switches

• Plugs and sockets

• Cable and wire conduits

5. Household Appliances:

• Washing machines

• Hairdryers

• Microwave internal and external parts

Common Problems and Solutions

1. Silver Streaks Issue: Silver streaks, also known as silver lines, water marks, or material streaks, are the most common issue with PC/ABS materials. These are silver-white  streaks that appear along the flow direction on the product surface, caused by gas interference. The gas mainly comes from three sources:

• Air: Air trapped during melting and injection stages.

• Moisture: Moisture inherent in the material.

• Decomposition Gas: Gases produced by hydrolysis or thermal decomposition at high temperatures.

Solution: First, check if the material is adequately dried. After confirming sufficient drying, adjust the injection molding process to improve the silver streaks defect. Additionally, mold venting is related to the issue of silver streaks.

2. Flow Marks Issue: Flow marks occur during injection due to poor material flowability. Unlike silver streaks, they are not caused by moisture or material decomposition and have a different appearance.

Solution: Improve material flowability by increasing the material temperature. Additionally, raising the mold temperature to enhance material flow within the mold and reducing the injection speed can resolve the issue.

3. Sink Marks and Dents Issue: Sink marks are caused by insufficient material filling in the mold cavity.

Solution: Improve material flowability by increasing mold and material temperatures, extend the injection holding time, increase injection pressure and speed, enlarge the gate size, and heat the runner to reduce and eliminate sink marks.

Dents are caused by improper material temperature and product design. Low material temperatures can cause both sink marks and dents, while high material temperatures and mold temperatures can cause excessive shrinkage during cooling, leading to dents. Appropriate processing methods, increasing injection speed, and other measures can be employed to mitigate these issues.

4. Warping and Deformation Issue: Warping and deformation of injection-molded parts are caused by unreasonable product      design, improper gate location, and injection molding conditions, leading to internal stresses and uneven or excessive shrinkage. High or uneven mold temperatures can cause the parts to stick to the mold, making demolding difficult and resulting in uneven cooling and warping.

Solution:

• Processing: Extend the molding cycle, lower injection temperature, adjust injection pressure and speed appropriately, slow down ejection speed, increase ejection area, and ensure balanced ejection force.

• Product Design: Increase wall  thickness, add reinforcing ribs, and strengthen rounded corners to reduce       warping.




5. Streaks Issue: Typically caused by"melt fracture" when the melt expands rapidly into the mold      cavity during high-speed injection.

Solution:

• Molding Process: Increase material temperature, nozzle temperature, and reduce injection speed to minimize       streaks.

• Mold: Increase mold temperature, add overflow grooves, enlarge gate size, and modify gate shape.




6. MottlingIssue:

Solution:

• Poor dispersibility: Add dispersants or oils, raise temperature, and increase back pressure.

• Check for mold issues by testing with other materials.

• Ensure sufficient drying time and temperature for the material.

• Adjust mold temperature.