Solutions to Bubbles and Black Spots During Hot‑Forming of Polycarbonate Sheet

Countermeasures for Bubbles and Black‑Spot Defects in Polycarbonate Sheet Hot‑Forming

To address bubbles and black spots occurring during hot‑forming of Polycarbonate Sheet for customers, systematic countermeasures shall be implemented from three dimensions: process control, packaging & storage, and raw‑material & processing traceability. Detailed professional descriptions are shown below.

1. Bubble Defects: Drying, Hot‑Forming Process and Storage Management

Bubbles are mainly caused by moisture vaporization or material decomposition. Key process parameters are listed in Table 1.

Table 1 Key parameters for bubble‑defect control

2. Black‑Spot Defects: Traceability from Sheet Production to Hot‑Forming Processing

1. Defects originating from sheet‑manufacturing commissioning
   If black spots are inside the sheet before hot‑forming and appear in specific batches of custom sheets, unstable conditions during initial commissioning at the sheet factory may be the cause. Manufacturers mitigate this by increasing scrap rates during commissioning.
2. Impurities in raw‑material pellets
   Tiny black inclusions inside raw‑material pellets are trace impurities inherent to raw materials and cannot be completely eliminated.
3. Excessively high hot‑forming temperature
   Overheating during hot‑forming can char acceptable‑range crystal points inside sheets into visible black spots on finished parts. Keep hot‑forming temperature ≤200 ℃.

3. Packaging and Storage Recommendations

To prevent moisture absorption of Polycarbonate Sheet during storage:

• Packaging: Fully wrap sheets with plastic film then place onto pallets.
• Warehouse environment: Store in dry‑and‑ventilated warehouses upon customer receipt.
• Mandatory operation: Regardless of intact plastic wrapping, drying treatment must be performed before hot‑forming.