Technical Insight
Why Polycarbonate Burns or Yellows During Laser Marking
Candidate controls include Antimony Tin Oxide (ATO). For PC burning or yellowing, separate bulk resin or colour degradation from intended mark formation by mapping the lowest energy that meets contrast and inspecting the unmarked heat-affected area.
Author: Aurexene Materials Engineering Team · Last updated: 2026-08-28
Quick Answer
For PC burning or yellowing, separate bulk resin or colour degradation from intended mark formation by mapping the lowest energy that meets contrast and inspecting the unmarked heat-affected area.
Evidence scope: This page provides method-conditioned engineering guidance. It does not claim that one commercial grade is a drop-in replacement, universally superior, or qualified for a finished part without matched evidence.
Problem
For PC burning or yellowing, separate bulk resin or colour degradation from intended mark formation by mapping the lowest energy that meets contrast and inspecting the unmarked heat-affected area.
The decision boundary includes the complete host formulation, colour package, supplied additive form, compounding and moulding history, part geometry, delivered laser state and the measurement method. A result is not transferable when one of those conditions changes without review.
Mechanism
Polycarbonate can undergo thermal and photochemical change near concentrated energy; moisture, pigments, flame retardants and repeated passes narrow the clean-mark window.
Laser marking is a coupled material-and-process response. Absorption and scattering determine where energy is deposited; pulse state, focus, overlap and path determine the local history; the polymer, pigments, fillers and geometry determine whether that history creates controlled contrast or a defect.
Tradeoff
Reducing pulse overlap or changing wavelength may limit yellowing but also reduce contrast or resolution.
The useful condition is a feasible region with margin, not the single darkest coupon. Contrast, edge, surface integrity, unmarked colour, processing, mechanical function, durability and cycle time must be evaluated together.
Material Strategy
Use ATO as application-specific screening candidates. The list is not a performance ranking and does not establish equivalence between chemistry families.
- Freeze the host grade, colour, thickness, geometry and acceptance criteria.
- Normalize active-content and supplied-form differences or explain why another comparison basis is used.
- Screen loading and laser variables in a bounded matrix and preserve failed runs.
- Confirm the selected window across relevant lots, parts, tools and exposures.
Recommended Architectures
| Architecture | Use when | First validation gate |
|---|---|---|
| Matched baseline | The current material, colour and laser recipe require a reproducible reference. | PC discolouration and damage boundary |
| Bounded screening ladder | Loading, supplied form, colour or delivered laser variables must be separated. | PC grade and additives; drying condition; wavelength and pulse; overlap and passes; yellowing outside the mark |
| Production confirmation | A candidate window must transfer across lots, geometry, tools or lifecycle exposures. | Margin, repeatability, failures and requalification triggers |
Controls That Must Stay Visible
| Order | Control | Review rule |
|---|---|---|
| 1 | PC grade and additives | Hold the other declared formulation, process, geometry and measurement conditions constant before attributing an effect. |
| 2 | drying condition | Hold the other declared formulation, process, geometry and measurement conditions constant before attributing an effect. |
| 3 | wavelength and pulse | Hold the other declared formulation, process, geometry and measurement conditions constant before attributing an effect. |
| 4 | overlap and passes | Hold the other declared formulation, process, geometry and measurement conditions constant before attributing an effect. |
| 5 | yellowing outside the mark | Hold the other declared formulation, process, geometry and measurement conditions constant before attributing an effect. |
Measurement & Validation
Primary response: PC discolouration and damage boundary.
Method: Compare colour coordinates, reflectance, line geometry and surface damage across energy, focus and moisture conditions with an unmarked control.
Report the unit or grade together with instrument or verifier geometry, specimen state, conditioning, repeats, distribution or uncertainty, failures and the acceptance limit. A scanner pass, photograph or supplier representative value is not a substitute for the declared method.
Qualification Boundary
- Record exact material and lot identities, active-content basis, carrier and colour package.
- Record compounding, drying, moulding, thickness, surface and geometry.
- Record source wavelength, pulse state, spot or focus, speed, hatch, passes, field and calibration.
- Measure marked and unmarked controls using the declared method.
- Confirm production and lifecycle variation, then define requalification triggers.
Primary Sources and Standards Boundary
No external standard establishes product-grade performance for this question. Use reviewed grade documents and matched laboratory or production evidence.
Related Products
Related Applications
Related Comparisons
No reviewed comparison page is required for this decision. Keep candidate comparisons inside a matched test matrix.
Downloads & Engineering Support
Need to apply this boundary to a grade, formulation, test method, or production route? Discuss it with the Aurexene Materials Engineering Team.