Carbon content in polycarbonate smartwatch housings should be determined by functional requirements and surface finishing processes — not by numbers alone.
In polycarbonate (PC) smartwatch cases, carbon additives such as conductive carbon black and carbon fiber
fundamentally influence both functional performance and surface finishing quality.
From an engineering perspective, a premium smartwatch housing is achieved by selecting the correct carbon loading for each manufacturing process — ensuring stable coating,
predictable conductivity, and long-term reliability.
Conductive carbon black and carbon fiber are the most commonly used fillers in PC smartwatch housings. Their dispersion quality and loading ratio directly determine conductivity stability, coating adhesion, and EMI shielding efficiency.
At a carbon content of 1%–3%, a continuous conductive network forms within the PC matrix.
Volume resistivity drops to 10⁶–10⁹ Ω·cm, enabling stable electrostatic spray coating.
Below 1%, conductivity is insufficient and conductive primers are required.
Above 5%, excessive conductivity may lead to uneven charge distribution,
resulting in orange peel or pinhole defects.
Carbon additives increase surface roughness in a controlled manner.
At low levels, coating adhesion remains stable.
At higher loadings (>15%), fiber exposure or agglomeration
may weaken the coating–substrate interface.
Industrial countermeasures include twin-screw compounding,
surface pretreatment, and carbon-specific primers.
At carbon contents between 5% and 20%,
EMI shielding effectiveness increases significantly.
A loading of 15%–20% can achieve 30–45 dB, suitable for smartwatch antennas
and sensitive electronic modules.
Excessive carbon content (>25%) must be carefully balanced
against mechanical toughness.
0%–1% · High-gloss, appearance-driven designs
1%–3% · Anti-static housings for electrostatic coating
5%–15% · EMI-shielded smartwatch housings
20%–30% · High-strength, lightweight outdoor watches
We manufacture both mechanical watch cases and smartwatch housings.
Our core expertise lies in stainless steel and aluminum alloy.
Plastic components are developed in close collaboration with long-term partner factories,
allowing us to jointly optimize materials, tooling, and surface finishing.
If you are developing a smartwatch project, we welcome the opportunity
to discuss technical details and manufacturing feasibility together.
How Can You Build Your Own Watch Brand with a Limited Budget?
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