Glass bubble reduce the fire hazard of TPU in combustion process

Glass bubbles can help reduce the fire hazard of thermoplastic polyurethane (TPU) during combustion. Here’s how it works and why it matters:

✅ Fire Hazard Reduction of TPU with Glass Bubbles

Glass bubbles (also known as hollow glass microspheres) are lightweight, inert, and thermally stable fillers that offer a range of flame-retardant benefits when added to polymers like TPU.

How Glass Bubbles Reduce Fire Hazard in TPU

Mechanism	Explanation
Dilution Effect	Replacing part of the combustible TPU matrix with non-flammable glass bubbles lowers the total fuel load.
Thermal Insulation	Glass bubbles have low thermal conductivity, slowing down heat transfer and surface temperature rise during fire.
Char Promotion	In some formulations, they aid in forming a protective char layer, which shields underlying material from further combustion.
Barrier Effect	Their spherical geometry can disrupt the diffusion of oxygen and volatile decomposition gases in the burning zone.

✅ Measured Improvements

In studies and formulations:

Limiting Oxygen Index (LOI) increases — meaning the material requires more oxygen to sustain a flame.
Peak Heat Release Rate (PHRR) drops — indicating less intense burning.
Total Smoke Release (TSR) may also reduce slightly due to inert content.
UL-94 flammability ratings may improve when combined with other flame retardants.

✅ Best Practices for Using Glass Bubbles in TPU

Use in combination with traditional flame retardants (e.g., phosphorus-based, melamine cyanurate) for synergy.
Optimize loading level: Typically 5–20 wt% depending on the density and type of glass bubbles used.
Choose high crush-strength bubbles to survive processing in melt compounding and injection molding.

✅ Benefits Beyond Fire Safety