Flammability Testing Chamber for Plastics According to UL 94
UL 94 (Underwriters Laboratories 94) is an international standard used to evaluate the flammability of plastic and polymer materials in electrical and electronic applications. It determines whether the material self-extinguishes, the burning rate, and whether flaming drips occur.
Main Test Methods in UL 94
Horizontal Burning Test (HB – Horizontal Burn)
- Sample placed horizontally.
- Measures flame propagation rate along the length.
- Classification: HB (weakest).
Vertical Burning Test (V – Vertical Burn)
- Sample placed vertically.
- Flame applied from the bottom.
- Evaluates self-extinguishing ability, burning duration, and whether flaming drips ignite cotton.
- Classification: V-0 (best), V-1, V-2.
Thin Material Test (VTM)
- Similar to Vertical Test but for thin, flexible materials.
- Classification: VTM-0, VTM-1, VTM-2.
5V Test
- Sample placed vertically, exposed to a stronger flame.
- Evaluates resistance under repeated flame application in a short time.
- Classification: 5VA (no hole formation), 5VB (with hole formation).
Summary
- HB: horizontal test only, easiest to achieve, lowest level.
- V-0 / V-1 / V-2: vertical test, stricter evaluation.
- VTM: for thin materials.
- 5VA / 5VB: highest level, withstands strong flame, hardest to achieve.
=> The higher the UL 94 rating (e.g., 5VA, V-0), the more flame-resistant and safer the material.
