Alcohol Blast Burner Combustion Test for Plastic Materials

The alcohol blast burner combustion test is a standardized flame-retardancy evaluation in which plastic and rubber specimens are exposed to a calibrated blue alcohol flame to measure afterflame time, char length, and dripping behavior. Widely mandated for polymer products used in underground coal mines and other fire-sensitive environments, this article explains the test principle, apparatus, specimen requirements, procedure, acceptance criteria, and typical applications for plastic materials.

Technical Overview

The alcohol blast burner combustion test is a small-scale laboratory fire test used to evaluate the flame-retardant and self-extinguishing properties of polymeric materials, including thermoplastics, thermosets, elastomers, and polymer-based composites. In the test, a specimen is exposed to the flame of an alcohol blast burner — a blast-type burner fueled by ethanol of at least 95% concentration that produces a high-temperature blue flame — for a defined period, and the burning behavior after removal of the ignition source is recorded.

The method is defined in the coal industry standard MT 113 (General test methods and judgment rules for flame retardant and antistatic properties of polymer products for underground coal mines) and is invoked by numerous product standards for mining polymers, including those covering flame-retardant conveyor belts, ventilation ducting, mine cables, hydraulic hoses, and plastic pipes. Compared with horizontal and vertical burning tests such as GB/T 2408, IEC 60695-11-10, or UL 94 — which use gas-fired Bunsen-type burners — the alcohol blast burner test exposes specimens to a hotter and more intense alcohol-fueled flame that better simulates ignition scenarios relevant to underground mining operations.

Key controlled parameters include fuel concentration, flame height (typically 150–180 mm of blue flame), and flame temperature at the calibration point (approximately 960 °C), which together ensure reproducible test severity across laboratories.

Testing Samples

The test is applied to finished products or representative material samples. For belt- and sheet-type products, specimens are typically cut as strips of approximately 360 mm × 50 mm at full product thickness, with sets of six specimens taken in both longitudinal and transverse directions. Specimens should be clean, free from surface contamination, and conditioned in a standard laboratory atmosphere before testing.

Flame-Retardant Conveyor Belts

Fabric whole-core flame-retardant conveyor belts and flame-retardant steel cord conveyor belts represent the largest application group. Specimens may be taken from the belt body as well as from the cover rubber layers, since both the carcass and the covers contribute to overall flame performance.

Ventilation Ducting and Coated Fabrics

Positive-pressure ventilation ducting for underground mines, PVC-coated fabrics, and flexible duct materials are tested because inadequately flame-retarded ducts can propagate fire rapidly along mine roadways.

Cables, Hoses, and Pipes

Sheathing and jacket compounds for mine cables, covers of hydraulic and pneumatic hoses, and flame-retardant PVC or polyethylene pipes used underground are qualified with this method, often alongside cable-specific flame propagation tests.

Other Polymer Products

Plastic mesh and safety netting, geomembranes, sheets, profiles, sealing strips, coatings, and molded components intended for use in gassy underground environments may also be evaluated using this method.

Testing Items

The test quantifies the following burning characteristics:

• Afterflame time: the time in seconds for which each specimen continues to burn with flame after the burner flame is removed; both single-value and aggregate results are reported.
• Afterglow time: the duration of flameless glowing combustion after flaming ceases.
• Charred (damaged) length: the extent of the carbonized or damaged area along the specimen.
• Flaming drips and falling debris: whether molten or burning material falls during the test and whether it ignites indicator cotton placed beneath the specimen.
• General burning behavior: observations of swelling, bubbling, smoke generation, and advancement of the flame front.

Typical acceptance criteria in coal mine product standards require each specimen to self-extinguish within approximately 3 seconds after removal of the flame, with the sum of afterflame times for the full specimen set (commonly six specimens) below a defined aggregate limit, and with no ignition of the indicator cotton. The exact limits are set by the applicable product standard.

Testing Methods

Apparatus and Flame Calibration

The core apparatus is a blast-type alcohol burner connected to a fuel reservoir and operated with ethanol of at least 95% concentration. The burner is adjusted to produce a stable blue flame 150–180 mm high, and the flame temperature at the specified reference position is verified at approximately 960 °C using a calibrated thermocouple. Testing is performed in a ventilated, draft-protected enclosure so that air movement does not disturb the flame or the burning specimen, while combustion products are safely extracted.

Specimen Preparation and Conditioning

Specimens are cut to the dimensions required by the governing product standard, marked with gauge lines for measuring the damaged length, and conditioned in a controlled laboratory atmosphere before testing. For products with directional structure, such as woven reinforcement or extrusion orientation, specimens are prepared in both the machine direction and the transverse direction.

Test Procedure

• Ignite the burner and adjust the flame to the specified height; allow the flame to stabilize.
• Verify the flame temperature at the calibration point before starting the exposure.
• Mount the specimen in the holding clamp in the position defined by the standard so that the flame impinges on the designated area of the specimen.
• Apply the flame for the specified exposure time — commonly 60 seconds, although some product standards specify other durations.
• Withdraw the burner and immediately start timing; record the afterflame time, afterglow time, and any flaming drips.
• After the specimen has cooled, measure the charred length and examine the indicator cotton for evidence of ignition.
• Repeat the procedure for all specimens in the set and calculate the individual and aggregate results.

Evaluation and Judgment

Results are compared against the acceptance limits of the governing product standard. Where an individual result marginally exceeds a limit under specifically defined conditions, many standards permit a repeat test on additional specimens to confirm conformity. The alcohol blast burner test is frequently performed together with the alcohol lamp combustion test, surface resistance measurement, and oxygen index testing (GB/T 2406 / ISO 4589) to demonstrate the complete flame-retardant and antistatic performance required for underground use.

Applications

The alcohol blast burner combustion test is a mandatory element of safety qualification for polymer products used in underground coal mines, including the Chinese Mining Product Safety Mark certification scheme. Typical users and applications include:

• Manufacturers of flame-retardant conveyor belts, ventilation ducting, cables, hoses, and plastic pipes seeking type approval and routine factory quality control.
• Compound formulators developing flame-retardant PVC, polyethylene, and rubber systems, who use the method to compare halogenated, halogen-free, and mineral-filled formulations.
• Mining companies and equipment manufacturers performing incoming material verification on safety-critical polymer components.
• Accredited third-party laboratories supporting certification bodies, market supervision, and failure analysis of field-returned materials.
• Underground and tunnel engineering projects where polymer products must demonstrate reliable self-extinguishing behavior under a specified alcohol flame exposure.

FAQ

What is the difference between the alcohol blast burner test and the alcohol lamp test?

The alcohol blast burner test uses a blast-type burner that premixes fuel vapor with air to generate a hot, well-defined blue flame at approximately 960 °C, producing a more severe and reproducible exposure. The alcohol lamp test uses a simpler wick-type lamp with a softer flame and is generally run as a complementary, less severe check of self-extinguishing behavior.

Which standards specify the alcohol blast burner combustion test?

The parent method is defined in the coal industry standard MT 113 for flame-retardant polymer products used in underground coal mines, and it is invoked by related product standards for conveyor belts, ventilation ducts, cables, and hoses. Laboratories may also perform the method as a contractual or comparative test for other applications.

Why is ethanol used as the fuel?

Ethanol of at least 95% concentration provides a clean, soot-free blue flame with a stable and reproducible temperature profile, allowing consistent flame calibration and comparable results between laboratories.

How many specimens are tested?

A complete test normally uses six specimens — typically three in the longitudinal direction and three in the transverse direction — so that orientation-dependent burning behavior is captured. The governing product standard defines the exact number and dimensions.

What results constitute a pass?

In common coal mine product standards, each specimen must stop flaming within about 3 seconds after removal of the burner, the total afterflame time of the specimen set must remain within the aggregate limit, and flaming debris must not ignite the indicator cotton. Char length limits, where applicable, must also be met. The specific limits should always be verified in the governing product standard.

Can the test be performed by third-party laboratories?

Yes. Accredited third-party laboratories equipped with calibrated alcohol blast burner apparatus and experienced in mining polymer product standards routinely perform this test for certification, factory audits, and product development purposes.

Is the test applicable to rubber as well as plastic materials?

Yes. Although often described in connection with plastics, the method covers polymeric materials in general, including elastomers, thermoplastics, thermosets, coated fabrics, and polymer composites intended for underground mining environments.