Plastic Burning Mass Loss Testing: Technical Overview, Standards, and Methods

Plastic burning mass loss testing measures the weight change of polymer materials during controlled combustion or thermal decomposition, delivering essential data on flammability, thermal stability, and fire behavior. The test is commonly performed to ISO 5660-1, ASTM E1354, and ISO 11358 in accredited third-party laboratories. This article explains the principles, sample requirements, test items, methods, and applications of mass loss testing for plastics.

Technical Overview

When plastics are exposed to heat, they pyrolyze: polymer chains break down into volatile combustible gases while leaving behind char, ash, or inorganic residue. Plastic burning mass loss testing quantifies this process by continuously and precisely weighing a specimen while it is heated or ignited under standardized conditions. The resulting mass-versus-time or mass-versus-temperature curve allows engineers to determine the mass loss rate, total mass loss, and residual char yield, which are direct indicators of combustion intensity and flame retardant effectiveness.

Mass loss data are typically obtained with a cone calorimeter in accordance with ISO 5660-1 or ASTM E1354, or with a thermogravimetric analyzer in accordance with ISO 11358 or ASTM E1131. Because mass loss rate correlates strongly with heat release rate, the test is a cornerstone of fire performance evaluation for plastics, composites, cables, foams, and flame-retardant formulations. Accredited third-party laboratories routinely offer these tests to support product development, quality control, and regulatory compliance.

• Quantifies decomposition and burning behavior through direct weight measurement
• Supports comparison of flame-retardant formulations and base polymers
• Complements ignition, flame spread, and smoke tests under the IEC 60695 fire hazard framework
• Applicable to research, development, certification, and production quality control

Testing Samples

Thermoplastic Resins and Products

Common test materials include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyamide (PA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET), supplied as pellets, plaques, sheets, films, or molded parts.

Thermosetting Plastics

Epoxy resins, phenolic resins, unsaturated polyesters, and rigid or flexible polyurethane foams can be evaluated to determine their char-forming tendency and high-temperature residue behavior.

Composites and Modified Plastics

Glass-fiber or carbon-fiber reinforced plastics, mineral-filled compounds, halogen-free flame-retarded grades, and intumescent formulations are frequently tested to verify the effect of additives on mass loss behavior.

Finished and Semi-Finished Products

Cable insulation and sheathing compounds, foam panels, decorative laminates, electrical enclosures, and automotive interior components may be tested either as coupons cut from products or as representative molded specimens.

Testing Items

Depending on the chosen method and standard, the following parameters are typically reported:

• Mass loss rate (MLR) and peak mass loss rate
• Total mass loss and percentage mass loss at defined endpoints
• Char yield and residual mass ratio at the final temperature
• Time to ignition and time to peak mass loss rate (cone calorimeter)
• Heat release rate, peak heat release rate, and total heat release (companion cone calorimeter outputs)
• Smoke production rate and total smoke release
• Thermal decomposition temperatures from TGA curves, including onset temperature, 5% and 10% mass loss temperatures, and maximum rate temperature from the derivative curve
• Loss on ignition and ash or filler content for quality control purposes

Testing Methods

Cone Calorimeter Method

In accordance with ISO 5660-1 and ASTM E1354, a specimen of 100 mm × 100 mm and up to 50 mm thickness is mounted on a load cell and exposed to a radiant cone heater at irradiances of 25, 50, or 75 kW/m². The specimen is ignited by a spark igniter, and its mass is recorded continuously throughout the test. The instantaneous mass loss rate is derived from the load cell data, while oxygen consumption measurements simultaneously yield heat release data. Both horizontal and vertical orientations are available depending on the intended application.

Thermogravimetric Analysis (TGA)

In accordance with ISO 11358 and ASTM E1131, a small sample of typically 5 to 20 mg is heated at a controlled rate, commonly 5 to 20 °C/min, in a nitrogen or air atmosphere up to approximately 600 to 900 °C. A microbalance records mass as a function of temperature, revealing individual decomposition stages, thermal stability limits, and the final char or ash residue. TGA is especially valuable for screening flame retardants and studying decomposition kinetics.

Tube Furnace and Loss-on-Ignition Methods

For material specifications that require simple gravimetric results, specimens are conditioned, weighed, heated in a tube furnace or muffle furnace at a specified temperature, and reweighed after cooling in a desiccator. These procedures determine loss on ignition, ash content, and non-combustible filler fraction, and are often specified in GB, EN, and JIS material standards.

Supplementary Burning Tests

Mass loss data are frequently interpreted together with UL 94 horizontal and vertical burning tests, ISO 4589-2 and ASTM D2863 limiting oxygen index tests, and IEC 60332 cable flame tests to build a complete picture of a material's fire performance.

Applications

Plastic burning mass loss testing is used across many industries where fire safety, material selection, and regulatory compliance are critical:

• Flame retardant research and development, including comparison of additive systems and optimization of loading levels
• Building products and construction materials, where mass loss and heat release data support classification under EN fire performance frameworks
• Wire and cable manufacturing, for evaluating insulation and sheathing compounds used in flame-retardant and low-smoke cable designs
• Electrical and electronic equipment, supporting the qualification of enclosures and components alongside UL 94 ratings
• Automotive, rail, and aerospace interior materials, where mass loss behavior contributes to fire risk assessment of cabins and passenger compartments
• Incoming material inspection and production quality control for filled, reinforced, and flame-retarded compounds
• Academic and industrial research on polymer degradation kinetics and fire modeling

FAQ

What is the difference between mass loss rate and heat release rate?

Mass loss rate describes how quickly a specimen loses weight due to pyrolysis and burning, measured directly by weighing. Heat release rate describes the energy released per unit time and is normally calculated from oxygen consumption in a cone calorimeter. The two parameters are closely correlated, but mass loss rate more directly reflects material decomposition behavior.

What specimen size is required for cone calorimeter mass loss testing?

The standard specimen is 100 mm × 100 mm with a thickness of up to 50 mm, wrapped in aluminum foil on the underside and mounted in a retainer frame. At least three replicates are normally tested for statistical reliability.

How much sample is needed for TGA mass loss testing?

Thermogravimetric analysis requires only a few milligrams, typically 5 to 20 mg of finely cut or ground material, making it suitable even when only small amounts of sample are available.

Which standard should I choose for my application?

ISO 5660-1 or ASTM E1354 is appropriate when bench-scale fire performance data such as ignition time, mass loss rate, and heat release are needed. ISO 11358 or ASTM E1131 is preferable for thermal stability screening, decomposition studies, and flame retardant development. Your end-use specification or certification scheme usually indicates the required standard.

Can mass loss test results be used for product certification?

Yes, when the tests are performed by accredited third-party laboratories under the applicable ISO, IEC, ASTM, EN, GB, UL, or JIS standards, the reports can be used to support product certifications, regulatory submissions, and customer acceptance. It is advisable to confirm the exact standard, specimen orientation, and irradiance level with the certifying body before testing.