Determination of Mass Loss in Plastics After Aging: Testing Methods, Standards, and Applications

Determining the mass loss of plastics after aging is a fundamental gravimetric test used to evaluate the long-term durability, formulation stability, and expected service life of polymeric materials exposed to heat, light, oxygen, and humidity. This article explains the technical principles, sample requirements, applicable international standards such as ISO 4892, ISO 2578, ASTM D1203, and IEC 60216, testing procedures, calculation methods, and typical industrial applications of plastic aging mass loss measurement.

Technical Overview

Plastic aging refers to the gradual and often irreversible deterioration of polymer properties caused by thermal energy, ultraviolet radiation, oxygen, moisture, and chemical agents over time. During aging, plastics may lose volatile components such as plasticizers, stabilizers, residual monomers, oligomers, and moisture, while oxidative degradation and chain scission can generate gaseous by-products such as water, carbon dioxide, formaldehyde, and hydrocarbons. The net effect of these processes is frequently observed as a measurable reduction in the mass of the exposed specimen.

Mass loss determination is a gravimetric method in which a conditioned specimen is weighed before and after a defined aging exposure, and the relative change in mass is calculated. Because the test is simple, quantitative, highly reproducible, and directly linked to material stability, it is widely used alongside mechanical and optical testing to assess aging behavior. A high or accelerating mass loss typically indicates plasticizer or additive depletion, inadequate stabilization, or advancing thermal-oxidative degradation, all of which correlate with embrittlement, shrinkage, cracking, and premature failure of the finished product.

The core measurement principle is expressed as: Mass Loss (%) = (m0 − m1) / m0 × 100, where m0 is the initial conditioned mass and m1 is the mass after aging and re-conditioning. Accredited third-party laboratories commonly perform this determination in conjunction with standardized aging protocols published by ISO, ASTM, IEC, and other standards organizations.

Testing Samples

Standard Molded Specimens

Compression-molded or injection-molded plaques and dumbbell specimens produced in accordance with ISO 294-1, ISO 293, or ASTM D4700 are the preferred sample form for fundamental aging studies. Typical dimensions include 50 mm × 50 mm plaques with thicknesses of 1 mm to 3 mm. Thin specimens are preferred when the objective is to observe volatile loss, because a high surface-to-volume ratio accelerates the migration and evaporation of low-molecular-weight components.

Films and Sheets

Plastic films, foils, and thin sheets used in packaging, agriculture, and construction are well suited to mass loss testing. Specimens are cut to a defined area, and results may additionally be reported as mass loss per unit area (g/m²), which is particularly useful when comparing materials of different thicknesses or when fogging and volatile emissions are of concern.

Finished Products and Components

Cable insulation and sheathing slices, automotive interior trim, gaskets, hoses, grommets, seals, and electronic enclosures can be tested either as whole parts or as representative sections cut from the part. Testing real components is valuable because processing history, wall thickness, and local additive distribution strongly influence aging behavior.

Granules and Compounds

Raw polymer granules and compounded pellets may be tested for volatile loss and moisture-related mass change to support incoming material inspection, quality control of formulations, and shelf-life studies before conversion.

Testing Items

Typical test items offered for plastic aging mass loss determination include:

• Mass loss after thermal (hot air) aging at elevated temperatures
• Mass loss after xenon-arc lamp weathering exposure
• Mass loss after fluorescent UV-condensation weathering exposure
• Mass loss after carbon-arc lamp exposure
• Volatile loss and plasticizer loss determined by the activated carbon method
• Plasticizer migration and extraction loss in contact with media
• Mass change after damp heat (humidity) aging
• Mass loss kinetics and retention curves across multiple exposure intervals
• Combined evaluation of mass loss with tensile strength, elongation at break, and color change retention

Testing Methods

Thermal Aging Followed by Gravimetric Determination

Specimens are exposed to controlled elevated temperatures in forced-ventilation air ovens in accordance with ISO 2578, ASTM D3045, or the thermal-endurance procedures of IEC 60216. Common exposure temperatures range from 70 °C to 150 °C depending on the polymer system, with duration selected from a ladder of intervals (for example 24 h, 72 h, 168 h, 336 h, 500 h, and 1000 h). After exposure, specimens are conditioned in a standard atmosphere of 23 °C and 50 % relative humidity per ISO 291 or ASTM D618 and weighed on an analytical balance with a resolution of at least 0.1 mg.

Artificial Weathering Exposure

Light-accelerated aging is performed using laboratory light sources to simulate outdoor or indoor service environments. Xenon-arc exposure is conducted per ISO 4892-2, ASTM G155, or ASTM D2565; fluorescent UV-condensation exposure per ISO 4892-3, ASTM G154, or ASTM D4329; and carbon-arc exposure per ISO 4892-4 or ASTM G153. After each irradiation interval, specimens are removed, cleaned of surface deposits, re-conditioned, and weighed to determine mass loss resulting from photo-oxidation, chalking, erosion, and volatilization.

Activated Carbon Volatile Loss Method

The loss of plasticizers and other volatile constituents is determined using the activated carbon methods of ISO 176 or ASTM D1203. Specimens are buried in activated carbon and held at a specified temperature (typically 70 °C to 100 °C) for a defined period. The carbon adsorbs volatiles as they migrate out of the plastic, and the resulting mass loss quantifies the volatility and retention of plasticizers and additives. This method is especially important for flexible PVC compounds.

Measurement and Calculation Procedure

The general procedure followed by accredited third-party laboratories comprises: initial conditioning of specimens to constant mass; measurement of initial mass m0 using a calibrated analytical balance; exposure under the selected aging protocol; cooling and re-conditioning to constant mass in the standard atmosphere; measurement of final mass m1; and calculation of percentage mass loss. Specimens should be handled with powder-free gloves and clean tools, and electrostatic effects should be minimized during weighing. Duplicate or triplicate specimens are recommended, with results reported as the arithmetic mean together with individual values.

Result Interpretation

A small, rapidly stabilizing mass loss usually reflects the evaporation of residual moisture or low-boiling volatiles. A continuous, approximately linear mass loss suggests ongoing plasticizer or additive migration. An accelerating mass loss accompanied by discoloration or embrittlement indicates progressive oxidative degradation of the polymer matrix. Acceptance limits are product-specific; for example, certain electrical and automotive specifications restrict total volatile loss to a few percent over the qualification exposure period.

Applications

Mass loss determination after aging supports material qualification, quality control, and service-life prediction across many industries:

• Automotive: interior trim, dashboard skins, door panels, seals, and under-hood components, where plasticizer loss leads to fogging, odor, embrittlement, and shrinkage
• Wire and cable: insulation and sheathing compounds evaluated against heat-ageing requirements of IEC 60811 and IEC 60216 series procedures
• Building and construction: PVC profiles, pipes, roofing membranes, geomembranes, and window gaskets exposed to weathering
• Packaging: films requiring low volatile content for food-contact compliance and dimensional stability
• Electronics and electrical equipment: connectors, housings, and insulating parts where additive loss affects tracking, flammability performance, and reliability
• Medical devices: sterilizable polymers subjected to repeated thermal and radiation exposure
• Renewable energy: photovoltaic encapsulant films and backsheets assessed for volatile loss during damp-heat and UV aging
• Research and development: comparison of stabilizer packages, plasticizer systems, and new polymer formulations under accelerated aging conditions

FAQ

What does a high mass loss value after aging indicate?

A high mass loss generally indicates depletion of plasticizers, stabilizers, or other volatile additives, or advancing thermal-oxidative degradation of the polymer itself. It often precedes or accompanies loss of flexibility, embrittlement, shrinkage, and cracking, and should trigger supplementary mechanical and compositional testing.

Which standards govern plastic aging mass loss testing?

There is no single universal standard; the measurement is defined by combining an aging exposure standard with a gravimetric procedure. Commonly referenced documents include ISO 2578, ISO 4892-1 to 4892-4, ISO 176, ISO 291, ASTM D3045, ASTM D2565, ASTM D4329, ASTM G154, ASTM G155, ASTM D1203, ASTM D618, and the IEC 60216 series for electrical insulating materials.

What balance precision is required?

An analytical balance with a readability of 0.1 mg is standard practice. Specimens should be conditioned to constant mass before each weighing so that normal mass fluctuation is negligible relative to the mass change being measured.

How long does an aging mass loss test take?

Test duration depends on the selected protocol. Short-term screening exposures may require only 24 h to 168 h, while qualification and service-life studies frequently extend to 1000 h or several thousand hours, often sampled at intermediate intervals to construct a mass loss versus time curve.

Can finished products be tested instead of molded specimens?

Yes. Sections cut from finished parts, or entire small components, can be aged and weighed in the same manner. Results from finished parts reflect real processing conditions and geometry, although comparison between different products is most reliable when specimen thickness and surface area are normalized.

Is mass change always a loss?

No. Some aging environments cause mass gain, for example moisture uptake during damp-heat exposure or oxidation in its early stages. Reporting the signed mass change, rather than absolute loss, avoids misinterpretation, which is why conditioning to constant mass before each weighing is essential.