Plastic thermal aging weight loss testing is an essential accelerated aging evaluation used to assess the long-term durability of polymeric materials by measuring mass loss after exposure to elevated temperatures. This test is widely applied to PVC compounds, engineering plastics, cable insulation, and sheathing materials to quantify plasticizer and volatile loss, predict service life, and verify compliance with international standards such as IEC 60811-401, ASTM D3045, UL 746B, and GB/T 2951.31. In this article, we explain the testing principles, sample requirements, procedures, calculation methods, and typical applications of thermal aging weight loss testing for plastics.
Technical Overview
Thermal aging weight loss testing (also referred to as heat aging mass loss testing) is an accelerated laboratory method that evaluates how plastic materials lose mass when exposed to elevated temperatures over a defined period. During thermal aging, plastic materials undergo physical and chemical changes, including the evaporation and migration of plasticizers, the release of residual solvents and volatile additives, thermal oxidation, chain scission, and, in some polymers, crosslinking. These processes manifest as a measurable reduction in specimen mass and a corresponding degradation of mechanical and electrical properties.
The test is particularly significant for polyvinyl chloride (PVC) compounds, whose flexibility and longevity depend heavily on plasticizer retention. Excessive mass loss during aging indicates that a material will harden, embrittle, and crack prematurely in service. By exposing standardized specimens to controlled temperatures in a forced-air circulation oven and measuring the resulting mass change, engineers can compare material formulations, verify compliance with product specifications, and estimate long-term thermal endurance. Accredited third-party laboratories routinely perform this test for wire and cable manufacturers, compound suppliers, automotive suppliers, and construction product manufacturers.
Thermal aging weight loss data also serve as an input to broader thermal endurance programs, such as relative temperature index (RTI) determination under UL 746B and thermal endurance characterization under IEC 60216, where property retention is tracked across multiple aging temperatures and times to construct Arrhenius-type lifetime extrapolations.
Testing Samples
PVC Insulation and Sheath Compounds
PVC compounds for wire and cable insulation and sheathing are the most common subjects of thermal aging weight loss testing. These materials contain significant quantities of plasticizers, stabilizers, and lubricants that are susceptible to volatilization at elevated temperatures. Standards such as IEC 60811-401 and GB/T 2951.31 specify dedicated mass loss requirements for PVC compounds used in rated cables.
Engineering Thermoplastics
Materials such as polyamide (PA), polycarbonate (PC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), and ABS are tested to evaluate thermal oxidation resistance and volatile loss. These results support material selection for electrical connectors, housings, and structural components exposed to sustained heat.
Elastomers and Rubber-Plastic Blends
Thermoplastic elastomers (TPE/TPU) and rubber-plastic blends are evaluated for plasticizer and oil extraction loss using oven aging methods aligned with ISO 188, ASTM D573, and JIS K 6257, often in combination with mechanical property retention measurements.
Films, Sheets, and Finished Products
Packaging films, PVC-U window profiles, gaskets, seals, and finished cable samples can also be tested either as standard multipurpose specimens or as representative product sections, depending on the applicable product standard.
Testing Items
A typical thermal aging weight loss test program includes the following evaluation items:
- Mass loss rate (percentage of mass change) after aging at specified temperature and duration
- Mass loss per unit surface area (mg/cm²) for PVC compounds per cable standards
- Tensile strength retention and elongation at break retention before and after aging
- Change in Shore hardness or indentation hardness after aging
- Visual assessment of surface cracking, warping, discoloration, and blistering
- Optional supplementary analysis such as thermogravimetric analysis (TGA) per ISO 11358 or ASTM E1131 for decomposition characterization
- Thermal endurance data supporting temperature index and RTI determination per IEC 60216 and UL 746B
Testing Methods
Specimen Preparation and Conditioning
Specimens are prepared according to the governing material or product standard, typically using multipurpose test specimens per ISO 3167 or ASTM D638 Type I dumbbells for combined mass and mechanical evaluation. Before testing, specimens are conditioned in a standard atmosphere of 23 ± 2 °C and 50 ± 5% relative humidity per ISO 291 or ASTM D618 for a minimum of 24 hours (or until mass stabilization). Initial mass (m0) is measured using an analytical balance with a resolution of 0.1 mg.
Oven Aging Procedure
Specimens are placed in a forced-air circulation oven complying with the temperature uniformity requirements of the relevant standard, with air exchange rates typically between 5 and 30 changes per hour for IEC 60811-401 testing. Specimens are suspended or supported with adequate spacing to allow free air circulation on all surfaces and to prevent contact between specimens. Common aging conditions include:
- 168 hours at 80 °C for PVC compounds per IEC 60811-401 and GB/T 2951.31
- 168 hours at 100 °C or 105 °C for higher temperature rated PVC insulation and sheath compounds
- 135 °C, 150 °C, or higher for crosslinked and engineering materials depending on the temperature class
- Multi-temperature aging sequences per ASTM D3045, ISO 188, and IEC 60216 for lifetime extrapolation studies
Measurement and Calculation
After aging, specimens are reconditioned in the standard atmosphere and weighed to obtain the final mass (m1). The mass loss percentage is calculated as: Mass Loss (%) = (m0 − m1) / m0 × 100. For cable PVC compounds, mass loss is frequently expressed per unit surface area in mg/cm². Acceptance limits are defined by product standards; for example, certain PVC insulation compounds per EN 50363-1 and related specifications are limited to a maximum of 2.0 mg/cm² after 168 hours at 80 °C, while general purpose PVC compounds under GB/T 8815 typically require mass loss not exceeding 7% after aging at designated conditions. Mechanical property retention is evaluated in parallel on tensile specimens aged under identical conditions.
Related and Alternative Methods
Where volatile loss through contact absorption is of concern, activated carbon methods per ASTM D1203 and ISO 176 may be applied to determine plasticizer loss. Thermogravimetric analysis per ISO 11358 provides complementary information on thermal decomposition onset and stability under controlled heating rates, although it does not replace long-duration oven aging for qualification purposes.
Applications
Thermal aging weight loss testing supports quality control, material qualification, and product certification across many industries:
- Wire and cable manufacturing: verifying PVC insulation and sheath compound compliance with IEC, EN, GB, and JIS cable standards, including mass loss and mechanical retention requirements
- Materials qualification: comparing compound formulations, plasticizer systems, and stabilizer packages during research and development
- Relative temperature index and thermal endurance programs per UL 746B and IEC 60216 for long-term service temperature ratings
- Automotive components: evaluating connectors, wire harness insulation, and under-hood plastic parts for sustained heat exposure
- Building products: assessing PVC-U profiles, pipes, and fittings for thermal stability and long-term durability
- Electronics and electrical equipment: confirming that polymeric parts in appliances and devices resist embrittlement over their rated service life
- Regulatory compliance and certification: generating test reports from accredited third-party laboratories for market access and customer approval
FAQ
What is plastic thermal aging weight loss testing?
It is an accelerated aging test in which plastic specimens are exposed to a specified elevated temperature in an air-circulating oven for a defined duration, after which the loss of mass is measured. The mass loss reflects the evaporation of plasticizers, volatiles, and other low-molecular-weight components, as well as thermal oxidative degradation, and is a key indicator of long-term material durability.
Which standards govern this test?
Commonly applied standards include IEC 60811-401 and GB/T 2951.31 for PVC cable compound mass loss, ASTM D3045 for heat aging of plastics without load, ISO 188 and ASTM D573 for elastomeric materials, IEC 60216 and UL 746B for thermal endurance and relative temperature index programs, and GB/T 7141 and GB/T 8815 for general plastics and PVC compound heat aging requirements.
What are the typical aging temperatures and durations?
The most widely used condition for PVC cable compounds is 168 hours at 80 °C per IEC 60811-401. Higher temperature classes may require 100 °C, 105 °C, 135 °C, or above, while thermal endurance studies use multiple temperatures and extended durations to enable lifetime extrapolation.
How should test results be interpreted?
Lower mass loss indicates better retention of plasticizers and additives and greater expected service life. Results are compared against the acceptance limits of the applicable product standard. A material that passes mass loss requirements but shows significant loss of elongation at break may still be considered at risk of embrittlement, so mechanical property retention should be evaluated together with mass loss.
What specimens and quantities are required?
Requirements vary by standard, but typically a minimum of three to five specimens per condition is tested. For combined mass loss and tensile evaluation, dumbbell specimens per ISO 3167 or ASTM D638 are used. Cable standards may also permit testing tubular insulation pieces or strips taken from finished cables, reporting results in mg/cm².
How does this test differ from thermogravimetric analysis?
Oven-based thermal aging weight loss testing exposes specimens to moderate temperatures for long durations (hours to weeks) to simulate service aging, whereas thermogravimetric analysis per ISO 11358 heats a small sample at a controlled rate to characterize decomposition behavior over a wide temperature range. The two methods are complementary and serve different evaluation purposes.