Test service for the reduction rate of breaking strength after aging resistance

Test Service for the Reduction Rate of Breaking Strength after Aging Resistance – Accredited ISO/IEC 17025 Material Durability and Performance Retention Assessment for the Croatian Market

The reduction rate of breaking strength after aging is a critical performance indicator that quantifies the loss of mechanical strength of materials when exposed to environmental stressors such as heat, humidity, ultraviolet (UV) radiation, ozone, and chemical agents over time. This parameter is essential for evaluating the long‑term durability, reliability, and safety of products used in automotive, aerospace, construction, medical devices, packaging, consumer goods, and industrial applications, where materials must maintain their structural integrity throughout their service life. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, the Ministarstvo graditeljstva i prostornoga uređenja, and the Carinska uprava enforce strict quality, durability, and safety standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of breaking strength retention after aging is essential for product certification, supplier qualification, type testing, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive testing service for the reduction rate of breaking strength after aging, applying standardized methods such as ASTM D573, ISO 188, ASTM D865, ASTM G154, ISO 4892-3, ASTM D1149, ISO 1431-1, ASTM D638, ISO 527, ASTM D412, and HRN EN ISO 188 to subject materials to controlled aging conditions and to measure the loss of tensile, tear, and bursting strength. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, product validation, and market access in Croatia and the European Union.

Materials and Components We Regularly Test

Our laboratory receives a wide variety of materials and components for aging and breaking strength reduction testing. Typical samples include:

• Elastomers and rubber compounds – natural rubber, SBR, NBR, EPDM, neoprene, silicone, and fluorocarbon rubbers for seals, gaskets, hoses, and tires.
• Thermoplastics and thermosets – polyethylene (PE), polypropylene (PP), PVC, polyamide (PA), polycarbonate (PC), epoxies, and polyesters for structural and automotive applications.
• Textiles and coated fabrics – for automotive interiors, outdoor furniture, protective clothing, and tarpaulins.
• Composite materials – fiber-reinforced plastics and laminates for aerospace, construction, and marine applications.
• Adhesives and sealants – structural adhesives, sealants, and bonding agents.
• Protective coatings and films – for corrosion protection and surface finishing.
• Prototype and new material formulations – submitted by manufacturers for validation of aging resistance before series production.
• Field-retrieved components – for failure analysis and remaining life assessment.

Thermal Aging and Breaking Strength Reduction – Evaluating the Effect of Heat on Mechanical Performance

Thermal aging is the most common aging mechanism for polymers and elastomers. Our tests expose the material to elevated temperatures for a specified duration and then measure the residual breaking strength (tensile strength, tear strength, or burst strength). The reduction rate is calculated as the percentage decrease from the original (un‑aged) breaking strength. Our procedures follow international standards and the requirements of the Croatian automotive, construction, and industrial sectors.

• Thermal aging test – standard method (ASTM D573 / ISO 188 / HRN EN ISO 188 / NTC 5600 – for rubbers and elastomers) – we place the test specimens in a forced‑air oven at a specified temperature (e.g., 70 °C, 100 °C, 125 °C, or 150 °C) for a specified duration (e.g., 7, 14, 21, 28, or 56 days). After the aging, we cool the specimens to room temperature and perform a tensile test (ASTM D412 / ISO 37) to measure the residual tensile strength and elongation at break. The reduction rate of the breaking strength is calculated as: Reduction Rate (%) = [(Strength_unaged – Strength_aged) / Strength_unaged] × 100. We report the residual tensile strength (in MPa), the residual elongation (in %), and the reduction rate (in %).
• Thermal aging test for plastics (ASTM D3045 / ISO 4577 / NTC 5601 – for thermoplastics and thermosets) – we age the plastic specimens in an oven at a specified temperature (e.g., 80 °C, 100 °C, or 120 °C) for a specified duration. After the aging, we perform a tensile test (ASTM D638 / ISO 527) to measure the residual tensile strength and the modulus. The reduction rate of the breaking strength is calculated. We report the residual tensile strength and the reduction rate.
• Thermal aging at different temperatures (NTC 5602 – for the Arrhenius extrapolation) – we perform the thermal aging test at multiple temperatures (e.g., 70 °C, 85 °C, 100 °C, 120 °C) for the same duration (or for different durations). The data is used to construct the Arrhenius plot and to predict the service life at the actual service temperature. We report the reduction rate at each temperature, the activation energy, and the predicted service life.
• Thermal aging under mechanical stress (NTC 5603 – for the stress‑enhanced aging) – we apply a constant tensile or compressive stress to the specimen during the thermal aging (e.g., using a spring‑loaded fixture). The combined effect of heat and stress on the breaking strength reduction is evaluated. We report the reduction rate under stress and the effect of the stress.
• Thermal aging in different media (NTC 5604 – for the aging in oil, air, or water) – we perform the thermal aging in a specified medium (e.g., in air, in mineral oil, in water, or in a specific process fluid) to simulate the actual service environment. The reduction rate of the breaking strength in each medium is reported. We report the reduction rate and the compatibility with the medium.

UV and Weathering Aging – Evaluating the Effect of Solar Radiation on Mechanical Performance

UV radiation and weathering are major causes of degradation for materials used outdoors. Our tests simulate the effects of sunlight (UV radiation) and moisture (condensation) on the breaking strength of materials, providing essential data for the design of outdoor products in the diverse Croatian climate (coastal, continental, and mountainous).

• UV aging test (ASTM G154 / ISO 4892-3 / HRN EN ISO 4892-3 / NTC 5610 – for the UV exposure) – we expose the test specimens to alternating cycles of UV radiation (UVA‑340 lamps) and condensation in a UV weathering chamber. The test is performed for a specified duration (e.g., 500, 1000, or 2000 hours) at a specified temperature (e.g., 60 °C during the UV exposure, 50 °C during the condensation). After the exposure, we perform a tensile test to measure the residual breaking strength. The reduction rate is calculated. We report the residual tensile strength, the reduction rate, and the UV exposure duration.
• Xenon arc weathering test (ASTM G155 / ISO 4892-2 / NTC 5611 – for the full‑spectrum sunlight simulation) – we use a xenon arc weathering chamber with daylight filters and water spray to simulate the full spectrum of sunlight (UV, visible, and infrared). The test is performed for a specified duration. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.
• Weathering test with humidity and water spray (NTC 5612 – for the combined effect of UV, moisture, and temperature) – we include water spray cycles (e.g., 18 minutes of spray per 2 hours of light exposure) to simulate the effect of rain and thermal shock. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength, the reduction rate, and the weathering conditions.
• UV aging at different irradiance levels (NTC 5613 – for the accelerated and natural exposure) – we adjust the irradiance level (e.g., 0.35, 0.55, or 0.85 W/m² at 340 nm) to accelerate the aging process. The reduction rate is measured at each irradiance level, and the acceleration factor is calculated. We report the reduction rate, the acceleration factor, and the irradiance level.
• UV aging on different material surfaces (NTC 5614 – for the surface‑specific degradation) – we expose the material to UV radiation on both the front (top) and the back (bottom) sides to evaluate the surface‑specific degradation. The reduction rate on each surface is reported. We report the reduction rate on each surface and the depth of the degradation.

Ozone Aging and Weathering – Evaluating the Effect of Ozone on Mechanical Performance

Ozone is a major cause of degradation for elastomers (especially those with unsaturated carbon bonds). Our ozone aging tests simulate the effect of atmospheric ozone on the breaking strength of rubber and elastomeric materials, which is essential for applications such as tires, seals, and hoses.

• Ozone aging test (ASTM D1149 / ISO 1431-1 / HRN EN ISO 1431-1 / NTC 5620 – for the ozone resistance) – we expose the test specimens to a specified ozone concentration (e.g., 50 ppb, 100 ppb, or 500 ppb) at a controlled temperature (e.g., 40 °C) and humidity (e.g., 50 % RH) for a specified duration (e.g., 24, 48, 72, or 168 hours). After the exposure, we inspect the specimens for cracks (using a magnifying glass) and measure the residual tensile strength. The reduction rate of the breaking strength is calculated. We report the residual tensile strength, the reduction rate, the crack rating, and the ozone concentration.
• Ozone aging under dynamic strain (NTC 5621 – for the dynamic ozone resistance) – we subject the test specimens to cyclic tensile or flexural strain (e.g., 10 % strain, 1 Hz) during the ozone exposure to simulate the dynamic conditions of a tire or a hose. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength, the reduction rate, and the dynamic strain.
• Ozone aging at different concentrations (NTC 5622 – for the threshold determination) – we perform the ozone aging test at multiple ozone concentrations (e.g., 10 ppb, 50 ppb, 100 ppb, 500 ppb) to determine the threshold concentration for the material. The reduction rate at each concentration is reported. We report the reduction rate at each concentration and the threshold concentration.
• Ozone aging with thermal cycling (NTC 5623 – for the combined ozone and temperature stress) – we combine the ozone exposure with thermal cycling (e.g., from 23 °C to 60 °C) to simulate the conditions of outdoor and industrial environments. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.
• Ozone aging on different materials (NTC 5624 – for the comparative evaluation) – we compare the ozone aging resistance of different elastomeric materials (e.g., EPDM, NBR, and silicone) by measuring the reduction rate of the breaking strength under the same test conditions. The comparative results are reported. We report the reduction rate for each material and the ranking.

Humidity and Moisture Aging – Evaluating the Effect of Water on Mechanical Performance

Humidity and moisture can significantly reduce the breaking strength of hygroscopic materials (e.g., nylon, cellulose, and certain composites) and can accelerate the degradation of adhesives and coatings. Our humidity aging tests simulate the effect of high humidity and water immersion on the mechanical properties, which is essential for applications in humid and coastal environments.

• Humidity aging test (ASTM D570 / NTC 5630 – for the moisture absorption) – we condition the test specimens at a high‑humidity environment (e.g., 40 °C, 95 % RH) for a specified duration (e.g., 7, 14, or 28 days) or immerse them in water at a specified temperature (e.g., 23 °C, 40 °C, 60 °C) for a specified duration. After the exposure, we measure the moisture uptake (in %), the dimensional change, and the residual breaking strength. The reduction rate is calculated. We report the residual tensile strength, the reduction rate, the moisture uptake, and the dimensional change.
• Humidity aging with thermal cycling (NTC 5631 – for the combined humidity and temperature stress) – we subject the material to repeated cycles of high humidity (e.g., 40 °C, 95 % RH) and elevated temperature (e.g., 60 °C) to simulate the tropical and industrial environments. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.
• Water immersion and salt spray effect (ASTM B117 / NTC 5632 – for the corrosive environment) – we expose the material to a 5 % NaCl salt spray at 35 °C for a specified duration (e.g., 240, 500, or 1000 hours). The residual breaking strength and the reduction rate are reported. We report the residual tensile strength, the reduction rate, and the corrosion rating.
• Humidity aging on adhesives and bonded joints (NTC 5633 – for the adhesive bond durability) – we expose bonded joints (e.g., single‑lap shear joints) to high humidity and then measure the residual bond strength (the lap shear strength). The reduction rate of the bond strength is reported. We report the residual bond strength and the reduction rate.
• Humidity aging and freeze‑thaw effect (NTC 5634 – for the cold‑climate applications) – we subject the material to repeated freeze‑thaw cycles (e.g., -20 °C to +20 °C) after a humidity exposure, to simulate the conditions of the Croatian continental climate. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.

Chemical and Environmental Aging – Evaluating the Effect of Chemical Exposure on Mechanical Performance

Chemical exposure to oils, solvents, acids, and bases can cause a significant loss of breaking strength in many materials. Our chemical aging tests simulate the effect of exposure to process fluids and environmental contaminants on the mechanical properties, which is essential for applications in the chemical, oil and gas, and automotive industries.

• Chemical immersion test (ASTM D543 / ISO 175 / NTC 5640 – for the chemical resistance) – we immerse the test specimens in a specified chemical (e.g., mineral oil, 10 % HCl, 10 % NaOH, gasoline, or a specific solvent) at a controlled temperature (e.g., 23 °C, 40 °C, 60 °C) for a specified duration (e.g., 7, 14, or 28 days). After the exposure, we measure the change in the mass, the dimensions, and the residual breaking strength. The reduction rate is calculated. We report the residual tensile strength, the reduction rate, the mass change, and the dimensional change.
• Chemical exposure with thermal aging (NTC 5641 – for the combined chemical and thermal stress) – we combine the chemical immersion with an elevated temperature (e.g., 60 °C) to simulate the conditions of hot process fluids. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.
• Chemical exposure under stress (NTC 5642 – for the stress‑corrosion cracking) – we apply a tensile or bending stress to the specimen during the chemical exposure (using a stress fixture) to evaluate the susceptibility to stress‑corrosion cracking (SCC). The residual breaking strength and the reduction rate are reported. We report the residual tensile strength, the reduction rate, and the SCC susceptibility.
• Chemical exposure with UV radiation (NTC 5643 – for the outdoor chemical resistance) – we combine the chemical exposure with UV radiation to simulate the conditions of outdoor equipment and storage. The residual breaking strength and the reduction rate are reported. We report the residual tensile strength and the reduction rate.
• Chemical exposure on different materials (NTC 5644 – for the comparative evaluation) – we compare the chemical resistance of different material grades (e.g., different rubber compounds or different plastic grades) by measuring the reduction rate of the breaking strength under the same exposure conditions. The comparative results are reported. We report the reduction rate for each material and the ranking.

Calculation and Interpretation of the Reduction Rate – Quantifying the Performance Loss

The reduction rate of the breaking strength is calculated from the measured residual strength and the original (un‑aged) strength. Our tests provide the reduction rate, the residual strength, and the retention of the strength (in %), which are essential for material selection and for the prediction of the service life.

• Reduction rate calculation (NTC 5650 – for the quantitative degradation assessment) – we calculate the reduction rate (RR) using the formula: RR (%) = [(Strength_unaged – Strength_aged) / Strength_unaged] × 100. We also calculate the strength retention (SR) as: SR (%) = (Strength_aged / Strength_unaged) × 100. We report the RR and the SR for each test condition.
• Statistical analysis and confidence intervals (NTC 5651 – for the data reliability) – we test a minimum of 5 specimens for each condition (unaged and aged) and report the average, the standard deviation, the coefficient of variation, and the 95 % confidence interval for the reduction rate. We report the statistical parameters and the confidence interval.
• Pass/fail criteria and compliance verification (NTC 5652 – for the specification compliance) – we compare the measured reduction rate with the maximum allowable reduction rate specified by the customer or the standard (e.g., a maximum reduction of 20 % for the tensile strength after 7 days at 70 °C). We report the compliance and the pass/fail status.
• Life prediction and extrapolation (NTC 5653 – for the service life estimation) – using the reduction rate data at different aging durations and temperatures, we apply the Arrhenius model (or another appropriate model) to predict the time required to reach a specified reduction rate (e.g., a 50 % reduction in strength) at the service temperature. We report the predicted service life and the acceleration factor.
• Comparative ranking of materials (NTC 5654 – for the material selection) – we perform the aging test on multiple materials (or different grades of the same material) and compare their reduction rates to select the material with the best aging resistance for the intended application. We report the ranking and the comparative results.

Complementary Tests – Hardness, Tensile, and Microstructure for Aging Correlation

To fully understand the cause of the breaking strength reduction and to correlate it with the physical and microstructural changes of the material, we perform complementary tests, including hardness testing, tensile testing (for the unaged material), and microstructural examination.

• Hardness testing (ASTM D2240 / NTC 5660 – Shore A or Shore D for elastomers and plastics) – we measure the Shore A or Shore D hardness of the material before and after the aging. The change in the hardness is correlated with the reduction rate. We report the hardness change and the correlation.
• Tensile properties of the unaged material (ASTM D412 / ISO 37 / NTC 5661 – for the elastomers; ASTM D638 / ISO 527 / NTC 5662 – for plastics) – we measure the tensile strength (in MPa), the elongation at break (in %), and the modulus (in MPa) of the unaged material. These properties are used as the baseline for the reduction rate calculation. We report the tensile properties of the unaged material.
• Microstructural examination (SEM – ASTM E1508 / NTC 5663 – for the surface and cross‑section analysis) – we use scanning electron microscopy (SEM) to examine the surface and the cross‑section of the aged material to detect the micro‑cracks, the voids, the phase separation, or the degradation of the filler‑matrix interface. The microstructural changes are correlated with the reduction rate. We report the SEM images and the microstructural changes.
• FTIR spectroscopy (ASTM E168 / NTC 5664 – for the chemical degradation analysis) – we use FTIR spectroscopy to analyze the chemical changes (e.g., the oxidation, the chain scission, or the loss of plasticizer) of the material after the aging. The chemical changes are correlated with the reduction rate. We report the FTIR spectra and the chemical changes.
• Differential scanning calorimetry (DSC) – ASTM D3418 / NTC 5665 – for the thermal transitions) – we use DSC to measure the glass transition temperature (Tg) and the melting temperature (Tm) of the material before and after the aging. The changes in the Tg and the Tm are correlated with the reduction rate. We report the Tg, the Tm, and the changes.

Test Report and Recognition in the Croatian Industrial, Automotive, and Construction Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (ovens, weathering chambers, universal testing machines, and analytical instruments) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the material (manufacturer, material type, batch number, dimensions, and intended application).
• Detailed description of the test methods applied (ASTM/ISO/HRN EN/NTC standards, test conditions, aging duration, and exposure parameters).
• Numerical results: residual tensile strength (MPa), residual elongation (%), reduction rate of the breaking strength (%), strength retention (%), hardness change (points Shore), mass change (%), and property retention after aging (%).
• Graphical data: reduction rate vs. aging time curves, Arrhenius plots, and FTIR spectra.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ASTM D573, ISO 188, ASTM G154, HRN EN ISO 188, and the requirements of the HZN, Ministarstvo graditeljstva, and Državni inspektorat).
• Photographs and micrographs (SEM) of the material before and after the aging, showing the surface cracks, the degradation, and the structural changes.
• Recommendations for material selection, formulation optimization, and quality control measures to reduce the reduction rate and to enhance the aging resistance.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo gospodarstva i održivog razvoja for industrial and energy compliance, by the Državni inspektorat for market surveillance, by the Ministarstvo graditeljstva i prostornoga uređenja for building materials approval, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of polymeric, elastomeric, and composite materials. Additionally, we offer consulting services for the selection of aging‑resistant materials, the design of durable products, and the implementation of quality control programs for aging performance, contributing to the safety, reliability, and longevity of products in the diverse and growing Croatian market, from the automotive and aerospace sectors to the construction, medical, and consumer goods industries.