Polymer peel strength testing service

Polymer Peel Strength Testing Service – Accredited ISO/IEC 17025 Adhesive Bond Performance Assessment for the Croatian Market

Polymer peel strength is a critical adhesion property that quantifies the force required to separate two bonded flexible adherends, or to peel a flexible adherend from a rigid substrate, at a specified angle and speed. This property is essential for ensuring the reliability, safety, and performance of adhesive tapes, labels, medical patches, flexible packaging, laminates, protective films, and structural bonded joints used in automotive, aerospace, electronics, healthcare, and consumer goods industries. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Državni inspektorat, the Ministarstvo gospodarstva i održivog razvoja, the Agencija za lijekove i medicinske proizvode (HALMED), and the Carinska uprava enforce strict quality, safety, and regulatory standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of peel strength is essential for product certification, supplier qualification, type testing, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive polymer peel strength testing service, applying standardized methods such as ASTM D903, ISO 8510-1, ASTM D1876, ISO 11339, ASTM D3330, ISO 29862, ASTM D3167, and HRN EN ISO 8510-1 to measure peel force, peel strength, failure mode, and adhesive fracture energy under controlled conditions of angle, speed, and temperature. 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.

Polymer Samples and Adhesive Assemblies We Regularly Test

Our laboratory receives a wide variety of polymer materials, adhesive joints, and flexible assemblies for peel strength testing. Typical samples include:

• Adhesive tapes and labels – pressure‑sensitive tapes, double‑sided tapes, and self‑adhesive labels for packaging, electronics, and automotive applications.
• Flexible packaging laminates – multi‑layer films, pouches, and bags for food, pharmaceutical, and consumer goods.
• Medical patches and drug‑delivery systems – transdermal patches, wound dressings, and skin adhesives.
• Protective films and surface covers – for automotive paint protection, electronic displays, and construction surfaces.
• Structural bonded joints – automotive body panels, aerospace composites, and architectural panels.
• Coated textiles and flexible composites – for technical and protective clothing.
• Prototype and new adhesive formulations – submitted by manufacturers for validation of peel strength before series production.
• Field‑retrieved adhesive bonds – for failure analysis and remaining life assessment.

180° Peel Testing – Standard Method for Flexible Adherends

The 180° peel test is the most widely used method for evaluating the peel strength of flexible polymer assemblies. A flexible adherend is peeled back at a 180° angle from a rigid or flexible substrate, and the force required to continue the peel is measured. Our procedures follow international standards and the requirements of the Croatian packaging, automotive, and medical device sectors.

• 180° peel test (ASTM D903 / ISO 8510-1 / HRN EN ISO 8510-1 / NTC 5700 – for flexible adherends) – we prepare a peel test specimen (typically 25 mm wide and 150 mm long) with the flexible adherend bonded to the substrate over a specified length. The specimen is mounted in a universal testing machine, and the free end of the flexible adherend is clamped in the upper grip. The test is performed at a specified peel speed (typically 50 mm/min, 150 mm/min, or 300 mm/min) and at a 180° angle. The peel force (in N) is measured continuously over the peel length. The peel strength (in N/mm or N/25 mm) is calculated as the average peel force divided by the width of the specimen. We report the peel strength, the peel force curve, and the failure mode (adhesive, cohesive, or substrate failure).
• 180° peel test at different peel speeds (NTC 5701 – for the speed‑dependence evaluation) – we perform the peel test at multiple peel speeds (e.g., 10 mm/min, 50 mm/min, 150 mm/min, 300 mm/min, 600 mm/min) to evaluate the rate‑dependence of the peel strength. We report the peel strength at each speed and the speed‑sensitivity curve.
• 180° peel test at different temperatures (NTC 5702 – for the thermal effect) – we perform the peel test at elevated temperatures (e.g., 40 °C, 60 °C, 80 °C) or at low temperatures (e.g., -10 °C, -20 °C) using a temperature‑controlled chamber. We report the peel strength at each temperature and the temperature coefficient.
• 180° peel test after aging (NTC 5703 – for the durability assessment) – we age the peel test specimens (e.g., by thermal aging, UV exposure, humidity, or chemical exposure) and then perform the peel test. We report the peel strength after aging and the retention of the peel strength (in %).
• 180° peel test with different substrates (NTC 5704 – for the substrate compatibility) – we test the same adhesive on different substrates (e.g., metal, glass, polymer, and paper) to evaluate the substrate compatibility and the adhesion to different surfaces. We report the peel strength for each substrate.

T‑Peel Testing – Method for Flexible‑to‑Flexible Bonded Joints

The T‑peel test is used to evaluate the peel strength of a flexible‑to‑flexible bonded joint, where both adherends are flexible. The specimen is bent into a T‑shape, and the two flexible legs are pulled apart at a 180° angle. Our procedures follow international standards and the requirements of the Croatian packaging, textile, and automotive industries.

• T‑peel test (ASTM D1876 / ISO 11339 / HRN EN ISO 11339 / NTC 5710 – for flexible‑to‑flexible joints) – we prepare a T‑peel specimen (typically 25 mm wide and 150 mm long) with the two flexible adherends bonded together over a specified length. The free ends of the two adherends are clamped in the upper and lower grips of the testing machine. The test is performed at a specified peel speed (typically 50 mm/min or 150 mm/min). The peel force (in N) is measured continuously. The T‑peel strength (in N/mm or N/25 mm) is calculated as the average peel force divided by the width of the specimen. We report the T‑peel strength, the peel force curve, and the failure mode.
• T‑peel test at different peel speeds (NTC 5711 – for the rate‑dependence evaluation) – we perform the T‑peel test at multiple peel speeds (e.g., 10 mm/min, 50 mm/min, 150 mm/min, 300 mm/min) to evaluate the rate‑dependence of the T‑peel strength. We report the T‑peel strength at each speed.
• T‑peel test at different temperatures (NTC 5712 – for the thermal effect) – we perform the T‑peel test at elevated temperatures (e.g., 40 °C, 60 °C) and at low temperatures (e.g., -10 °C) to evaluate the effect of temperature on the peel strength. We report the T‑peel strength at each temperature.
• T‑peel test after environmental exposure (NTC 5713 – for the durability assessment) – we expose the T‑peel specimens to a corrosive environment (e.g., salt spray, humidity) or to thermal aging, and then we perform the T‑peel test. We report the T‑peel strength after exposure and the retention of the peel strength.
• T‑peel test with different adhesive thicknesses (NTC 5714 – for the adhesive layer optimization) – we test T‑peel specimens with different adhesive layer thicknesses (e.g., 0.1 mm, 0.2 mm, 0.5 mm) to evaluate the effect of the adhesive thickness on the peel strength. We report the T‑peel strength for each thickness.

90° Peel Testing – Method for Tapes and Films

The 90° peel test is used to evaluate the peel strength of pressure‑sensitive tapes and films from a rigid substrate. The test is performed at a 90° angle, which provides a more uniform stress distribution and is less sensitive to the stiffness of the flexible adherend. Our procedures follow international standards and the requirements of the Croatian electronics, medical, and consumer goods industries.

• 90° peel test (ASTM D3330 / ISO 29862 / HRN EN ISO 29862 / NTC 5720 – for tapes and films) – we apply a tape or a film to a rigid test panel (stainless steel, glass, or other specified substrate) using a specified pressure (e.g., a 2 kg roller, two passes). The test is performed at a 90° angle using a test fixture that holds the rigid panel in a horizontal position. The peel force (in N) is measured at a specified peel speed (e.g., 300 mm/min). The peel strength (in N/25 mm) is calculated as the average peel force divided by the width of the specimen. We report the peel strength, the peel force curve, and the failure mode.
• 90° peel test at different peel speeds (NTC 5721 – for the rate‑dependence evaluation) – we perform the 90° peel test at multiple peel speeds (e.g., 50 mm/min, 150 mm/min, 300 mm/min, 600 mm/min) to evaluate the rate‑dependence of the peel strength. We report the peel strength at each speed.
• 90° peel test after aging (NTC 5722 – for the durability assessment) – we age the tapes (e.g., by thermal aging, UV exposure, or humidity) and then perform the 90° peel test. We report the peel strength after aging and the retention of the peel strength.
• 90° peel test on different substrates (NTC 5723 – for the substrate compatibility) – we test the same tape on different substrates (e.g., steel, aluminum, glass, and polyethylene) to evaluate the substrate compatibility. We report the peel strength for each substrate.
• 90° peel test with different dwell times (NTC 5724 – for the contact time effect) – we apply the tape to the substrate and wait for different dwell times (e.g., 1 minute, 10 minutes, 1 hour, 24 hours) before performing the peel test, to evaluate the effect of the contact time on the peel strength. We report the peel strength at each dwell time.

Floating Roller Peel Testing – Method for Structural Adhesives

The floating roller peel test is used to evaluate the peel strength of structural adhesive joints, where the flexible adherend is peeled from a rigid substrate at a 90° angle while the rigid substrate is allowed to rotate on a floating roller. This test provides a more consistent peel angle and is less sensitive to the stiffness of the flexible adherend.

• Floating roller peel test (ASTM D3167 / ISO 4578 / NTC 5730 – for structural adhesives) – we prepare a peel specimen (typically 25 mm wide and 150 mm long) with the flexible adherend bonded to the rigid substrate. The specimen is mounted in a floating roller peel test fixture. The test is performed at a specified peel speed (typically 50 mm/min or 150 mm/min). The peel force (in N) is measured continuously. The peel strength (in N/mm) is calculated as the average peel force divided by the width of the specimen. We report the peel strength, the peel force curve, and the failure mode.
• Floating roller peel test at different temperatures (NTC 5731 – for the thermal effect) – we perform the floating roller peel test at elevated temperatures (e.g., 40 °C, 60 °C, 80 °C) using a temperature‑controlled chamber. We report the peel strength at each temperature.
• Floating roller peel test after environmental aging (NTC 5732 – for the durability assessment) – we expose the peel specimens to a corrosive environment (e.g., salt spray, humidity) or to thermal aging, and then we perform the floating roller peel test. We report the peel strength after exposure and the retention of the peel strength.
• Floating roller peel test with different substrate thicknesses (NTC 5733 – for the geometry effect) – we test peel specimens with different flexible adherend thicknesses to evaluate the effect of the adherend thickness on the peel strength. We report the peel strength for each thickness.
• Floating roller peel test with different adhesive cure conditions (NTC 5734 – for the process optimization) – we test peel specimens with different adhesive cure conditions (e.g., different cure temperatures, different cure times) to evaluate the effect of the curing process on the peel strength. We report the peel strength for each cure condition.

Environmental and Aging Effects – Evaluating Long‑Term Adhesive Durability

The peel strength of polymer adhesive bonds can change over time due to thermal aging, UV exposure, humidity, chemical attack, and mechanical stress. Our environmental and aging tests evaluate the long‑term stability of the peel strength, ensuring the reliability of the adhesive bond over its service life in the diverse Croatian climate (coastal, continental, and mountainous).

• Thermal aging and its effect on peel strength (ASTM D573 / ISO 188 / NTC 5740 – for the heat‑aged adhesives) – we age the peel specimens in an oven at a specified temperature (e.g., 70 °C, 100 °C) for a specified duration (e.g., 7, 14, or 28 days), and then we perform the peel test. We report the peel strength after aging and the retention of the peel strength (in %).
• UV aging and its effect on peel strength (ASTM G154 / NTC 5741 – for the UV‑exposed adhesives) – we expose the peel specimens to UV radiation (UVA‑340) and condensation cycles for a specified duration (e.g., 500 hours), and then we perform the peel test. We report the peel strength after UV exposure and the change.
• Humidity and water immersion effect (ASTM D570 / NTC 5742 – for the moisture‑exposed adhesives) – we immerse the peel specimens in water (or expose them to a 95 % RH environment) at a specified temperature (e.g., 40 °C, 60 °C) for a specified duration (e.g., 7, 14, or 28 days), and then we perform the peel test. We report the peel strength after moisture exposure and the retention of the peel strength.
• Chemical exposure effect (ASTM D543 / NTC 5743 – for the chemically exposed adhesives) – we immerse the peel specimens in various chemicals (e.g., mineral oil, 10 % HCl, 10 % NaOH, or a solvent) for a specified duration (e.g., 7 days), and then we perform the peel test. We report the peel strength after chemical exposure and the compatibility.
• Salt spray effect (ASTM B117 / NTC 5744 – for the corrosion‑exposed adhesives) – we expose the peel specimens to a 5 % NaCl salt spray at 35 °C for a specified duration (e.g., 240, 500, or 1000 hours), and then we perform the peel test. We report the peel strength after salt spray exposure and the retention of the peel strength.

Failure Mode and Fracture Surface Analysis – Identifying the Weakest Link

The analysis of the failure mode and the fracture surface is essential for understanding the cause of the failure and for identifying the weakest link in the bonded joint. Our tests and inspections classify the failure mode, which is crucial for the design improvement and the quality control of adhesive assemblies.

• Failure mode classification (NTC 5750 – for the adhesive, cohesive, and substrate failure) – we inspect the fracture surface of the peeled specimen and classify the failure mode as adhesive failure (failure at the adhesive‑substrate interface), cohesive failure (failure within the adhesive layer), substrate failure (failure of the substrate), or mixed failure (a combination of these). We report the failure mode and the percentage of each type.
• Microscopic examination of the fracture surface (SEM – ASTM E1508 / NTC 5751 – for the detailed analysis) – we use scanning electron microscopy (SEM) to examine the fracture surface at high magnification to identify the micro‑mechanisms of failure (e.g., brittle fracture, ductile failure, void formation, or debonding). We report the SEM images and the failure mechanism.
• Visual inspection of the failure surface (NTC 5752 – for the macroscopic analysis) – we inspect the fracture surface with a magnifying glass (or a low‑power microscope) to identify the location of the failure (e.g., at the edge, in the center, or near the load application point). We report the visual observations and the failure pattern.
• Fracture energy calculation (NTC 5753 – for the energy‑based analysis) – we calculate the fracture energy (the work of adhesion) from the area under the peel force‑displacement curve. The fracture energy is an indicator of the toughness of the adhesive joint. We report the fracture energy (in J/m²).
• Correlation of failure mode with the peel strength (NTC 5754 – for the process improvement) – we correlate the failure mode with the measured peel strength to identify the causes of the low peel strength (e.g., poor surface preparation, inadequate adhesive curing, or a mismatch of the adhesive and the substrate). We report the correlation and the recommendations.

Complementary Tests – Thickness, Hardness, and Surface Energy for Adhesive Correlation

To fully understand the peel strength performance and to correlate it with the material properties, we perform complementary tests, including thickness measurement, hardness testing, and surface energy measurement.

• Adhesive layer thickness measurement (NTC 5760 – for the adhesive thickness) – we measure the thickness of the adhesive layer (in μm) using a non‑destructive thickness gauge (e.g., a magnetic induction gauge for steel substrates) or by cross‑section microscopy. The adhesive thickness is correlated with the peel strength. We report the adhesive thickness and the correlation.
• Hardness testing (ASTM D2240 / NTC 5761 – Shore A or Shore D for the adhesive) – we measure the Shore A or Shore D hardness of the cured adhesive. The hardness is correlated with the peel strength and the flexibility of the adhesive. We report the hardness and the correlation.
• Surface energy measurement (ASTM D7490 / NTC 5762 – for the surface preparation evaluation) – we measure the contact angle of the substrate surface (using the goniometer method) and calculate the surface energy. A high surface energy (and a low contact angle) indicates a clean and wettable surface, which is essential for good adhesion. We report the contact angle and the surface energy.
• Differential scanning calorimetry (DSC) – ASTM D3418 / NTC 5763 – for the adhesive Tg and the curing degree) – we use DSC to measure the glass transition temperature (Tg) of the adhesive and to verify the degree of curing. An incomplete curing can reduce the peel strength. We report the Tg and the curing degree.
• FTIR spectroscopy of the adhesive (ASTM E168 / NTC 5764 – for the chemical composition and the degradation) – we use FTIR spectroscopy to analyze the chemical composition of the adhesive and to detect any degradation (e.g., oxidation, chain scission) caused by the aging or the environmental exposure. We report the FTIR spectra and the chemical changes.

Test Report and Recognition in the Croatian Industrial, Medical, and Packaging Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (universal testing machines, peel test fixtures, and environmental chambers) 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 test sample (adhesive type, substrate material, surface preparation, and curing conditions).
• Detailed description of the test methods applied (ASTM/ISO/HRN EN/NTC standards, peel angle, peel speed, temperature, and duration).
• Numerical results: peel strength (N/mm or N/25 mm), T‑peel strength (N/mm), average peel force (N), failure mode classification, adhesive thickness (μm), hardness (Shore), and peel strength retention after aging (%).
• Graphical data: peel force vs. displacement curves and peel strength vs. time curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ASTM D903, ISO 8510-1, ASTM D1876, ASTM D3330, HRN EN ISO 8510-1, and the requirements of the HZN, HALMED, and Državni inspektorat).
• Photographs and micrographs (SEM) of the fracture surfaces, showing the failure mode and the interfacial condition.
• Recommendations for material selection, surface preparation, and adhesive curing to achieve the required peel strength and durability.
• 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 Agencija za lijekove i medicinske proizvode (HALMED) for medical device certification, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of adhesives, tapes, and bonded components. Additionally, we offer consulting services for the selection of adhesives with high peel strength, the design of surface preparation processes, and the implementation of quality control programs for adhesive bonding, contributing to the safety, reliability, and performance of products in the diverse and growing Croatian market, from the automotive and aerospace sectors to the medical, packaging, and consumer goods industries.