Multiple speed peel testing for the assessment of adhesive tapes

In laboratories responsible for adhesive tape development or production quality control, high sample throughput is often required. Repetitive peel tests on adhesive tapes can create operational bottlenecks, particularly when multiple test conditions such as peel speed or loading rate must be evaluated separately.

Automation of mechanical testing workflows can therefore provide a significant advantage. By reducing operator intervention and enabling sequential testing of multiple specimens, automated systems improve laboratory productivity while maintaining high levels of measurement repeatability.

A further benefit arises when test protocols require the evaluation of adhesive performance across a range of loading rates or peeling speeds. Since the viscoelastic behaviour of pressure-sensitive adhesives is strongly dependent on strain rate, peel speed can significantly influence measured adhesion forces.

Automated multiple sample testing

To address these requirements, the Automated Linear Indexing System (ALIS) has been developed for integration with the TA.XTplusC Texture Analyser. The system enables automated testing of multiple adhesive samples with minimal operator supervision.

ALIS allows a series of specimens to be mounted in custom support plates positioned on a linear indexing platform. During testing, the platform automatically advances between sample positions, enabling sequential measurement without manual repositioning.

Once the operator defines the test protocol and mounts the samples, the instrument performs the full sequence of measurements and reports the results automatically. This reduces operator workload and ensures consistent test execution across large sample sets.

From an operational perspective, automation offers several advantages:

• Increased sample throughput

• Reduced operator-induced variability

• Improved reproducibility of test conditions

• Enhanced laboratory safety due to reduced manual handling

Software-controlled batch testing

Exponent Connect software provides a batch-testing interface that supports automated sample indexing and multi-stage test protocols. The software controls platform movement and manages testing parameters while collecting force, displacement and time data during each measurement.

Within a batch test sequence, the platform can move incrementally in either direction across predefined distances, allowing individual specimens to be tested in succession. This functionality is particularly useful for high-volume adhesive testing where numerous samples must be evaluated under identical conditions.

Multi-speed 90° peel testing

A key capability enabled by the ALIS system is multi-speed peel testing within a single experiment. This feature is particularly valuable when assessing pressure-sensitive adhesives because peel strength is strongly dependent on separation rate due to the viscoelastic nature of the adhesive layer.

Traditional peel testing typically evaluates adhesion at a single crosshead speed, requiring multiple independent tests to investigate the effect of peel rate. In contrast, the ALIS protocol allows several peel speeds to be incorporated into a single continuous test.

In a typical 90° peel test, an adhesive strip is applied to a test platform using a controlled application method to ensure consistent contact pressure and dwell conditions. The free end of the tape is then secured in a tensile grip connected to the instrument crosshead.

The operator defines a sequence of test stages that specify:

• Peel distance for each stage

• Peel speed during that stage

The system supports peel speeds ranging from 0.01 mm/s to 40 mm/s, enabling the characterisation of adhesive behaviour across a wide range of peeling speeds, all within one test.

During the test, the adhesive strip is peeled continuously from the substrate. At the transition point between stages, the instrument automatically adjusts the crosshead speed while maintaining the peel geometry. This produces a single force-distance curve containing multiple segments corresponding to different peel rates.

Data acquisition and analysis

Throughout the test, the Texture Analyser records force, displacement and time data with high resolution. These data are displayed as real-time graphs and stored for post-processing.

A software macro is applied to the recorded dataset to segment the curve according to the predefined test stages. For each peel-speed interval, parameters such as:

• Mean peel force

• Peak force

• Work of adhesion

can be calculated and compared.

Plotting these results against peel speed provides insight into the rate-dependent behaviour of the adhesive, which is an important characteristic of pressure-sensitive systems governed by viscoelastic deformation and energy dissipation mechanisms.

Operator interaction and workflow control

The testing workflow can also incorporate customisable operator prompts, allowing instructions or safety warnings to be displayed during sample preparation or instrument setup. This feature helps ensure that consistent procedures are followed across operators and laboratories.

Practical implications for adhesive development

By combining automated sample indexing with multi-speed peel testing, the ALIS system significantly improves efficiency in adhesive evaluation. The ability to capture multiple peel-rate conditions within a single experiment provides several advantages:

• Reduced total testing time

• Improved consistency between peel-speed measurements

• More comprehensive characterisation of adhesive viscoelastic behaviour

• Higher laboratory throughput for routine testing

For adhesive formulators and quality-control laboratories, this approach enables faster screening of candidate materials and more detailed understanding of how adhesive performance changes with loading rate.