Packaging Material Impact Strength Testing: Methods, Standards, and Quality Assurance

Impact strength testing evaluates the ability of packaging materials to withstand sudden mechanical shocks during manufacturing, filling, handling, and transportation. This technical article reviews the principal test methods—including free-falling dart, pendulum impact, Izod/Charpy, and full-package drop testing—together with the relevant ISO, ASTM, EN, GB, and JIS standards. Understanding these procedures enables manufacturers to select suitable materials, optimize packaging design, and safeguard product integrity throughout the distribution chain.

Technical Overview

Impact strength, also referred to as impact resistance or impact toughness, describes the capacity of a material or package to absorb energy from a sudden blow, shock, or drop without cracking, puncturing, or catastrophically failing. Packaging materials are routinely exposed to dynamic loads: high-speed filling and sealing lines, drops during manual or automated handling, impacts between stacked units, and shocks transmitted through transport vehicles. A material with inadequate impact resistance may fail in a brittle manner, resulting in leaks, product contamination, spoilage, or physical damage to the goods inside.

Impact strength inspection therefore serves several purposes within a quality management system:

• Verification that incoming raw materials (resins, films, sheets, boards) meet contractual and regulatory specifications
• Comparison of candidate materials during packaging design and development
• Monitoring of production consistency, including the influence of processing parameters such as film orientation, cooling rate, and sealing temperature
• Assessment of environmental effects, such as reduced toughness at low temperatures or after accelerated aging
• Compliance demonstration against international standards and customer-specific performance criteria

Accredited third-party laboratories typically perform impact testing in temperature- and humidity-controlled environments (commonly 23 ± 2 °C and 50 ± 10% relative humidity) with preconditioned specimens, so that results are reproducible and comparable between laboratories.

Testing Samples

Flexible Films and Laminates

Single-layer and multilayer plastic films used for pouches, bags, overwraps, and liners, including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA), and aluminum-foil-based laminates. These materials are primarily evaluated by free-falling dart and pendulum (ball burst) methods because their thin-gauge geometry makes conventional notched-bar methods unsuitable.

Rigid and Semi-Rigid Plastic Packaging

Bottles, jars, drums, trays, closures, blister bases, and thermoformed containers made from PET, HDPE, PP, PVC, or polystyrene. Sheet or molded plaques cut from these containers can be machined into notched or unnotched bars for Izod, Charpy, or tensile impact testing.

Paper-Based Packaging

Corrugated fiberboard boxes, folding cartons, and solid board. While these are more commonly assessed by burst, puncture, and compression tests, filled transport packages are subject to drop and horizontal impact testing to simulate distribution hazards.

Foam and Cushioning Materials

Expanded polystyrene (EPS), expanded polyethylene (EPE), expanded polypropylene (EPP), and other cushioning foams, which are evaluated for their energy-absorption characteristics under dynamic loading.

Composite Containers and Finished Packages

Complete, filled packages—boxes, drums, crates, and unit loads—tested as assembled systems to verify that the material, structure, and closure design together survive realistic impact events.

Testing Items

Depending on the material form and the intended use of the package, the following impact-related parameters are typically measured and reported:

• Free-falling dart impact resistance, expressed as the F50 dart mass (the mass at which 50% of specimens fail) or as total impact energy
• Pendulum (ball burst) impact strength, expressed as the energy in joules required to rupture a film specimen
• Izod impact strength, notched or unnotched, in kJ/m²
• Charpy impact strength, notched or unnotched, in kJ/m²
• Tensile impact strength for materials too thin or too flexible for flexed-beam tests, in kJ/m²
• Drop impact resistance of complete filled packages, expressed as the maximum drop height survived or the pass/fail height for a specified orientation
• Failure mode classification (brittle, ductile, or partial fracture) and, where required, the brittleness temperature at which failure transitions from ductile to brittle

Testing Methods

Free-Falling Dart Method

A hemispherical-headed dart of adjustable mass is dropped from a fixed height onto a clamped film specimen. The dart mass is increased or decreased according to a staircase (bruceton) sequence after each pass or fail, and the statistical F50 value is calculated. The method is specified in ASTM D1709 (Methods A and B), ISO 7765-1, and GB/T 9639. It is the industry reference method for gauging the toughness of packaging films and laminates.

Pendulum (Ball Burst) Impact Method

A pendulum-mounted hemispherical striker swings through a specimen clamped over a circular aperture, and the energy absorbed at rupture is read directly from the loss of pendulum energy. This method, covered by ASTM D3420, ISO 7765-2, and GB/T 8809, is sensitive to small differences in film toughness and is well suited to quality control of high-speed packaging lines.

Izod and Charpy Impact Methods

For rigid plastics, rectangular bars—usually notched with a standardized cutter—are struck by a swinging pendulum either in the cantilever (Izod) configuration per ASTM D256, ISO 180, and GB/T 1843, or in the three-point bending (Charpy) configuration per ISO 179-1 and GB/T 1043. The absorbed energy is normalized by specimen width or cross-sectional area. Multiple specimens are tested to obtain mean values and to identify brittle versus ductile failure behavior.

Tensile Impact Method

Specimens with reduced gauge sections are fractured under a high-speed tensile pulse delivered by a pendulum or falling-weight apparatus, per ASTM D1822 and ISO 8256. This method is useful for materials that show excessive flexural deflection in beam-type tests and for evaluating the effect of notch sharpness at high strain rates.

Complete Package Drop and Impact Testing

Filled transport packages are dropped from a specified height onto corners, edges, and faces, or subjected to programmed horizontal impacts, in accordance with ASTM D5276, ISO 2248, and GB/T 4857.5. These system-level tests verify that the combined package—material, structure, cushioning, and closure—protects the contents under realistic distribution hazards. Horizontal and rotational edge drops may be performed using inclined-plane or shock-test equipment.

Instrumented and Environmental Impact Testing

Instrumented strikers fitted with force transducers record full force–displacement curves, allowing analysts to distinguish initiation energy from propagation energy. Testing can also be repeated at sub-ambient or elevated temperatures to determine the temperature range over which the packaging material retains adequate toughness, which is critical for frozen-food packaging and cold-chain logistics.

Applications

Impact strength inspection supports quality and safety decisions across all major packaging sectors:

• Food and beverage packaging: verifying that films, pouches, and bottles survive filling, capping, palletizing, and distribution without puncture or fracture
• Pharmaceutical and medical packaging: confirming that blister films, sachets, and sterile barrier systems resist handling shocks while remaining intact and tamper-evident
• E-commerce and parcel shipping: qualifying corrugated shippers and cushioning systems against repeated drops encountered in sortation networks
• Industrial and chemical packaging: demonstrating that drums, jerrycans, and intermediate bulk containers withstand impact loads in accordance with dangerous-goods performance requirements
• Electronics and precision goods: validating protective packaging that must absorb impact energy without transmitting damaging shock to sensitive contents
• Material development and supplier qualification: benchmarking resin grades, additives, and recycled-content levels against impact performance targets

FAQ

What does F50 mean in dart drop testing?

F50 is the dart mass at which 50% of the tested specimens fail. It is derived from a statistical (staircase) analysis of pass/fail results across a series of dart masses and is the standard reporting value for film impact resistance.

Which method should be used for flexible packaging films?

Free-falling dart testing (ASTM D1709, ISO 7765-1, GB/T 9639) and pendulum ball burst testing (ASTM D3420, ISO 7765-2, GB/T 8809) are the most appropriate. The dart method suits general qualification, while the pendulum method offers high sensitivity for routine process control.

How are specimens conditioned before testing?

Specimens are normally conditioned at 23 ± 2 °C and 50 ± 10% relative humidity for a defined period—commonly at least 40 hours for plastics—and tested in the same atmosphere to ensure reproducible results. For cold-chain applications, additional conditioning at the intended service temperature is recommended.

What is the difference between Izod and Charpy impact tests?

Both use a swinging pendulum to break a notched specimen, but the Izod test strikes a cantilever-held specimen (ASTM D256, ISO 180), while the Charpy test strikes a simply supported specimen in three-point bending (ISO 179-1). The choice depends on material behavior, specimen availability, and the governing specification.

Can finished packages be tested instead of material samples?

Yes. Complete filled packages are drop-tested or impact-tested per ASTM D5276, ISO 2248, and GB/T 4857.5. System-level testing complements material-level data because it captures the contribution of design, geometry, closures, and internal fitments to real-world impact performance.

How are results interpreted and reported?

Reports from accredited third-party laboratories typically state the test standard, specimen dimensions and preparation, conditioning, test temperature, individual and mean impact values, failure modes, and a clear pass/fail conclusion against the specified acceptance criteria, providing objective evidence for quality audits and customer submissions.