Tear Strength Testing Standards for Packaging Materials: Methods, Samples, and Applications

Tear strength testing measures the ability of packaging materials to resist the propagation of an initiated tear, a critical performance parameter for films, laminates, papers, and woven packaging. This article summarizes the major international and national testing standards—including ISO, ASTM, TAPPI, EN, JIS, and GB methods—and explains test samples, testing items, procedures, and typical applications. Whether you perform in-house quality control or outsource to accredited third-party laboratories, this guide will help you select the correct tear force test method for your packaging materials.

Technical Overview

Tear strength, also referred to as tear resistance or tear propagation force, is the force required to continue tearing a packaging material after an initial cut or nick has been introduced. Unlike tensile strength, which measures the force needed to rupture an intact material, tear testing evaluates how easily an existing flaw propagates through the material under stress. This distinction is essential because virtually all real-world packaging failures begin at a small defect, a seal edge, a fold line, or a tear notch.

Packaging materials are subjected to tear-inducing stresses throughout their life cycle: during converting and printing, machine filling and sealing, transport vibration and compression, retail handling, and consumer opening. A material with insufficient tear resistance may split during shipment and cause product loss or contamination, while a material with excessive tear resistance may defeat intentional easy-open features. Tear force testing therefore serves as a key quality control and product design tool for flexible packaging converters, paper mills, and brand owners.

Numerous standards organizations publish tear testing standards, and the correct choice depends on the material type and the failure mode of interest:

• ISO – ISO 6383-1 (trouser tear for plastic film and sheeting), ISO 6383-2 (Elmendorf method for plastic film), ISO 1974 (paper, Elmendorf method)
• ASTM International – ASTM D1922 (Elmendorf tear of plastic film), ASTM D1004 (Graves tear of plastic film and sheeting), ASTM D1424 (Elmendorf tear of woven fabrics), ASTM D689 (paper internal tearing resistance)
• TAPPI – TAPPI T 414 (internal tearing resistance of paper)
• GB (China national standards) – GB/T 16578 series (tear of plastic films), GB/T 455 (tearing of paper), GB/T 3917 series (tear of textiles and packaging fabrics)
• EN and JIS – European and Japanese national adoptions covering equivalent film, paper, and textile tear methods

Test results are typically expressed in millinewtons (mN) or newtons (N), and many methods report tear strength normalized by thickness or specimen count. Because tear behavior is highly directional, testing is almost always performed in both the machine direction (MD) and transverse direction (TD) of the material.

Testing Samples

Plastic Monolayer Films

Single-layer films such as LDPE, LLDPE, CPP, BOPP, BOPET, and BOPA are the most common substrates for tear testing. These materials, typically ranging from about 20 µm to 200 µm in thickness, exhibit pronounced anisotropy due to molecular orientation introduced during film extrusion and orientation. Specimens are usually die-cut with clean, nick-free edges, since any unintended edge defect will invalidate the measurement.

Multilayer Laminated Films

Laminated structures such as PET/AL/PE, BOPP/VMPET/CPP, PA/PE, and paper/foil/polyethylene combinations are widely used for food, pharmaceutical, and industrial packaging. Tear testing of laminates evaluates the combined structure, including interlayer adhesion effects. Delamination during tearing is recorded because it can significantly alter propagation behavior compared with individual layers.

Paper and Paperboard

Kraft wrapping paper, sack paper, coated papers, and carton board are tested for internal tearing resistance, which reflects fiber bonding and refining quality. Paper tear strength is strongly influenced by moisture content, so strict conditioning in a standard atmosphere is mandatory before testing.

Aluminum Foil and Foil Laminates

Bare and converted aluminum foils used in blister lidding, chocolate wraps, and barrier laminates are evaluated for tear and nick sensitivity. Foil structures often fail by tear propagation from pinholes or score lines, making controlled tear testing important for converting operations such as die cutting and easy-tear scoring.

Woven and Nonwoven Packaging Fabrics

PP woven sacks, FIBC liner fabrics, jute packaging, and nonwoven shipping bags are tested using fabric tear standards. The tongue (single-rip) tear method is commonly applied, and results are reported per specimen or normalized by fabric construction.

Testing Items

Depending on the material and the selected standard, the following tear-related properties are typically measured and reported:

• Elmendorf tear resistance – the mean force, in mN, required to propagate a tear through a slit specimen at high speed using a pendulum-type instrument
• Trouser tear force – the average force, in N, required to tear a trouser-shaped specimen at a constant separation speed on a tensile tester
• Graves tear strength – the maximum load, in N, required to initiate tearing of a notched specimen at low crosshead speed
• MD and TD tear strength – directional tear values used to characterize anisotropy and verify balanced film orientation
• Tear strength retention – tear performance after heat aging, flex cracking, or environmental conditioning
• Statistical reporting – mean value, standard deviation, and coefficient of variation across the required number of specimens, as specified by each method

Testing Methods

Elmendorf Pendulum Method (High-Speed Tear)

The Elmendorf method is the most widely used procedure for packaging films and paper. A rectangular specimen is clamped in a pendulum tear tester, a precise slit of defined length is cut in one edge, and the pendulum is released. The energy absorbed in propagating the tear is converted into a tear force reading. Digital instruments use optical encoders and electronic energy calculation, improving repeatability compared with purely mechanical scales. Principal standards include ISO 6383-2 and ASTM D1922 for plastic films, ISO 1974, TAPPI T 414, ASTM D689, and GB/T 455 for paper, and ASTM D1424 with GB/T 3917 for woven fabrics. Pendulum capacity is selected so that the measured value falls within the calibrated range of the instrument, and appropriate reinforcement, such as linen or polyester strips, may be applied to very weak or extensible films as permitted by the standard.

Trouser Tear Method (Constant-Rate Extension)

In the trouser tear method, a specimen with a central cut forming two legs is gripped in a universal tensile testing machine. The legs are pulled apart at a constant speed, typically on the order of 200–250 mm/min, and the force required to propagate the tear is recorded. The average tear force is calculated from the force plateau over the tear distance. This method, covered by ISO 6383-1 and the corresponding part of the GB/T 16578 series, is preferred for evaluating materials where slow, controlled tear growth is representative of service conditions and for materials too flexible for reliable pendulum testing.

Tongue and Graves Tear Methods (Initiation Testing)

For rigid or semi-rigid sheeting, ASTM D1004 (Graves tear) measures the maximum force to initiate tearing of a notched specimen at a low crosshead speed of 51 mm/min. Tongue tear procedures within the GB/T 3917 series are applied to coated fabrics and heavy packaging textiles. These initiation-focused methods complement propagation methods and are useful when package failure is driven by tear start rather than tear growth.

Specimen Preparation and Conditioning

Accurate tear results depend heavily on specimen quality and conditioning:

• Cut specimens with sharp dies to produce parallel edges free of nicks and burrs
• Condition plastic films at 23 °C ± 2 °C and 50% ± 5% relative humidity per ISO 291 or ASTM D618 for a minimum of 40 hours
• Condition paper and board at 23 °C ± 1 °C and 50% ± 2% relative humidity per ISO 187 or TAPPI T 402
• Test at least the number of specimens required by the standard, typically 10 per direction, reporting MD and TD separately
• Verify slit geometry and instrument calibration, including pendulum capacity verification, before each test series

Applications

Tear strength data from these standardized methods support a wide range of industry activities:

• Flexible food packaging – qualifying snack pouches, coffee bags, and retort laminates for transport durability and puncture-induced tear resistance
• Pharmaceutical packaging – verifying tear performance of sachets, stick packs, and lidding foils consistent with dose integrity requirements
• Easy-open feature development – balancing tear initiation and propagation so packages open cleanly along laser scores, notches, or perforations
• Material qualification and incoming inspection – confirming resin batches, film deliveries, and laminate structures against purchase specifications
• Transport and heavy-duty packaging – evaluating woven sacks, valve bags, and liner films intended for bulk solids and long logistics chains
• Failure analysis – comparing tear data from failed field samples against retained reference material to identify root causes
• Regulatory and customer compliance – generating standardized test reports from accredited third-party laboratories for export documentation and supplier approval

FAQ

Which tear testing standard should be used for plastic packaging film?

For high-speed tear propagation of plastic films up to about 250 µm, ISO 6383-2 or ASTM D1922 (Elmendorf method) is the standard choice. For slower, controlled tearing, ISO 6383-1 or the trouser tear method within the GB/T 16578 series is more appropriate. Many converters run both methods to characterize initiation and propagation behavior.

What is the difference between tear strength and tensile strength?

Tensile strength measures the force required to break an intact, unnotched specimen, while tear strength measures the force required to propagate a tear from an existing slit or nick. Packaging failures in the field usually initiate at defects, so tear data often correlate better with real-world durability than tensile data alone.

Why are MD and TD tear results so different for the same film?