Testing Information
A tear test is a mechanical evaluation that measures the resistance of flexible sheet materials — plastics films, rubber sheets, textiles, paper, nonwovens, coated fabrics and leather — to propagation of a tear initiated from a small cut or notch, and ZHONGXI Testing provides this testing service for manufacturers, converters and quality departments across packaging, medical, apparel, automotive and construction supply chains. The test quantifies the force or energy required to continue tearing a material after an initial slit has been introduced, producing values such as tear strength in newtons, tear resistance in millinewtons, or tear propagation energy in joules. Unlike tensile testing, which measures the force to break an intact strip, the tear test deliberately concentrates stress at a pre-cut tip, reflecting real-world damage scenarios such as a punctured shipping sack, a snagged garment, a nicked sterile pouch or a torn tarpaulin exposed to wind flutter.
The purpose of conducting a tear test is to verify that a material will neither fail catastrophically from a small incidental cut nor resist tearing so strongly that intended tear-off features — such as notches on sachets, easy-open packaging lines or disposable glove cuffs — stop functioning. Two principal techniques dominate the field. The Elmendorf method uses a pendulum released from a fixed height; the energy lost by the pendulum as it tears the specimen through a fixed distance is converted into tear resistance, typically reported in millinewtons or grams-force. The trouser-leg method is a tensile-based procedure in which a rectangular specimen with a central precut is pulled so that the two legs separate and the tear runs along the cut line; the average and peak forces are recorded. Supplementary procedures include the tongue tear method used for woven textiles, the Baumann tear approach for paper, and the Delft and wing-shaped specimen geometries used for thin films where trouser tearing is unstable. Data reduction distinguishes initial tear force, propagation force, maximum force and integral energy, and conditioning of specimens at standard atmosphere — commonly 23 °C and 50% relative humidity — is specified because moisture content and temperature measurably shift tear values, especially in cellulose-based and hydrophilic polymer materials.
A typical testing process begins with sampling representative material from a production roll or converted part, conditioning the specimens, and then cutting standardized shapes with a sharp die to avoid edge defects that bias results. For pendulum testing, the operator selects a pendulum capacity so that the measured energy falls between roughly 10% and 80% of full scale, verifies the pointer zero, clamps the specimen, makes a precise slit of defined length with a built-in knife, releases the pendulum and reads the tearing force after applying the pendulum factor. For trouser testing, the operator sets a constant crosshead speed — commonly 200 mm/min or as specified — grips the two legs, and records the force-displacement curve from which mean and maximum tear forces are calculated. Core parameters reported include tear resistance per specimen thickness, tear strength normalized per unit thickness (kN/m or mN per layer), tearing energy, anisotropy ratio between machine direction and transverse direction, statistical mean, standard deviation and coefficient of variation across at least five and preferably ten replicates per direction. Machine direction tearing in blown films, for example, frequently differs from transverse direction tearing by a factor of two to four due to molecular orientation, and this anisotropy is often the deciding figure of merit for down-gauging studies and material substitution decisions.
Testing Instruments
- Elmendorf pendulum tear testers with interchangeable pendulums covering ranges from 200 gf to 6400 gf and beyond, including digital models with automatic energy calculation.
- Electronic pendulum tear testers with encoder-based angle measurement, reducing operator reading error and storing replicate statistics.
- Universal tensile testing machines with load cells from 10 N to 5 kN, used for trouser, tongue and wing tear configurations.
- Pneumatic side-action grips with rubber-faced jaws that secure film and fabric legs without slippage during tear propagation.
- Precision specimen cutting dies for trouser, tongue, wing and rectangular geometries, hardened for repeatable slit profiles.
- Digital thickness gauges with deadweight pressure feet for measuring specimen gauge at the test location.
- Slitting knives and blade holders that create the initial cut in pendulum specimens with consistent length and depth.
- Conditioning chambers maintaining 23 °C and 50% relative humidity for specimen equilibration prior to testing.
- Low-temperature cabinets and environmental enclosures permitting tear testing at temperatures down to −40 °C for cold-crack evaluation.
- Xenon-arc and UV-fluorescent weathering instruments used to pre-expose specimens before tear measurement.
- Air-circulating ovens for heat aging of polymers and coated fabrics ahead of tear retention measurement.
- Data acquisition software that records force-displacement curves, calculates mean/maximum tear forces and integration energies, and exports replicate statistics.
- Analytical balances with 0.001 g resolution for grammage determination used in normalizing tear values of nonwovens and paper.
Testing Items
- Elmendorf tear resistance — pendulum energy-based value, in mN or gf, defining the force needed to propagate a tear across a slit specimen of film, paper or nonwoven.
- Trouser tear strength — mean and maximum force recorded when the two legs of a precut strip are separated at constant speed, the standard figure for flexible sheet materials.
- Tear test in machine direction — quantifies propagation resistance along the extrusion or machine orientation axis, often the weaker direction in blown films.
- Tear test in transverse direction — quantifies propagation resistance across the machine axis, needed with the machine value to compute anisotropy ratio.
- Tear propagation energy — integral of force over displacement during tearing, distinguishing tough materials that tear slowly from brittle ones that fail instantly.
- Initial tear force — the force at the moment the tear starts moving from the precut tip, relevant to puncture-initiated field failures.
- Peak tear force — the maximum transient force during the tear record, used for quality acceptance limits in coated fabrics and nonwovens.
- Tear strength per unit thickness — normalized value in kN/m or N/mm allowing comparison of films with different gauges.
- Tear anisotropy ratio — machine-to-transverse tear ratio that determines whether a sack or pouch will split lengthwise when damaged.
- Tongue tear strength (single rip) — textile-industry parameter measuring the force to tear a tongue-shaped woven specimen on a tensile frame.
- Wing tear strength — variant for very thin films where trouser tearing is unstable, using wing-shaped specimens to stabilize the tear path.
- Baumann-type tear resistance — continuous tear measurement for paper products, reported as force to sustain tearing along a defined path.
- Statistical spread of tear data — mean, standard deviation and coefficient of variation across replicates, indicating process uniformity of extrusion or coating.
- Tear resistance after heat aging — compares tear values before and after oven exposure to verify retention of toughness in service.
- Tear resistance after UV or xenon weathering — measures embrittlement of greenhouse films, tarpaulins and outdoor textiles caused by photodegradation.
- Tear resistance after low-temperature conditioning — evaluates cold-crack behavior of PVC coatings and rubber sheets by testing at subzero temperatures.
- Tear resistance after sterilization — verifies that ethylene oxide, steam or gamma exposure has not degraded medical packaging materials.
- Tear resistance after flex fatigue — repeated flexing followed by tear measurement to simulate creasing of packages and garment laminates.
- Effect of specimen slit length — verifies the sensitivity of tear values to knife-cut geometry, a routine method-validation check.
- Pendulum capacity selection and factor verification — instrument-level check ensuring measured energy stays within the valid working range of the chosen pendulum.
- Thickness and grammage correlation with tear values — companion measurements needed to normalize tear data and detect gauge variation.
- Tear behavior of welded and sealed areas — tear propagation across heat seals, showing whether the seal tears cleanly at the intended peel line or delaminates.
- Directional tear mapping of laminates — machine, transverse and diagonal tear values for composite structures where layers contribute differently.
Testing Scope
- Low-density polyethylene (LDPE) films for carrier bags and liners, tested in machine and transverse directions after conditioning.
- Linear low-density polyethylene (LLDPE) stretch films and cling films, including cast and blown grades with different orientation levels.
- High-density polyethylene (HDPE) films for T-shirt sacks, where anisotropic tear behavior governs sack failure mode.
- Biaxially oriented polypropylene (BOPP) films used in laminates for snack packaging and label facestock.
- Cast polypropylene (CPP) and metallocene polyethylene films for thermoformable and peelable lidding structures.
- Polyethylene terephthalate (PET) films and coated polyester films for flexible laminate substrates.
- Polyamide (nylon 6 and nylon 66) films used in vacuum-packaging and boil-in-bag constructions.
- Polyvinyl chloride (PVC) films for cling wrap, blister lidding and medical device packaging.
- Multi-layer coextruded barrier films containing EVOH and tie layers, tested as complete laminates.
- Aluminum foil laminates for coffee, pharma blister and retort pouches, to assess foil crack and tear propagation.
- Tyvek-type flash-spun polyolefin nonwovens used for sterile medical device pouches and sterile barriers.
- Spunbond-meltblown-spunbond (SMS) polypropylene nonwovens for surgical gowns, drapes and face mask layers.
- Woven polypropylene fabric for FIBC bulk bags, woven sacks and geotextile containers.
- Rubber sheets and vulcanized rubber compounds for conveyor belting, diaphragms and sealing membranes.
- Natural rubber and nitrile latex films for examination gloves and sterile surgical gloves.
- Coated industrial fabrics including PVC-coated polyester tarpaulins, tents and truck-side curtains.
- PU-coated and acrylic-coated textiles for outdoor apparel, inflatable boats and flexible tank liners.
- Automotive interior trim materials including PVC/ABS skins, headliner fabrics and seat cover laminates.
- Apparel textiles including woven cotton, polyester-cotton blends, ripstop nylon and softshell laminates.
- Geotextiles and geomembranes made from polypropylene, polyester and HDPE for civil engineering works.
- Paper and paperboard including kraft sack paper, tissue and wrapping papers evaluated by pendulum tear methods.
- Leather, synthetic leather (PU and PVC on textile backing) and thermoplastic polyurethane films for footwear and upholstery.
- Adhesive tapes, tear strips and easy-open features in corrugated and folding carton packaging.
- Battery separator films made from PE or PP, where tear integrity affects cell winding and safety.
- Films for photovoltaic module backsheets including PET-based and PVF-based multilayer constructions.
- PE and EVA greenhouse films and silage films exposed to weathering, tested before and after artificial aging.
FAQ
How long does a tear test take?
Standard tear testing typically completes within 7 to 15 working days from sample receipt. Conditioning at 23 °C and 50% relative humidity, replicate testing in multiple directions, and any pre-exposure steps such as heat aging, UV weathering or sterilization extend the schedule, with weathering programs adding several weeks of exposure time before tear measurement begins.
How much does tear testing cost?
Cost is determined by the number of testing items selected — for example, Elmendorf tear in one direction only versus machine, transverse and diagonal directions, or tear testing combined with thickness, tensile and post-aging comparisons. A quotation covering the exact item list, specimen count and turnaround can be obtained from the engineering team after the material type and applicable method are confirmed.
Which items does tear testing include?
The item list depends on the product type and applicable method: pendulum tear resistance for films, paper and nonwovens; trouser or tongue tear strength for coated fabrics and textiles; wing tear for very thin films; plus derived values such as tear strength per unit thickness, anisotropy ratio and tear propagation energy. Optional items include tear testing after heat aging, UV exposure, low-temperature conditioning or sterilization.
How much sample should be prepared for a tear test?
For film and nonwoven materials, a sheet of at least A4 size (about 300 × 300 mm) is usually sufficient to cut ten or more specimens in each direction, corresponding to roughly 100–500 g of material. For coated fabrics, textiles and paperboard, samples of about 500 mm × 500 mm allow die cutting of trouser or tongue specimens with spare area for retests, and full-thickness product samples are preferred whenever the finished article, rather than raw roll stock, is the object of evaluation.
Why do tear results differ between machine direction and transverse direction?
Molecular and fiber orientation introduced by blown-film extrusion, casting, calendering or weaving makes the tear propagate differently along and across the orientation axis. In blown LLDPE film, transverse tear resistance is often several times the machine direction value because the tear must cut across highly oriented molecules; the anisotropy ratio is itself a reported parameter used to judge whether a sack or pouch will split lengthwise when damaged.
Summary
Tear test service at ZHONGXI Testing covers pendulum, trouser, tongue and wing tear measurement of films, nonwovens, rubber, coated fabrics, textiles, paper, leather and laminates, including directional tear mapping, anisotropy evaluation and tear testing after aging, weathering, low-temperature or sterilization exposure. Standard turnaround is 7 to 15 working days depending on the item list and sample type, and the scope extends from single-direction quality checks to full multi-direction programs with companion thickness, grammage and tensile measurements.