Plastic Woven Fabric Breaking Force Testing: Standards, Methods and Quality Control Guide

FIBC Body Fabric

Heavy-duty woven fabric in the range of approximately 140 g/m² to 250 g/m², often UV-stabilized for outdoor exposure. Breaking force, along with UV-retained strength after xenon-arc weathering, is a key safety parameter for bulk bag design.

Tape Yarn and Narrow Woven Webbing

Individual flat tape yarn or narrow woven strips can be tested to characterize yarn tenacity (cN/dtex or N/tex), supporting warp beam setup, denier control, and raw material verification.

Testing Items

Depending on the product standard and customer specification, the following parameters are commonly determined:

• Warp-direction breaking force (N, per 50 mm strip width)
• Weft-direction breaking force (N, per 50 mm strip width)
• Elongation at break or elongation at maximum force (%)
• Breaking tenacity of tape yarn (cN/dtex or N/tex)
• Seam or hem breaking strength (bottom seam, side seam, stitched joints)
• Coefficient of variation (CV%) of breaking force within a specimen set
• Breaking force retention after thermal aging or artificial weathering, when required

Testing Methods

Specimen Preparation

For the strip method, specimens are cut with an effective width of 50 mm after raveling edge yarns, and a length sufficient to provide a 200 mm gauge length plus adequate clamping allowance, typically 500 mm to 600 mm in total. At least five valid specimens are prepared for each direction. For the grab method, specimens of approximately 100 mm × 150 mm are used, and no raveling is required.

Conditioning

Specimens are conditioned in a standard laboratory atmosphere, commonly 23 °C ± 2 °C and 50% ± 5% relative humidity for plastic materials, or 20 °C ± 2 °C and 65% ± 4% relative humidity when following textile conventions, for a minimum of 24 hours or until moisture equilibrium is reached. Testing is carried out under the same atmosphere.

Strip Method (ISO 13934-1 / GB/T 3923.1 / ASTM D5035)

A constant-rate-of-extension (CRE) universal testing machine is used with a gauge length of 200 mm. The rate of extension is selected according to the expected elongation of the fabric: 20 mm/min for elongation not exceeding 8%, 100 mm/min for elongation between 8% and 75%, and 200 mm/min for higher elongation. PP and HDPE woven fabrics, which typically elongate between 15% and 30%, are commonly tested at 100 mm/min. The specimen is mounted centrally with slight pretension, extended until rupture, and the maximum force is recorded.

Grab Method (ISO 13934-2 / GB/T 3923.2 / ASTM D5034)

The grab method evaluates fabric strength in a manner closer to real-world localized loading. The specimen is clamped in the center of the jaw faces with a gauge length of 100 mm and tested at a speed of 50 mm/min. This method is quicker and less sensitive to yarn damage during raveling, making it suitable for routine production control and for coated or laminated fabrics.

Equipment Requirements

The testing machine should comply with ISO 7500-1 force verification, preferably accuracy class 0.5 or 1. Serrated, pneumatic, or lined grips must hold the specimen without slippage or premature jaw breaks, and the selected force range should place the breaking force between roughly 20% and 80% of full scale for best accuracy.

Data Processing and Acceptance

The breaking force of each specimen is recorded in newtons and averaged for each direction; results are normally expressed per 50 mm width of fabric. Elongation at maximum force is calculated as the extension divided by the original gauge length, multiplied by 100%. Specimens that break within 5 mm of the jaw line or that slip in the grips are discarded and replaced. Product standards such as GB/T 8946 specify minimum breaking force values according to bag type and declared loading capacity, typically ranging from around 500 N to well above 1000 N for a 50 mm strip, and the batch is judged against these limits together with the coefficient of variation.

Applications

Breaking force testing of plastic woven fabric supports quality assurance and safety certification across many sectors:

• Cement, concrete additives, and dry mortar packaging in heavy-duty woven sacks
• Fertilizer, seed, grain, flour, sugar, and animal feed packaging
• Chemical, mineral, and metal powder packaging requiring UN or dangerous-goods performance verification
• FIBC jumbo bags for bulk logistics, including top-lift and stacking safety design
• Tarpaulins, scaffolding safety nets, and cover fabrics for construction and transport
• Woven geotextiles used in soil separation, filtration, and reinforcement engineering
• Supplier incoming-material inspection, batch release testing, and claim or failure analysis after bag rupture during handling or drop events

FAQ

What is the difference between the strip method and the grab method?

The strip method tests the full width of a 50 mm raveled strip, so essentially all yarns across the width share the load, giving the fundamental fabric strength. The grab method clamps only the central portion of a wider specimen through small jaw faces, so part of the load is transferred through cross-yarn interaction, better simulating localized stress such as a bag being gripped. Strip results are usually higher and are used for specification compliance, while grab results are useful for comparative production control.

Why do specimens often break at the jaw line, and how can this be avoided?

Jaw breaks occur when grip pressure concentrates stress at the clamping edge. They can be reduced by using pneumatic grips with appropriate pressure, serrated or rubber-lined jaw faces, protective tabbing at the gripping points, correct alignment of the specimen, and a suitable crosshead speed. Results from specimens breaking within 5 mm of the jaws should be discarded unless documented otherwise.

How many specimens are required per direction?

Standards generally require a minimum of five valid specimens in the warp direction and five in the weft direction, with specimens distributed across the width of the sample and avoiding the same yarns. Additional specimens are tested when invalid breaks occur or when a statistical evaluation with lower uncertainty is needed.

What breaking force is considered acceptable for a woven sack?

Acceptance depends on the declared loading capacity and bag construction. Product standards such as GB/T 8946 assign minimum warp and weft breaking force limits per 50 mm strip for each bag category, and many buyers impose higher contractual values for safety margins. The laboratory report should always state the applied standard, specimen width, gauge length, speed, and conditioning atmosphere so results can be compared correctly.

Do temperature and humidity affect the test results?

Yes. Polypropylene and polyethylene are viscoelastic and temperature-sensitive; higher temperatures reduce breaking force and increase elongation, while humidity has only a minor direct effect but still influences conditioning equilibrium. Strict control of the standard atmosphere before and during testing is essential for reproducible results, and reports must record the test conditions.