ISO 11897:1999

Overview

ISO 11897:1999 specifies a standardized laboratory method to measure tear propagation on edge folds of sacks made from thermoplastic flexible film. The test quantifies how much an edge fold reduces tear resistance by comparing tear propagation force on folded and unfolded specimens and reporting the residual resistance as a percentage. This packaging standard supports quality control, material selection and performance benchmarking for flexible-film sacks.

Key Topics and Requirements

• Specimen preparation: Trapezoidal specimens with an incision and perforation are cut so the incision coincides with the edge fold; unfolded specimens are cut adjacent to the fold. A template (informative Annex A) is recommended to ensure smooth, notch-free edges.
• Number of tests: Whenever possible, take five specimens from the folded edge and five corresponding unfolded specimens.
• Conditioning and atmosphere: Condition specimens 24 h in standard laboratory atmosphere G (temperature and humidity as specified by the standard) prior to testing.
• Thickness measurement: Measure specimen thickness close to the base of the incision on both sides of the fold using ISO 4593 methods.
• Test apparatus and method:
  • Use a tensile-testing machine appropriate for films (clamps to hold specimen marks; clamps span 100 mm).
  • Carry out the tensile test at the test speed stated in the standard and record the maximum force attained.
• Evaluation and calculation:
  • Compute the arithmetic mean of maximum forces for folded and unfolded specimens separately.
  • Calculate residual resistance = (F_fold / F_film) × 100 %.
• Test report: Include reference to ISO 11897, material identification, production dates, specimen count, conditioning, thickness, F_fold, F_film, residual resistance, any unusual tear behavior, deviations from the standard, and test date.

Applications and Users

• Manufacturers of sacks and tubular thermoplastic film who need to validate edge-fold performance and durability.
• Packaging engineers and material scientists assessing film formulations, sealing and folding methods.
• Quality control and independent test laboratories performing acceptance testing or failure analysis.
• Suppliers and converters evaluating the impact of edge folds on tear resistance for transport packaging design.

Related Standards

• ISO 527-3 - Plastics: tensile test conditions for films and sheets (for tensile-testing machine requirements).
• ISO 2233 - Packaging: conditioning of complete filled transport packages (laboratory atmosphere guidance).
• ISO 4593 - Plastics: film thickness measurement (method for specimen thickness).

Keywords: ISO 11897, tear propagation, edge fold, thermoplastic flexible film, packaging standard, residual resistance, sack testing, tensile test.