Last reviewed: August 12, 2026
A custom PE bag should be approved against a written specification, not a general statement such as “high quality,” “food grade” or “industrial strength.” The required measurements and tests depend on the material, construction, packed product, filling process, distribution environment and destination-market requirements.
This guide describes information that buyers and manufacturers can define for a custom polyethylene packaging project. It does not prescribe one universal standard or acceptance limit for every bag.
Start with a Complete Product Specification
An approved specification may identify:
- Bag type and construction
- Finished width, length, gusset and closure dimensions
- Single-layer or total combined thickness
- Resin, additives, colorants and recycled-content requirements
- Printing method, colors, coverage and registration requirements
- Seal, zipper, slider, adhesive or closure construction
- Vent holes, perforations, warnings, labels or additional components
- Unit packing, carton quantity, pallet and export-packing requirements
- Intended use, packed-product weight and distribution conditions
- Inspection method, sampling plan and acceptance criteria
The specification should include a version number and approval date. Artwork, samples, test reports and inspection records should reference the applicable version.
Thickness Must Be Defined and Measured Consistently
Film thickness affects weight, flexibility, seal behavior, puncture resistance and material consumption. A thickness value is incomplete unless the parties agree on:
- Whether the value is per layer or total combined thickness
- The nominal value and unit of measurement
- The permitted upper and lower limits
- The instrument and measurement method
- Measurement locations and number of readings
- The treatment of embossed, textured or reinforced areas
- Lot-acceptance and corrective-action rules
ISO 4593 describes mechanical-scanning measurement for plastic film and sheeting and notes that the method is not suitable for embossed film or sheeting. Buyers should confirm whether this or another method is appropriate for the construction being evaluated.
Official reference: ISO 4593 — Determination of thickness by mechanical scanning .
The permitted thickness tolerance must be technically appropriate for the selected material, nominal gauge, film width and bag construction. The upper and lower limits, measurement method, sampling plan and acceptance rule become binding only when stated in the approved quotation, product specification or quality agreement.
Tensile Results Require Controlled Test Conditions
Tensile strength, elongation and modulus can help characterize film and compare controlled samples. Results can be affected by specimen thickness, preparation, orientation, test speed, grips and extension measurement.
Commonly referenced methods include:
- ASTM D882 — Tensile Properties of Thin Plastic Sheeting
- ISO 527-3 — Test Conditions for Plastic Films and Sheets
A purchase specification should state the selected method and edition, machine direction and transverse direction requirements, conditioning, specimen dimensions, test speed, sample quantity and acceptance limits. Results obtained under different conditions should not be treated as directly equivalent without technical review.
Seal Strength Is Not the Same as Leak Integrity
Seal strength measures the force required to separate a seal under defined conditions. It can support process control and comparison, but it does not by itself demonstrate that a package is leak-free or suitable for every packed product.
ASTM F88/F88M is a commonly referenced method for measuring seal strength in flexible barrier materials. The specification should define specimen width, tail orientation, test speed, conditioning, seal location, number of specimens and the result to be reported.
Official reference: ASTM Committee F02.20 flexible-packaging test methods .
Leak, burst, closure and package-integrity requirements should be defined separately when relevant. The correct method depends on the package design and failure risk.
Tear, Puncture and Impact Tests Must Match the Failure Risk
A bag used for smooth apparel does not necessarily require the same evaluation as packaging for metal parts, sharp components or heavy industrial products. Buyers should identify the expected failure mechanism before selecting a test.
Possible evaluations may include:
- Tear propagation in machine and transverse directions
- Slow-rate puncture resistance
- Dart-impact resistance
- Filled-bag drop or handling simulation
- Seal and side-seam failure under load
- Closure cycling or opening-force checks
Test values should not be selected only because a method is widely known. The method, specimen and acceptance limit should correspond to the actual package and distribution risk.
Printing Requires Measurable Approval Criteria
A printed-bag specification may define:
- Approved artwork and revision
- Printing process and number of colors
- Color reference and acceptable variation
- Print position and registration tolerance
- Ink coverage and opacity
- Adhesion, rub or transfer requirements
- Barcode readability where applicable
- Restrictions applying to inks or coatings
Approval of a digital image does not replace review of a physical print sample when appearance, color or ink performance is critical.
Visual Quality Needs Defined Defect Criteria
Terms such as “clear,” “clean” and “good appearance” are subjective unless they are supported by agreed defect descriptions, reference samples or measurement methods.
Visual criteria may address:
- Contamination, gels, black specks and foreign material
- Wrinkles, blocking, distortion and uneven winding
- Seal alignment, incomplete seals and edge condition
- Haze, gloss, color and odor
- Printing defects and registration
- Zipper, slider or adhesive operation
The parties should define critical, major and minor defects where appropriate and agree on the sampling and acceptance approach before mass production.
Regulatory Evidence Is Separate from Physical Testing
Dimensional, tensile, seal or puncture results do not establish food-contact, restricted-substance, recycled-content, PFAS, recyclability or other market compliance. Regulatory evidence should be reviewed separately against the legal entity, tested sample, material, intended use, destination market, date and scope.
Likewise, a management-system certificate does not certify every finished bag. Review available evidence and its limitations in Flexon Pack's Compliance Evidence Center.
Minimum Technical Approval Package
- Approved specification and version number
- Approved artwork and color references
- Approved sample or documented sample status
- Defined inspection methods and acceptance limits
- Applicable test methods and editions
- Sampling plan and reporting format
- Material and production-batch identification
- Required declarations, certificates or test reports
- Change-control and nonconformance procedure
Flexon Pack's Specification-Based Approach
Flexon Pack is the international B2B packaging brand operated by Dongguan Chenghua Industrial Co., Ltd. The legal entity was incorporated in 2015, and its packaging operations trace to 2012.
Material, dimensions, thickness, printing, closure, inspection and packing requirements are reviewed against the proposed order. Test methods, tolerances, sampling and acceptance criteria apply only when they are technically feasible and stated in the approved specification, quotation or quality agreement.
Request a custom PE packaging specification review.
Technical References
- ISO 4593 — Film and sheeting thickness by mechanical scanning
- ASTM D882 — Tensile Properties of Thin Plastic Sheeting
- ISO 527-3 — Tensile Test Conditions for Films and Sheets
- ASTM F02.20 — Physical Properties of Flexible Barrier Packaging
This article provides general specification and testing information. It does not reproduce the complete requirements of any standard, prescribe a test for every package or certify a product. Buyers and laboratories should use the current authorized edition of the selected standard and define project-specific acceptance criteria.
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