Technical Articles
What Is Sack Kraft vs Extensible Kraft for Packaging?
Technical comparison of sack kraft and extensible kraft for packaging buyers: stretch, toughness, typical uses, converting notes, and how to write grade into RFQs.
Quick answer
Sack kraft is a strong packaging kraft family often used where toughness and converting efficiency matter for bags and industrial wraps. Extensible kraft is engineered for higher stretch/energy absorption, useful when packs see impact or need to survive rough handling without tearing as easily.
Where buyers use each
Sack kraft appears in many carrier and industrial bag programs. Extensible grades are chosen when tear resistance under dynamic loads matters more than stiffness alone.
Do not equate names with GSM
Suppliers use grade names inconsistently. Lock measurable properties—GSM, tensile, stretch, burst—plus a retained sample, rather than relying on marketing grade labels.
Converting effects
Handles, perforations, heavy print, and wet glue seams change which grade survives. Trial the real construction, not only flat sheet tests.
RFQ language
Named grade family; GSM; key strength/stretch targets
End use (bag, mailer, wrap); converting steps
Sample sheets; lot retention; humidity notes
Approved alternate grades, if any
Related PackTrades Knowledge
How to Spec Kraft Paper GSM for Shopping Bags and Mailers, Kraft Paper Supplier Guide for Packaging Buyers, Kraft Paper vs Corrugated Board, How to Verify Kraft Paper Suppliers for Packaging Converters.
Buyer Checklist
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