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100Module 6 of 15

Paperboard & Corrugate Substrates

Grades, calipers, flute types, recycled vs. virgin fibre, print compatibility, sustainability, and matching structure to weight and brand feel.

8 minutes
materials
Next: Plastics & Flexible Packaging
Lesson Video
Paperboard & Corrugate Substrates
Module Content

1) Executive Summary

Top insights (5–7)
  1. Measure, don’t guess: Grammage (ISO 536), thickness/density (ISO 534), conditioning (ISO 187), and water absorptiveness/Cobb (ISO 535) are the backbone test methods for paper & board specs. [1]–[4] (ISO)
  2. Flute choice drives both protection and print:Typical profiles—A (~33 flutes/ft), B (~47), C (~38), E (~90)— trade off cushioning/stack strength versus surface for graphics. [5] (Fibre Box Association)
  3. Box strength is predictable enough to design:Use ECT (ISO 3037) + McKee equation to estimate BCT and right-size board; then validate with ASTM D642 compression tests. [6]–[8] (ISO, Esko docs, ASTM)
  4. Recyclability is codifying fast: EU uses EN 643 grade list; 4evergreen provides recyclability evaluation; UK relies on OPRL rules; US uses How2Recycle guidance. EPR obligations are expanding in UK (from 2025) and several US states. [9]–[13]
  5. Fibre sourcing compliance matters: EU Deforestation-Free Regulation (EUDR) obligations now apply from 30 Dec 2025 (large operators), 30 Jun 2026 (SMEs)—affecting wood-derived inputs (liners, pulps). [14]
  6. Food-contact is regional: EU relies on BfR XXXVI recommendations; US uses 21 CFR 176.170/176.180; UK largely aligns with retained EU law and UK FSA guidance. [15]–[17]
  7. Design for print early: Flexo/offset/digital impose different limits (surface energy, roughness, Cobb). For barcode and regulatory marks, follow GS1 General Specifications (e.g., GS1-128 X-dimension ≥ 0.495 mm for general distribution). [18]
Recommended actions (3–5)
  • Standardize substrate specs on ISO/TAPPI methods; add ECT and Cobb targets to drawings. [1]–[4],[6]
  • Choose flute by product mass + logistics + print intent(e.g., E-flute or microflutes for high-graphics; C/B for shipping; double-wall for high BCT). [5]
  • Build recyclability/EPR into briefs (OPRL/How2Recycle categories; 4evergreen tests; UK EPR recyclability assessment from 1 Jan 2025). [10]–[12]
Key risks (12–24 months)
  • Regulatory slippage → surprise costs: EUDR and UK EPR fee modulation timelines; state-level US EPR rollout. [11],[14],[19]–[22]
  • Green claims: Mislabeling recyclability where coatings/laminates exceed thresholds (see OPRL). [10]
  • Under-engineered transit: Ignoring humidity/stack time can halve BCT; always test to ASTM D642/ISTA as needed. [8]

2) Definitions & Concepts

Glossary (plain English)
  • Grammage (gsm): Mass per unit area per ISO 536. [1]
  • Caliper (thickness): Thickness per ISO 534 (paper/board) and ISO 3034 (corrugated). [2],[23]
  • Cobb (g/m²): Water absorptiveness per ISO 535. [4]
  • ECT (Edge Crush Test): Edgewise crush resistance of corrugated (ISO 3037). [6]
  • BCT (Box Compression Test): Compressive strength of filled/empty containers (ASTM D642). [8]
  • Flute: Corrugation profile (A/B/C/E/F) determining caliper, flute count, and performance. [5]
  • EN 643: EU list of recovered paper/board grades. [9]
Concept map (bullets)
  • Inputs → Fibre (virgin/recycled) → Sheet properties (gsm, caliper, stiffness, Cobb) → Combine(liners + medium, flute) → Board performance (ECT, BCT, printability) → Conversion (die-cut, fold, glue) → Compliance (food contact, recyclability/EPR, sourcing) → Market fit(brand feel, graphics, cost, risk).

3) Standards, Regulations, and Governance (US/EU/UK)

Core test standards
  • ISO 536 (grammage), ISO 534 (thickness/density), ISO 187 (conditioning), ISO 535 (Cobb) govern paper/board metrics. [1]–[4]
  • Corrugated: ISO 3034 (thickness), ISO 3037 (ECT); flat crush (ISO 3035, where applicable). [6],[23],[24]
  • Compression of containers: ASTM D642. [8]
Recyclability & sourcing frameworks
  • EU: EN 643 grades; 4evergreen recyclability evaluation guidance. [9],[12]
  • UK: OPRL labelling rules; mandatory recyclability assessments from 1 Jan 2025 under UK packaging EPR reporting. [10],[11]
  • US: How2Recycle member guidance (paper). [13]
  • EUDR (EU 2023/1115) deforestation-free products: application 30 Dec 2025 (large), 30 Jun 2026 (SMEs). [14]
Food-contact controls
  • EU: BfR XXXVI for paper/board; special cases (XXXVI/2).
  • US: 21 CFR 176.170 (aqueous/fatty), 176.180 (dry food).
Per-region highlights (selected)
TopicUSEUUK
Testing backboneISO/TAPPI; ASTM D642 for BCTISO 536/534/535/187; ISO 3034/3037Same ISO set retained/adopted
Recovered fibre gradesISRI specs; How2Recycle labelsEN 643; 4evergreen evaluationOPRL; UK EPR recyclability assessment
EPR statusState EPR laws (ME/OR/CO/CA)PPWR coming; EUDR dates aboveFull packaging EPR; assessments live
Upcoming changes
  • EUDR application dates in 2025/2026 will trigger due diligence on wood-derived inputs. [14]
  • UK EPR: recyclability assessments are part of producer reporting; fee modulation expected to tighten around recyclability outcomes. [11]

4) Evidence Base & Benchmarks

Corrugated flute benchmarks (typical)
FluteFlutes/foot (approx.)Typical role
A~33Cushioning/high stacking; bulkier shipper cases. [5]
B~47Better print surface than A; die-cutting; trays. [5]
C~38–39“All-purpose” shipper. [5]
E~90Microflute for high graphics/litho-lam; retail packs. [5]
Strength correlations
  • ECT (ISO 3037) correlates with BCT via McKee; use as design starting point (then validate). [6]–[8]
Package & unit-load behavior
  • Switching to E-flute can reduce unit-load deflection by up to ~40% vs. B/BC for certain sizes (pallet load bridging study). [24]
  • BCT prediction varies with die-cuts/cut-outs; McKee may under- or over-estimate—adjust with modifiers per peer-reviewed models, then validate by ASTM D642. [25],[26],[8]
Paperboard grade families (overview)
  • SBS/SBB (GZ): Bleached chemical pulp; premium graphics.
  • FBB (GC1/GC2): Multi-ply with mechanical core; high stiffness at lower gsm.
  • WLC/“GD”: White-lined chipboard; recycled middle plies; economical. Trade bodies summarize construction and common uses. [27],[28]
Barrier metrics
  • WVTR measured by ISO 2528 (cup/gravimetric). Provide method + target per application; values vary widely by coating.Evidence gap: consolidated public benchmark ranges for coated barrier boards (WVTR/OTR) by coating class; resolve via supplier datasheets + ISO 2528/TAPPI T464 tests. [29]

5) Design & Production Implications

Rules of thumb (with standards hooks)
  • Conditioning before test/spec acceptance: 23 °C/ 50% RH per ISO 187. [3]
  • Moisture sensitivity: Higher Cobb (ISO 535) often implies need for coatings or tape/glue adjustments; specify Cobb60 limits for shipper boxes exposed to humidity. [4]
  • Print intent → substrate: Flexo on corrugated: prefer E/B or top-sheet litho-lam for fine detail; check roughness and minimum traps per FIRST guidance (typical total trap tolerances ≤ ~0.4 mm segment-dependent; confirm with your printer). Offset on cartonboard: smoother, coated SBS/FBB; control trapping (~0.15–0.3 pt depending on colors), proof to ISO-based tolerances. Digital (inkjet/electrophotographic): ensure primer/hold-out; validate against your press QA (ISO 15311 family where in scope).
  • Barcodes/marks: GS1-128 for logistics: X-dimension 0.495–0.94 mm (general distribution), min symbol height ≈ 31.75 mm; maintain quiet zones per GS1. [18]
Material/format trade-offs (qualitative)
  • SBS/SBB: best print/emboss; lower bulk per gsm; higher fibre cost.
  • FBB (GC): higher stiffness at lower gsm → lightweighting; great for beauty/food cartons.
  • WLC: cost-effective; watch odour/taint risk for sensitive foods (use functional barriers/liners per food-contact rules). [15]–[17]
  • Corrugated (E/B/C; single vs double wall):balance ECT/BCT targets, print needs, and cube efficiency. [5]–[8]
Manufacturability flags
  • Set knockouts/traps per process; avoid ≤ 1% tone values in flexo artwork (converter guidance).
  • Define glue-flap widths, score allowances, and folding sequences on drawings; validate critical dimensions on first article.

6) Sustainability & Compliance Considerations

Recyclability design cues (fibre-first)
  • OPRL (UK): follow material-specific rules (e.g., coating thresholds for “Recycle”). [10]
  • How2Recycle (US): use paper-based labels/adhesives where possible; avoid plastic windows unless program-accepted. [13]
  • 4evergreen (EU): apply testing protocol/scorecard for fibre-based packaging recyclability. [12]
  • Recovered grades: design with EN 643 in mind (avoid non-paper components that downgrade bales). [9]
EPR implications
  • UK (2025→): obligated producers must assess recyclability and report outcomes; fees expected to modulate by recyclability. [11]
  • US: EPR programs phasing in across ME/OR/CO/CA; design for curbside compatibility to limit fees. [19]–[22]
Claims risk
  • Avoid absolute “plastic-free” or “recyclable everywhere” if coatings/fitments may block recycling; substantiate with program rules and, where needed, lab tests (ISO 2528 for WVTR, repulpability where relevant). [29]

7) Workflow & Tooling (PDA-ready)

Checklists (extracts)
  • Print-ready cartonboard: ISO 536/534 values on spec; surface finish noted; proof target; trap/overprint rules; barcode X-dimension & quiet zones; food-contact declaration (EU BfR or 21 CFR). [1]–[4],[10],[15]–[18]
  • Corrugated shipper: Flute profile; combined board caliper (ISO 3034); ECT (ISO 3037); McKee BCT calc + ASTM D642 validation plan; humidity/stack time assumptions. [6],[8],[23]
  • Recyclability/EPR: OPRL/How2Recycle decision; EN 643 grade impact; EUDR sourcing recordkeeping if selling in EU. [9]–[14]
Decision trees (sketch)
  • Choose flute: Product mass & fragility → required BCT → ECT target → candidate flutes → graphics need (E/micro?) → cube efficiency → validate with D642. [5]–[8]
  • Pick cartonboard: Brand finish (uncoated/coated/ whiteness) → stiffness at target gsm (SBS vs FBB) → food-contact need → recyclability/OPRL outcome.
Calculator blueprints
  • BCT (simplified McKee): BCT ≈ k · ECT · (Perimeter · Caliper)0.5 (use metric/imperial form; calibrate k to board family). Validate by ASTM D642. [7],[8]
  • Barcode sizing: enforce GS1-128 X-dimension ≥ 0.495 mm & height ≈ 31.75 mm (general distribution). [18]
  • Yield math: blanks per sheet via floor-packing with trim & grain—export to tooling bill.
Template specs (starter fields)
  • Material: grade family (SBS/FBB/WLC), gsm (ISO 536), caliper (ISO 534), brightness/whiteness if needed, Cobb60 (ISO 535). [1],[2],[4]
  • Corrugated: flute, liners/medium gsm, ISO 3034 caliper, ISO 3037 ECT target, humidity assumption. [6],[23]
  • Compliance: food-contact basis (BfR XXXVI or 21 CFR), OPRL/How2Recycle label, EUDR sourcing (EU). [10],[14]–[17]

8) Category-Specific Guidance

Beauty
  • FBB/SBS for high-whiteness/emboss/deboss; E-flute litho-lam for gift sets. Ensure barcode X-dimension and foil trapping rules. [18],[31]
Food
  • Select board per moisture/grease: set Cobb60, consider barriers; verify BfR XXXVI (EU) or 21 CFR (US). [15]–[17]
Beverage
  • Wet-strength carrier boards; double-wall or high-ECT shippers; validate via D642. [8]

9) Case Studies (Problem → Approach → Result)

1. Unit-load deflection & flute type
Problem: Pallet deflection & product damage in mixed unit loads.
Approach: Switch from B/BC to E-flute where appropriate; analyze load bridging.
Result: Up to ~40% reduction in unit-load deflection reported for E-flute in studied cases (size-dependent). Generalizable to retail-ready packs where rigidity/graphics both matter. [24]
2. Cut-outs & box compression
Problem: Die-cut hand holes reduce BCT unpredictably.
Approach: Use finite-element + empirical testing; compare to McKee.
Result: McKee alone can mis-estimate with cut-outs; adjust with modifiers per peer-reviewed models, then validate by ASTM D642. [25],[8]
3. Optimizing double-wall composition
Problem: Over-spec boards inflate cost/carbon.
Approach: Algorithmic selection of liners/mediums for five-layer boards; sensitivity to paper choices.
Result: Demonstrated lightweighting potential without compromising performance; roadmap for supplier-customer co-design. [26]

10) Common Pitfalls & Red Flags

  1. Specifying cartonboard only by “pt” without ISO 534 thickness + ISO 536 gsm. [1],[2]
  2. Using C-flute for high-graphics retail when E-flute would print cleaner at lower cube. [5]
  3. Omitting conditioning before QA acceptance—results shift with RH. [3]
  4. Barcodes under-sized (X-dimension < 0.495 mm for GS1-128 logistics). [18]
  5. Unsubstantiated “recyclable” claims where coatings exceed program thresholds. [10]

15) References (primary standards first; numbers match in-text)

Primary standards & methods
  1. ISO 536:2019 — Paper and board—Determination of grammage.
  2. ISO 534:2011 — Paper and board—Determination of thickness.
  3. ISO 187:2022 — Standard atmosphere for conditioning and testing.
  4. ISO 535:2023 — Determination of water absorptiveness (Cobb method).
  5. Fibre Box Association — What is Corrugated? (flute profiles).
  6. ISO 3037:2022 — Corrugated fibreboard—Edgewise crush resistance (ECT).
  7. Esko — Case Compression Strength (McKee) formula reference.
  8. ASTM D642 — Compression resistance of shipping containers and components.
  9. BS EN 643:2014 — European grades for recycling.
  10. OPRL — How to use labels (UK).
  11. UK GOV — EPR for packaging: data reporting & recyclability assessments.
  12. 4evergreen Alliance — Recyclability evaluation guidance for fibre-based packaging.
  13. How2Recycle — Guidelines for paper packaging.
  14. EU EUDR — Deforestation-Free Regulation application dates (2025/26).
  15. BfR XXXVI — Paper and board for food contact.
  16. 21 CFR 176.170 — Aqueous/fatty food contact.
  17. 21 CFR 176.180 — Dry food contact.
  18. GS1 — GS1-128 size/X-dimension (General Specifications).
  19. US state EPR programs (ME/OR/CO/CA) — program portals and summaries.
  20. Virginia Tech/USDA-FS study — Flute type & unit-load deflection.
  21. Peer-reviewed studies — Compression strength estimation with cutouts (Materials, MDPI; PMC/MDPI entries).
  22. Pro Carton — Grade family overviews (glossary/fact files for SBS, FBB, WLC).
  23. BS ISO 2528:2017 — WVTR (gravimetric) and TAPPI T464 context.
  24. ISO 3034:2011 — Corrugated single-sheet thickness.

Designer tip / Compliance watch / Manufacturing note

  • Designer tip: Start with functional targets (BCT, Cobb, print intent), then back-solve to flute + board family and graphics rules. Lock GS1 barcode sizes first—they drive quiet zones and artwork geometry. [18]
  • Compliance watch: If selling in the EU from Dec 2025, build EUDR due diligence for all wood-derived inputs (liners, pulps, labels). [14]
  • Manufacturing note: Always validate calculated BCT with ASTM D642 on real packs at end-of-line humidity; theoretical safety factors rarely cover seasonal RH swings. [8]

Evidence gaps called out

  • Public, comparable OTR/WVTR ranges for coated barrier boards by chemistry (PVOH, EVOH, dispersion, extrusion)—resolve via OEM datasheets/certs + ISO 2528/TAPPI tests. [29]
  • Process-specific trap minima by substrate/line for your suppliers (use FIRST/press SOPs + printer-verified values). [30],[31]
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