Materials and Grades
Flute types
- A – 4.8–5.3 mm – Cushioning
- B – 2.5–3.2 mm – Crush resistance, print
- C – 3.5–4.0 mm – General, Cushioning
- E – 1.1–1.6 mm – Micro flute, Fine print)
- F/G (very fine, retail)
Verity of Papers:
- Liner Paper: Kraft liner (virgin), Test liner (recycled), White-top liner
- Fluting paper: Corrugator Medium, Semi-chemical Fluting
Basis Weights
- Typical liner 125–340 gsm;
- Medium 112–180 gsm.
Selection driven by compression targets and logistics.
Board combinations
- Single wall (e.g., B, C, E),
- Double-wall (e.g., BC, EB)
- Triple-wall (e.g). B & C)
Adhesive
- Mostly starch-based (corn/tapioca) with caustic/borax;
- Hotmelt or resin only for special cases (wet-strength, cold-set).
Key Performance Metrics
- Box Compression Strength (BCT):
- Predicts top-to-bottom stacking strength.
- Estimated by McKee formula: BCT ≈ k × ECT × √(perimeter × board caliper). Target set by pallet height and supply chain stacking time.
- Edge Crush Test (ECT): kN/m or lb/in; correlates with stacking strength (e.g., 32–44 ECT common for shipper cartons).
- Bursting strength (Mullen): kPa; legacy spec for rough handling. Often 200–350
- Flat Crush/Concora (CMT/CCT): flute strength.
- Tear Test
- Cobb (water absorbency),
- Moisture content (6–9%),
- Compression creep for long-term stacking.
(BfR/EC 1935/2004, FDA 21 CFR).
Cost-down options
- Replace Kraft with Test liner
- Use recycled paper where ECT still meets spec.
- Optimize caliper: E over B for small, graphics-led packs.
- Use low grammage papers with high bursting strength
- Use of high-quality adhesive materials