Materials · Bag Encyclopedia
EVA Panels for Structured Bags
When a bag needs to hold a rigid 3D shape — hardshell cosmetics case, moulded boot bag, camera bag divider, racket compartment — the material of choice is EVA. Compression-moulded and thermally welded, EVA gives structure without weight.
What EVA is and why it's used
EVA (Ethylene-Vinyl Acetate) is a copolymer that behaves like a flexible closed-cell foam. Its cell structure traps air, giving it low weight and shock absorption. Because the cells are closed, it doesn't absorb water — key for boot bags and outdoor cases. Above 80°C EVA becomes plastic and holds any shape it's pressed into.
Compression moulding process
Aluminium moulds are CNC-machined to the panel geometry — one top half, one bottom half. A flat EVA sheet is placed between the halves, the moulds are heated to 80–110°C and pressed together at 5–10 tonnes of force. The sheet softens, flows into the cavity and cools into the finished 3D shape.
- Dwell time — 40–90 seconds depending on thickness.
- Trim — moulded panels are die-cut to remove excess flash.
- Tooling cost — USD 800–2,500 per mould, amortised over the production run.
- MOQ — realistic minimum 500 pieces per moulded panel to justify tooling.
Density and hardness grading
| Grade | Hardness | Application |
|---|---|---|
| Soft EVA | 45–55 Shore C | Cushion inserts, cosmetic bag interiors |
| Medium EVA | 55–65 Shore C | Boot bag shells, backpack laptop dividers |
| Hard EVA | 65–75 Shore C | Camera hardshells, racket compartments, tool cases |
| Rigid EVA | 75+ Shore C | Instrument cases, gun cases, premium hardshells |
Bonding EVA to fabric
A moulded EVA shell is rarely used raw — it's covered with fabric for hand-feel and branding. Two bonding routes:
- Adhesive bonding — contact cement applied to both EVA and inner fabric, pressed together. Standard for boot bags and camera shells.
- Sewn edging — fabric wrapped over the EVA edge and stitched, no adhesive. Slower but preferred for premium retail programmes.
- External finish — 1680D polyester, PU leather or PVC laminated over the moulded surface. This is the visible face of the bag.
Where EVA panels earn their place
- Boot bags — moulded shell with ventilation holes for wet/muddy football boots.
- Camera bags — rigid dividers and impact-absorbing top shell.
- Racket bags — moulded thermal compartments (tennis, padel, badminton).
- Cosmetics cases — hardshell exterior, structured interior compartments.
- Instrument cases — rigid shells for musical instruments, guns, tools.
Prototype an EVA-shell bag
Send a sketch or CAD file — we'll return a moulding-cost quote, density recommendation and 3D-printed prototype timeline for approval before committing to aluminium tooling.