Cooler Bag Fabric & Insulation: A Sourcing Guide (600D vs 900D, PEVA vs PU vs TPU, Foam Thickness)
A soft cooler's performance and cost come down to three build layers, and specifying each one is what turns a base model into your product. The outer shell is usually Oxford polyester by denier: 600D is the cost-effective, print-friendly standard, while 900D adds abrasion resistance and a more premium hand for outdoor and sports positioning. The liner is what touches food and holds water: PEVA is the food-safe, PVC-free default; PU coating is light and cheap but less waterproof; TPU is the premium, heat-weldable, recyclable, cold-flexible choice (typically 20–30% dearer than PU). The insulation is closed-cell PE foam (low thermal conductivity, roughly 0.033–0.040 W/m·K) as the workhorse, with EPE foam a lower-cost entry option; thicker foam improves cold retention but adds bulk and shipping volume. Cold-hold time is always approximate and ambient-dependent — a well-built soft cooler keeps contents cold for several hours in typical conditions, but no honest maker guarantees a fixed number of hours. As a private-label manufacturer, Trade Entrust lets you specify each layer, then applies your logo, colours and retail packaging at container MOQ.
Updated July 2026
The three layers that define a soft cooler
Every insulated soft cooler is a sandwich of three functional layers, and each one is a lever you pull on your OEM spec:
1. Outer shell — the visible fabric that carries your logo, takes the abuse, and sets the perceived quality. Almost always Oxford polyester, graded by denier (D). 2. Insulation core — the foam between shell and liner that does the actual thermal work. Type and thickness drive cold retention. 3. Inner liner — the food-contact, water-holding surface. This is where food safety and leak resistance live.
Spec these three together, not in isolation: a premium 900D shell over a thin, low-grade foam and a cheap liner is a mismatched bag. The rest of this guide compares your options at each layer so you can brief a build that matches your price point and use case.
Outer shell: 600D vs 900D Oxford (and beyond)
Denier (D) is the linear density of the yarn — higher denier means a heavier, thicker, more abrasion-resistant weave. For soft coolers the practical choice is almost always Oxford polyester, and the decision is mostly 600D vs 900D:
| Shell fabric | Typical use | Durability | Print / branding | Relative cost | Best for |
|---|---|---|---|---|---|
| 420D–600D | Everyday, promotional, lunch/tote coolers | Good for daily use | Excellent — 600D is a sweet spot for digital print and heat-transfer detail | Lowest–standard | Volume, promo, grocery/delivery |
| 900D | Outdoor, sports, heavy-duty | Higher abrasion resistance, more rugged hand | Very good | Higher | Premium outdoor / sports positioning |
| 1680D ballistic | Rugged / expedition | Highest | Good | Highest | Niche premium, confirmed on quote |
Most brands land on 600D for the balance of cost, durability and crisp branding, and step up to 900D where the retail story is 'rugged outdoor'. Denier is not the only fabric variable — weave, coating and recycled (rPET) options are all customisable and confirmed on your OEM quote. Our [cooler bags](/c/cooler-bags) and [cooler backpacks](/c/cooler-backpacks) base models list the shell spec on each product page.
Inner liner: PEVA vs PU vs TPU
The liner is the food-contact and waterproofing layer, and it is where cheap builds cut corners. Three materials dominate:
| Liner | Food-safe | Waterproofing | Cold-flexibility | Recyclable / PVC-free | Relative cost |
|---|---|---|---|---|---|
| PEVA | Yes — non-toxic, odourless, PVC-free | Good; welded-seam PEVA seals well | Good | PVC-free | Low (default) |
| PU coating | Depends on grade — check food-safe spec | Moderate (lower hydrostatic head than TPU) | Moderate | Not inherently | Low–standard |
| TPU | Yes (food-safe grades) | Highest; heat-weldable / high-frequency sealed for seamless, leak-tight joints | Excellent — stays flexible, resists cracking in cold | Recyclable, no plasticisers/chlorine | Premium (roughly 20–30% above PU) |
PEVA is the sensible default for most cooler bags: food-safe, PVC-free and cost-efficient, and with welded seams it holds water well. PU coating is light and inexpensive but seals and waterproofs less reliably. TPU is the premium choice — fully waterproof, heat-weldable for seamless liners, cold-flexible and recyclable — which is why higher-end and 'leakproof' coolers specify it, at a cost premium. For any 'leakproof' retail claim, brief a welded-seam liner (PEVA or TPU), not a stitched-and-taped one. Exact liner grade and food-safe documentation are confirmed on your OEM quote.
Insulation: PE foam vs EPE foam, and thickness
The insulation core is the thermal engine. Two foams cover most soft coolers:
| Foam | Cell structure | Thermal conductivity (indicative) | Cold retention | Cost | Notes |
|---|---|---|---|---|---|
| Closed-cell PE foam | Closed cell — air locked in | ~0.033–0.040 W/m·K (lower = better) | Stronger, more consistent over time | Standard | The workhorse; most common core |
| EPE foam | More open, expanded structure | Higher (insulates less) | Entry-level; can lose performance as air moves through cells | Lower | Cost-driven, entry products |
Closed-cell PE foam is the better insulator and the default for a serious cooler; EPE is a cost option for entry tiers. Thickness matters: increasing foam from ~5 mm toward ~8 mm meaningfully improves cold retention, but every extra millimetre adds bulk and shipping volume — so thickness is a deliberate trade-off between performance and cartons-per-container. A common pattern is ~5 mm for slim lunch/tote coolers and ~8 mm+ for outdoor and larger bags. The right thickness for your target price and use case is confirmed on your OEM quote. See [how many units fit in a container](/guides/how-many-units-fit-in-a-container) — thicker foam can reduce units per 40′ HQ, so spec it with landed cost in mind.
What we can — and can't — promise on cold retention
Cold-hold time is the number buyers most want, and the one no honest manufacturer should guarantee as a fixed figure. Real-world retention depends on ambient temperature, sun exposure, how full the bag is, ice/gel-pack quantity, how often it's opened, and pre-chilling — none of which the bag controls. A well-built closed-cell soft cooler keeps contents cold for several hours in typical conditions, and thicker/closed-cell foam plus a welded liner extend that — but we state cold retention as approximate and ambient-dependent, never as a guaranteed 'X hours cold'. If your retail packaging needs a performance claim, we help you word it truthfully (e.g. 'keeps contents cold for hours in typical use') rather than a fixed guarantee that field conditions can break.
Speccing your private-label soft cooler
Bringing the layers together, a clean OEM brief names each one:
- Shell: denier (600D vs 900D), colourway, recycled-content option, logo method (print, heat-transfer, woven label, embroidery). - Liner: PEVA / PU / TPU, welded vs stitched seams, food-safe requirement. - Foam: PE vs EPE, target thickness (mm). - Hardware & format: zips, handles/straps, capacity — and whether it's a bag, backpack or duffel.
Decide the carry format first: our [cooler bag vs cooler backpack](/guides/cooler-bag-vs-backpack) guide compares handheld totes, hands-free backpacks and larger [cooler duffels](/c/cooler-duffels) by use case and branding surface. Then choose depth of customisation — branding a proven base model (OEM) versus bespoke tooling (ODM) — in [OEM vs ODM](/guides/oem-vs-odm), and plan your first run with [MOQ, sampling & lead times](/guides/private-label-moq-and-sampling). Every base model is container-MOQ, with a branded pre-production sample before mass production.
Frequently asked
600D or 900D Oxford — which should I choose for my cooler bag?
600D is the cost-effective standard: durable enough for daily use and excellent for crisp logo printing, which is why most brands and promotional programmes use it. 900D adds abrasion resistance and a more rugged, premium hand — worth the cost step-up when your retail story is outdoor or sports. Both are Oxford polyester; the exact grade and any recycled (rPET) option are confirmed on your OEM quote.
Is PEVA safe for food, and how does it compare to TPU?
Yes — PEVA is non-toxic, odourless and PVC-free, and it's the food-safe default for cooler bag liners. TPU is the premium alternative: fully waterproof, heat-weldable for seamless leak-tight seams, cold-flexible and recyclable, but typically about 20–30% more than PU coating. PU coating sits in between — light and inexpensive but less waterproof. For a 'leakproof' claim, brief a welded-seam liner (PEVA or TPU).
How long will the cooler keep things cold?
Cold retention is approximate and ambient-dependent — it varies with outside temperature, sun, how full the bag is, ice/gel-pack quantity, opening frequency and pre-chilling. A well-built closed-cell soft cooler keeps contents cold for several hours in typical conditions, and thicker closed-cell foam plus a welded liner extend that. We don't guarantee a fixed number of hours, and we help you word any packaging claim truthfully.
What foam thickness do you recommend?
Closed-cell PE foam is the default core because it insulates better and more consistently than lower-cost EPE. On thickness, roughly 5 mm suits slim lunch/tote coolers and ~8 mm+ suits outdoor and larger bags — thicker foam improves cold retention but adds bulk and reduces units per container. The right thickness for your price point and use case is confirmed on your OEM quote.
Can I mix specs — say a 900D shell with a TPU liner and thicker foam?
Yes. Shell denier, liner material, foam type and thickness, hardware and format are all independently customisable on our private-label base models. A common premium build is 900D shell + welded TPU liner + thicker closed-cell PE foam; a value build is 600D + PEVA + 5 mm PE. We'll confirm the exact combination, food-safe documentation and cost on your OEM quote.
What's the MOQ and can I get a branded sample first?
MOQ is set by the container — typically one full container load to start, and base models can be mixed to fill it. Yes, we produce a pre-production sample with your logo, colours and packaging so you can inspect and sign off before mass production. The exact per-model MOQ and lead time are confirmed on your OEM quote.