Cold-retention performance is not determined by insulation thickness alone. The bag’s shape, opening size, seam construction, lining, zipper and how often it is opened all affect the result.
Choose the outer layer for the operating environment
Non-woven fabric can suit lightweight or promotional applications. Oxford cloth offers a familiar balance of cost and durability. TPU or laminated structures are useful where cleaning, water exposure or welded construction matters.
Match insulation and lining to the use
EPE or pearl-cotton layers provide structure and thermal separation. Aluminum foil and PEVA-type linings support different cost, cleaning and presentation goals. Food-contact or recycled-material claims need project-specific documentation.
Control the opening and air exchange
A wide lid improves access but releases more cold air. Small quick-access panels can reduce repeated full opening. Zipper type, flap design and closure pressure should be reviewed with the expected user behavior.
Write a realistic test brief
State starting temperature, ambient condition, load, ice or cold-pack method, opening frequency and test duration. Without those conditions, two “24-hour” claims may describe very different products.