Composite strap versus woven strap: how to compare two polyester buckle systems

Composite strap and woven strap are often offered side by side. Both are polyester, both close with a wire buckle and both are tensioned with a hand tool. On a price list they can look interchangeable. On a packing floor they behave differently, and a buyer moving from one to the other is changing a system, not a consumable.

The question has extra weight in June 2021. European flat-steel prices were still climbing in early June, according to MetalMiner on 3 June 2021, and a team that reviews steel band against polyester for cost reasons soon faces a second choice, between coated composite and woven strap. This guide sets out the differences that matter and the questions to put to a supplier.

Two constructions, one family

In composite strap, polyester yarns run along the length of the band and are held in a polymer coating, giving a smooth, fairly stiff strap. Woven strap is made by weaving polyester yarns into a flexible textile band without a coating. Both are closed with a one-way wire buckle. Cordstrap’s strapping page shows one manufacturer’s standard pairing: composite polyester strap with a galvanized steel buckle.

When either strap is used as a lashing rather than only to bundle goods, it sits closest to what the IMO/ILO/UNECE CTU Code calls web lashings with one-way hardware, as distinct from reusable ratchet lashings, chains or steel band. The Code relates the maximum securing load of single-use web lashings to 75% of their breaking strength and says their elastic elongation at that load should not exceed 9%. Those are general figures for the category, not values for any particular strap.

Where the two differ in use

Point of comparison	Composite (coated) strap	Woven strap	What to verify on your load
Surface	Smooth coating	Textile, uncoated	Grip on the packaging and behaviour at edges
Stiffness	Stiffer; easier to push under a pallet or through a gap	Flexible; follows curves and irregular shapes	Whether operators can thread it in your layout
Yarn exposure	Yarns enclosed by the coating	Yarns exposed	Storage and route conditions
Cut ends	Coated edge	Textile edge that can fray	Handling practice at the packing station
Closure	Wire buckle sized to the strap	Wire buckle sized to the strap	Buckle wire diameter, finish and grip on that strap

The table is a framework, not a ranking. Neither construction is better in general; one may suit a given load and packing method better than the other.

Stretch is the property that changes the joint

The big technical difference is between polyester strap and steel band. The CTU Code notes that steel band elongates only about 0.3% at its maximum securing load, which makes it prone to losing pre-tension when cargo settles or shrinks. The GDV Container Handbook adds that steel strapping cannot be re-tensioned once applied. For friction securing, where tension has to hold over a long journey, the Code therefore prefers synthetic web lashings.

Between composite and woven strap, elongation varies by product, grade and width. Rather than relying on a general statement that one stretches less than the other, ask for the elongation of each specific strap, measured the same way and at a stated load, and compare like with like.

The buckle decides the system strength

A strap’s breaking strength is not the strength of the secured band. The joint, where the strap passes through the buckle and folds back on itself, usually limits the system. The buckle has to suit the strap width and thickness, its wire diameter has to suit the expected load, and the tensioner has to apply tension consistently.

When comparing offers, ask for the system strength of strap and buckle together, tested with a stated tool. The wire buckle diameter guide explains why a thicker wire is a dimension, not a rating, and the joint selection guide covers the wider system.

Finish follows the route. A galvanized buckle carries a zinc coating; a phosphated buckle has a dark conversion finish. The finish comparison frames that choice without assuming that a finish name settles corrosion performance on its own.

Edges, pre-tension and the rest of the securing plan

The CTU Code treats bundling and strapping as an auxiliary measure that should always be combined with direct securing or friction securing. Strap alone does not make a load secure inside a container. The Code also warns that sharp edges substantially reduce the capacity of lashings, so edge protection belongs in the comparison whichever strap you choose.

On pre-tension, the Code suggests that where no labelled standard tension is available, 10% of the lashing’s breaking strength, but not more than 10 kN, may be used in securing calculations. That is a planning assumption for a calculation, not a target for an operator with a hand tensioner.

Questions to ask before switching

1. What is the strap’s breaking strength, and what is the system strength with the proposed buckle and tensioner?
2. How was elongation measured, and at what load?
3. Which buckle wire diameter and finish are matched to each strap width?
4. Does the load need edge protection with this strap?
5. Will existing tensioners handle the new strap, or does the tool change too?
6. Can both straps be trialled on a representative load before approval?

Ask about woven strap and matching buckles

Ask about YAKU’s woven strap together with galvanized or phosphated wire buckles. Use with composite strap is reviewed as a system, case by case, and system strength for a specific strap, buckle and tool is on request. Send your load, current strap and tensioner through the enquiry page.