Steel strapping retains the highest break strength of the three common industrial strap families and is the default for sharp-edged heavy loads such as sheet metal, pipe bundles, and machinery [S2]. Polyester (PET) strapping is a versatile plastic substitute that, on a per-width basis, can carry higher tensile load than steel while stretching just enough to absorb shift and settle [S1]. Polypropylene (PP) strapping is the lowest-cost plastic option, suited to light-duty bundling, carton closing, and unitizing where break strength is not the limiting factor [S3].
Selection is driven by four engineering inputs: load weight, edge geometry, expected in-transit shift, and worker handling exposure. The same article set also flags a tooling and safety gap: the three materials are NOT drop-in interchangeable. Tensioners, sealers, and sealing methods (notch vs clip vs weld vs buckle) differ, and substituting one strap with another's tool is a common source of strap failure and hand injuries [S5].
Mechanical Properties: Break Strength, Tensile, and Elongation
Steel strap delivers the highest break strength of any strapping material, and its near-zero elongation makes it the right choice when a load must be held rigid for long periods without settling [S2]. Published dimensions for steel strapping are 3/8 inch to 1-1/4 inch wide and 0.020 inch to 0.035 inch thick; thicker steel yields higher break strength but does not increase elasticity, because steel as a metal has very low elastic recovery [S1]. A practical consequence: when steel strap is bent at a right angle it loses roughly half its strength, which matters for rebar and structural steel loads that get handled at corners [S2].
Polyester (PET) strapping most commonly comes in 3/8 inch to 5/8 inch widths, with thickness ranging 0.02 inch to 0.05 inch, typically thicker than steel at the same nominal width [S1]. PET has higher tensile strength than steel by some manufacturer data, but its defining engineering property is elastic recovery: it stretches under load and returns, absorbing impact and accommodating settle without snap-back [S2]. PP strapping is made from a plastic resin blend and is described in current packaging guides as not offering the same strength as steel or polyester, with elongation higher than PET, which makes it suitable for compressible but light loads [S3].
Width, Thickness, and the Load-Size Trade
The general rule across vendors is: for a given strap family, width and thickness scale with break strength. Steel strapping width options span 3/8 inch up to 1-1/4 inch, and thickness options 0.020 inch to 0.035 inch, so a heavy coil of steel sheet will typically be specified at the upper end of both ranges [S1]. PET strapping width tops out lower (commonly 5/8 inch) but is run thicker (up to 0.05 inch) to recover the strength gap, which is why PET coils are physically larger per metre of strap than steel coils [S1].
PP strapping runs in narrower widths and thinner gauges still, and is the option most often specified for in-plant movement, newspaper bundling, and palletized cartons where strap cost per metre, not absolute break strength, is the deciding factor [S3]. PP also differs visibly from PET: PET has a glossy, smooth finish, while PP typically has a matte, embossed surface that improves friction on cardboard [S6].
Cost, Handling Safety, and Tooling
PET is significantly less expensive than steel, and PET pricing is more stable than steel, which tracks hot-rolled coil and is exposed to metal-market fluctuation [S4]. Steel is also heavier and sold in shorter rolls, so a given line length of steel strap requires more coil changes and more storage footprint than the equivalent PET length [S1]. PP is the cheapest of the three and is the strap most often paired with low-cost consumables such as buckles and manual tensioners [S5].
Handling safety is a real differentiator, not marketing. Plastic strapping (PET and PP) is safer to handle than steel: it does not recoil, does not produce sharp edges on cut, and does not rust-stain the load [S5]. Steel strap tools split into manual (separate tensioner, sealer, shear) and pneumatic all-in-one notchers, while plastic tools add battery-powered friction-weld tools and buckles for light-duty PP [S5]. Steel pneumatic tools require clean, dry compressed air; plastic battery tools give mobility that steel cannot match, which is the single biggest ergonomic argument for converting lines from steel to PET [S5].
Decision Matrix: Steel vs PET vs PP on Four Criteria
Compare the three strap families against four decision criteria drawn from the research. On break strength, steel wins for sharp-edged heavy loads, PET is close behind on tensile but wins on recovery, PP is the weakest [S1][S2]. On elongation and impact absorption, steel is near-zero (a liability when loads settle), PET is the engineered middle (stretches then recovers), PP is the highest elongation and lowest retained tension [S2][S3]. On cost per metre, PP is lowest, PET is moderate and stable, steel is highest and volatile [S4]. On worker safety and tooling simplicity, PP and PET both allow battery tools and buckles; steel requires notchers, sealers, and clips, with documented hand-injury risk during cut and tensioning [S5].
Use the matrix as a flow: if the load is sharp-edged, heavy, and does not settle (steel coils, rebar, machinery), specify steel strapping in the 3/8 inch to 1-1/4 inch width range and 0.020 inch to 0.035 inch thickness [S1]. If the load is heavy but shifts, settles, or expands (timber, cinder block, palletized beverage, brick), specify PET strapping in 3/8 inch to 5/8 inch width and 0.02 inch to 0.05 inch thickness [S1][S2]. If the load is light, compressible, or unitized for in-plant movement (cartons, newspaper, light pallets), specify PP strapping and use buckles or low-cost manual tools [S3][S5].
Use Cases, Limitations, and Conversion Signals
Steel is the only one of the three suited to very heavy stable loads, hot environments, and prolonged UV exposure, but it is NOT suited to loads that expand, contract, or settle with humidity, because its low elasticity means strap tension does not adjust to load movement [S1]. PET is NOT suited to the heaviest sharp-edged loads where absolute break strength matters more than recovery, because on those applications steel still wins on raw break-strength-per-strap [S2]. PP is NOT suited to heavy or sharp-edged loads; it stretches under sustained tension and loses retained tension faster than PET, which is why long-haul palletizers still use PET even when PP is cheaper per metre [S2][S3].
Two trackable signals for converting a line from steel to PET in 2026: rising steel price volatility (drives TCO calculation toward PET even before ergonomic savings) and a switch to battery-powered friction-weld tools, which is the single biggest enabler of plastic strap on a line that was previously steel-bound [S4][S5]. A third signal is the spread of composite cord strapping (vertically oriented polyester fibers coated in polypropylene) for delicate or irregular loads where neither steel nor PET is ideal, because it is non-abrasive, non-staining, weather-proof, and lighter than steel [S3]. For a deeper look at how the same mild-steel vs alloy trade-off shows up in mechanical power-transmission components, see Why Most Taper Bushes Use Mild Steel.
Two anchor points to keep in front of any procurement decision: always match the strap to the sealing method (steel notch or clip, PET friction-weld or clip, PP buckle or clip), and never assume the same tool can run both steel and plastic, because the geometry of the seal joint is fundamentally different [S5]. For specification context on load handling downstream of strapping, see Standard AGV Load Capacity for Unit-Load Pallet Transport, which covers the unit-load end of the same logistics chain.
Spec-level background on the components involved: strapping band, strapping machine, and alloy steel.