Case Study: Polyurethane Rollers in Steel and Printing

Steel mills and printing presses may seem like they have little in common, but both rely on polyurethane roller coatings — and each environment makes almost opposite demands on the coating material.

Polyurethane roller coatings are used in steel mills and printing facilities because they combine high abrasion resistance with precise hardness control. Steel mill rollers typically use 80A–95A Shore A formulations to handle load and mill oils. Printing rollers use softer 25A–75A grades for controlled grip and ink resistance. In both applications, correct formulation selection is the primary factor determining service life. For a full overview of the application category, see polyurethane roller coatings.

This polyurethane roller case study covers the specifications and outcomes for each environment, then examines why the formulation logic diverges — and what failure looks like when the specification is wrong.

1. Steel Mill Applications: Specifications and Performance

A rolling mill puts three stresses on a roller coating at once: abrasive mill scale, rolling oils and coolants, and sustained nip pressure. Industrial roller applications in steel mills rank among the harshest coating environments — for work-roll support, strip-guide, and deflector positions, Shore A 80–95A is the correct hardness band. Harder grades in this range resist permanent deformation under nip load and hold their geometry against abrasive scale contact.

Pepson’s Polyether TPU grades — E580A through E595A — cover Shore A 80±3 to 95±3. Compression set at 70 °C ranges from 32% to 40% across this hardness band, tested to ASTM D395-18 Method B (constant deflection, 70 °C/22 hours). That compression set figure matters: a coating that permanently deforms under load changes contact geometry and accelerates uneven wear across the roller face.

Temperature drives chemistry selection. Pepson’s Polyether series operates from −40 °C (−40 °F — the only temperature where the two scales coincide) to 80 °C. Above 70 °C in a coolant-rich environment, ester-based PU risks hydrolytic degradation from mill oils. Ether-based chemistry is the required choice in those conditions.

Standard coating thickness runs 10–25mm on machined steel cores. Thicker coatings accommodate eccentric wear patterns that develop across service cycles. Adhesion is qualified using ASTM D4541 or ISO 4624:2023, both of which specify pull-off test methods for polymer coatings on metal substrates. For surface preparation and primer requirements, see the article on bonding polyurethane to steel rollers.

For engineers: Have a technical challenge? Talk to our engineering team

2. Printing Applications: Specifications and Performance

The demands in printing environments are the inverse of steel mill requirements. Where steel mills need hardness to resist mechanical deformation, printing applications need softness to enable conformal contact — the coating must yield slightly to maintain even ink distribution across the web.

Impression rollers are specified at Shore A 25–55A. Harder grades in this position produce uneven ink distribution. Feed and delivery rollers run at Shore A 60–75A — firm enough for dimensional stability across web tension changes while still providing controlled grip.

Low compression set matters in printing for a different reason than in steel mills. In printing, permanent set shifts print registration. Even a small dimensional change compounds across a long print run, producing density variation visible in solid coverage areas. Pepson’s Special Polyester series (E680A–E698A) achieves 18–55 mg Taber abrasion loss and compression set at 30–35%, with oil resistance and flex resistance listed as key characteristics.

The dominant chemical stress in printing environments is solvent exposure from press cleaning agents. Ester-based PU swells with ketone and aromatic solvents, growing the roller out of tolerance. This failure mode is often misdiagnosed as a press alignment problem. Ether-based PU is the correct chemistry default for printing roller applications because of its resistance to the cleaning agents used in commercial press environments. For a direct comparison of PU and rubber performance in printing environments, see the polyurethane vs rubber roller coatings comparison article.

3. Why the Formulation Decisions Differ

Steel mills demand Shore A 80–95A because the primary failure vector is mechanical deformation under nip load. In this hardness range, abrasion resistance increases with Shore A — both requirements reinforce each other.

Printing demands Shore A 25–55A for impression rollers because conformal contact is the performance requirement. High hardness and consistent ink distribution are inversely related: a harder coating distributes ink unevenly. The hardness that solves one problem creates the other.

Both applications converge on ether-based PU chemistry, but for different reasons. Steel mills need it for hydrolysis resistance in coolant-rich environments above 70 °C. Printing needs it to resist solvent-based cleaning agents. The chemistry is the same; the failure mode it prevents is different.

Hardness specification follows ASTM D2240 — the reference standard for Shore A and D durometer testing of elastomers. For the full formulation decision framework, see the article on selecting the right polyurethane formulation for roller applications. For testing and validation criteria, see the roller coating quality standards article.

4. Common Failure Modes by Application

Steel Mill Failure Modes

Premature delamination traces to bond failure at the steel–PU interface. The most common cause is inadequate blast profile or surface contamination before primer application. The coating lifts rather than wears.

Compression set failure results when hardness is too low for the nip load. The coating takes permanent set, altering contact geometry and accelerating uneven wear across the roller face.

Chemical swelling occurs when ester-based PU is used in a coolant-rich environment. Coolant ingress causes dimensional swelling that first breaks tolerance, then separates the coating from the core.

Printing Failure Modes

Solvent swelling is ester-based PU exposed to ketone or aromatic cleaning solvents. The roller grows out of tolerance and print registration drifts — commonly misdiagnosed as a press alignment problem.

Compression set in impression rollers results from an overloaded low-hardness coating that permanently deforms. Ink distribution becomes uneven across the web width, visible as density variation in solid coverage areas.

Abrasive scoring occurs when particulate contamination in ink — dried ink deposits or foreign material — scores rollers specified below the hardness threshold for the contamination level present.

FAQ

How long do polyurethane-coated rollers last in steel mill environments?

Service life varies by roller position and hardness specification. PU-coated rollers consistently outlast rubber equivalents in mill environments because PU combines abrasion resistance with resistance to coolant-induced degradation — two properties that degrade independently in rubber. The two primary variables controlling service interval are correct hardness selection for the nip load and regular inspection to catch compression set before it progresses to delamination.

What Shore hardness is best for printing press rollers?

The answer depends on the roller’s position in the press. Impression rollers are specified at Shore A 25–55A to maximize conformal contact and ink distribution across the web. Feed and delivery rollers run at Shore A 60–75A, which maintains dimensional stability under web tension while preserving grip. Misspecifying by 10–15 Shore A points in either direction produces measurable print quality problems.

Can polyurethane rollers handle the heat and pressure of steel rolling?

Yes, with the correct formulation. Pepson’s Polyether TPU series handles operating temperatures from −40 °C to 80 °C and resists hydrolytic degradation from mill oils. The critical constraint is temperature: above 70 °C in a coolant-rich environment, ether-based chemistry is required. Ester-based PU in those conditions risks hydrolytic breakdown and dimensional swelling that breaks coating tolerances.

How does PU roller coating reduce downtime in industrial applications?

PU roller coatings extend the interval between scheduled replacements by combining abrasion resistance with dimensional stability. The maintenance ROI comes from fewer total roller replacements per year across a mill or press line, not from the cost of any individual replacement. Predictable wear behavior also enables proactive replacement scheduling rather than reactive response to unplanned failures.

What causes polyurethane roller coatings to fail prematurely?

Most premature failures trace to three root causes: wrong hardness for the load, wrong chemistry for the chemical environment, or a bond failure from poor surface preparation. In steel mills, compression set from an undersized Shore A specification is the most common. In printing, solvent swelling from ester-based PU exposed to cleaning agents dominates. Bond failures — where the coating delaminates rather than wears — almost always trace to surface contamination or an inadequate blast profile on the steel core before bonding.

Conclusion

Steel mills and printing presses make opposite hardness demands on polyurethane roller coatings — harder to resist mechanical deformation under load, softer to enable conformal ink contact — but both converge on ether-based chemistry and both fail the same way when the formulation is wrong.

The failure mode breakdown in Section 4 gives maintenance engineers a starting point before a roller reaches end of service. Delamination, compression set, and chemical swelling each point to a different specification error. Identifying which mode is active narrows the corrective action from “replace the roller” to “revise the specification on the next order.”

When a PU-coated roller does reach the end of its service cycle, refacing and recoating can extend the asset’s useful life without replacing the steel core. See the roller refurbishment and recoating services article for how that process works.

For procurement: Ready to source? Request a quote from Pepson