A roller in a belt conveyor wears out in a few weeks when abrasive passes over it every day: sand, slag, grain with mineral dust or wet cardboard. Every replacement means stopping the line, dismantling the unit and re-centring the barrel. Coating a roller with polyurethane removes this cycle, because the cast layer withstands wear 2-5 times longer than rubber and returns the roller to its working geometry without buying a new shaft. Below I explain exactly where polyurethane wins on rollers, how to select hardness for a specific line, by which technology the layer is applied and what you need to provide for an order to your drawing.
Why polyurethane outlasts rubber and caprolon on rollers
Polyurethane wears 2 to 5 times less than rubber under the same load, and at the same time it cushions impacts, which stiff caprolon cannot do. That is why coating rollers with polyurethane has become the standard solution wherever the unit fails from surface wear rather than from a broken core.
The key figure is wear under DIN 53516. For cast polyurethane it is 38-39 mm³, whereas for SBR rubber it reaches 100-200 mm³ and for NBR rubber 80-150 mm³. In practice this means the polyurethane layer on a roller lasts several times longer under the same flow of abrasive, and the frequency of line stops falls. Caprolon (PA6/PA66) has a wear of 30-90 mm³, that is closer to polyurethane, but it is hard and brittle on impact, cushions runout poorly and absorbs moisture, so the roller loses geometric accuracy in a humid shop.
The second argument is temperature and elasticity. TIMOL polyurethane keeps its working properties from -60 to +100 °C, it does not harden in the cold and does not soften in a heated zone. SBR rubber is limited to a range of -40 to +80 °C, and natural rubber becomes brittle already at deep sub-zero temperatures. For rollers on bucket elevators, drying lines and cold stores, this difference directly determines service life.
A numbers-based comparison of materials for rollers
Polyurethane beats rubber, caprolon and a bare metal core for the combination of wear resistance, temperature range and the ability to absorb impact. Below is a summary of reference characteristics from standard tests, so you can compare the materials parameter by parameter.
| Material | Wear (DIN 53516), mm³ | Working temperature, °C | Hardness | Tensile strength, MPa | Oil resistance |
|---|---|---|---|---|---|
| Polyurethane (TIMOL) | 38-39 | -60…100 | 85A-95A | 39-87 | excellent |
| SBR rubber | 100-200 | -40…80 | 40A - 80A | 8-20 | low |
| NBR rubber | 80-150 | -30…100 | 40A - 90A | 10-25 | good |
| Caprolon (PA6/66) | 30-90 | -40…100 | 75D - 85D | 60-85 | good |
| UHMW-PE | 15-30 | -200…80 | 60D - 70D | 17-45 | good |
The table should be read together with the task of the unit. UHMW-PE has the lowest wear (15-30 mm³), but its tensile strength is only 17-45 MPa, it deforms under a constant load and is not elastic, so it holds belt tension poorly. Caprolon is strong (60-85 MPa), yet stiff and shatters under impact regimes. Polyurethane gives a balanced set: low wear of 38-39 mm³, high strength of 39-87 MPa and an elasticity that dampens impacts and micro-runout of the axle. For most drive, pressure and guide rollers this is the optimum.
Rubber remains cheaper at the start, but its wear of 80-200 mm³ means more frequent stops for replacement. When you count the cost of ownership including downtime, a polyurethane roller comes out cheaper already in the first year of work on an abrasive line.
Weight and inertia should be considered separately. The density of polyurethane is 1.05-1.25 g/cm³ versus 7.7-7.9 g/cm³ for steel, so a massive polyurethane roller is lighter than a solid metal one and puts less load on the bearings and the drive during acceleration and braking. On long conveyors with dozens of rollers this reduces energy consumption and wear of the bearing units, not only of the working surface.
Roller coating technology: the stages of free casting
Coating a roller with polyurethane is not painting the surface but forming a monolithic elastomer layer on a metal core using free casting technology. The sequence of operations determines whether the layer will hold under cyclic load.
First the old coating is removed from the roller and the core is prepared: runout is checked, the surface is levelled, and sandblasting is done to develop the micro-relief. Then an adhesive layer is applied that chemically bonds the metal and the polyurethane; this is a critical stage, because delamination most often starts precisely at the metal-polymer boundary if adhesion is done carelessly. Next the polyurethane is poured into the mould by free casting and cured, after which the roller barrel is ground to size for the fits and bearing seats.
On rollers where accurate cylindricity and grip with the belt matter, I advise against chasing maximum hardness. A softer layer in the 85-90 Shore A zone hugs the belt better, gives a larger contact area and higher traction force, while wear stays low. Take stiff polyurethane of 60-70 Shore D only for heavy drive rollers with high specific pressure, otherwise you will lose grip.
The thickness of the polyurethane layer is selected for the load and the core diameter. A thin layer wears down to the metal faster, an overly thick one heats up and dissipates heat worse at high speeds. The factory calculates the optimum for the specific regime. You can learn more about the material properties in the Reference information section.
Where polyurethane rollers are used and how they are mounted
Polyurethane rollers work in transport, pressure, traction and guide units on conveyors, in printing, pulp and paper production, metallurgy, mining and the food industry. Their job is to guide the belt or web, press the material, transmit traction force without slipping and dampen micro-impacts.
Mounting depends on the roller type. Transport rollers are usually fitted on an axle through bearing units secured with snap rings; drive rollers are set on a shaft with a press fit or through a keyed joint. Maintenance comes down to periodically cleaning the surface of build-up and checking the integrity of the layer, because dirt sticks poorly to polyurethane and the material itself does not corrode or grow mould. When the layer reaches the wear limit, the roller is not discarded but sent for re-coating, which is faster and cheaper than making a new unit. See the ready sizes and product types in the catalogue.
Roller wear is easier to prevent than to cure. The first signs that the surface is nearing its limit are the appearance of belt slippage, local hollows on the barrel and a rise in the noise level of the unit. If you notice them in time and remove the roller for re-coating before the wear reaches the metal core, the core and the bearing seats can be kept intact. But when the layer is worn through to the metal, the roller starts to snag the belt, and the core can suffer abrasive damage after which restoration is already more expensive. Therefore, on abrasive lines it is worth building a planned check of the layer thickness into the maintenance schedule.
How to order roller coating for your own unit
The most precise route is to give the factory the roller drawing or the worn sample itself together with the operating conditions: linear load, speed, temperature, the type of material in contact with the roller and the grip requirements. Using this data, the technologist selects the hardness, the layer thickness and the polyurethane grade, while production reproduces the geometry for the fits using free casting technology.
This approach suits both a one-off restoration of a single roller and serial coating of a batch for a new line. To get a calculation for your task, contact the TIMOL factory through the Contacts page: send the drawing or sample, describe the operating regime and receive a technical proposal for the specific unit.