TPU Roller Sleeves for Conveyors: Material, Dimensions and Extrusion Challenges
A TPU roller sleeve is a flexible tube installed over a steel, aluminum or plastic conveyor roller. It can increase traction, cushion the conveyed product, reduce noise and protect both the roller and product surface. In many applications the sleeve is held in place by an interference fit rather than adhesive.
Quick answer: Polyether TPU is often the safer starting point for roller sleeves exposed to washdown, humidity, condensation, cool rooms or microbial growth. It generally retains properties better than conventional polyester TPU under hydrolytic and wet-service conditions. That does not make polyether TPU the automatic choice for every conveyor. Dry systems with severe abrasion, oil or grease exposure may favor a polyester grade. The final sleeve must be selected as a system: material chemistry, hardness, dimensions, fit, roller condition and extrusion process all matter.
What the TPU sleeve must do
A conveyor roller cover looks simple, but it works as several components at once.
It must generate enough friction to move boxes, trays, food packages, sheet material or other products without uncontrolled slip. It also cushions impact, reduces metal-to-product contact and can lower noise. At the same time, it must resist repeated compression as the roller rotates under load.
The sleeve also has to remain fixed on the roller. If the interference is too low, the cover may creep, rotate independently or walk sideways. If it is too high, installation force rises and the sleeve may be overstressed before the conveyor starts running.
Commercial products show how application-dependent the design can be. One extruded TPU roller-cover line uses 85 Shore A TPU, interference-fit installation, 0.062-inch and 0.125-inch wall options, and roller diameters from 1.375 to 6 inches. These are useful market references, not universal design values. Another installation approach uses water-soluble lubricant or compressed air to temporarily expand a polyurethane sleeve as it is pushed over the roller.
Why polyether TPU is often selected
The preference for polyether TPU usually comes from the service environment rather than from the conveyor itself.
Water, humidity and washdown
Polyester TPU contains ester groups in its soft segment. Prolonged exposure to water, especially at elevated temperature, can break ester bonds and reduce molecular weight. The result can be a loss of strength, elongation, toughness or surface integrity over time.
Polyether TPU does not depend on the same ester-based soft segment and normally has better hydrolytic stability. Lubrizol's TPU extrusion guide specifically identifies hydrolytic stability, low-temperature flexibility and fungal resistance as reasons to select polyether-based polyurethane over polyester-based polyurethane.
This matters on conveyors used in:
- food and beverage plants with routine washdown;
- cold rooms where condensation forms on equipment;
- produce, seafood and meat handling;
- humid factories;
- outdoor or semi-outdoor material handling;
- systems where the sleeve may stay wet between production cycles.
Polyether TPU is water-resistant, not indestructible. Temperature, cleaning chemicals, disinfectants, pH, contact time and mechanical load still affect service life. A food-contact statement also has to be confirmed for the specific grade and color package; "polyether" by itself does not establish regulatory compliance.
Low-temperature flexibility and microbial resistance
Polyether TPU often keeps flexibility better at low temperature and generally has stronger resistance to fungal or microbial attack than conventional polyester TPU. These properties can help in refrigerated, wet or intermittently cleaned systems.
The exact performance depends on the grade. Hard-segment content, molecular weight, additives and stabilizers can change the result, and stabilized polyester grades may close part of the hydrolysis-performance gap.
When polyester TPU may still be appropriate
A dry conveyor does not automatically need polyether TPU. Polyester TPU can be attractive where sliding abrasion, oil or grease contact and dry mechanical performance dominate. It may also provide a different balance of tensile strength, tear resistance and wear.
The practical choice is therefore:
| Operating condition | Starting chemistry to evaluate | Main validation concern |
|---|---|---|
| Repeated washdown, condensation or prolonged humidity | Polyether TPU | Property retention after hot-water and cleaning-cycle aging |
| Refrigerated wet service | Polyether TPU | Low-temperature flexibility, wet traction and microbial resistance |
| Dry abrasive conveying | Polyester or polyether TPU | Wear rate, heat buildup and conveyed-product marking |
| Oil or grease contact | Grade-dependent; polyester may be considered | Swelling, softening and loss of interference fit |
| Food or pharmaceutical handling | Compliant grade of either suitable chemistry | Regulatory status of resin, pigment and additives |
| Outdoor exposure | Stabilized grade selected for the environment | UV, ozone, hydrolysis and temperature cycling |
The dimensions that control fit and roller performance
A useful drawing needs more than nominal roller diameter and sleeve length. The following dimensions should be controlled and measured after the sleeve has conditioned following extrusion.
What diameters are typical?
Published roller-sleeve catalogs show a broad range rather than one standard diameter:
- Small and medium conveyor rollers commonly use sleeves for roller ODs around 22–50 mm. Volta lists combinations such as 22 × 27, 30 × 35, 40 × 45 and 50 × 55 mm, where the first number is the metal roller OD and the second is the covered roller OD.
- Larger conveyor rollers commonly fall around 60–95 mm. Published smooth-sleeve sizes include 60 × 65, 65 × 73, 73 × 78, 80 × 85, 85 × 90, 88.9 × 94 and 90 × 95 mm.
- Heavy-duty or special rollers can reach approximately 100–150 mm. Spiratex lists TPU covers for roller ODs up to 6 inches, or 152.4 mm, while also offering sizes around 101.6, 111.1 and 114.3 mm.
These dimensions are market examples, not design limits. The important distinction is between the bare roller OD, the sleeve's free ID and the covered roller OD. A designation such as 80 × 85 mm does not mean the free sleeve ID is exactly 80 mm; the ID normally has to be smaller than the roller so that the installed sleeve develops an interference fit.
Commercial packaging also hints at the manufacturing difference. Volta supplies sleeves through 50 × 55 mm in long rolls, while sleeves from 60 × 65 mm are supplied as shorter straight tubes. A large, soft sleeve is more likely to flatten, take a set or distort when wound.
| Specification | Why it matters | What to verify |
|---|---|---|
| Roller outside diameter | Establishes the required interference fit | Measure at several axial and circumferential positions; include roller tolerance and coating condition |
| Free sleeve inside diameter | Controls grip, installation force and hoop strain | Define the ID tolerance and the intended interference, then confirm it by installation testing |
| Sleeve wall thickness | Affects cushioning, final OD, heat buildup, wear life and cost | Check average wall and local minimum wall around the circumference |
| Finished outside diameter | Influences conveyor height, product contact and line speed | Measure after installation because the sleeve expands over the roller |
| Concentricity and wall eccentricity | Uneven wall creates cyclic loading, vibration and uneven wear | Measure a full cross-section, not only two caliper points |
| Ovality | Affects fit, installation and roller runout | Set a roundness limit or maximum/minimum diameter limit |
| Cut length | Controls roller coverage and end clearance | Include post-extrusion relaxation and any trimming allowance |
| Longitudinal shrinkage | Can expose roller ends or create end stress | Measure after conditioning and after thermal or washdown cycling |
| Roller runout | Can be mistaken for sleeve thickness variation | Check the bare roller and the covered roller separately |
Interference should not be copied from another project. A softer 70–80A sleeve, a harder 90A sleeve, a thin wall and a heavy wall do not expand or install the same way. Roller surface roughness, seams, corrosion, end geometry and installation lubricant also change the required fit.
For long rollers, the part may need an air-assisted installation tool. The process temporarily expands the tube and reduces sliding friction. The trial should record insertion force, air pressure, installation time, lubricant, recovery time and whether the sleeve migrates during operation.
Mechanical requirements beyond Shore hardness
Hardness is useful, but it cannot define a roller sleeve by itself. An 85 Shore A target is common in commercial extruded TPU covers, yet two 85A grades can behave differently under repeated rolling load.
How resin properties translate into sleeve performance
From a TPU-resin standpoint, the sleeve requirements should be translated into properties on the grade's technical data sheet and then verified on the finished extrusion.
| Sleeve requirement | Resin property to examine | What the property means in practice |
|---|---|---|
| Stretching the sleeve over the roller | Elongation at break, stress at 100%/300% strain, tensile set | The material must expand during installation without cracking, yielding or remaining permanently enlarged |
| Maintaining interference fit | Modulus at the actual installation strain, tensile set, creep and stress relaxation | Determines the circumferential force that keeps the sleeve on the roller after hours or months of service |
| Surviving installation damage | Tear strength and notch sensitivity | Indicates whether a small cut at the sleeve end will propagate while the tube is being stretched over the roller |
| Carrying repeated roller load | Compression set, creep, rebound and dynamic fatigue | Controls flat-spot formation, recovery after loading and long-term change in contact geometry |
| Providing cushioning | Shore hardness, low-strain modulus and hysteresis | Softer TPU generally cushions better, but may deform more, generate heat and allow more product indentation |
| Providing traction | Surface coefficient of friction, hardness and surface finish | Determines grip against the actual box, tray, belt or product; it cannot be predicted from Shore hardness alone |
| Resisting wear | Abrasion-volume loss, tear strength and fatigue resistance | Lower abrasion-volume loss normally indicates better laboratory wear resistance, but the actual contact mode still matters |
| Running at higher speed | Rebound, hysteresis, dynamic modulus and heat-aging retention | Low energy loss helps limit internal heat buildup during repeated compression |
| Surviving washdown | Retention of tensile, elongation, hardness and tear after hydrolysis/chemical aging | Initial values are less useful if the material loses them after hot water, humidity or cleaning exposure |
| Holding dimensions | Compression set, tensile set, creep, thermal shrinkage and stress relaxation | Determines whether ID, length and installed OD change during storage and service |
The most overlooked values are often modulus, tensile set, creep and stress relaxation. Tensile strength describes the stress at failure, but a correctly installed sleeve should never operate near failure. It operates at a much lower circumferential strain for a long time. The stress generated at that installation strain, and how much of that stress remains after aging, determine whether the sleeve continues to grip the roller.
The nominal installation strain can be estimated from the roller OD and the sleeve's conditioned free ID:
installation strain (%) = (roller OD − free sleeve ID) ÷ free sleeve ID × 100
The TPU stress-strain curve should then be reviewed around that strain level. A high-modulus grade produces more holding force but is harder to install and places more stress on sleeve ends. A lower-modulus grade installs more easily but may creep, relax or migrate on the roller. This balance cannot be selected from hardness alone.
Resin data also needs careful interpretation. Supplier TDS values may come from injection-molded, compression-molded or annealed specimens. A continuously extruded sleeve can have different molecular orientation, cooling history, moisture damage and residual stress. Final approval should therefore use specimens cut from the conditioned production sleeve, followed by installation and rotating-load tests.
The specification should consider:
- Tensile strength and elongation: The sleeve must stretch over the roller without cracking and recover without excessive permanent growth.
- Tear resistance: Important at cut ends, around installation damage and where conveyed parts have sharp edges.
- Abrasion resistance: Evaluate the actual contact mode. Sliding cartons, metal sheet and wet food packages create different wear mechanisms.
- Compression set and creep: Excessive permanent deformation can flatten the contact surface and change traction.
- Coefficient of friction: Test against the real conveyed product in dry, wet and contaminated conditions. A generic friction value against polished steel may not predict conveyor behavior.
- Rebound and hysteresis: These affect cushioning, rolling resistance and heat generation at higher speed.
- Heat buildup: Repeated deformation can raise sleeve temperature even when the surrounding air is cool.
- Wet-aging property retention: Compare hardness, tensile, elongation and tear before and after representative water, humidity or cleaning exposure.
- Surface and color transfer: The sleeve should not mark, stain or damage the product.
- Chemical resistance: Check cleaners, oils, greases, sanitizers and process fluids individually.
Useful laboratory methods may include ISO 48-4 or ASTM D2240 for hardness, ISO 37 or ASTM D412 for tensile properties, ISO 34-1 or ASTM D624 for tear, ISO 4649 or ASTM D5963 for abrasion, and ISO 815-1 or ASTM D395 for compression set. These tests help compare grades, but the final decision should include a rotating-roller endurance test under actual load, speed and environmental conditions.
Why TPU roller-sleeve extrusion is difficult
The hard part is not simply making a tube. It is holding ID, wall thickness, roundness and surface quality over a long production run while processing a soft, elastic and moisture-sensitive polymer.
Moisture changes the melt before the sleeve is formed
TPU absorbs moisture from the air. During extrusion, excess moisture can cause hydrolytic degradation, lower melt viscosity and produce bubbles, streaks, roughness or unstable output. BASF and Lubrizol processing guidance recommends drying TPU to a very low residual moisture level; Lubrizol cites 0.02% or less for its extrusion grades. The exact drying temperature and time must come from the selected grade's technical data sheet.
Resin, color masterbatch, additive concentrate and regrind all need moisture control. Dry resin can quickly reabsorb water in an open hopper or transfer line, so dryer performance and closed material handling matter as much as the initial drying cycle.
TPU has a narrow useful processing window
If melt temperature is too low, pressure rises and the surface may become rough or show flow lines. If it is too high, the tube may sag, become tacky, lose melt strength or degrade during residence in the barrel and die.
Screw speed also changes shear heating and residence time. Output variation at the extruder becomes ID or wall-thickness variation downstream. Covestro notes that a melt pump can improve tubes and profiles requiring low dimensional tolerance by compensating for extruder output fluctuation.
The hot tube has little dimensional stability
A TPU tube leaving the die is soft and elastic. Puller speed, internal air pressure, die swell, drawdown, gravity and cooling all act on it at the same time.
Lubrizol notes that TPU does not draw down as readily as polyethylene and recommends minimizing drawdown. Its tubing guidance also warns that conventional sizing rings can drag against soft TPU and cause erratic size. Roundness may instead require controlled internal air or a low-vacuum chamber. Covestro similarly recommends constant calibrating air for thin-walled tubing and air pre-cooling before water contact to prevent collapse and surface marks.
This makes a tight interference-fit ID difficult to control. A small ID shift can change installation force and sleeve retention even when the outside diameter looks acceptable.
Larger diameters magnify the extrusion problem
For a thin-wall tube, the polymer cross-sectional area is approximately proportional to mean diameter multiplied by wall thickness. Increasing sleeve diameter at the same wall and line speed therefore requires more melt output. If output cannot increase, the line must run more slowly, which changes residence time, cooling and puller control.
A larger annular flow path is also harder to balance around the full circumference. Small temperature, pressure, die-gap or centering differences can create a thick side and a thin side. The die and mandrel are larger, so alignment, support and thermal uniformity become more demanding.
Gravity has more opportunity to deform the hot sleeve. The soft tube can sag before entering the cooling bath, become oval, or develop heavier wall at the bottom. Controlled internal air can support the tube, but the useful pressure window is narrow: too little air allows collapse, while too much changes the OD and wall thickness.
Cooling becomes less forgiving. More polymer must be cooled per unit length, yet all points around the circumference must cool at similar rates. Uneven air pre-cooling, water flow or calibrator contact produces differential shrinkage, ovality and residual stress. A large-diameter sleeve may look round while hot and move out of tolerance after conditioning.
Haul-off tension and winding create another problem. TPU does not tolerate large drawdown as easily as polyethylene. A small puller-speed change can neck the tube, reduce wall and shift ID. Once the diameter becomes too large for stable winding, the sleeve may need to be cut and handled as straight lengths, increasing floor-space and handling requirements.
For large sleeves, stable production often requires a well-centered die, balanced melt flow, low and steady drawdown, precise internal-air control, long uniform cooling, non-marking haul-off and inline OD/ovality monitoring. A melt pump can help when extruder output fluctuation is the main source of dimensional variation, but it cannot correct an off-center die or uneven cooling.
Cooling affects dimensions and surface quality
The cooling bath must be close enough to support the sleeve before it sags, but aggressive cooling or calibrator contact can mark or distort the surface. TPU often needs a longer cooling section than common commodity thermoplastics. The required length depends on hardness, wall thickness, line speed and sleeve diameter.
Uneven cooling causes ovality and circumferential wall variation. Insufficient cooling allows the puller or winding tension to deform the tube. Excessively cold conditions can also increase tack or blocking for some polyether grades.
Elastic recovery continues after extrusion
The sleeve can relax and shrink after it leaves the line. Winding tension, storage temperature, annealing and conditioning time can shift the measured ID and length. Covestro notes that annealing can be important for reaching optimum compression-set performance. For an interference-fit sleeve, dimensions should therefore be released only after a defined conditioning procedure, not directly at the end of the water bath.
A practical validation plan
A development program should use production-intent rollers and the real installation method.
- Define the service environment. Record load, roller speed, duty cycle, temperature, washdown, humidity, chemicals and conveyed product.
- Measure the roller population. Check OD range, runout, surface roughness, seams and end geometry across several rollers.
- Select two or three extrusion-grade TPUs. Compare chemistry, hardness, melt strength, hydrolysis resistance, abrasion and regulatory status.
- Extrude a dimensional trial. Track resin moisture, melt pressure, melt temperature, screw speed, puller speed, internal air, water temperature and line speed.
- Condition before inspection. Use a defined time and temperature before measuring ID, wall, ovality, length and shrinkage.
- Run installation trials. Record insertion force or air pressure, lubricant, installation time, recovery and any end damage.
- Test on the conveyor. Measure traction, sleeve migration, runout, noise, temperature rise, wear and product marking under representative load.
- Age and retest. Repeat key mechanical and dimensional checks after water, humidity, cleaning chemical and temperature exposure.
Information to send for material and extrusion review
A useful sample request should include:
- roller material, OD tolerance, face length and runout;
- target sleeve ID, wall thickness, finished OD and length;
- required hardness and color;
- conveyor speed, load per roller and duty cycle;
- dry, wet, washdown, cold-room or outdoor exposure;
- oils, cleaners, sanitizers or other chemicals;
- food-contact or other regulatory requirements;
- conveyed-product surface and marking limits;
- installation method and acceptable installation force;
- expected service life and current failure mode.
GOAFLEX can use this information to compare polyether and polyester TPU options, identify suitable extrusion-grade candidates and plan a dimensional and application validation trial.
Why GOAFLEX FormMax is well suited to roller sleeves
The GOAFLEX FormMax series features an ultra-high-crystallinity TPU formulation together with a proprietary manufacturing process. This material architecture is designed to provide higher tensile strength and modulus at the same Shore hardness when compared with conventional TPU reference formulations.
That distinction matters for an interference-fit roller sleeve. Increasing Shore hardness is one way to raise stiffness, but it can also increase installation force and reduce cushioning. FormMax is designed to provide stronger mechanical performance without requiring an unnecessarily hard sleeve. At the selected hardness, the higher tensile strength and modulus can support sleeve integrity during installation, circumferential holding force on the roller and resistance to repeated mechanical loading.
The combination of strength, modulus, elasticity and application-specific polyether chemistry is why FormMax is a preferred material platform for demanding TPU roller-sleeve applications. The final grade should still be validated against the required sleeve dimensions, installation strain, conveyor load, speed, washdown conditions and service temperature.
Ready to review a TPU roller-sleeve application?
Send GOAFLEX the roller OD, sleeve ID and wall thickness, target hardness, load, line speed, operating environment and current failure mode. Contact hello@goaflex.com or review our TPU material capabilities.
Sources and further reading
- BASF, Elastollan TPU Processing Recommendations: View source ↗
- BASF, Elastollan Material Properties: View source ↗
- Lubrizol, TPU Extrusion Processing Guide: View source ↗
- Covestro, Processing of TPU by Extrusion and Special Processes: View source ↗
- Spiratex, Spiratite TPU Roller Covers: View source ↗
- Volta Belting, Roller Coating Sleeves: View source ↗
- Dura-Belt, Conveyor Roller Covers, Sleeves and Lagging Tubes: View source ↗
- Polyurethane Products, Slip-On Conveyor Roll Covers (installation context; product chemistry varies): View source ↗
Image credits
- falco / Wikimedia Commons — CC0 1.0. Image used for application or process context; it does not indicate endorsement or verify TPU chemistry.
- R. Galgan / Wikimedia Commons — CC BY-SA 3.0. Image used for application or process context; it does not indicate endorsement or verify TPU chemistry.
- Kay-Uwe Rosseburg / Wikimedia Commons — CC BY 3.0. Image used for application or process context; it does not indicate endorsement or verify TPU chemistry.
- Cjp24 / Wikimedia Commons — CC BY-SA 3.0. Image used for application or process context; it does not indicate endorsement or verify TPU chemistry.
- Metaroller / Wikimedia Commons — CC BY-SA 4.0. Image used for application or process context; it does not indicate endorsement or verify TPU chemistry.
