Which is better for bushings — polyurethane or capron (nylon)?

For dynamic bushings under impact and vibration, polyurethane is better: rebound elasticity of 34-61 % absorbs impacts instead of transmitting them, and it does not absorb moisture. Capron (PA6/PA66) is stiffer and close on abrasion (30-90 mm³ vs 38-39 for polyurethane), but its rebound elasticity is only 5-15 % and moisture absorption is 2-8 %, which changes dimensions in a wet environment. For rigid sliding guides without impact, capron can be the better choice.

Does polyurethane absorb moisture the way capron does?

No. Polyurethane moisture absorption is minimal — fractions of a percent. Capron absorbs 2-8 % by mass, which causes swelling and dimensional change over time. In a wet or humid environment this makes polyurethane the preferred material for close-tolerance parts.

Which material has better impact resistance — polyurethane or engineering plastic?

Polyurethane has excellent impact resistance because it deforms elastically under impact and recovers its geometry. Engineering plastics like capron absorb impact poorly: they may chip or crack under sharp dynamic loads even though they are hard. For impact-absorbing nodes — shock elements, bumpers, guards — polyurethane is the better choice.

Is polyurethane more expensive than capron?

Per kilogram, polyurethane may be slightly more expensive than capron. But the cost comparison for a node over a year is different: the longer service life of a polyurethane part and the absence of moisture-caused replacement reduce total costs. For a critical node, the economics are calculated over the full service cycle, not per part.

In which applications does capron outperform polyurethane?

Capron (PA6/PA66) is better than polyurethane in tensile strength (60-85 MPa vs 39-87), specific stiffness, and machinability to tight tolerances. For precision gears, load-bearing structural slides, and threaded elements under sustained load without impact, capron is the preferred material. For dynamic and abrasive nodes requiring elasticity and damping, polyurethane wins.

Polyurethane vs Engineering Plastics: Which Is Better for Industrial Parts?

A process engineer selecting material for an industrial bushing, scraper, or structural guide faces a common question: is polyurethane better than engineering plastics — capron (nylon PA6/PA66), polycarbonate, or UHMW-PE — or does one of the plastics win? The answer is not universal: the materials occupy different niches, and choosing the wrong one costs a shortened service life and early replacement. This article compares polyurethane with capron PA6/PA66 as the most common competitor in the same industrial applications, giving the comparison in numbers rather than adjectives.

How Polyurethane and Engineering Plastics Differ by Nature

Polyurethane is an elastomeric material: it deforms under load and recovers its geometry, absorbs impacts, and has a rebound elasticity that engineering plastics lack. This property is the source of both polyurethane’s advantages (impact resistance, vibration damping, tight surface contact) and its limitations (creeps under sustained compression load if hardness is insufficient).

Engineering plastics — capron PA6/PA66, polycarbonate PC, UHMW-PE — are rigid structural polymers. They deform very little, hold tight tolerances well, and are excellent under sustained static load. But precisely because they are rigid, they cannot absorb dynamic impact: under sharp shock loading, rigid plastics chip or crack, while polyurethane deforms and recovers. The operating niche for each material follows directly from this distinction.

Capron (nylon PA6/PA66) is the most frequent competitor to polyurethane in engineering applications. It has high tensile strength (60-85 MPa), low friction coefficient, good machinability, and abrasion lower than polyurethane (30-90 mm³ vs 20-45). But it absorbs moisture — 2-8 % by mass — which causes dimensional change and swelling in wet environments, and its rebound elasticity is only 5-15 %, making it unsuitable for impact-absorbing nodes.

Comparison in Numbers

The table compares polyurethane and capron PA6/PA66 on the parameters that determine the choice of material for a specific application.

Parameter	Polyurethane TIMOL	Capron PA6/PA66
Abrasion DIN 53516, mm³	38-39	30-90
Operating temperature, °C	-60…+100	-40…+100
Tensile strength, MPa	39-87	60-85
Shore hardness	85A-95A	75D - 85D
Rebound elasticity, %	34-61	5-15
Moisture absorption, %	minimal	2.0-8.0
Density, g/cm³	1.05-1.25	1.13-1.15
Impact resistance	excellent	limited

The numbers clearly define the two niches. Capron wins on tensile strength and is competitive on abrasion — but its near-zero elasticity means it cannot damp impact, and moisture absorption makes it a risk in wet environments. Polyurethane wins on elasticity, moisture resistance, and impact resistance — but yields on tensile strength and absolute abrasion to hard capron grades. Density is similar for both, so weight is not a differentiating factor.

Engineer’s tip: if the node works in a wet environment or periodic immersion, always prefer polyurethane over capron. Capron absorbs moisture in a cycle of swelling and drying that causes microscopic fatigue and dimensional drift — a close-tolerance bushing will develop play after a few months in a wet environment. Polyurethane does not absorb moisture and holds its dimensions across humidity cycles without change.

When Polyurethane Wins

Polyurethane is the correct choice for nodes with impact, vibration, or abrasive contact in a wet or oily environment:

Impact-absorbing elements. Buffers, bumpstops, suspension elements, dampers, and shock pads work under repeated shock loading. Polyurethane deforms and recovers; capron chips or cracks under the same load.

Abrasive contact in wet or oily environments. Scrapers, conveyor rollers and idlers, linings, and seals work in oil or water together with abrasive particles. Polyurethane is oil-resistant, does not absorb moisture, and wears slowly. Capron swells and loses dimensional stability.

Seals and cuffs. A seal must maintain tight contact pressure across the full range of rod travel and pressure cycles. Elastic polyurethane self-energises with pressure and recovers contact after each stroke. Rigid capron does not provide reliable sealing in dynamic nodes.

Automotive suspension elastomers. Silent blocks, bushings, and spacers must absorb road vibration while holding arm geometry. The 34-61 % rebound elasticity of polyurethane delivers both; capron in suspension applications produces harsh, knock-through behaviour at low temperatures.

When Engineering Plastics Win

Engineering plastics — primarily capron — are the correct choice when stiffness, tight tolerances, and sustained load matter more than impact resistance:

Precision gears and slides. A gear tooth or precision slide works under sustained low-impact load with tight dimensional tolerances. The high tensile strength and stiffness of capron hold shape better than polyurethane, which would creep under sustained stress at moderate hardness.

Threaded and fastening elements. Threaded inserts and fasteners need dimensional stability under sustained assembly load. Capron holds thread geometry where soft polyurethane would deform.

Structural slide bearings in dry conditions. For a dry sliding contact without impact, capron and UHMW-PE give lower friction and dimensional stability than polyurethane. In oily sliding contact the advantage shifts to polyurethane.

Conclusion

Polyurethane and capron are not interchangeable: each has its niche. Polyurethane is the choice for dynamic, abrasive, wet, or oil-exposed nodes where impact resistance and elasticity are required. Capron is the choice for rigid, static, or high-load structural applications where dimensional stability and high tensile strength matter.

For the most common industrial applications — conveyor parts, suspension elastomers, hydraulic seals, wear-resistant linings — polyurethane consistently outperforms engineering plastics. The detailed materials range and part types are in the product catalogue; technical property explanations are in the reference information section. To discuss material selection for your specific node and order production, contact TIMOL factory.