How to Choose the Right Polyurethane Hardness (Shore A Guide)

Hardness is the most important parameter when specifying cast polyurethane. The Shore durometer scale measures resistance to permanent indentation — but choosing the right hardness involves understanding the relationship between hardness, load-bearing capacity, impact absorption, and abrasion resistance.

Understanding the Shore Scales

Two Shore scales are commonly used for polyurethane:

Shore A: Used for soft to medium-hard elastomers. Range 0–100, where 0 is completely soft and 100 is very hard rubber. Most cast PU falls in Shore A 20–95.
Shore D: Used for hard materials. Shore D 40 is approximately equivalent to Shore A 95. Hard PU grades (Shore D 40–80) are used for structural wear parts.

Hardness vs. Application Guide

Hardness	Typical Applications	Key Properties
Shore A 20–40	Vibration isolation mounts, soft seals, medical pads	Maximum flexibility, high energy absorption
Shore A 40–60	Impact bars, bumpers, dock bumpers, noise damping pads	Good impact absorption, moderate load capacity
Shore A 60–75	Rollers, wheels, conveyor components, general wear parts	Balanced hardness and flexibility
Shore A 75–85	Screen panels, skirt boards, pump liners, hydrocyclone inlets	Good abrasion resistance, maintains aperture shape
Shore A 85–95	Hydrocyclone apexes, chute liners, structural wear parts	High abrasion resistance, maximum load capacity
Shore D 40–60	Solid wheels, high-load bearings, precision wear components	Near-plastic rigidity with elastomer toughness

How Hardness Affects Performance

Abrasion Resistance

Contrary to intuition, harder PU is not always more abrasion resistant. For sliding abrasion (e.g., material flowing across a liner), medium-hard grades (Shore A 70–85) often outperform very hard grades because they can deform slightly to absorb abrasive particles. For impact abrasion (e.g., large rocks hitting a screen panel), harder grades perform better.

Load-Bearing Capacity

Harder grades support higher static and dynamic loads without permanent deformation. If a PU component shows "creep" (gradual deformation under constant load), specify a harder grade or switch to Shore D.

Need Help Selecting the Right Hardness?

Our technical team can recommend the optimal hardness grade for your application. Send us your application details and we'll provide a free recommendation.

fengjian@jsltupe.com