URETHANE SPRINGS GUIDE

Physical properties and features of urethane

Item Urethanes for heavy loads High-deflection
type
urethane
foams
(porous)
Low repulsion
urethanes
H type M type S type L type Economy type
Hardness (Shore A) 95 90 80 70 90 N / A (foam) 70
Catalogue No. TUSUSUSN EXQXEST
ESBTESU
ESUBAEEL
LACAXCX
AZAZXUT
UTHUDUDH
- - AELAECE
AEXCEX
PAPLA ANLANCNN
ANXCNXAZN
AZNXUTN
UDN
Tensile strength
(N/cm2)
{kgf/cm2}
4511{460} 4462{455} 2941{300} 3138{320} 2452{250} 490{50} 1176{120}
Elongation (%) 450 550 500 650 540 250 250
300% modulus
(N/cm2)
{kgf/cm2}
1755{179} 1304{133} 931{95} 372{38} 1225{125} - -
Repulsion elasticity
(%)
23 28 56 51 42 50 6
Tearing strength
(N/cm2)
{kgf/cm2}
1206{123} 1147{117} 539{55} 451{46} 686{70} 294{30} 343{35}
Specific gravity 1.28 1.27 1.26 1.16 1.02
Permanent strain
(%) *
26 24 27 25 27 25 1
Operating environment temperature (°C) -20~+70 -5~+80 -20~+70
Melting point
(°C)
220 200 180 230~250 200
Embrittlement point
(°C)
-70 -60 -45 -70 -50
Ignition point (°C) 500 450 400
Features Weather resistance Each type has better weather resistance than ordinary rubber materials.
Water resistance Can be used even if exposed to a small amount of water. (Cannot be used under conditions of constant water immersion.)
Oil resistance Can be used even if exposed to a small amount of cutting oil. (Cannot be used under conditions of constant oil immersion.)
Discoloration Becomes discolored when exposed to ultraviolet rays (including sunlight), however there is no adverse effect on performance. Relatively more discoloration occurs with high-deflection type urethane foams than with other types.
Properties •Provides the largest load resistance, for better contour forming.
•Because of the small deflection amount, this type can be used only for simple forming.
This type has physical properties intermediate between the H and S types, and can be used for general purposes. Although the load resistance is lower, the larger deflection amount allows deeper forming. Although the hardness is equivalent to general rubber materials, this type has superior abrasion resistance and mechanical strength. Although the load resistance and durability (permanent strain) are somewhat inferior to the M type, the prices are lower. •Can be used for high deflection (40%max.)
and high load applications.
•The lateral expansion is about half that of the M type at an equivalent deflection.
•Because this type is foamed urethane, it provides excellent heat radiation performance.
With low permanent strain and excellent shock absorbing performance, this type can deliver antivibration performance.
Applications
(reference)
Machining of thin stainless steel plates or steel plates approximately 2mm thick Machining of thin plates of materials such as aluminum or brass •Bulging
•Shallow drawing
•Drawing
•Guerin method
•Wheelon method
More suitable for smallvolume production than the M type. Often used as pad cushions and cam return cushions. •Vibration proofing
•Machining of soft materials such as films.
The above figures are actual measurements at room temperature 23°C, and do not constitute guaranteed specifications.
  *method of measuring permanent strain (JIS K7312)
   1) 24 hours at 70°C with 25% compression
   2) Cooled for 30 min. in laboratory at 23°C
   3) Strain is measured.

Comparison of urethane springs, coil springs, and gas cushions

: Excellent : Satisfactory : Slightly poor : Unacceptable
Item Cost to load ratio Machinability High speed endurance Load stability Permanent strain Initial pressure Operating environment temperatures
Urethane springs
Coil springs
Gas cushions

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