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Millathane® 55

A Low Viscosity, High Performance Millable Polyether Polyurethane Rubber

Millathane 55® is a high performance polyether millable urethane rubber which has been developed primarily for applications requiring low viscosity, high hardness sulfur-cured compounds.

Compared with Millathane E34 in sulfur cured compounds, Millathane 55 compounds have higher hardness, but with lower compound viscosity, so processing is improved. Compounds also have excellent abrasion resistance, high resilience (rebound), excellent ozone resistance, moderate oil and fuel resistance, and very good hydrolytic stability.  Check out our New Bulletin for additional information about Millathane 55.   

Millathane 55® is sold in bales, not pellets, for ease of processing on rubber mills.   

For more information about Millathane® and Thanecure® products, please contact: Lynn Zylka at (727) 540-1358 or contact Lynn here.

Millathane 55 is processed by techniques which are common to the rubber industry: Compounds can be mixed on two-roll rubber mills or in internal mixers. Compounds can be calendered, extruded, or injection, transfer or compression molded to produce finished polyurethane parts.

Millathane 55 compounds typically contain reinforcing fillers to achieve meet hardness and mechanical strength requirements. Reinforcing fillers like precipitated silica, usually with silane coupling agents, are commonly used for non-black compounds, and fine particle carbon blacks are used for black compounds. Millathane 55 is sulfur, peroxide or isocyanate-curable, although the best properties are obtained with sulfur cures. The best sulfur cure system is a combination of MBTS, MBT, Thanecure® ZM, and sulfur, with zinc stearate as an activator/process aid.

Any of the typical peroxides can be used for peroxide curing, including dicumyl peroxide and DBPH. Coagents, such as TMPTMA or TAC can be used along with peroxides to modify hardness, processing and other properties.

Isocyanate cures, using a combination of Thanecure® T9SF, HQEE and an accelerator, can be used for specialty, high hardness compounds with excellent strength and abrasion resistance properties.


Chemical type Polyether polyurethane
Color Pale to dark amber
Physical form Solid bale or milled sheets
   Solid bale*: 38 lb (17.2 kg) carton
   Premilled sheets* 50 lb. (22.7 kg) carton
   *Bale wrap Strippable film (not meant to be incorporated into the compound)
Odor Faint, characteristic
Specific gravity 1.04
Mooney viscosity,

25 – 45
Storage stability 3 years from date of manufacture, when stored under dry and cool conditions


Hardness range 55 to 90 Shore A
Tensile strength Up to 4300+ psi, (30+ MPa)
Tear strength Up to 400 lb/in (70 kN/m)
Compression set Fair (Sulfur cure)/Good (Peroxide cure)
Heat aging Fair (Sulfur cure)/Good (Peroxide cure)
Ozone resistance Excellent
Hydrolysis resistance Very Good
Oil & fuel resistance Good
Weathering Very good (black compounds)
Abrasion resistance Excellent
Resilience 40-55%


Printing rollers Tile molds
Molded goods Technical rubber goods




- Millathane 55 Millathane 34
Millathane E55 100 --
Millathane 34 -- 100
Zinc Stearate 0.5 0.5
Ultrasil VN3 (precipitated silica) 45 45
Silquest A-189 (mercapto silane) 1.0 1.0
TP-95 (DBEEA) 3.0 3.0
Carbowax 3350 2.0 2.0
Struktol WB-222 1.0 1.0
AC617A (polyethylene) 2.0 2.0
Struktol WB-222 1.0 1.0
MBTS 4.0 4.0
MBT 2.0 2.0
Sulfur, 80% 2.5 2.5
Thanecure ZM 1.0 1.0
Mooney Viscosity, ML(1+4)/100ºC
Polymer/Compound 33/93 46/97
Rheometer, MDR, 20'/160ºC
ML, lb-in 6.5 6.3
   dNm 7.5 7.3
MH, lb-in 36.3 29.2
   dNm 41 33
ts1, minutes 2.7 2.5
t90, minutes 10.8 10.0
Physical Properties, cured t90/160ºC
Hardness, Shore A 83 76
TSE-100*, psi 695 463
   MPa 4.8 3.2
TSE-300*, psi 2410 1713
   MPa 16.6 11.8
Tensile Strength, psi 4250 4090
   MPa 29.3 28.2
Elongation, % 485 583
Tear, Die C, lb/in 271 273
   kN/M 47.4 47.8
Tear, Die B, lb/in 440 468
   kN/M 77 81.9
*TSE-xxx=Tensile Stress at xxx% Elongation
Bashore Resilience, % 43 42
Compression Set, 22 hr/70°C, % 63 68
DIN Abrasion, mm³ loss (rotating) 57 63