Millathane® 76

A general purpose polyester millable urethane rubber for abrasion resistant applications.

Millathane 76 is a polyester millable urethane having improved processing properties over a wide Mooney viscosity range. Compounds can be compression, transfer, or injection molded in a hardness range of 30 to 90 Shore A. Millathane 76 can be vulcanized by either sulfur or peroxide cure systems.

Millathane 76 has excellent damping properties useful in vibration control for many automotive applications. Many o-rings, seals and gaskets are made from Millathane® 76 because of its excellent oil and fuel resistance. Millathane 76 is comparable to nitrile in oil and fuel resistance, but has better low temperature properties and excellent ozone resistance.

Millathane 76 can be used to replace conventional elastomers such as natural rubber, nitrile, and EPDM. Millathane 76 possesses excellent abrasion resistance combined with toughness, low temperature flexibility, ozone resistance, good damping, high tear strength and good stress relaxation properties. Such a combination of properties makes Millathane 76 a suitable choice in many applications such as bushings, small copier rolls and bumpers, o-rings, hydraulic seals, belts, solid tires, and many other high performance polyurethane parts.

*Millathane 5004 and Millathane CM were formerly known as Vibrathane 5004 and Adiprene CM. Adiprene® and Vibrathane® are registered trademarks of Chemtura Corp.

Processing

Millathane 76 is processed by techniques which are common to the rubber industry. Compounds can be mixed on an open mill or in an internal mixer; molded articles can be produced via compression, transfer or injection molding; calendered sheets can be press or rotocured.

Compounding

Millathane 76 compounds typically contain reinforcing fillers to achieve meet hardness and mechanical strength requirements, but gum compounds, with little or no fillers, have good properties. Reinforcing fillers like silica and small particle carbon black are easily incorporated into Millathane 76. It is sulfur or peroxide-curable.

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 (SR-350, from Sartomer), are commonly used along with peroxides to modify hardness, processing and other properties.

Properties

Typical Polymer Properties

Chemical type Polyester polyurethane
Color Light to dark amber Physical form Solid bale (or milled sheets*)
Packaging
   Solid bale: 45 lb (20.4 kg) carton
   Premilled sheets* 50 lb. (22.7 kg) carton
Odor Faint, characteristic
Specific gravity 1.22
Mooney viscosity,
   ML(1+4)/100°C) 25 – 70 (35±10 typical)
Storage stability 2 years when stored under dry and cool conditions

*milled sheets contain 1.5 phr of polymeric carbodiimide (Millstab™ P) for improved hydrolysis resistance

Typical Compound Properties

Hardness range 25 – 90 A
Tensile strength Up to 5000+ psi, (35+ MPa)
Tear strength Up to 400 lb/in (70 kN/m)
Compression set Very good (peroxide cure)
Heat aging 100º C (212º F) Good (sulfur cure)
Very good (peroxide cure)
Ozone resistance Excellent
Hydrolysis resistance Fair-Good
Oil & fuel resistance Excellent
Low temperature - 40º C (-40º F) brittle point
Weathering Good
Abrasion resistance Excellent
Resilience 10 - 20%

Typical End Uses
Printing rollers Industrial solid tires
Drive belts Vibration isolators
O-rings Suspension bushings
Specialty hose Conveyor belting
Can tester pads Copier rolls
Grease seals Dust covers
Packing gaskets Chute linings
Suction cups Hydraulic seals
Seals

Vulcanization Conditions

Compounds based on Millathane 76 are vulcanized at temperatures of 150º - 175ºC, depending on the cure system used, with typical cure times of 5 to 20 minutes for compression molded lab sheets.

Formulation Example

(See the Millathane Formulary for other compound examples)

Millathane® 76 100.0
Zinc Stearate 0.5
N330 Black 30.0
MBTS 4.0
MBT 2.0
Thanecure® ZM 1.0
Sulfur 1.5
Cured Properties, press cure 10'/155ºC
Hardness, Shore A 70
100% Modulus, MPa 3.7
200% Modulus, MPa 8.5
300% Modulus, MPa 14.9
Tensile Strength, MPa 32.8
Elongation at break, % 539
Tear Die C, kN/m 61
Brittle Point, ºC -35
Bashore Resilience, % 14
Compression Set, 22 hr/70ºC, % 36