Millathane® Millable Polyurethane Rubber and Thanecure® Reactive Additives

Introduction to Millathane® | Key Properties | Applications | Millathane® Grades | Ask Dr. Millathane®

TSE Industries, Inc. is the world’s largest manufacturer of millable urethane rubber, sold under the trade name of Millathane®. TSE has been working with millable urethanes since 1962 and producing Millathane millable urethanes since 1976. TSE Industries has two facilities in Clearwater, Florida (USA).

Introduction to Millathane® Millable Urethane

Millable polyurethane rubbers (sometimes known as millable gums) are solid polymers that can be processed on standard rubber processing equipment such as internal mixers (Banbury® mixers) and rubber mills. The properties of millable urethanes are generally comparable to castable (liquid) urethanes, which require different processing equipment and molding techniques. Millable urethane rubbers are used in many demanding applications, especially those that require excellent mechanical strength, oil resistance, ozone resistance and abrasion resistance.

Polyurethanes are made by reacting a diisocyanate with a polyol and usually a chain extender. Millable polyurethane rubbers are made from both polyester and polyether polyols. Diisocyanates like MDI, TDI, H12MDI and others are commonly used, along with many different chain extenders. Millable gums are, in general, under-indexed urethanes which means that there is a stoichiometric deficiency of isocyanate groups compared to hydroxyl groups in the overall reaction (NCO:OH ratio is less than 1.0). Liquid (castable) urethanes have a slight excess of isocyanate groups. Being under-index results in the need for millable urethanes to be vulcanized by peroxide or sulfur cure systems.

Like other synthetic rubbers, cure sites must be present to radically cure with peroxide or sulfur. Cure sites can be accomplished by the use of MDI as the isocyanate or by introducing carbon-carbon double bonds in the chain extender. Thus vulcanization can be accomplished with heat and pressure utilizing sulfur or peroxide cure systems. An important part of the sulfur cure system is the accelerator Thanecure® ZM, used along with MBTS, MBT and sulfur.

Key Properties

Millathane compounds can be made into dense, solid materials or sponge materials (foamed or blown). Dense compounds can have hardnesses from approximately 25 to 99 Shore A (60 Shore D), tensile strengths over 5000 psi (35 MPa) and DIN abrasion values as low as 30-40 mm³ loss. Sponge compounds can be produced with densities as low as 0.4 g/cc.

Millable urethane rubbers possess a combination of physical properties not found in natural or synthetic rubber such as:

• Outstanding abrasion resistance
• Excellent oil, oxygen and ozone resistance
• Excellent gas (e.g., nitrogen) permeability resistance, especially with polyester grades
• Low temperature flexibility
• Dynamic load bearing ability
• High resilience
• Excellent resistance to compression set
• Withstands temperatures up to 120° C

Applications

Millathane® millable polyurethane rubber is useful to rubber molders or fabricators who wish to make abrasion and oil resistant parts without employing techniques or equipment required for cast or thermoplastic polyurethanes. Applications for millable polyurethane include:

Rollers and Belting

Millathane millable urethanes are widely used in rubber covered rolls because of their excellent combination of abrasion resistance, oil resistance and resistance to glazing, so they retain their coefficient of friction as they age. This is important for rollers and belts in paper and currency handling applications. Several grades that are often used in rollers are Millathane E34, Millathane 5004 and Millathane 76.

Medical Applications

The strength properties of urethanes, including tensile strength and abrasion resistance, make it useful for critical applications for (non-implantable) medical devices. Millathane grades that find use in this application area include Millathane 76, Millathane E34 and Millathane 26.

Military and Aeronautical Applications

Many rubber applications in military and aerospace, including parts on airplanes and helicopters, require the high abrasion resistance of Millathane millable urethanes along with very good low temperature properties. Millathane CM and Millathane E40 are two of the Millathane grades that are excellent for both abrasion resistance and low temperature properties and are used in these applications.

Electronics Applications

The wear resistance, excellent frictional characteristics and excellent ozone resistance make Millathane millable urethanes the polymer of choice for applications such as keypads, belts and rollers. Millathane grades used include Millathane 5004, Millathane 66 and Millathane 97.

Footwear

The excellent abrasion resistance of urethanes like Millathane E34, Millathane CM and Millathane E40 make these polymers desirable for tough footwear applications, especially in the sporting shoe industry. The good wet and dry frictional properties of millable urethanes make it good for shoe soles. The transparency of Millathane 97 is the reason it has been used in transparent footwear applications for over 20 years. Download our Millathane Footwear Brochure from our Millathane Technical Information page.

Oil and Fuel Resistant Applications

Polyester grades of Millathane millable urethanes are widely used in o-rings, gaskets and seals, where the excellent resistance to petroleum based oils, fuels and hydraulic fluids is important. Millathane grades used for oil resistant applications include Millathane 5004, Millathane 66, Millathane 76 and Millathane HT.

Industrial Tires

The abrasion resistance of Millathane millable urethanes, coupled with their excellent oil resistance and frictional characteristics, make them the choice for specialty industrial tires that require these properties. Millathane grades that are used in this application include Millathane 76 and Millathane E34.