Knowde Enhanced TDS
Identification & Functionality
- Chemical Family
- Polymer Name
- Technologies
- Product Families
- Chemical Composition
Synthetic rubber based on ester/TDI polyurethane.
Features & Benefits
- Materials Features
Applications & Uses
- Applications
- Cure Method
- Plastics & Elastomers End Uses
- Product Applications
- The excellent balance of properties of Millathane 76 makes it a perfect choice for various rubber parts including seals, diaphragms, bushings, test pads, suction cups, rubber-covered rollers and solid tires.
Properties
- Appearance
- Amber to light solid bales
- Typical Properties
- Product Properties
- Vulcanizates based on Millathane 76 can be produced in hardnesses ranging from approximately 30 to 95 Shore A, and offer very good abrasion resistance, excellent oil resistance, good resistance to gas permeability and low resilience (high damping).
- Sulfur cured Millathane 76 compounds get excellent strength properties at low hardnesses (30-50 Shore A).
- Peroxide cures give improved compression set and heat aging properties.
| Value | Units | Test Method / Conditions | |
| Specific Gravity | approx. 1.22 | — | — |
Regulatory & Compliance
- Certifications & Compliance
- Chemical Inventories
Technical Details & Test Data
- Processing Information
- Millathane 76 is processed by techniques which are common to the rubber industry.
- Compounds can be mixed on open mills or in internal mixers. Very often a compound can be mixed in one step including the vulcanization chemicals.
- Molded articles can be produced via compression, transfer or injection molding.
- Injection molding Millathane 76, mostly done with peroxide cures, provides very short cycle times, excellent flow and demolding and shows negligible mold fouling.
- Most compounds can be calendered for fabrication of rubber covered rollers or conveyor belting, or calendered sheets can be press cured or rotocured.
- Compounding Information
- Reinforcing Fillers
- Reinforcing fillers like N330 carbon black or precipitated silica increase the mechanical strength of Millathane 76 compounds.
- Fumed silicas such as Wacker HDK N20 or Cabosil M-5 will give somewhat higher reinforcement than precipitated silicas and will give translucent cured compounds (depending on other ingredients).
- Clay, talc and calcium carbonate can also be used as fillers to modify properties and processing, but are less reinforcing than silicas and blacks.
- Silane coupling agents like Silquest A189 and Si69 (in sulfur cures) and Silquest Y-15866, RC-1, or A172 (in peroxide cures) will improve the tear strength and set properties of mineral filled / reinforced compound and are recommended to beadded at about 2% of the mineral filler content.
- Plasticizers
- TP-95 (DBEEA) is a plasticizer that is very compatible with Millathane76, with compounds containing 25 phr and more usually not showing signs of bleeding or incompatibility.
- Other plasticizers such as Mediaplast NB-5 and Benzoflex 9-88SG can also be used to plasticize and soften compounds.
- Coumarone indene resins such as Cumar P10 and Cumar P25 can be used to plasticize sulfur-cured compounds and improve uncured tack, although high levels (>20 phr) may give tacky cured surfaces.
- The antistatic plasticizer Struktol AW-1 can be used to a limited extent, to lower surface resistivity, but may tend to bleed at levels over 10 parts. Vulcanized vegetable oils (factices) are often used in soft compounds to assist with plasticizer incorporation. Sulfur-free factice like Akrofax 758 is good for sulfur or peroxide cures; sulfur-containing factices can be used in sulfur cures only.
- White factices should not be used, as they retard the cure.
- Stabilizers / Antidegradants
- Millathane 76, being a polyester polyurethane, is prone to the effect of hydrolysis, where water can attack the polyester linkage of the polymer chain.
- The effect is accelerated by higher temperatures or acidic conditions. The inclusion of a small amount (1-3 phr) of hydrolysis stabilizer such as MillstabTMP will greatly inhibit the effect of hydrolysis.
- Higher levels of stabilizer will generally provide improved or longer protection.
- Using Premilled Millathane 76, which contains 1.5 phr of Millstab P, is highly recommended and is a convenient way to include that amount of stabilizer in the compound, and the incorporated stabilizer improves shelf stability of the polymer as well.
- Small amounts (0.5-2 phr) of antioxidants like Naugard 445 and Irganox 1010 may provide some benefit to the heat aging characteristics of Millathane 76 compounds.
- Process Aids
- Small amounts of process aids are normally used to prevent sticking to processing equipment and to improve flow during molding.
- For sulfur-cured compounds, the 0.5 phr of zinc stearate used as an activator is usually adequate.
- For more release, 0.5 - 2 phr of another process aid such as Struktol WB222 or Vanfre AP-2 can be used.
- For peroxide cures, 0.2 - 0.5 phr of stearic acid is used in place of zinc stearate.
- A low molecular weight polyethylene like AC617A, added at 1 - 4 phr, gives good release for calendering and molding.
- Process aids are best added at the very beginning of the mix cycle, to prevent sticking to mills and mixing equipment.
- Curing Agents: Sulfur and Peroxide Cures
- The best physical properties and abrasion resistance are achieved with sulfur cures, while the best compression set, heat aging and reversion resistance comes from peroxide cures. The sulfur cure system is a combination of MBTS (4 phr), MBT (2 phr), Thanecure® ZM (1 phr) and sulfur (1.5-2.0 phr), along with zinc stearate (0.5 phr), used as an activator.
- Sulfur dispersions, typically with about 20% process oil, are often used for optimal sulfur dispersion.
- Peroxide cures can be used for better set and heat aging characteristics. Typical peroxides used are dicumyl peroxide and DBPH, typically used at about 0.6 – 1.2 phr active peroxide (1.5 – 3.0 phr of 40% active). The use of low levels of coagents such as triallyl cyanurate (TAC) and trifunctional methacrylates like SR350 (TMTPMA) increase the crosslink density and improve compression set.
- Blends of the difunctional methacrylates SR231 (DEGDMA) or SR297 (BGDMA) with the trifunctional methacrylate SR350 are recommended for high hardness compounds, as the blend gives a good balance of strength properties, elongation and set.
- High crosslink densities, seen with high peroxide and/or coagent levels, will improve compression set but strength properties and elongation may be adversely affected.
- Vulcanization Conditions
- Sulfur-cured compounds are typically molded at temperatures of 150 - 165°C; higher temperatures can give poor cures due to reversion.
- Peroxide-cured compound can be cured from 145 - 175 °C, depending on the peroxide, dimensions of the part etc.
- Rubber covered rollers can be vulcanized in hot air (electric) or steam autoclaves, but it is extremely critical to completely protect the compound from direct contact with steam and to not over-cure the rollers. Autoclave temperatures can range from 130 - 150°C, with times dependent on roller size.
- Please contact TSE for recommendations regarding roller compounding, fabrication and curing! Millathane 76 cannot be cured in direct contact with open steam or hot air, and, hence, for applications like hose, its use is usually limited to inner liners.
- Calendered sheets can be press-cured, Rotocured, or cured in autoclaves.
- TP-95 (DBEEA) is a plasticizer that is very compatible with Millathane millable polyurethanes, with compounds containing 25 phr and more usually not showing signs of bleeding or incompatibility. Other plasticizers such as Mediaplast NB-4 and Benzoflex 9-88SG can also be used to plasticize and soften compounds.
- The antistatic plasticizer Struktol AW-1 can be used to a limited extent, to lower surface resistivity, but may tend to bleed at levels over 10 parts.
- Antidegradants
Polyurethanes are generally very resistant to ozone and oxygen attack because of their saturated polymer backbones (like EPDM). Small amounts (0.5-2 phr) of antioxidants like Naugard 445 and Irganox 1010 can provide some benefit to the heat aging characteristics of peroxide-cured Millathane 55 compounds.
- Process Aids
- Small amounts of process aids are normally used to prevent sticking to processing equipment and to improve flow during molding.
- For sulfur-cured compounds, the 0.5 phr of zinc stearate used as an activator is usually adequate.
- For more release, 0.5-2 phr of another process aid such as Struktol WB222 or Vanfre AP-2 can be used.
- For peroxide cures, 0.2-0.5 phr of stearic acid is used in place of the zinc stearate. A low molecular weight polyethylene like AC617A, added at 1-4 phr, gives good release for calendering and molding.
- Curing Agents
- The best physical properties and abrasion resistance are achieved with sulfur cures, while the best compression set, heat aging and reversion resistance come from peroxide cures. The sulfur cure system is a combination of MBTS (4 phr), MBT (2 phr), Thanecure® ZM (1 phr) and sulfur (1.5-2.0 phr), along with zinc stearate (0.5 phr), used as an activator.
- Peroxide cures can be used for better set and heat aging characteristics.
- Typical peroxides used are dicumyl peroxide and DBPH, typically used at about 0.6 – 1.2 phr active peroxide (1.5 – 3.0 phr of 40% active).
- The use of low levels of coagents such as triallyl cyanurate (TAC) and trifunctional methacrylates like SR350 (TMTPMA) increase the crosslink density and improve compression set.
- Blends of the difunctional methacrylate SR231 (DEGDMA) with the trifunctional methacrylate SR350 are recommended for high hardness compounds, as the blend gives a good balance of strength properties, elongation and set. High crosslink densities, seen with high peroxide and/or coagent levels, will improve compression set but strength properties and elongation may be adversely affected.
- Millathane 55 can also be cured with the isocyanate cure system (a combination of Thanecure® T9SF, HQEE, and accelerator), which gives excellent tensile and tear strengths at high hardnesses.
- Vulcanization Conditions
- Sulfur-cured Millathane 55 compounds are typically molded at temperatures of 150 - 165°C; higher temperatures can give poor cures due to reversion. Peroxide-cured compounds can be cured from 145 - 175°C, depending on the peroxide, dimensions of the part etc.
- Isocyanate-cured compounds are typically cured at 120 - 135°C.
- Rubber covered rollers are often cured in steam or electric autoclaves, under pressure, at 130-155°C for 1-6 hours (very large rolls for longer times at lower temperatures), depending on the compound and roll geometry. See publication TIPS V2-4 for additional information on autoclave curing.
- Resilience/Damping
Millathane millable urethanes can have resilience (rebound) values varying from below 10%, as seen with some Millathane 76 compounds, to over 60%, as seen with several polyether grades.
Low resilience compounds generally have excellent vibration damping characteristics and are used in instrument packaging and other vibration damping applications.
High resilience compounds tend to have lower heat build-up in dynamic applications such as rubber-covered rollers.
Generally, resilience will be higher with low filler loadings than with higher filler loadings. Peroxide cures will tend to give higher resilience than sulfur cures.
- Abrasion Resistance
- Abrasion resistance is the ability of a surface to resist wearing due to contact with another surface moving with respect to it.
- High resistance to abrasion is important in applications like rollers, belting, and helicopter dust covers.
- The DIN Abrasion Test (ASTM D5963) is one of the most common tests for measuring abrasion resistance.
- It's where a rotating cylindrical sample is passed across a rotating drum of abrasive and the amount of sample volume lost is measured.
- Typical abrasion resistance values for Millathane millable urethane compounds is 50-80 mm³.
- Some compounds can have abrasion resistance values as low as 25 mm³, depending on the polymer, cure system, and formulation.
- Polyurethane rubber provides the highest abrasion resistance of any rubber, synthetic or natural.
- Laboratory tests do not always predict the advantage of Millathane compounds over other rubbers, but field experience often shows a tremendous improvement in product lifetime when millable urethane replaces conventional rubber.
- Compression Set
- Peroxide-cured Millathanes have very good compression-set characteristics at temperatures up to 125°C, with the set increasing as the temperature increases (as is typical for all rubbers).
- The chart below compares the compression set of four polyester Millathane grades at 70°C, 100°C, and 125°C.
- Even lower compression sets can be achieved with compounds, with Millathane 66 giving the best (lowest) set at elevated temperatures.
- Generally, polyester urethanes will have improved compression set compared to polyether grades.
- Peroxide-cured billable urethane compounds will have much better (lower) compression set compared with sulfur-cured compounds, especially when coagents are included along with the peroxides.
- Compression Deflection
- Three different carbon black reinforced Millathane® millable polyurethane compounds (76, E34, and 5004) were tested for compression deflection per ASTM D575 Method A.
- The Millathane 76 and E34 compounds were sulfur cured, and the Millathane 5004 compounds were peroxide cured.
- Two hardnesses of each compound were tested. The samples had a shape factor of 0.5 (cylinders 1 inch (25.4 mm) in diameter and 0.5 inches (12.7 mm high).
- Compression deflection was tested at 23°C (room temperature), 50°C, and 70°C.
- The data shows the softer compounds have lower compression deflection curves than harder compounds.
- When comparing the compounds at similar hardnesses, Millathane 76 shows the lowest compression deflection values, while the Millathane E34 and 5004 compounds had somewhat similar compression deflection.
- The compression deflection results at higher temperatures show the expected trend of less stress required to deflect the samples, as shown in the 70°C data for all compounds and the 63 Shore A Millathane 5004 compound data for all temperatures.
- Oil, Fuel and Solvent Resistance
- Polyester grades will have significantly better resistance to oil and solvents than polyether grades.
- Polyester grades should be chosen for applications requiring optimum resistance to these materials, such as printing rollers and seals.
- The chart below compares four polyester Millathane grades for their resistance to IRM 903 Oil.
- All of the compounds showed minor hardness and volume changes after the elevated temperature oil exposure.
- Millathane 5004 and 76 had the lowest volume changes, and Millathane 5004 had the least change in hardness.
- Gas Permeability
- Millathane millable urethanes have very good resistance to gas permeability, with polyester grades approaching that of butyl rubber.
- A comparison of the nitrogen permeability of several Millathane grades vs. neoprene (CR), nitrile (NBR), and butyl (IIR) rubber is shown in the chart below.
- Polyester millable urethanes have very low gas permeability, comparable to or slightly better than nitrile rubber and slightly defensive to butyl rubber.
- Millathane E34, a polyether polyurethane, had higher (poorer) nitrogen permeability, similar to that of neoprene rubber.
- Electrical Properties
- Millathane compounds can be formulated to be antistatic or semi-conductive by the addition of conductive carbon.
- Antistatic compounds are important for static dissipative rollers and belting, typically for use in business machines where paper products are conveyed.
- Sulfur-cured Millathane 76 compounds, which varied in conductive black from 10 to 40 parts and plasticizer from 5 to 25 parts, had electrical resistivity values from 10⁸ down to 10³.
Packaging & Availability
- Packaging Information
Package size/carton: 45 pounds (20.4 kg).
Storage & Handling
- Shelf Life
- 2 years
- Storage Information
Stored under dry and cool conditions.