millable polyurethane for shoes

Millable Polyurethane for

Shoes

Luis Antonio TormentoLT Químicos/TSE Industries18/08/2016

Introduction Polyurethanes are based on polyols of the

polyether or polyester types, including polycaprolactone and aromatic diisocyanates MDI and TDI. Aliphatic diisocyanates produce transparent polymers having excellent ultraviolet light resistance. There are special types with FDA approval.

Types based on polycarbonate polyols are used in medical applications and have exceptional transparency.

Types of Polyurethane

Polyurethane polymers used on shoe manufacturing can be divided into three (3) main groups:

Tipos de Poliuretano Thermoplastics: processed like any other

thermoplastic, using typical equipment such as extruders and plastic injection molding.

The thermosetting bicomponent: processed by casting, pre-cured and then demoulded and post-cured in an oven. In its production specific equipment are needed.

Thermosets: processed like any other elastomer in typical equipments of rubber industry.

Comparison of Polymers

Properties Polyurethane Polychlooprene NBR NATURAL EPDM

Tensile Strength E B-E R B-E R

Hardness, Shore A 10-95 10-95 20-100 30-100 25-90

Max Temperature (ºC) 100 120 120 100 175

Ozone Resistance E R-B P P E

Cut Resistance E B R B R

Tear Strength E B R B R

Compression Set R-B B R-B R B

Abrasion Resistance E B-E R B R

Heat Generation E E P R-B R-B

E - Excelent, B - Good, R - Regular, P - Fair

Disadvantages

Among its disadvantages include: Poor resistance to hydrolysis,

especially in polyester types (AU); polyether types (PAUR) resist very well to water.

Poor resistance to ketones, concentrated acids and bases

Typical Applications

Among the typical applications of polyurethane shoes include: Insoles Absorbing Impact Soles


1 – Insole to absorb impacts

Insoles

Insoles They are produced in two distinct ways: 1 - From a foamed polyurethane latex over

a woven - polyester, cotton, nylon, etc- insoles can be manufactured of different densities and thicknesses

2 - from an extrusion / calendering, a gas is entrapped between layers of the material which encourages the creation of an area with the function of a shock absorber

Insoles

Advantage Absorbs shock Reduces fatigue in the feet, legs and

ankles Make the most comfortable shoes Provide lasting support It remains in place and maintains its

resilience Prevents proliferation of bacteria Gives no odor


4 – Sole – Polyuretane Millable

Millathane 97

Millathane 97 is a polyether based polyurethane rubber which produces parts with outstanding durability, high coefficient of friction and good stability to UV. This polyurethane rubber is for applications in shoe soles / inserts, roll coating and other applications where necessary transparency, light brightness or artifact pieces of decoration.

Millathane 97

Millathane 5004 MILLATHANE 5004 is a polyester based polyurethane

elastomer, which has excellent processing characteristics. MILLATHANE 5004 Compounds can be rapidly processed in conventional rubber equipment. The vulcanization can be done by using dicumyl peroxide or Varox.

Compounds of MILLATHANE 5004 press-cured, achieve optimum vulcanization within 15 minutes at 160°C, or 30 to 45 minutes at 152 ° C . The vulcanization can be accelerated to 3 to 4 minutes at higher temperatures, 177-204°C. The rubber compound is of high quality, has good performance at low temperatures and good resistance to hot air. The vulcanized has also excellent abrasion resistance and tear strength at high temperatures and excellent resistance to oxygen, ozone, fuel and oils

Millathane E34 Millathane E34 is a rubber based on polyether

polyurethane, high performance, designed for applications that require high abrasion resistance, low temperature flexibility, ozone resistance, resistance to oil and fuel, hydrolytic stability and improved handling.

Millathane E34 may be composed and processed with conventional equipment for rubber. For example, Millathane E34 can be mixed in an open mixer or internal mixer. The compounds can be calendered, extruded, injected, transferred or compressed, to produce finished polyurethane parts.

Millathane E34 is vulcanized using organic peroxides or using sulfur and thiazoles accelerators.

Soles with MIllathane

Soles with Millathane

Polyurethanes polyester and polyether types may be used in blends with other rubbers, in order to give them better abrasion resistance, tear resistance and penetration resistance.

Soles with Millathane

Posible blends are: With NBR and NBR/PVC With SBR With BR With EPDM With HNBR

Millable Polyurethane

The millable elastomer - commonly

called gum - was one of the first forms of polyurethane.

When the urethane was invented, the standard process used to convert elastomers to finished products employed the same techniques of rubbers.

Millable Polyurethane They differ from other polyurethanes in

the methods used in their healing, the intense composition and processing. The millable polyurethane rubbers are processed on rubber conventional equipment at temperatures of 120 - 130oC.

Molded polyurethane liquid, but with properties similar to polyurethane millable require specific procedure sized equipment, greenhouses and other machinery.

Millable Polyurethane Specifically, these properties are:

- Superior resistance to abrasion; - Excellent resistance to cutting; - Excellent resistance to ozone, fuels and oils; - High flexibility compression (load bearing); - Great flexibility at low temperatures.

These are the joint properties that distinguish them from other polymers polyurethanes.

Main Properties The abrasion resistance and durability of the

polyurethanes are the key properties which lead to choose polyurethanes from other polymeric systems, factors up to 10 to 1.

The long durability of polyurethanes is reversed in cost reduction. The hardness of the urethane elastomer makes it an ideal elastomer for shoe soles in applications such as: sports shoes for use in sandy or abrasive ground, such as tennis courts, not to slip on wet or dry ground; They are used in shoes for basketball practice, and jogging. By having a strong puncture resistance and flexibility at low temperature, it is used in soles for climbing boots.

POLYETHER and POLYESTER The polyethers are used in most applications in

contact with water, especially at high temperatures, because they exhibit greater hydrolytic stability compared to polyesters.

Many of cylinders cured in autoclaves are polyethers, because they resist better to the effect of water vapor during cure.

The hydrolytic stability of polyester compounds may be significantly improved with the addition of polycarbodiimide (Stabaxol P).

Polyether rollers also tend to develop less heat when compared to polyester cylinders.

POLYETHER and POLYESTER

Polyethers are used in most applications in contact with water, especially at high temperatures, because they exhibit greater hydrolytic stability compared to polyesters.

Many of rolls cured in autoclaves are polyethers, because they resist better to the effect of water vapor during cure.

The hydrolytic stability of polyester compounds may be significantly improved with the addition of polycarbodiimide (Stabaxol P).

Polyether rollers also tend to develop less heat when compared to polyester rolls.

Compounding and Mixing Composition practices of other

rubbers like: natural or synthetic can usually be employed in the composition of the millable elastomers, but also specific practices for these polymers were developed.

Compounding and Mixing As filler, carbon black is used to obtain maximum

mechanical resistance and abrasion resistance. The silica is usually used as the white charge. The silanes are often used with the silica to

reduce heat generation and promote increased physical properties and abrasion resistance.

Vulcanized vegetable oils are used especially in low durometer compounds to help absorb high levels of plasticizer contributing to softening and aid in processing and extrusion, and promote dimensional stability.

Compounding and Mixing As plasticizer, adipates, phthalates,

esters and coumarone-indene resin have shown good characteristics in manufacturing operations.

The coumarone-indene resin plasticizers are effective in curing of sulfur-based compounds, but are not used in the peroxide curing due to the interaction with the curing agent.

Compounding and Mixing Since most synthetic rubbers,

millable polyurethanes can be cured by any systems based on sulfur or peroxide.

Peroxide cure are primarily used to obtain low permanent set and improved heat resistance properties.

Compounding and Mixing Uretanos com altos níveis de poliéster podem

também ser curados com isocianato. Compostos curados por este método são vulcanizados rapidamente e têm baixa estabilidade na armazenagem.

No entanto, os vulcanizados exibem boas propriedades físicas, especialmente em aplicações de 78A a 70D Shore.

Co-agentes à base de acrilatos como o Sartomer SR-350 ou Saret 500, podem ser usados com sucesso para aumentar a dureza de compostos curados à base de peróxido quando usados de 10 a 20 phr. A forma líquida desses produtos também ajuda a controlar a viscosidade em compostos com alto peso molecular.

Compounding and Mixing The processing aids used

effectively in urethane compounds include polyethylene glycol, low molecular weight polyethylene, stearic acid and TE 88 XL.

Mixing Techniques

The millable polyurethane compounds may be mixed with conventional mills, internal mixers, and other internal mixers.

Molds

The molds must be chrome plated or made of stainless steel as the peroxide vulcanization is extremely corrosive

References

TSE Industries – Technical Literature Rubber Technology - Morton

Thank You

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millable polyurethane for shoes

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