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Old January 29th, 2018, 10:44 PM   #1
goldleader
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Default Urethane question

What type of urethane is used to make Skate wheels?
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Old January 30th, 2018, 08:29 AM   #2
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What type of urethane is used to make Skate wheels?
Both types.
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Old January 30th, 2018, 12:53 PM   #3
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Roll-line makes urethane wheels and plastic wheels and a mixture of urethane and plastic wheels, the lower duro wheels are urethane, the mid duro and high duro wheels are either plastic (high duro) or a combination, everyone but Roll-line makes wheels from urethane.

Skateboard wheels are typically mass-produced in an industrial setting. They are made of polyurethane, a versatile and durable synthetic material. According to 1skates.com, Frank Nasworthy invented polyurethane skateboard wheels in 1970. With their rubber-like grip on the pavement, polyurethane wheels expanded the potential of ways that skateboards could be used. Different types of polyurethane skateboard wheels vary mainly in terms of their durometer, diameter, color, and shape. The durometer is a measure of how hard the wheel is. Soft wheels, best for cruising on hard surfaces, have low durometers, such as 87A. Hard wheels, which absorb little shock, have a higher durometer, like 100A. The diameter is the height of the wheel. Making polyurethane skateboard wheels involves the use of specialized chemicals and machinery. This process is indicative of the basic industrial processes by which polyurethane wheels are made.

I digress with the date of the discovery of urethane skate wheels, bought my first skate board, a 28" deck with urethane wheels in '63-64

TDI and MDI are both building blocks of polyurethane, and are base forms of urethane resin. However, MDI (methylene di-ioscyanate) needs non-Moca Type curatives, whereas TDI (toluene di-isocyanate) needs Moca Type curatives.

MOCA has been used for many years as a curative for various TDI based polyurethane systems. The raw material cost effectively provides good mechanical properties in many polyurethane applications. However, MOCA has also been under the scrutiny of many regulatory bodies due to health & safety concerns when handling the material in production. To ensure safeguards are maintained, The European Chemical Agency (ECHA) has conducted a thorough review and now plans to restrict use of the material under the REACH regulatory process in late 2017.
The processing character for MOCA

Granular solid contains powder presenting a dust exposure hazard
Ventilation requirement
High melting point ~100C
Requires exposure monitoring for operators
SDS code: UN3077 (Environmentally Hazardous Solid)

The processing benefits of Gantrade formulated GoCure curatives

Liquid or waxy solid that eliminates dust exposure hazard associated with MOCA
Lower melting point (~ 85 C) allows processing temperatures as low as 50 C
Not a suspected carcinogen
SDS code: UN3082 (Environmentally Hazardous Liquid)

Results for two series of Gantrade formulated GoCure curatives

One group of the GoCure curatives has a short gel time that can be used for mix-machine processing eliminating the need for catalyst
The second group offers longer gel time for manual processing. Various gel times are available for different open time requirements

The hardness, tensile and Die C tear strength of the formulation cured material are comparable or better than MOCA cured material. Detailed physical testing data is listed for comparison with MOCA and other common curatives like DMTDA and MCDEA. Dynamic Mechanical Analysis was utilized to test against materials cured by formulation, MOCA, MCDEA and DMTDA. Results showed they have as good dynamic properties as MOCA and better than DMTDA cured material.

MDI Curative for High Temperature Urethanes
In response to regulation changes, some TDI systems processors switched to MDI systems to avoid using MOCA as a curative. However the most commonly used MDI curative, 1, 4-BDO, imparts thermoplasticity to the final products, polyurethane parts, especially in the high hardness category. HQEE is another readily available curative for MDI prepolymers. It has a melting point of 98C but it easily solidifies at cold spots, potentially blocking the transfer line. To prevent this from happening, all HQEE transfer lines must be heated, which increases energy consumption. Gantrade developed a group of curatives that offer good hardness and tensile retention at high temperatures to 177C (350F). A comparison of physical properties was done using the same prepolymer cured with mentioned curatives: 1, 4-BDO, HQEE & Gantrade curative A243 then heated at 350F overnight.

The hardness of the BDO cured material dropped from 92A to 60A when heated to 150C (300F) and melted at 177C (350F). HQEE cured material dropped from 50D to 89A at 177C (350F). The formulation based on A243 gave the highest hardness with this prepolymer after heating at 177C (350F), dropping to 94A from 63D. Tensile strength and tear strength showed similar trends.

60D MDI Ester/A243 & TDI Ester/MOCA Heated at 350 F
Furthermore, a comparison with a similar hardness MOCA cured TDI LF polyester material was done. The hardness drop of TDI/MOCA was from 64D to 87A at 177C (350F) oven. The drop of MDI/A243 was 63D to 94A. The strong tensile of TDI/MOCA material deteriorated to 1/3 of its original value after heating at 177C (350F) overnight. Under the same conditions, the MDI/A243 retained 90% of its initial tensile strength and retained its original Die C strength and exhibited good overall property retention after prolonged heating at 150C (300F).

Gantrade Europe Limited will be exhibiting at PSE Europe 2017, stand #450, scheduled to take place in Munich on the 27-29th June 2017. The company plans to communicate the breadth of their solution based capabilities for polyurethane manufacture in the areas for medical, industrial, automotive and construction markets.





Polyurethane Wheels

Mix a batch of polyurethane. Combine the chemical components of the polyurethane in the appropriate proportions in a metering machine. A metering machine is a machine that heats, mixes and dispenses polyurethane.

Add color. When the polyurethane in the metering machine is a liquid, add dye or some other type of pigment to the batch. This is only necessary if you want your skateboard wheels to have a color.

Pour polyurethane into molds. The molds should be made of aluminum and reflect the shape and size you want your wheels to be.

Remove the polyurethane "slugs" from the mold after the polyurethane has solidified. Slugs are the basic, unfinished form of your polyurethane skateboard wheels. Place the slugs on a flat surface to fully cure.

Shape the wheel. Use a lathe to cut the slug into shape. The sides and riding surface of the wheels should be cut to match each other exactly. A lathe is a piece of machinery that turns an object as it shapes it. In this case the lathe turns the slug as it cuts away excess polyurethane.

Tips

Heat is not necessarily required to mix polyurethane, though it may produce a higher quality wheel.

Warnings

According to Exploratorium.edu, clear, uncolored wheels may be the strongest. Adding pigments or dye, which displace the polyurethane, may weaken the wheel.
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Old January 30th, 2018, 11:56 PM   #4
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Quote:
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Both types.
Country and Western.
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Old January 31st, 2018, 12:03 AM   #5
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Lord, where did you get all that?

Quote:
Originally Posted by ursle View Post
A metering machine is a machine that heats, mixes and dispenses polyurethane.
You assume hot pour urethane. There are also competent cold pour chemistries.

Quote:
Originally Posted by ursle View Post
Place the slugs on a flat surface to fully cure.
May need to be in a low temp oven to fully outgas.
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Old January 31st, 2018, 12:50 AM   #6
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Sunnyapes answer was a confounder, and the question is....extreme, so I googled, note, the mocha has been illegal in the US and is now illegal in the UK.

Cold pour, great.
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