Polyurethanes are known as reaction polymers formed by synthesizing urethane links. The component polymers are isocyanates and polyols. The physical properties of urethanes which are specified by ASTM are dependent upon the specific classification for urethanes. These classifications include:
- Microcellular urethane
- Urethane coatings
- Flexible cellular materials such as molded, bonded and slab urethane foams
ASTM tests each of these classifications of urethanes differently and also with different testing classifications. For example, ASTM D2370 – 98(2010) tested the tensile properties of urethane coatings. These properties include:
- Tensile strength
In testing microcellular urethane, ASTM D3489 – 11, the properties included plasticity, specific gravity (SpG) and density.
In ASTM testing of flexible cellular materials, the properties included hardness with a range of 20A to 75D, density, specific gravity and viscosity.
It should be noted that due to the fact that urethanes are used in a number of common products for industrial uses (ex: urethane rollers) and home use (ex: polyurethane coated flooring), testing of the physical properties follow ASTM’s guidelines for plastics. As such, it can be expected that these diverse uses would also require physical property differentials. For example, thermoplastic polyurethane’s physical properties include resistance to oil and grease, as well as elasticity and transparency.
As an elastomer, the properties of urethane or polyurethane are resiliency and elasticity. The physical properties for urethane coatings for wood flooring would necessitate durability and resiliency. These properties are also found in thermal insulation used in homes and buildings to protect the interior from drafts and to reduce the cost of energy.
How the Physical Properties and ASTM Figure into Urethane Uses
ASTM relies on standardization to produce testing results that reflect a specified classification for each material tested. For example, when ASTM tests urethane for hardness, the results allow the producers of products to rely on the findings of ASTM’s standards as a guide to how to produce a broad range of urethane products with varying levels of hardness. This is also true for urethane coatings. Flooring designers and manufacturers rely on the durability of urethane used to produce flooring materials.
Density is another physical property of urethane that affects manufactured materials like coatings for window lineals and siding for buildings. Since urethane is used in end products, the physical properties as outlined by ASTM provide reasonable design, manufacture and buyer confidence children’s car seats, vehicle body parts and sports gear.
Generalized Urethane Roller Industry Tests
It is important to note that even though there are many tests available to test polyurethanes and urethane’s, the urethane roller industry utilizes a general set of tests (the specific testing method may vary):
- Hardness – ASTM D2240
- Tensile strength – ASTM D412
- Elongation – ASTM D412
- Tensile Stress 100%, 200% & 300% Modulus – ASTM D412
- Tear strength – ASTM D624
- Split tear – ASTM D470
- Rebound – ASTM D2632
- Compression set – ASTM D395
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