- The modulus of elasticity means how the product reacts to the strain put on it.
Why it Matters: Depending on the application, you may require a part that’s able to withstand stress without breaking or failing.
The three primary types of elastic moduli are:
- Young’s modulus - measures the elasticity of an object when tension is given in one direction. An example of this is a polyurethane rod that is crushed and stretched horizontally, then returns to its original state.
- Shear modulus - describes the object’s response to shear stress. An example of this would be attempting to cut it with dull scissors.
- Bulk modulus - describes the elasticity when it relates to volumetric stress (or compression). It is usually used to describe the behavior in relation to fluid compression, but is also used for solids and gases.
- The hardness refers to the material’s ability to withstand deformation from pressure.
Why it Matters: A key benefit to polyurethane is that it delivers outstanding performance through various ranges of hardness such as in the sole of a shoe or a bowling ball. Many applications take advantage of the range of hardness in polyurethane, such as in shock absorbers and wheels.
While hardness is an indicator of a specific material’s modulus, it by itself doesn’t say whether the material performs well overall. For example, two different polyurethane formulations can have identical hardness but act differently.
Hardness is measured via overlapping scales: Shore A and Shore D, and in some cases Shore OO or Rockwell R. To measure Shore hardness, a durometer is used, which presses a needle-like rod into the material’s surface to measure the depth of indentation.
What’s beneficial about polyurethane is it has a wide range of hardness from soft, gel-like material to hard, such as in the case of a bowling ball.
If hardness is a crucial feature you require, we can design and mold the component based on your specific needs.">
- Tear strength is how well the material resists the beginning and growth of tears.
Why it Matters: If you need a product that functions well in an abrasive or destructive environment, tear strength is something to consider, especially with polyurethane when the potential exists for cuts.
Tear strength depends much on several properties including modulus and tensile strength, both of which can be manipulated by the formation of the polyurethane. And, just like hardness, the tear strength can be tailored specifically for your application.
The most popular way to test tear strength is in pounds per linear inch (kN/m) of object thickness, but there are a variety of acceptable ASTM tests to measure the tear strength in polyurethane, each of which uses a tensile test machine to test the product until failure.
Below are the standard tests one would perform to determine the object’s tear strength.
- ASTM D-624, Type C — Standard Test Method for Vulcanized Rubber and Thermoplastic Elastomers, which measures for the object’s resistance to the beginning of a tear.
- ASTM D-1938 — Standard Test Method for Tear-Propagation Resistance of Plastic Film and Thin Sheeting by a Single-Tear Method, which measures how resistant the product is to the growth of a tear.
- ASTM D-470 — Standard Test Methods for Crosslinked Insulations and Jackets for Wire and Cable, which measures how well the object resists the growth of a split or tear.
- Compression Set refers to how deformed the product becomes due to a compressive force.
Why it Matters: If your application includes bumpers or equipment mounts, compression set is an essential factor to consider because it indicates how well it retains its properties and shape under heavy compression.
If you have a compound with a low compression set, the compound recovers quickly even if it remains compressed for a significant time. Alternatively, if you have a compound with a high compression set, it won’t recover well after high compression stress.
Compression set depends on properties like modulus and molecular cross-linking specified in the design of the polyurethane.
Compression set is measured in percentages of deformation that’s caused by the load. The standard test is the ASTM D-385 — Standard Test Method for Rubber Property, Compression set. This test is conducted for a length of time, typically 22 hours at 70ºC (158ºF) and then allowed to recover at room temperature for a half an hour, after which time the deformation is measured.
The typical range for compression set for polyurethane is 5-40%.">
- Chemical Resistance refers to how well the material resists degradation by chemicals.
Why it Matters: Polyurethane is a wise choice as a material because of how well it resists chemical degradation, making it ideal for a variety of industrial applications. Polyurethane’s chemical resistance depends on its formulation, which is why it’s essential to identify chemicals the product may be exposed to in your particular use so it can be formulated for maximum resistance.
To measure chemical resistance, the tests include immersing the polyurethane in samples of the chemicals or chemical in question. Testing is performed at room temperature and goes on for several days.
While chemical resistance varies depending on the formulation, generally speaking, polyester-like polyurethane resists oils, solvents, and weak acids and bases. Polyether resists water, so depending on your particular needs, we can engineer a polyurethane to withstand a wide range of chemicals to fit your specific needs.">
- The temperature range tells how well the polyurethane responds to the minimum and maximum temperatures.
Why it Matters: In most applications, a substance has to perform within a range of temperatures, from cold winters to hot summers, and it’s one of the primary advantages of polyurethane because it can withstand a wide range of temperatures without failing. However, we can design your polyurethane product with a specified temperature range in mind if you require.
To measure the temperature range of a polyurethane product, a Dynamic Mechanical Analysis (DMA) is used. The DMA indicates how well the substance performs over a wide range of temperatures. In most cases, polyurethane can survive in temperatures ranging from -62ºC to 93ºC (-80ºF to 200ºF). However, individual formulations of polyurethane can extend its performance range to 150ºC (300ºF).">
- Flame resistance tells how well the polyurethane resists fire and can be made more flame resistant by adding fire-retardant ingredients during the manufacturing of the compound.
Why it Matters: Because polyurethane products are used in a variety of applications, being resistant to fire is a crucial feature in both the industrial and home setting.
Flame retardant testing can be done by a variety of methods including the DIN 4102-B2 vertical burn test which places the specimen in a chamber with the sample mounted vertically to test if and how quickly flames reach the top of the specimen. Likewise, the BS 4735 is a horizontal burn test that calculates the horizontal burning characteristics of the sample.
Depending on the application, we can engineer a polyurethane product to meet your flame resistance needs.">
- Polyurethane Resilience refers to how well the material recovers from deformation.
Why it Matters: When you’re using a product in heavy stress applications, resilience is essential for shock absorption and durability. To put it another way, the durability of an object is enhanced by having a high resilience factor.
Materials with perfect elasticity return all energy from distortion during recovery, and more viscous materials return less energy because of heat loss during compression. Heat loss occurs when internal friction happens within the elastomer (hysteresis). Materials of high elasticity or resilience return the energy sustained in deflection (think a rubber ball bouncing). Materials with low resilience do not bounce back as well.
Polyurethane resilience is measured via several tests, the most used being the Bashore Rebound Test, which measures resilience on a scale from 0 to 100%. Materials with a 100% resilience return all the energy received through input.">
- Bulk modulus refers to how well a substance performs when exposed to uniform externally applied pressure.
Why it Matters: Much like resilience, bulk modulus is essential when using a polyurethane product in an industrial environment or application which places the product under high and/or repeated stress.
We calculate bulk modulus using various formulas and factor in pressure, volume and the deviate pressure and how it relates to volume. Also, we factor in the pressure derivative and how it affects the rate of pressure with volume changes. ">
- One of the key selling points of polyurethane is its natural electrical insulation capability. This makes it ideal for use in industrial applications where electricity is present.
Why it Matters: In applications where electricity is generated, one may find a buildup of static electricity between parts caused by friction. This buildup, if not controlled may discharge, and disrupt other mechanisms. Because of the electrical insulation properties, you can minimize and avoid this transfer or discharge.
Polyurethane’s electrical properties are most often measured by:
- Dielectric Strength
- Dielectric Constant
- Power Factor
- The FDA approves food grade polyurethane for use in applications where the material comes into contact with food.
Why it Matters: Polyurethane products are used extensively throughout the food processing industry from production to manufacturing and shipping.
The US FDA sets high standards and rigorous safety measures for food that comes into contact with material such as polyurethane and goes so far as to regulate these materials through Title 21 of the US Code of Federal Regulations.
Our polyurethane products can be designed to your specific needs, whether it be dry food, wet food, or a combination of both.
Keep in mind that while it’s essential to match the polyurethane product to the specific food application, you also must keep in mind the temperatures you need the product to operate in as well as the sanitizing and cleaning it will undergo.">
- Coefficient of friction refers to the ratio of friction force from objects and the force pressing the objects together.
Why it Matters: When you have an application in which two objects rub against one another, the coefficient of friction (COF) will help determine how well those objects function in that capacity.
A low COF is preferred in situations where you want low friction or sliding to occur, such as the case in ball bearings or bushings. However, a high COF is ideal if your application requires minimal slippage such as in the case of a drive wheel. The COF depends on the materials in both objects, the type of surface and the relative velocity between them. For polyurethane, hardness also becomes a factor as well.
The ASTM D-1894 Standard Test Method best measures COF for polyurethane for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting. Harder polyurethanes have lower COF, and softer ones have higher.">
- Vibration dampening is essential for applications where the product is exposed to vibration and stress. Too much vibration can lead to noise or premature failure in a part.
Why it Matters: Polyurethane is ideal to use in heavy-use applications because of its superior vibration dampening capabilities. Polyurethane products can be used alone, or they can be integral parts of a more complete system to improve its vibration dampening properties.
Because of polyurethane’s dynamic properties, it’s an ideal material for use in applications that require vibration isolation. Vibration dampening is achieved through the hysteresis component of the elastomers in polyurethane. This takes mechanical energy and converts it to heat which dissipates.
Urethane is used to isolate vibration through various means, including Natural frequency, frequency ratio, and vibration damping.">
- A key selling point of polyurethane is that it can be produced in virtually any color.
Why it Matters: Color is used in industries to identify hazards easily or to be used for branding purposes.
We can engineer your polyurethane product in a variety of colors.">
- Abrasion resistance means how well the product withstands wear and tear.
Why it Matters: Resistance to abrasion is a primary advantage of polyurethane and it’s why it’s so heavily used in applications that exhibit high levels of wear such as in bushings, bearings, wheels, and sprockets.
Because of its unique properties, polyurethane withstands most types of abrasion, impingement, and slurry, and recovers quickly from particle impacts associated with those types. Depending on the venue, you may have a mix of the following types of abrasions:
- Sliding — Occurs when one surface slides or rubs against another.
- Impingement and Slurry — Occurs when particles come into contact with a surface.
- Tensile strength refers to the product’s ability to resist tears and the growth of a tear.
Why it Matters: Tensile strength is essential in applications where the polyurethane is likely to encounter nicks, cuts, and abrasions.
To measure tensile strength, the specimen thickness is measured in pounds per linear inch (kN/m), and there are a variety of ASTM tests used to measure tear strength in polyurethane.
If you require high tear strength, we can achieve that through the use of polyester type polyurethanes. For example, a Type C tear strength can run up to 1,000 pounds per linear inch.">
- Here at TPC, we have our own urethane casting machine equipment, giving us full control over all aspects of production from start to finish. The diversity of polyurethane molding techniques allows for multiple options as far as mold material, and design.
Aluminum and silicone molds are common for many polyurethane projects, but machined metal molds are by far the longest lasting, and best suited for large production runs. At TPC, we work with our customers to understand the requirements of their projects. Based on these inputs, we help design a mold program to accomplish production in the most accurate way, while also being cost effective. If you’re looking to scale up your current production, we can help.">
- Being able to measure how much load is placed on a part in imperative when it comes to best finding a suitable material.
Based on our customer requirements, we can formulate both high-load applications, as well as delicate parts that are not meant to have heavy loads applied. We will work with you to find the best polyurethane for your project.">
- A material’s resistance to fatigue is an important factor when selecting the right fit for you application.
Materials subject to repeated compressive forces can cause molecular bonds to break down if the material is not properly formulated. At TPC, we pride ourselves in working with our customers to properly test materials during the Research and Development phase, and make sure they will perform as desired in the field for the long term.">
- Getting polyurethane parts that are the correct dimension the customer requires takes skill and special consideration. We factor in all the variables that go along with polyurethane production into our mold designs to make sure your components come out as desired.
Our complete in-house machine shop has the ability to work on both metal and urethane parts to exacting tolerances. You can have peace of mind knowing TPC will measure and confirm required tolerances on your parts ahead of delivery.">
- When a force is applied to an object, the measurable lag between the action and reaction is called Hysteresis.
Polyurethanes with a low hysteresis force curve will have minimal rebound times, and react to applied forces extremely quickly. For anti-vibrational applications, a low hysteresis force curve may be desirable to help attenuate sonic vibration.
Let us know what your project requires, and TPC will help you find exacting solutions.">
- Due to polyurethane’s ability to resist degradation and attack by chemical compounds, bonding urethane is a demanding task, requiring multiple steps to properly adhere the material to various surfaces. Whether you are bonding to metal, fabric, or plastics, TPC has the expertise, and control over production to ensure your parts are able to survive the toughest conditions, without the worry of the polymer de-bonding. ">