Well in an a round about answer it is probably “that depends”. So in this article we will try and answer the question by asking a few of our own. What is polyurethane and what is rubber? In the automotive world what are the benefits of rubber versus polyurethane?
First we should talk about where the rubber meets the road…
Rubber is either a synthetic or naturally made product. In its natural form it is an elastomer or polymer made up of many monomers and used in a variety of applications. Natural rubber accounts for less than 35% of all production of rubber and is collected in the form of rubber latex from rubber trees. Most of these trees are in Asia where most of the natural rubber comes from. Once it is harvested the latex is transported into large storage tanks to avoid coagulation and damage to the latex form. From there it is processed from this natural form into a concentrated product for further use as a final produced good.
Synthetic rubber is made up of petroleum byproduct monomers and mixed with other monomers in different configurations to produce wide range of differing properties. It is this variability that has made synthetic rubber more widely used by over two-thirds than its natural rubber counterpart. One way synthetic rubber came about was from the increased use of the automobile and its need for tires. Today synthetic rubber is vital in the manufacturing process of automobiles for tires, hoses, belts, and seals.
For automotive use rubber is sometimes vulcanized to make harder bushings. Vulcanized rubber is heated and chemicals are added to improve the resistance and life of the part. Vulcanized rubber products are often used in motor mounts and suspension bushings. In other products vulcanized rubber is used to make bowling balls, hockey pucks, the soles of shoes and other hard rubber products.
In bushings rubber is used on control arms, motor and transmission mounts, sway bar, end links and much more. Until polyurethane rubber was the material of choice for most vehicle bushings.
Then we should ask ourselves does polyurethane really stack up…
Polyurethane dates back to the mid 1930s and are basically organic units attached by urethane links. They are called reaction polymers and are versatile in their varying degrees of cross linking which helps determine how flexible or rigid the product will be.
Polyurethane is most desirable in the creation or manufacturing of foam. Both closed and open cell foams are used in the manufacturing of mattresses and thermal insulation products. The two major components to manufacture polyurethane are isocyanates and polyols and it is made by mixing two or more liquid streams. Most commonly referred to as an A and B side when mixed, and other additives added, the result is polyurethane.
Polyurethane is from there used in the manufacturing industry by either pouring and molding, used as a coating, or machining parts from blocks.
So what are the hard facts about rubber and polyurethane?
Both rubber and polyurethane are measured in Durometer, which is the measure of the hardness of the material. This is important to determine the functionality of our next discussion. Rubber versus Polyurethane and which is better. For instance a rubber tire has a durometer of Shore 60A. Polyurethane usually is in the range of 80A to 95A (similar to a hard skateboard wheel). Vulcanized Rubber has a durometer between 18A and 60A.
There has been a long going debate about which material is better for performance increases in vehicles. In most cases the answer is both. In the case of tires, seals, and some belts, rubber is the best material. In the case of bushings, lift spacers, and suspension component replacements then polyurethane is the better choice.
Polyurethane has higher abrasion, cut, and tear resistance. It can be made in a higher hardness rating and has better load bearing capacity. Polyurethane is oil and in some cases chemical resistant. In the manufacturing process it is easily colored and a lot easier to mold into all kinds of shapes and sizes.
Now rubber by its soft nature allows the vehicle mounts to absorb vehicle vibrations and noise which may give rise to the notion that polyurethane makes the ride harsher when these mounts are replaced with polyurethane equivalents. In most cases customers have noticed an increase in road vibrations due to polyurethane mounts but they have also stated this has decreased over time. Either they get used to it or it actually decreases.
So what is the answer, which product is better, come on we want to know!!!
In most cases polyurethane outperforms its rubber counterparts in replacement of bushings and mounts. The products will last longer, standing up to road debris, chemicals and oils, and compression and load. They will perform better by removing additional sloppiness in suspension performance due to worn, damaged, or missing bushings. And finally polyurethane looks better than rubber. In some cases this will not matter but a lot of vehicles, show or otherwise, have areas where these bushings show and a polyurethane bushing looks a lot better than its rubber counterpart.
So in the end if you are going for performance or upgrading your vehicle with new components then I would go with polyurethane bushings. They will outperform the rubber ones and last longer. Nowadays you can buy complete bushing kits and replace all of the bushings in your vehicle at one time.