Bushings, a type of bearing that facilitates movement between two parts while reducing friction, are often overlooked in various applications. In reality, they are critical components that ensure the smooth operation of machinery and mechanical systems by reducing wear, absorbing shock, and minimizing vibration. Bushings primarily act as a protective interface between two parts by absorbing shock, preventing wear and isolating vibration. Essentially, bushings dampen the transmitted energy between two parts. Traditionally materials like rubber and metal have been used for bushings. However, in the mid-1990s, this changed with the advent of polyurethane bushings.
In today’s article, PSI investigates the differences between rubber, metal and polyurethane bushings. We explore bushings by delving into the materials traditionally used and their key characteristics. We then dive deeper by looking at the key characteristics of polyurethane bushings and compare them to both rubber and metal bushings, respectively. We conclude with a brief discussion regarding how to choose the correct durometer, a measure of hardness, to ensure you choose the right polyurethane for your bushing.
Overview of Bushing Materials
To be able to compare bushing materials, we first need to understand what a bushing is and where it is used. As we explained in the introduction, bushings are components placed between two moving parts that then dampen energy transmission between the parts. The dampening includes reducing vibrations, lessening friction, and absorbing shock. Bushings are commonly found in machinery like industrial presses, automotive suspension systems, and various other industrial equipment. Traditionally bushings were made from metal and rubber, but in the mid-1990s polyurethane was added to the list of bushing materials. This addition was thanks to its superior performance characteristics including its durability, customizable hardness and vibration damping. Below we provide a brief overview of metal, rubber and polyurethane bushings to better understand their properties and applications.
Metal Bushings:
Metal bushings are commonly made from steel, bronze, and other alloys, and are extremely durable. These bushings are designed for applications that involve high loads or extreme wear conditions like construction equipment. They are known for their rigidity and strength but require regular maintenance to ensure effectiveness and mitigate corrosion.
Rubber Bushings:
Rubber bushings have been a go-to solution across various industries for decades. They are highly effective in absorbing vibrations and reducing noise. Rubber, however, degrades when exposed to oils, chemicals like acetone or gasoline, and UV light. Rubber also becomes brittle over time which brings about cracking and tearing, leading to reduced performance and frequent replacement. Rubber bushings are commonly used in low-load environments like office equipment.
Polyurethane Bushings:
Polyurethane bushings offer a combination of flexibility and strength and are known for their elasticity and toughness potential. Polyurethane is customizable, meaning that its physical qualities like flexibility and durometer value (hardness) can be adjusted to fit any application. Polyurethane also has excellent resistance to most chemicals, oils, and temperatures, making it suitable for a wide range of applications from automotive suspensions to heavy-duty machinery. Below we discuss the key characteristics of polyurethane to better understand its use as a bushing.
Have a look at the range of custom bushing specifications available at PSI.
Key Characteristics of Polyurethane Bushings
Polyurethane holds several key characteristics that make it a material perfectly suited for bushings. In the section below we look at polyurethane’s most applicable characteristics concerning bushings. If you want to know more about polyurethane, be sure to read our Polyurethane 101 article.
Durability and Resistance
Polyurethane’s durability and resistance stem from its unique chemical structure, which is made up of cross-linked polymers. This structure allows polyurethane to resist wear, impact, and extreme conditions better than rubber or metal. Polyurethane bushings are engineered to outperform rubber and metal bushings when it comes to durability as it doesn’t degrade or corrode. These bushings are extremely resistant to wear and tear and can provide dampening and friction reduction under a wide range of conditions, including high temperatures and exposure to the elements and chemicals like oils, solvents, and fuels.
Performance Across Durometers
One of the most remarkable characteristics of polyurethane is its ability to be customized to a wide range of hardness levels. The hardness of polyurethane is measured in durometers and the hardness of a polyurethane bushing can be as soft as rubber or even as rigid as some metals like steel or aluminum. This customizability allows polyurethane to be used in a wide range of applications, from those that require dampening like automotive suspensions to supporting heavier loads like bushing in industrial machinery.
Vibration Damping
The ability to absorb vibrations and reduce noise is a standout characteristic of polyurethane, especially when compared to bushing materials like metal. Metal bushings are known for transmitting vibrations which can lead to increased wear on the parts of machinery. Metal bushings are also inherently less effective in damping noise. Rubber bushings are great for damping vibrations, but do not provide the same strength as a metal bushing. Polyurethane is the sweet spot in the middle where strength and damping meet.
Curious about the advantages that polyurethane bushings can bring to your operation?
Below we will compare polyurethane bushing to rubber and metal bushings and investigate the advantages and disadvantages associated with each.
Comparing Polyurethane to Metal Bushings
Polyurethane offers several advantages over metal bushings which can be broken down into three main sections. These are flexibility, noise reduction, and impact resistance. We will investigate these three factors below and show where polyurethane bushings are better suited.
Flexibility: Unlike metal bushings, polyurethane bushings are flexible, while also offering strength for heavy-load applications. Its flexibility allows it to absorb shocks and vibrations that metal bushings cannot, making it ideal for applications where dynamic movement is involved.
Noise Reduction: Metal bushings often generate noise due to their sound conductivity. On the other hand, polyurethane bushings absorb sound and lead to less noise generated and a quieter operation. This is advantageous in environments like factories or machinery where noise reduction is essential.
Impact Resistance: Polyurethane bushings are much better adept at absorbing shock than metal. This is due to the elasticity of polyurethane. Unlike metal, polyurethane is perfectly suited to function in dynamic environments like industrial presses or automotive suspensions.
From this comparison it may be seen that a majority of applications will benefit from transitioning from metal to polyurethane bushings. In applications that require high-temperature resistance or involve extremely heavy loads, however, metal is still a valuable choice.
Curious about how to switch to polyurethane bushings? Contact PSI today and get started.
Comparing Polyurethane to Rubber Bushings
The advantages and disadvantages of polyurethane and rubber bushings can be broken down into three main sections. These are longevity, chemical resistance and load-bearing capacity. Below we look at these three factors and why polyurethane is the better choice.
Longevity: When it comes to longevity, polyurethane is a clear winner. This is due to the tendency of rubber to crack and degrade as time passes. Polyurethane is specifically engineered to last, remaining flexible and functional much longer than rubber.
Chemical Resistance: Unlike rubber, polyurethane bushings are resistant to most chemicals, UV light, oils and solvents. This makes polyurethane a preferred material in environments where exposure to chemicals is a regular occurrence such as oil refineries or chemical plants.
Load-bearing Capacity: Polyurethane bushings can withstand much higher loads than rubber, while retaining their structural strength and remaining functional. This makes polyurethane ideal for applications that require both absorption and high load-bearing qualities such as automotive suspensions and heavy industrial machinery.
Contact PSI today and start enjoying the longevity of polyurethane.
While polyurethane offers various advantages over metal and rubber bushings, it is important to note that not all applications are the same. One of the key factors that affect the durability of a polyurethane bushing is its durometer. Below we look at the importance of choosing the correct durometer of polyurethane.
Selecting the Right Durometer for Your Application
The durometer of polyurethane needs to be suited for the intended application. If it’s too soft the bushing will have no resistance to load, and if it is too hard the damping properties may be affected.
Polyurethane bushings with lower durometers offer better vibration isolation and noise reduction, making them ideal for automotive suspensions and other components where comfort and control are important. Higher durometer polyurethane on the other hand provides greater strength and load-bearing capacity, making it suitable for heavy-duty automotive applications such as engine mounts and high-load suspension systems.
The choice of durometer also impacts the longevity of a polyurethane bushing because a durometer too soft for the application can wear out faster. At the same time, a durometer too hard can cause unnecessary stress on other components. To ensure you choose the right durometer for the application, speak to an expert at PSI for guidance.
Polyurethane bushings are a highly adaptable and durable alternative to materials like rubber and metal. Its ability to withstand wear, resist chemicals, and perform in demanding environments makes it a top choice for various industrial and automotive applications. Whether you’re looking for enhanced durability, better vibration control, or customized hardness levels, polyurethane bushings offer a tailored solution that excels in most settings.
Ensure you choose the right durometer for your application. Speak to one of PSI’s experts to ensure a fit-for-purpose choice.
We hope this polytechnical guide has provided you with a better understanding of the key differences between polyester and polyurethane.
If you require further information or are curious about how to implement polyurethane in your operations, get in touch with one of the experts at PSI.