What is ApexPAI?
ApexPAI is the highest performing material available for dry-running, low friction bushings and bearings in demanding racing applications. Polyamide-imide (PAI), is a thermoplastic material chemistry regularly found in aerospace, defense, semiconductor, and other extreme performance applications. RaceBushings.com brings ApexPAI to the racing and performance aftermarket markets where winning races is the reward for accepting no compromises in quality or performance.
ApexPAI is a rigid thermoplastic which offers the ultimate precision in chassis feedback, while still providing a small amount of vibration dampening. Its ability to withstand repeated abuse is unrivalled by any nonmetallic bushing material available before now.
Race Bushing Factory offers ApexPAI as finished parts and kits for specific applications, finished parts to meet customer specifications, or solid rod stock material.
ApexPAI Performs flawlessly in repeated high-load environments
ApexPAI has a high resistance to deforming after repeated or sustained high loads found in racing and performance applications. This deformation is called creep, as the bushing material “creeps”, or flows away from its initial shape. Material is squeezed and the bushing sleeves become sloppy until ultimately the bushing fails, all the while the suspension system is losing its ability to accurately maintain accurate geometry through the range of motion.
ApexPAI Maintains high strength up to 250°C (482°F)
This means ApexPAI components near the exhaust, engine, or brakes continue to operate at their full potential for sustained periods of time with no ill-effects. The material’s composite formulation using carbon fiber also means the thermal conductivity matches closely to that of steel, ensuring precise fits and clearances are maintained at elevated temperature.
ApexPAI Impact is formulated from high molecular weight, unfilled (not composite) polyamide-imide. It is a rigid material best used for applications where impact energy needs to be absorbed, such as for transmission shift bushings where other plastic materials are too weak to last, and metal replacements transfer harsh shock loads to the transmission components. ApexPAI Impact has good sliding properties and creates low friction environments with lubrication, and can sometimes be used dry depending on the application.
ApexPAI takes the excellent properties of the Impact grade and turns it up a notch. Compressive strength is boosted by adding micro carbon fiber which bonds to the polymer, increasing stiffness and further reducing friction. A dry lubricant additive package also enhances sliding wear characteristics and reduces friction. This material is best used in suspension bushings where high cornering loads are commonplace, and robust consistency is crucial. The material’s ability to minimize friction and bind allows the suspension to move through its range of motion freely while the springs and dampers to do their jobs unencumbered.
How Does ApexPAI Compare with other Bushing Materials?
Delrin, AKA Acetal, AKA POM (polyoxymethylene) is an engineering thermoplastic often used in suspension bushings. It has very low friction. Repeated high compressive loads cause this material to creep, or permanently deform, making it useful as a suspension bushing for only a short time, or in low performance applications. Any high loads or impact forces applied to this material can result in the bushing deforming permanently and increasing play between bushing sleeves. POM has approximately half the strength of ApexPAI, making it a suitable low-cost option for bushings which are not subjected to high sustained loads or impact forces. Load-bearing bushings such as those in lower control arms, or in race cars with large amounts of mechanical grip should not use POM due to its inability to keep its shape.
PTFE, AKA Teflon is a material which is manufactured by pressing or ram extruding powder into solid form, then heating (sintering) the material in an oven. PTFE has very good lubricity, but does not perform well as a mechanical material due to its low strength. PTFE is also prone to creep, or continually flowing. PTFE is in what is called a “rubbery” state at room temperature, since its glass transition temperature (when it transitions to a “glassy” state) is below room temperature. PTFE is very widely used as a liner material in spherical rod ends to keep friction down, and because it is able to deform with the metal as the spherical bushing housing is swaged into place.
If you’ve ever had a PTFE lined spherical rod end in your chassis (chances are you do), it doesn’t take many hours on the chassis to notice free-play in these connections, even in clean operating environments. This is due to creep.
Polyurethane, AKA Urethane, AKA PUR is a thermosetting elastomer available in varying durometers from ultra-soft to hard. It is attractive as a bushing material in low-buck suspension kits due to it’s very low material and manufacturing cost. It is also has very elastic behavior, meaning it will return to its original form after being deformed from high loads. Softer durometer polyurethanes on the Shore A scale generally do a good job isolating noise or vibration when designed and installed correctly.
Polyurethane bushings require constant grease in suspension bushing applications to keep from sticking and/or squeaking to their sliding steel sleeves. Unfortunately for the grease, polyurethane does exceptionally well squeezing grease out of where it needs to stay. Some have added dry lubricant packages to their polyurethane bushing formulations, which minimizes sticking, but not enough to sufficiently overcome the base material’s tendency.
Aluminum is attractive as a solid bushing material due to it’s availability, machinability, and high strength.
Aluminum bushings also require grease to keep from wearing away in sliding applications. Aluminum offers no vibration absorption and generally transfers all high loads and impact forces through the chassis via the suspension components. It’s ability to withstand repeated high loads are compromised due to low fatigue strength.
ApexPAI’s strength-to-weight ratio, maintenance-free operation, and fatigue strength outperform aluminum, especially in road race, rally race, or endurance racing applications where maintenance and inspection intervals are sometimes many race hours.