Not all seals are created equal, from design and development all the way through to production and distribution, each seal has a different journey, and while most seals have shared similarities, often the biggest and most crucial difference lies in the material the seals are made of. Differing qualities of chemicals and processes create a product that can vary between seal manufacturers. And while the seals may look similar in profile, the material they are produced from will be one of the key factors in determining longevity and performance of your cylinder.
Modern materials, particularly polyurethanes play the crucial role in cylinder performance as they are used for the most demanding aspects of the sealing system, being used as the primary seal on the rod and piston. These two sealing positions have similar requirements, the rod seal commonly works one way (single acting) and needs to be optimised for high- and low-pressure sealing, react fast enough to fluctuations in pressure to ensure no bypass while maintaining form and function while also being flexible for ease of fitting and have high resistance to abrasion and wear. It is a tough ask; however, these are the demands of the industry. The piston seal is often made from a harder material due to the pressures experienced from both sides (double acting). This is where we will delve further, highlighting the importance of material, how different materials can handle extrusion better and why it’s time to move away from PTFE capped seals for most of your Hydraulic needs.
Polytetrafluoroethylene aka PTFE was discovered accidently in late 1930’s by Roy Plunkett while working for DuPont. While PTFE was crucial during the second world war, particularly with regards to the Manhattan project, it wasn’t until the 60’s where different additives were added to the White Virgin PTFE R. Plunkett discovered that gave it properties that rendered it suitable for use in Hydraulics. Different fillers such as glass, carbon or bronze help increase the mechanical characteristic of PTFE and market leaders such as Accofluor also offer specialised PTFE products such as their AF7615 and ATXC66 which offer mechanical and physical properties far exceeding these traditional fillers. HSA uses Accofluors PTFE’s on all applications that are exposed to excessive speeds, chemicals or temperatures above 150°C.
Most common Bronze filled PTFE capped seals are supplied from markets that aren’t known for quality, this can result in poor ratio of fillers and poor quality leading to failure due to cold flow (creep), poor extrusion resistance and poor resistance to abrasion. Modern polyurethanes, particularly our MAX XSH can meet or exceed these Bronze filled PTFE seals across most, if not all of these performance measures.
MAX XSH is an extra hard, self-lubricated polyurethane. Its composition brings together several properties that allow for high performance operations.. Firstly, being elastomer based, it has memory and will rebound back to its original shape allowing ease of fitting, it does not need to be heated on installation and as such is less likely susceptible to damage on assembly. Its hardness tolerates larger extrusion gaps for the same pressure as Bronze filled PTFE, in fact close to double the extrusion for the same pressures. It will also hold load and not creep as with PTFE, offers very high wear resistance, and due to the added lubricants it has a very low coefficient of friction helping eliminate stick slip and allows for use in low lubrication applications. The introduction of Alpanas MAX XSH offers a further benefit with a increased temperature range up to 150°C.
Selecting the right materials holds greater significance than ever before. Embracing modern materials and solutions, rather than clinging to outdated conventions is pivotal for staying at the forefront of progress. This approach guarantees optimal performance and durability for your hydraulic cylinders.
