Unique PolySlide® Features

Seal-Friendly Bore Surface

The patent pending bore surface of the PolySlide® cylinder is designed to reduce the common causes of seal wear. Friction is the primary cause of seal wear. There are two types of friction that tend to oppose each other in the design of the bore surface. These are adhesion and interlocking friction.

Adhesion Friction is the physical attraction of two smooth surfaces brought into close contact with each other. As the contact area increases so does the adhesion between the surfaces. A smooth surface reduces the gap between the surfaces resulting in higher adhesion. Adhesion acts as a frictional force when the one object slides against the other. The friction between O-ring seals and bore surfaces increases significantly as the surface finish of the bore is reduced from 16 Ra to 6 Ra. Therefore, a higher Ra bore surface finish will reduce the seal adhesion friction and thereby extending seal life.

Interlocking Friction is the result of shear forces encountered from the interlocking of irregularities between contacting surfaces during sliding motion. By the nature of machined surfaces such as boring or honing of metallic cylinders, microscopic rough edges exist that tend to penetrate and shear the softer seal material, thereby reducing seal life. Obviously, for metallic cylinders a lower Ra bore finish specification (smoother surface) is desirable to reducing the interlocking friction resulting in extended seal life.

Typically, the means of achieving the optimum Ra finishes for the two types of frictional conditions oppose each other. Historically, users of metal cylinder tubing must compromise their specification of the Ra value for an ideal bore finish in metallic cylinders. One of the unique features of the PolySlide® bore surface is that it is not formed by a machining process, but by a molding process. Another feature is that the wear resistant material at the bore surface is microscopically round in nature. Taken together, these features allow the seal to naturally slide over the bore surface contour. These two features minimize interlocking friction.

Since interlocking friction is not a significant issue with the PolySlide® bore surface, the Ra finish does not play the same role as in conventional metals. PolySlide® cylinder contact surfaces are undulating; rounded and cylindrical in nature.

In addition to the topographic advantages of the PolySlide® bore surface, is the actual material composition of the sliding surface itself. Lubricants are incorporated within the bore surface material for the purpose of lowering the surface tension at the bore surface with respect to the seal material. Also, wear resistant additives are incorporated within the bore surface material that result in a very hard wear surface with a Rockwell hardness of 50C to 60C.

The combination of these features provides a seal-friendly bore surface. Examples of actual specific performance studies will be presented throughout this design guide in further detail.

High Strength/Non-Metallic Cylinder Material

The strength of the PolySlide® cylinder comes from continuous fiberglass filament reinforcement within an epoxy matrix that are filament wound into a composite cylinder. The cylinder exhibits orthotropic material properties as compared to isotropic properties for metals. An orthotropic material means the physical properties vary with the geometric coordinates of the cylinder. The ability to vary the orthotropic properties of a filament wound structure within a specific geometry gives versatility to a composite cylinder, a versatility that can not be accomplished with isotropic metallic cylinders. Typical physical property values of an PolySlide® cylinder are shown in chart at top of page. Consult a Polygon Sales Engineer for information relating to specific applications.

Corrosion Resistance

PolySlide® cylinders do not rust and are resistant to many chemicals that corrode metallic cylinders. Galvanic corrosion is not a problem with composite cylinders. In addition, PolySlide® is not limited to the use of non-corrosive lubricants or fluids common to hydraulic fluids. As an example, water could be used as a replacement to hydraulic fluid because PolySlide® is compatible with water. A separate tech data sheet and resistance guide with compatibility to various types of chemicals is available from Polygon.

Polygon's chemical exposure recommendations are based on long term exposure by physical containment of these chemicals in question. For short term exposures, PolySlide® cylinders may work fine even for those not recommended chemicals. Contact Polygon's Sales Engineers with any questions concerning chemical exposure.

Dielectrically Insulative Cylinder

The PolySlide® cylinder is a dielectrically insulatable material. It will not conduct electricity. It is ideal for external limit switch positioning controls and other types of electronic positioning devices.

Static Discharge

Due to the versatility of composite materials, PolySlide® cylinders can be specially designed to meet most static discharge requirements.

Low Thermal Conductivity

The low thermal conductivity characteristics of the PolySlide® cylinder makes it "warm to the touch" as compared to metallic cylinders that are "cold to the touch" under the same conditions. This property also impacts the ability of PolySlide® to perform consistently across a wide temperature range.

Impact Resistant

The high strength filament wound composite structure resists impact damage from debris, as in railroad brake or dump cylinders, without causing a permanent deformation in the cylinder wall. The high impact resistance of the composite structure makes it ideal for applications where moderate velocity debris can cause metal cylinders to fail due to impingement problems.

Light Weight

The PolySlide® cylinder weighs less than aluminum. It is approximately four times lighter than steel. It is about the same weight as magnesium.

Smooth Cylinder Walls

Very smooth cylinder walls help prevent material build-up and piston leakage. This also provides an improvement over traditional stick/slip phenomena common when metal cylinders sit in a static condition for extended periods of time. Typical inner surfaces measure 6-20 µ-inch.