Insulation Tubing

PTFE liner: production, variants and application

By the end of the 1960s, Markel Corporation had already established itself as a major supplier to the automotive sector with a wide range of plastic-based tubing components such as heat shrinkable tubing, braided fiberglass sleeving, and silicone rubber tubing as a major supplier to the automotive sector. At that time, automotive engines were becoming increasingly sophisticated, and the low-temperature applications typically made of polyethylene were no longer able to meet the increase in temperature requirements. This significantly increased the risk of traffic accidents due to melting cables and wires. To compensate for this problem, Markel’s research and development team developed an extrusion process to manufacture the novel and significantly more temperature-resistant fluoropolymer PTFE into liners. These improved Fluoropolymer products proved resilient to temperatures as high as 200°C (392°F). The resulting AR product line remains the industry standard up until today and is also included in the GREMCO product line in an optimized version as the FITCO® product line.

Production of PTFE liners

A complex and optimized production process, including the extrusion of PTFE fine powder, is used to manufacture our high-quality PTFE liners. The powder is sieved, optionally enriched with the desired fillers and lubricants, and then loaded into the extruder in compressed form. There, the material is forced through the die and mandrel under high pressure, giving the product the desired inner and outer dimensions. By this, the computerized extrusion process allows exceptionally tight tolerance control over inside and outside diameters. Since the extruders used are the longest of their kind in the world, GREMCO is also able to offer exceptionally long liner lengths of the same quality. Furthermore, the liner undergoes a vaporization process to remove lubricants. Subsequently, the PTFE liner is subjected to a high-temperature treatment, which sinters it.

Properties of AR/ FITCO® products

PTFE liners can generally be categorized as natural and filled. While natural PTFE liners tend to exhibit so-called cold flow behavior under pressure, filled PTFE products exhibit significantly greater strength and stability. Furthermore, the filled PTFE products are provided with different fillers, resulting in liners with different performance characteristics in different price classes. This is particularly significant regarding the enormous price pressure in the automotive industry. In addition, natural PTFE linings are particularly suitable for less demanding applications. The most significant products in the AR/ FITCO® range are the following PTFE liners.

• AR 500/FITCO® Liner HP 500
• AR 650/FITCO® Liner HP 650
• AR 750/FITCO® Liner HP 750
• AR 280/FITCO® Liner HP 280

Applications of the PTFE liners

The AR 500/FITCO® Liner HP 500 filled PTFE tubing is the standard industrial product in the automotive sector and is used in a wide range of temperature-intensive applications. The AR 650/FITCO® Liner HP 650 and AR 750/FITCO® Liner HP 750 filled PTFE liners, on the other hand, are ideal for heavy-duty applications thanks to their exceptional mechanical strength. In particular, the AR 750/FITCO® Liner HP 750 stands out as the best liner worldwide in terms of abrasion resistance and friction efficiency. For light-duty cable applications, on the other hand, the AR 280/FITCO® Liner HP 280 is optimized for small gauge sizes and thin wall thicknesses.