Varflex Uncoated & Coated
Electrical Insulating Sleevings

Varflex manufactures electrical insulating sleevings that are suitable for high and low temperature applications; high and low voltage applications; as well as for abrasive and other physically demanding applications and environments. The voltage and temperature ratings of Varflex sleevings are recognized by UL (Underwriters Laboratories), certified by CSA (CSA International) and meet the requirements of military specifications Many of them are flame retardant. For applications not satisfied through the use of its standard products, Varflex stands ready to supply special coatings and treatments, extra heavy, double- wall and triple- wall constructions, as well as special braiding and overbraiding.

Although electrical applications are most common, Varflex braided sleevings can also be used to jacket wire or other small devices from intense heat, radiative environments, ultraviolet light, abrasion, flexing and intermittent exposure to chemicals.

In most cases, the dielectric strength breakdown voltage (puncture voltage) influences the selection of the braided sleeving used, thereby satisfying critical electrical requirements. Other electrical properties such as radiation resistance, volume resistivity, and corona discharge may also dictate and become guiding factors in the selection process. Some sleevings, on the other hand, are chosen to satisfy thermal and physical requirements only.

Varflex does all of its own braiding, in house, and the sleevings we produce are braided, primarily, with fiberglass yarns whose properties include high tensile strength, nonflammability, heat resistance and excellent resistance to fungus, moisture and chemicals. Although fiberglass filaments are the most popular, sleevings of nylon, polyester, Nomex®, Dacron®, Kevlar®, polypropylene and other yarns are also available.

All are available with inside diameters corresponding to AWG (American Wire Gage) and larger fractional sizes, some as large as four, five and six inches. Most sleeving is produced in standard wall thicknesses, but some heavy walls, as well as double and triple wall constructions are available to satisfy specific design requirements while, of course, affording the normally high temperature resistance associated with fiberglass.

Initially, the proper choice of sleeving can usually be determined by coordinating the end-use characteristics required in a customer’s application with the performance characteristics of the sleeving. This, of course, is achieved through close liaison with the customer with regard to their particular application.

An untreated braided sleeving is very flexible in all directions because of the construction which permits the individual strands to slide over each other. However, because of the apertures or openings between the plied (twisted) filaments in the braid, there are some types of protection, especially high-voltage electrical, which the untreated sleeving cannot provide.

To serve as primary electrical insulation, braided sleeving must be coated with a continuous coating (insulating material) which fills the interstices or apertures between the filament bundles. In addition to improving dielectric strength, coatings, as well as saturations which only partially impregnate the individual bundles with resins, alter other properties of the sleeving, particularly flexibility, and must be considered for each application.

As soon as the braid is saturated or coated there is inhibition of flexibility due to a “cementing” together of the strands in the braid. Therefore, the flexibility of the product is largely limited by the flexibility of the coating material.

Braided fiberglass sleeving products manufactured by Varflex, generally, can be divided into two categories, uncoated (untreated or lightly treated) sleevings and coated sleevings.

Uncoated Sleeving
Uncoated (untreated or lightly treated) sleevings are used for secondary insulation, harnessing, physical protection, and serve as good anchors for varnish treatments in electrical units. Because of this, treated sleevings find extensive application with potting plastics where the sleeving acts as a substratum to support potting compounds to enhance the electrical and mechanical properties of a system.

Sleevings which do not have a continuous coating will provide only space factor (wall thickness) electrical insulation equal to the dielectric strength of an equivalent thickness of air. Consequently, they frequently are used in low-voltage applications where the sleeving will be exposed continuously to operating temperatures exceeding the capability of coated sleevings. The majority of Varflex sleevings are braided from fiberglass yarns made from “E” glass, an electrical grade that maintains its physical properties indefinitely at 250°C (482°F) and can withstand up to 760°C (1400°F) for shorter periods. Specialized applications requiring greater heat resistance for extended periods can utilize Varglas S1600 Sleevings which are produced from special high-temperature S-2 Glass® yarns developed by Owens Corning. S1600 Sleevings can be exposed continually to 500°C (932°F) and intermittently to 950°C (1742°F).

These sleevings can be untreated or be subject to one or both of the following treatments:

Heat Cleaning (Normalizing)
A process used to remove the lubricants and starches introduced during the yarn manufacturing procedure thereby providing better adhesion for some types of insulating compounds. This process is of particular importance because it also represents one of the first in a series of steps taken to insure that the sleeving is produced to the specific size desired.

Resin Treatment
A light saturating process to provide resistance to fraying and abrasion. The resins used can be either natural in color or dyed (if a particular color is desired). Some can, as in the case of Volan®, act as a tie-coat or coupling agent between the fiberglass and thermosetting coatings applied over it.

In summary, the space factor to resist low puncture voltage, the ability to reinforce through encapsulation (potting), fray resistance (the ability to resist splaying at the ends) and flame resistance are among the important characteristics of uncoated fiberglass sleeving.

A more comprehensive list of Varflex uncoated products and their attributes is in our Varflex Product Line page under the heading “Uncoated Sleevings”.

Coated Sleeving
Coated sleevings are used to satisfy electrical, as well as, thermal, physical and chemical requirements. Generally, braided electrical insulating sleevings which have been continuously coated are characteristically identified with a temperature classification (thermal level at which sleeving can operate continuously) and a grade (defined through dielectric strength breakdown or puncture voltage).

A more comprehensive list of Varflex coated products and their attributes is in our Varflex Product Line page under the heading “Coated Sleevings”.