Mastic Electrical Tape

  • Image of 3M™ Scotch® Vinyl Mastic Tape 2200 wrapping a low voltage cable in an irrigation hole.

    Putty on a roll.

    The term “mastic” is widely used in the construction industry, especially by tile setters. Many electricians don’t realise that the gooey electrical tape they use to resist moisture is also a mastic. But this mastic rubber material is specially formulated for use as a dielectric insulator. Mastics from 3M are compatible with thermoplastic rubber wire insulation.

    When you are working with odd shaped components or needing to tuck in some insulation where your tape won’t reach; mastic is the product to use. Think of it as putty on a roll.

Moisture Resistance

Humidity? Moisture? Wrap it up!

  • Still image from 3M™ Scotch® Vinyl Mastic 2200 Pad: Moisture Sealing, Padding & Shaping video.

    This tape has healing properties.

    In addition to low-voltage electrical insulation, mastic tape offers the best moisture resistance of any electrical tape made by 3M. They create a barricade around splices and terminations, so that they are resistant to contaminants and particles that can corrode your wire and connections. Mastic tapes are often used in outdoor applications because the rubber is ‘self-healing’, meaning that when it is punctured, the material will flow to fill in the void.

    We recommend it for use within industrial environments where steam and aerosols are commonly present, and outdoor environments where connections need to resist humidity and moisture. For electrical connections that are continually submerged in liquids, 3M has other solutions like Electrical Resins

Padding, Smoothing, Shaping

Built for the odd shape and the long stretch.

  • Image of 3M™ Scotch-Seal™ Mastic Sealing Tape 2229 wrapping around a low voltage cable with sealing connector covered with Scotch® 2510 Varnish Cambric Tape.

    Pad your connections

    Mastic tapes provide mega-stretch−up to 1000 times their original length. Sharp edges and bolted connections create potential puncture risks and failure modes for your splices which can result in costly downtime and repairs. With multiple configurations and thicknesses of moldable and stretchable stretchable rolls and putty you can shape, smooth and pad just about any electrical connection. 3M mastic products provide plenty of options for insulating and weatherproofing odd shapes and complex configurations like:

    • Bolted connections on bus bar
    • Split bolt connectors
    • Service drops
    • Ducts and cable ends

Diagram showing cable jacket, wire insulation, and stripped wire.
Scotch Mastic Pro-tip:

Exceptionally pliable; it can be rolled into tubes or spheres or crafted into any shape to fill crevices left by tape splicing, especially on bifurcated cables. A mastic that’s used for this purpose is 3M™ Scotchfil™ Electrical Insulation Putty. Scotchfil putty is 3.2 mm / 125 mil thick and comes on a linered roll for easy transport and flexible sizing for your application.

Pest Control

  • Image of red ants walking along a cable.

    What's eating your cables?

    There is another mastic application electricians may be surprised to learn about. Mastic tape can be used to deter pests. Ants create headaches for electricians by attacking pad mounted transformers, traffic control panels and ground level air conditioning units. *According to research done at Texas A&M University, the insects are attracted to the electrical fields, especially around relay switches. Power surges caused by these pests can cost thousands of dollars in electronics repairs or even human lives if those relays operate train switches.

    Pests and rodents can cause havoc. Help reduce your regular maintenance costs with a simple mastic solution.

    *Merchant, Mike. “Insects in the City: Fire ants shock homeowners.” (accessed September 15, 2017).

Protecting your Mastic with Vinyl or Rubber Tapes

Jackets required. This tape can ooze.

  • Mastic is going to flow. So, for the better mechanical protection and to help prevent it from making a mess in your application; mastic should be completely overwrapped with another protective material like vinyl (PVC) or rubber tape. To make your job easier, 3M offers solutions for such applications.  

    "Example 1: 3M™ Bore Pump Cable Joint Kits use Scotch-Seal™ 2229 Mastic Tape, which is overwrapped with either Scotch® 23 Rubber Splicing Tape or Scotch® 130C Linerless Rubber Splicing Tape. The next step is to overwrap the final layer with Scotch® Super 33+ ™ Vinyl Electrical Tape."

    Example 2: Scotch® Rubber Mastic 2228 is used for high voltage jointing applications to build jacket diameter (padding). It also has an ethlene propylene rubber backing to help resist liquid ingress.

Solid orange background image.
Scotch Mastic Pro-tip:

If Scotch® Rubber Mastic 2228 is applied in a gritty, rough environment, electricians may create added mechanical protection by overwrapping with Scotch® Vinyl Electrical Tape Super 88. Vinyl tape helps your splices and terminations resist copper corrosive chemicals and acids.

Mastic Electrical Tape Do’s and Dont's

  • DO
    • Use on split bolt connections to smooth out irregular shapes
    • Apply like putty in the inside of a multi-conductor cable where tape can’t quite reach
    • Keep a roll of mastic on the truck or in the plant for quick and critical fixes
    • Use underground to help protect from moisture that may corrode conductors
    • Use indoors where water and aerosols are sprayed or present
    • Use on solar panels and wind towers where there’s a consistent need for UV protection
    • Use in environments that require higher continuous operating temperatures
    • Use as a moisture seal at ground wire exit points
  • DON'T
    • Use on connections where re-entry is needed without pre-wrapping with varnished cambric or backwound (adhesive side out) vinyl
    • Use as the primary insulation on voltages >1kV. (Can be combined with rubber tape for higher voltage applications)
    • Use without the proper protective jacket
    • Apply in temperatures below 0°C

Mastic Tapes for Insulating and Sealing

There is a mastic for virtually every application.

Mastic comes in tape and roll form and in a variety of thicknesses and operating temperatures.

  • Choose thinner mastics for moisture resistance in lower voltages and tight spaces.
  • Choose thicker mastics when you need extra padding and durability from sharp edges or heavy vibrations.
  • Save time and eliminate the added step of overwrapping when you use pre-laminated rubber mastic products.

Even with a lot of information, understanding the pros and cons and picking a tape can be tricky. Let 3M save you time with these application summaries and quick product comparisons to find the right mastic solution for your application.

  • Image of 3M™ Scotchfil™ Electrical Insulation Putty applied over split bolt wrapped with Scotch® Self-Fusing Silicone Rubber Tape 70 HDT.
    Mastic Rolls & Putty

    Choose mastic only when you need padding, flexibility and conformability to manipulate the material to fit on or in your application. At 3.2 mm / 125mil , they are your thickest options - but these tapes and putty are versatile and can be cut, stretched, scrunched and rolled to fit in even small spaces. However, you will still have to wrap another material like vinyl over it to contain the mastic and provide jacketing protection.

    Premium Tape

    3M™ Scotch-Seal™ Mastic Tape 2229

    3M™ Scotchfil™ Electrical Insulation Putty

  • Image of 3M™ Scotch® Rubber Mastic Tape 2228 wrapping a medium voltage cable in a manhole.
    Rubber and Mastic Rolls

    Choose rubber mastic for insulating, padding and resisting moisture in high voltage applications up to 35 kV. Rubber and mastic tapes dissipate heat and work up to 90°C with an overload temperature of 130°C .

    Premium Tape

    Scotch® Rubber Mastic Tape 2228

  • Image of 3M™ Scotch® Heavy Duty Mining Tape 31 application.
    Mining and Cable Jacket Repair Tapes

    Choose a cable jacket repair tape for preventative cable maintenance, and on-site repairs in rough environments like construction sites, steel mills, petrochemical plants and industrial manufacturing. They include flame-retardant mastic to keep moisture away and provide excellent adhesion to a variety of cable jacket materials.

    Premium Tape

    Scotch® Cable Jacket Repair Tape 2234

3M™ Sealing and Insulating Mastic Tape Comparison Chart

You have a wide array of choices. This easy to read chart will give you performance ratings in a glance.

  • Scotch® Premium Electrical Tapes

    The key to selecting the right electrical tape for your application.

    There are some basic rules to follow when you’re selecting electrical tape.

    • Vinyl backed tapes have a strong, flexible, abrasion resistant PVC backing which provide a barrier from moisture and corrosive elements. They are often the first and most economical choice for primary and secondary insulation.
    • Mastic tapes offer excellent adhesion and sealing characteristics to metals, rubbers, synthetic cable insulations and jackets. They provide UV resistance and are designed for outdoor conditions because they quickly and easily seal out moisture.
    • Rubber tapes are designed for use in splicing and terminating wires and cables with options rated up to 69kV. They have excellent physical and electrical properties and are ideal for adding moisture protection and padding to electrical connections and cables.

    Get more information on product selection, applications and training in our Electrical Resource Center.