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Polyken Extreme Weather FSK (Foil/Scrim/Kraft) Tape (438X)

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  • Quantity
    View "Full Pricing Table" below for details including case sizes and volume pricing.
  • Color
  • Size
    3 in. x 50 yds.
  • Price
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Before ordering, please read the "Product Description & Specs" tab content for more information about this item.

Product Description

Polyken/Nashua 438X Extreme Weather FSK Tape is a Foil, Scrim, Kraft laminate tape with acrylic adhesive suitable for use in a wide range of temperatures. Used to seal and patch FSK duct boards and insulation. Provides an extra-strength seal to maintain vapor barrier integrity. Polyken / Nashua 438X is specially designed to meet high strength, tear-resistant sealing tape requirements. Provides excellent adhesion to substrates over extreme temperature ranges (from -35°F to 260°F). Diamond pattern matches most FSK boards and blankets. 438X is UV, moisture and mold resistant and is non-solvent for less odor. It also has low VOC content and contributes toward satisfying EQ Credit 4.1 (Low Emitting Materials, Adhesives & Sealants) under LEED®. Meets flammability requirements for use in construction, aerospace and marine applications. Comes on a paper release liner. Country of Origin: United States.


Technical Information

Polyken Extreme Weather FSK (Foil/Scrim/Kraft) Tape (438X)
  • Standards Met: UL723, FAR 25.853(a); LEED - EQ Credit 4.1
  • Carrier/Backing: foil/tri-directional fiberglass/paper
  • Adhesive: acrylic   How are adhesives different?
  • Release Liner: paper
  • Thickness: 6 mils (carrier, adhesive)   What is mil thickness?
  • Adhesion: 75 ounces per inch (to stainless steel test panel)
  • Adhesion to Backing: 70 ounces per inch
  • Tensile Strength: 30 pounds per inch (longitudinal)
  • Service/Operating Temperature: -35°F to 260°F
  • Application Temperature: -25°F (minimum)
  • Core: 3" diameter
  • Flame Spread Index: 0
  • Smoke Development Index: 0
  • Country of Origin: United States
Note: Specifications are those given by manufacturers and are not tested for accuracy.

Download Datasheets

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438X Standard sizes


3 in. x 50 yds.

Actual Size: 72mm x 46m

438X/ 350

UPC = 653461993277

Single Item (1-15 Items)

1 - 4 Cases (16-79 Items)

5 - 9 Cases (80-159 Items)

10+ Cases (>= 160 Items)


a 5% discount

a 6% discount

a 7% discount





Question & Answers

User Reviews

[ viewing reviews 1 through 1 of 1 total ]
Attn: H. Verified Buyer Jun 12, 2019
438X extreme tape
Polyken 438X Extreme Weather FSK (Foil/Scrim/Kraft) Tape
Good tape but was incorrect for my application. Turn out is does Not adhere to foil surfaced insulation.
Made in the USA
hot melt rubber (synthetic)
Offers the widest range of application flexibility available. Exhibits excellent processing performance whether manually or automatically applied. Has superior tensile strength, adhesion properties and holding force which ensures consistent, reliable seals. Hot melt adhesive will bond faster to a surface which is referred to as quick-grab or quick-stick. It typically has higher tack (will feel stickier to the touch), but is also softer. It has lower heat resistance, shear resistance, and sometimes UV resistance than an acrylic adhesive. NOTE: it is called hot melt because the adhesive is applied hot by the manufacturer and then hardens as it cools (you do not need to apply heat to the tape yourself).
natural rubber
Properties are similar to that of hot melt rubber, but natural rubber often holds where other adhesives won't (recycled fibers, dust, cold, heat and heavy loads). It provides good overall adhesion and moisture resistance.
Offer excellent performance, especially for applications in temperatures less than 40°F and greater then 120°F. It provides excellent clarity, has high shear strength, is usually more permanent/durable even when exposed to moisture, and it ages well over extended periods in fluorescent and sunlight. Since it remains clear for the life of the application and does not yellow over time it is ideal for applications such as sealing white cartons. While it has good initial adhesion it does take 24-48 hours to cure and to achieve its maximum bond strength (has gradual adhesion buildup). Another difference between hot melt rubber and acrylic adhesive is if you fold tape over making the two adhesive sides touch the acrylic adhesive will remain attached to the carrier (e.g. paper, film) while a hot melt adhesive will stick to itself and pull off of the carrier. It is the best choice for clarity, UV resistance and aging characteristics.
Is great for extreme temperature applications since silicone adhesive can work in continuous operating temperatures from -100°F to 500°F. They also exhibit good chemical resistance, retain electrical properties, and remove cleanly with little or no residue.
zinc oxide
Zinc oxide based adhesive formula is a skin-friendly adhesive which is commonly used on sports medicine tapes.
Thickness, AKA caliper or gauge, refers to the distance from one surface of a tape backing, or adhesive, to the other.
1 mil = 1/1000 of an inch
Examples: 1/16 inch = 62.5 mils; 1/32 inch = 31.25 mils
The cut level indicates how many grams of cutting load a glove can withstand from a sharp blade before being penetrated.
Lower gauge gloves are heavier - have thicker construction, fewer stiches knitted per inch and offer less dexterity.
Higher gauge gloves are lighter - have thinner/finer construction, more stitches knitted per inch and offer more dexterity.
Gloves offered typically runs from 7 to 18 (12 and 13 are in the middle of the scale).
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