Insultab has a lot of experience spotting where people go wrong when it comes to measuring heat shrink tubing. It’s actually simple when you have a common vocabulary and know the right formulas.

Here is the information you will need to get your tubing measurements right – so you get exactly what you need for your project. …or better yet, call Insultab’s Customer Service team, and they will do it for you.

One of the most important tasks is choosing the size of tubing needed for your project. Here is how it is done. First, take your tubing and lay it flat on a smooth surface. Next measure the width of the flattened tubing. Then multiply the width by 2 and divide this number by Pi (I bet you remember this one from school 3.1416) and you have your answer – this is the tubing diameter you will need for your project.

1. Determine the diameter size of the tubing.

Measure the diameter of the underlying materials to be covered – at the widest part.

Select tubing that is 20% – 30% larger than this measurement by referring to the product’s Technical Data.

Diameter

2. Determine the shrink ratio of the tubing.

Heat shrinkable tubing is available in 2:1, 2.5:1 or 3:1 shrink ratios meaning the tubing has been expanded to twice, two and a half times or three times its fully recovered size. The greater the size variations of the underlying materials being covered, the larger the shrink ratio required.

For example:

  • 2:1 shrink ratio: 1/2″ will recover to 1/4″ — 50% shrinkage.
  • 3:1 shrink ratio: 3/4″ will recover to 1/4″ — 67% shrinkage.
Shrink ratio

3. Determine the wall thickness of the tubing.

Nominal Recovered Wall Thickness – The target thickness of the wall after complete recovery. The Wall Thickness of the tubing is measured in inches (in.) or millimeters (mm). Refer to the tubing’s Technical Data to determine the thickness of the wall.

Wall thickness

4. Determine the length of the tubing.

Longitudinal Shrinkage: Heat shrinkable tubing has a small loss of length during the recovery process. Take into account the change of length of the recovered tubing (after shrinking). Longitudinal shrinkage varies from 5% to approximately 15% – depending on the material. Refer to the Tubing’s Technical Data for the shrinkage information.

Length of Tubing
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Which Heat-Shrinkable tubing material should I use?

In selecting the best type of tubing for your application, the critical factor to consider is the environment where tubing will be used.

Select the tubing material that operates within the temperature range of the environment.

Material Temperature Range
Polyolefin -55°C to 135°C
PVC -20°C to 105°C
Cross-Linked PVC -20°C to 105°C
Multi-Wall Polyolefin -55°C to 110°C
Multi-Wall PVC -20°C to 105°C
Polyvinylidene Difluoride (PVDF) -55°C to 175°C
Chlorinated Polyolefin Elastomer -70°C to 121°C
Fluoroelastomer -55°C to 200°C
Medical Grade -55°C to 121°C
Food Grade -55°C to 121°C
Will the tubing stand up to abrasion or will it be used to provide protection from damage and abuse?

Material Abrasion Resistance
Polyolefin Good
PVC Excellent
Cross-Linked PVC Excellent
Multi-Wall Polyolefin Good
Multi-Wall PVC Excellent
Polyvinylidene Difluoride (PVDF) Excellent
Chlorinated Polyolefin Elastomer Excellent
Fluoroelastomer Excellent
Medical Grade Excellent
Food Grade Excellent
Will the tubing be exposed to: acids, solvents, fuels, oils?

Material Acids Solvents Fuels/Oils
Polyolefin Excellent Good Good
PVC Excellent Excellent Excellent
Cross-Linked PVC Excellent Excellent Excellent
Multi-Wall Polyolefin Excellent Good Good
Multi-Wall PVC Excellent Excellent Excellent
Polyvinylidene Difluoride (PVDF) Excellent Excellent Excellent
Chlorinated Polyolefin Elastomer Excellent Good Excellent
Fluoroelastomer Excellent Excellent Excellent
Medical Grade Resists a Wide Range of Chemicals
Food Grade Resists Many Chemicals & Oils

Tensile Strength is a measurement of the amount of stretching required to break or rupture the tubing. Tensile strength may be affected by the thickness of the tubing wall.

Material Tensile Strength
Polyolefin 1500 psi
2600 psi
PVC 3000 psi
Cross-Linked PVC 3000 psi
Multi-Wall Polyolefin 2100 psi
2200 psi
Multi-Wall PVC 3000 psi
Polyvinylidene Difluoride (PVDF) 5500 psi
Chlorinated Polyolefin Elastomer 2100 psi
Fluoroelastomer 2400 psi
Medical Grade 3200 psi
3600 psi
Food Grade 2500 psi
Dielectric Strength is a measure of the electrical insulation provided – the voltage that the tubing can withstand before dielectric breakdown occurs.

Material Dielectric Strength
Polyolefin 500 vpm
900 vpm
PVC 1083 vpm
Cross-Linked PVC 1083 vpm
Multi-Wall Polyolefin 700 vpm
800 vpm
900 vpm
Multi-Wall PVC 1,083 vpm
Polyvinylidene Difluoride (PVDF) 900 vpm
Chlorinated Polyolefin Elastomer 800 vpm
Fluoroelastomer 500 vpm
Medical Grade 1800 vpm
2,000 vpm
Food Grade 1,800 vpm
Will the tubing be exposed to water, salt water, liquids, moisture?

Material Water Resistance
Multi-Wall Polyolefin Provides Flexible, Tough, Permanent, Water Resistant Protection
Multi-Wall PVC Provides Permanent, Water & Salt Water Resistant Protection, Excellent UV Resistance for Outdoor Applications, Irradiated Multi-Wall PVC Available
Medical Grade Self-Sealing – Unique Heat Sealable Property Without Glue Prevents Moisture from Entering Into the Underlying Substrate
Tubing materials range from very flexible to semi-rigid.

Material Flexibility
Polyolefin Very Flexible
PVC Flexible
Cross-Linked PVC Flexible
Multi-Wall Polyolefin Flexible
Multi-Wall PVC Flexible
Polyvinylidene Difluoride (PVDF) Semi-Rigid
Chlorinated Polyolefin Elastomer Flexible – Even at Low Temperatures
Fluoroelastomer Very Flexible
Medical Grade Flexible
Food Grade Flexible
Underwriter’s Laboratories (UL) operates a testing and accreditation service for electrical and electronic materials and equipment. VW-1 is a flammability test conducted by UL or CSA (Canadian Testing Standards). Tubing with a VW-1 rating is highly flame-retardant.

Material UL VW-1 Flammability
Polyolefin UL VW-1 Colors Only – Not Clear
PVC UL VW-1 Colors & Clear
Cross-Linked PVC UL VW-1 Colors & Clear
Multi-Wall Polyolefin UL VW-1 Outer Jacket
Multi-Wall PVC UL VW-1 Outer Jacket
Polyvinylidene Difluoride (PVDF) UL VW-1
Chlorinated Polyolefin Elastomer No
Fluoroelastomer No
Will the tubing be exposed to UV light in outdoor applications?

Material UV Resistance
Polyolefin Poor
PVC Excellent
Cross-Linked PVC Excellent
Multi-Wall Polyolefin Poor
Multi-Wall PVC Excellent
Polyvinylidene Difluoride (PVDF) Fair
Chlorinated Polyolefin Elastomer Good
Fluoroelastomer Fair
Medical Grade NA
Food Grade NA
Heat shrink tubing shrinks and conforms to the underlying materials. The greater the size variations of the underlying materials being covered, the larger the shrink ratio required.

Material Shrink Ratio
Polyolefin 2:1
3:1
PVC 2:1
Cross-Linked PVC 2:1
Multi-Wall Polyolefin 2:1
3:1
2.5:1
Multi-Wall PVC 2:1
Polyvinylidene Difluoride (PVDF) 2:1
Chlorinated Polyolefin Elastomer 2:1
Fluoroelastomer 2:1
Medical Grade 2:1
Food Grade 2:1
In addition to its standard colors, Insultab does custom color matching.

Material Standard Colors
Polyolefin Black, Clear, White, Red, Yellow, Green, Blue
PVC Black, Clear, White, Red, Yellow, Blue
Bright Colors – Crystal Clear
Cross-Linked PVC Black
Multi-Wall Polyolefin Black
Multi-Wall PVC Black
Polyvinylidene Difluoride (PVDF) Translucent
Chlorinated Polyolefin Elastomer Black
Fluoroelastomer Black
Medical Grade Black, Clear, Blue, White
Food Grade Black, Clear, Blue, White
A quick overview of the special operational features of the various tubing materials.

Material Special Features
Polyolefin Excellent Electrical, Chemical, Physical Properties
PVC 30% Stronger than Polyolefin, Low Shrink Temperature, Clear & Vivid Colors are UL VW-1, Excellent UV Resistance
Cross-Linked PVC Irradiated, 30% Stronger than Polyolefin, Highly Abrasion Resistant, Excellent UV Resistance
Multi-Wall Polyolefin Provides Permanent, Water Resistant Protection, Flame Retardant Jacket
Multi-Wall PVC Provides Permanent, Water Resistant Protection, Excellent UV Resistance, Flame Retardant Jacket, Irradiated Multi-Wall PVC Available
Polyvinylidene Difluoride (PVDF) High Abrasion, Cut-Through, High Temperature Resistance, Flame Retardant, Transparent
Chlorinated Polyolefin Elastomer Broad Operating Temperature Range, Excellent in Severe Outdoor Environments and Rugged Applications
Fluoroelastomer Excellent Continuous High Temperature Operating Performance
Medical Grade Highly Lubricious, Non-Toxic, Self-Sealing, Meets USP Class VI Requirements
Food Grade Environmentally Friendly, Resists Sunlight, Moisture, Fungus, Meets USFDA Requirements