Can
Liners 101

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Why Gauge Isn’t Always Important

Film thickness is no longer a satisfactory standard for judging overall strength. The development of improved LLDPE resin in the liner industry has completely changed the standard method for selecting the correct can liners. These materials have allowed manufacturers to produce thinner, lighter trash bags which are stronger and more durable than the thicker bags previously made from low density resin. This is why gauge is no longer an effective way to determine liner strength. Instead of stating actual thickness, it is now generally accepted to use terminology such as “Light”, “Medium”, “Heavy”, and “Extra Heavy”.

Each manufacturer has its own blend formulations, so the proportions of these materials vary from one producer to another. The best way to determine the correct liner is to actually test some suggested samples. At Pitt Plastics, we have our own testing laboratory where we can test our liners or those of another manufacturer and provide you with the test results.

Definitions

It’s important to know a little bit about what can liners are actually
made of, and how thicknesses are measured. That way you can
determine which of the polyethylene resins and liner gauges
will work best for your particular application.

Resin

The basic raw material from which can liners are made. There are 3 types of resins: Low Density, Linear Low Density and High Density Polyethylene.

Linear Low Density Polyethylene

This resin is highly puncture and tear resistant. These properties make this the best choice for applications where additional strength and stretch are required. Works well for waste with sharp or jagged edges.

High Density Polyethylene

Liners made from this resin are generally available in lower gauges, and are more temperature resistant.

Low Density Polyethylene

An older resin still used mainly in lower end utility liners. It has largely been replaced by Linear Low Density Polyethylene. Pitt Plastics does not use this resin in any of our can liners!

Post

Consumer and Post-Industrial Polyethylene- This is made from recycled post-consumer plastics such as milk jugs and industrial scraps. These are reprocessed and blended with other types of resins to produce new high quality liners.

Gauge

A term used to describe the thickness of a liner. Low density liners are measured in mils, while High Density liners are generally measured in microns.

Mil

Measurement based on one hundred thousandths of an inch (.000). For example, a .55 mil bag would be 55 thousandths of an inch thick. Common low density liners range from .37 to 1.8 mil in thickness.

Micron

Based on thousandth of a Millimeter (.000000). High Density liners usually range from 6 to 22 microns in thickness.

Advantages of Linear Low
Density Can Liners

  1. Maximum puncture and stretch resistance compared to High Density.
  2. Multi-purpose applications.
  3. Most prevalent type of film used in the industry today.
  4. Manufactured in a wide variety of colors.
  5. Compared to traditional low density film, linear low can be run at a lighter gauge with equal strength.

Advantages of High Density Can Liners

  1. HMW/HD liners are about 3 times stronger and more durable than ordinary polyethylene liners of the same thickness.
  2. HMW/HD liners require two-thirds less petroleum based raw material to manufacture. Accordingly, they can be made about one-third the thickness of ordinary low density polyethylene liners, so they require only about one-third the ordinary shipping, storage and warehousing cost.
  3. Substantial cost savings per liner.
  4. When they are properly made, HMW/HD liners will rarely “zipper” if punctured.
  5. Extremely wide range of temperature resistance from -40 degrees F to +212 degrees F (boiling).
  6. USDA and FDA approved (natural colored liners).

Measuring for Correct Liner Size

Bag Width

Use 1/2 of the outer circumference of the receptacle.

Bag Length

Use the height of the receptacle, plus 1/2 of the container bottom, plus 3 inches (for overhang). For square or rectangular receptacles, use the diagonal of the receptacle bottom rather than the diameter.

Or, go to the calculator here.

Convert Microns to Mils

To convert microns to mils, divide the micron by 25.4 to arrive at the true mil thickness. Or, go to the calculator here.

Convert Mils to Microns

To convert mils to microns, multiply the mil by 25.4 to calculate the true micro thickness. Or, go to the calculator here.

How to Figure Case Weights

Linear Low

Width x Length x Mil /15 = Lbs per 1000 bags.
Calculator here.

High Density

Width x Length x Mic x .0027034 = Lbs per 1000 bags.
Calculator here.

Types of Bag Seals

Star Seal (or X-Seal)

The star seal has become the most common type of seal in the market today. Designed without gussets, the star seal eliminates gaps along the seal where leaks can occur. This unique design allows the bag to conform more easily to the shape of the container and distributes the weight of the refuse evenly around the bag. Star seal liners maximize the bag’s carrying capacity and virtually eliminate leaks. Star Seal liners are designated in two dimensions, i.e., 40×46.

Gusseted Seal

A flat style bag manufactured with both sides tucked in to form gussets. Where indented, the bag has to be sealed through four layers of film, while the middle of the bag has only two layers. This leads to an inherently weak bottom seal. Gusseted seal liners are designated in three dimensions, i.e., 23x17x46.

Flat Seal

Just as the name infers, a flat seal is simply a two-dimensional bag with a bottom seal. Flat seal bags are generally leak-proof, but are very clumsy to handle. Also, they do not conform very well to the shape of most trash receptacles. Flat seal liners are designated in two dimensions, i.e., 40×46.

Calculator

Linear Low Density

High Density