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 It has largely been replaced by Linear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 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 one hundred
thousandths of an inch (.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).
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., 40x46.
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., 40x46.
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