IQS Newsroom Articles on Plastic Bags
About Plastic Bags and Plastic Bag Manufacturers
Including: Baggies, Clear Plastic Bags, Poly
Bags, Shopping
Bag, Vinyl
Bags, & Zip
Lock Bags.
Plastic bags, often referred to as poly bags, remain a popular choice for packaging
because of the advantages to manufacturers and consumers, which include
cost effectiveness, flexibility, durability and insulation. The flexibility of plastic allows
plastic bag manufacturers to produce a wide range of sizes and shapes, including grocery shopping bags, clear plastic bags, zip lock bags, vinyl bags and plastic baggies. Plastic bags are waterproof
and chemically resistant and also provide ample thermal and
electrical insulation. In addition to various sizes, shapes and styles,
plastic bag features often include color and custom printing. Because of their versatility, plastic
bags abound in almost every industry, providing utility in various applications
in the medical, pharmaceutical, engineering/construction, automotive,
electronic, computer and retail industries.
Plastic bag manufacturers create plastic bags from plastic resins through
polymerization, the process in which a chemical reaction links together
monomers to form a polymer. In the plastics industry, the term polymer
is synonymous with plastic. Polyethylene (PE) and polypropylene (PP)
are two plastic resins frequently used in the production of plastic bags.
There are a few types of polyethylene, which have distinct advantages,
depending on the application. High density polyethylene (HDPE) is non-porous
and non-stretching, creates a moisture and vapor barrier and usually
is about half the cost of low density polyethylene (LDPE). HDPE is perfect
for general packaging applications and trash storage, although HDPE bags are susceptible to tears and are non-recyclable. LDPE is porous and somewhat
stretchable, has good clarity and is great for everyday packaging needs
and all-purpose trash collection. Linear low density polyethylene (LLDPE)
is non-porous, very stretchable, puncture and tear resistant and about 15-50% less costly than LDPE. LLDPE serves the same purposes
as LDPE. Metallocene is a new-generation polyethylene resin that is very
tough and extremely tear resistant, much more so than LDPE. Polypropylene
is very different than polyethylene. It is non-porous, super transparent,
non-stretching and typically stronger and more rigid than types of PE.
PP is utilized in food packaging and retail displays. Many plastic bag manufacturers now specialize in biodegradable packaging films, including biodegradable polymer bags.
There are several determining factors in determining which type of plastic bag is right for a specific application. Once the size of the bag is determined (length x height x diameter), materials must be chosen based on application requirements for tear resistance, strength, durability, recyclability and cost. Other considerations include side-sealed bags or bottom-sealed bags, closure type (if any) such as slider grip, zipper
or draw-string and handle requirements, which will be determined by the bag's expected weight capabilities. Printed logos may be chosen to display brand or store names. Anticipated storage and use environments, such as warehouse storage or consumer shopping must also be considered when determining plastic bag specifications.
The non-recyclable nature of plastic bags has become a major environmental
concern across the globe. Only 0.5% of consumer plastic is recycled.
In the United States, four out of five grocery bags used are plastic.
South Africa has banned grocery bags, as Americans know them, and has
replaced them with a thicker, recyclable plastic. Germany and Sweden
have taken steps to phase out the use of plastic bags by retailers, and
Australia is beginning to follow suit. A progressive company in India
has been taking plastic bags, pressing them into colorful sheets and
using those sheets to create trendy fashion accessories, such as handbags
and wallets. Other uses for the pressed plastic sheets include tablemats
and notepad covers. Several U.S. plastic bag manufacturers have made strides in creating biodegradable polymer films and polymer alternatives, although these have yet to see significant exposure on the mainstream market.
Plastic Bag Types
-
contain an anti-static additive that disseminates static electrical
charges. Anti-static bags are ideal for short-term storage.
- are thin, disposable plastic bags used for storage, packing, and food preparation.
- Clear plastic bags are used for promotion, product display, retail, furniture
covers, food storage, dry cleaning garment bags and many other applications in
business and consumer industries. Clear bags are typically extruded from LDPE,
although clear plastic totes can be made from thicker acrylic sheets, while
"crystal clear plastic" bags are extruded from a polyester resin.
- are flat bags containing a hole at
the top of the bag for carrying. Die-cut bags are common in retail
settings and trade shows.
- contain either plastic or cotton drawstrings inserted
inside the rim of the bag. The drawstrings allow for easy closure and
provide handles with which to carry the bags.
- , which provide exterior protection
from static charges, are made from carbon-impregnated polyethylene.
- , commonly known as "sandwich" bags,
have a lip that is folded back with side seals.
- provide versatile plastic packaging for items of many shapes
and sizes that are heat-sealed on either the side or the bottom of
the bag. Bottom-sealed bags provide extra support for heavier items.
- are bags made from polyethylene resin to maintain
the freshness of the food items and are often sealed with slider grips
or
zippers. Food storage bags, which include sandwich bags, freezer bags
and produce bags, increase the life of perishable foods.
- contain folds or pleats called gussets, which allow
the bag and the bag opening to expand in order to accommodate large
or
bulky items. Gusseted bags include bottom-sealed, side-gusseted bags
and side-sealed,
bottom-gusseted bags.
- are side-weld bags that are loaded
and sealed from the bottom. Header bags have a continuous seal along
the top, which is
2-3" below
the fold, and a hang hole.
- are flat bags with a die-cut handle reinforced
by a heat-sealed patch for added strength.
- are bags derived from polyethylene or polypropylene, although
this term usually refers to polyethylene bags.
- , which include zipper bags, are top-sealed. Reclosable
bags can be made with or without a tamper-evident adhesive seal.
- include all bags used to store and carry merchandise.
- are supplied by retailers for the transportation of purchased goods. They can have handles and are usually printed with the names of retail stores.
- are sealed on the side and have no bottom seal.
- are receptacles made of thin plastic that are used to store goods.
- include all trash can liners
and bags, as well as bags used to remove hazardous waste. Waste removal
bags
are often manufactured
from high density polyethylene resin because of the strength
and cost-effectiveness of the resin, but may also be made out
of linear
low density resin
because of its stretching ability.
- are plastic bags with interlocking strips for sealing.
Plastic Bag Terms
- Substance added to a polymer to increase
the effectiveness, but not the strength, of the polymer. Examples of
additives include flame-retardants, anti-static compounds, pigments and
lubricants.
- Also referred to as a "blend" or "hybrid," it
is two chemically dissimilar polymers bonded together to form a new substance.
However, each polymeric unit is representative of only one monomer.
- Common process of creating plastic bags in which
compressed air fills an extruded plastic tube in order to enlarge and
thin out the resin.
- A polymer made up of two monomers in which each repeating
unit in the chain consists of units of both monomers.
- Very thin cracks in a polymeric material caused by chemicals
or other agents, such as ultraviolet radiation.
- The
length of the molecular or monomeric units in a polymer chain. This length
determines the properties of the
polymer.
- A copolymer produced
through the chemical reaction of ethylene and vinyl acetate. EVA is often
added
to
plastic resins to increase the strength of the resin in temperatures
below freezing.
- A term referring to the thickness of
the material. The smaller the gauge number, the thinner the material.
- Term that reflects the temperature
when a substance changes from a hard glass to a rubber consistency. Polymers
become weak at temperatures below their transition temperature.
- Polymers originating from the same chemical family and
produced from the same company. However, they vary in weight, additives,
reinforcements and the manner in which they are processed.
- Fusing together two or more thermoplastic films,
such as low density polyethylene, through the application of heat and
pressure.
- A plastic material whose thickness
ranges from .941 -.965 g/cm3. HDPE is more expensive to process, but
maintains greater strength, resistance and stiffness than either LDPE
or LLDPE.
- The process of decreasing the weight of plastic
by using less resin, while retaining the strength and effectiveness of
the plastic.
- A plastic material that
is produced at lower temperatures and pressures than LDPE through copolymerization,
resulting in a crystalline structure responsible for greater stiffness
and a higher melting point than LDPE. Although it is more difficult to
process, LLDPE maintains greater tensile strength and a greater resistance
to stress cracking than LDPE.
- The longer side of the bag that allows the bag to be opened
more easily.
-
The most common and least expensive plastic bag material that maintains
a density of .910-.925 g/cm3. LDPE maintains its durability,
flexibility, water resistance and clarity under low temperatures, and
its low melting point makes it ideal for heat sealing.
- The temperature at which a substance converts from
a solid into a liquid.
- A puncture resistant material that is thinner and
stronger than LDPE.
- The most basic polymeric unit, usually a liquid or a
gas, consisting of molecules from the same organic substance. When chained
together, monomers form solid polymers.
- A chemical added to plastic resins to increase the
flexibility of the plastic.
- The most common plastic resin, it is a light,
chemically resistant thermoplastic used in packaging and insulation.
PE resins used in the production of plastic bags include low density,
linear low density and high density resins.
- Two or more
monomers bonded together through a chemical reaction. Each polymer consists
of a chain of repeating monomers.
- Light, durable thermoplastic with a high melting
point that is often used in packaging. PP contains polymers consisting
of propylene, a colorless, combustible gas found in petroleum.
- Substance added to a polymer to increase the strength
of the plastic. Examples include clay, mica and glass fibers.
- A class of polymers, or plastics, chemically different
to naturally occurring resin, a sticky substance obtained from certain
trees and plants. Examples of resins include polyethylene, polyurethane
and acrylics.
- An additive that aids in decreasing the slippage of stacked
packaged goods and prevents bags from sticking together.
- A bottom seal for liners that combines four sections
into a star design. Star seals are the strongest seals, and they maximize
carrying capacity.
- Cracking that occurs as a result of mechanical
stress. In most cases, tiny cracks caused from exposure of the plastic
to chemicals or ultraviolet radiation are already present.
- A polymer made up of three monomers in which each
repeating unit in the chain consists of units of all three monomers.
- The process of applying heat, pressure or suction
to create plastic sheets, according to specified sizes and shapes.
- Category of
plastics that has the potential to soften and reform when heated and to
harden again during cooling. During the process, the physical makeup of
the plastic does not change.
- A category of plastics that cannot be reformed upon
reheating. Thermosets remain permanently hard.
- A plastic additive that increases
the resistance of the plastic to the harmful effects of ultraviolet radiation,
such as fading of color and strength decrease.
- Thermoplastic coating or film that
safeguards sensitive items from harsh environmental conditions through
the release of a vapor that forms a protective layer on the surface of
the thermoplastic.