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GLOSSARY WRITING & READING PRODUCT CODES HOW ARE BAGS MEASURED? GAUGE (THICKNESS) CONVERSION CHART

GLOSSARY

Antistatic.- A kind of plastic, commonly pink-colored, but which may also be transparent or blue (Asian coding), whose main property is a low electrostatic emission, which is effected by additives that change its surface electric tension. It is not strictly necessary for high-performance products that are not vulnerable to moisture, but in those which are, its function is to absorb moisture in order to prevent electric charges to accumulate on its surface. It is important to note that this packaging feature is not a perfect shielding, since it is often not effective enough to protect a very sensitive electronic component from high energy electrostatic discharges. Additionally, this kind of plastic normally loses effectiveness over time, depending on the use is it subjected to and the kind of additive used in making it.

Bag Making Machine.- Machine used for making bags. It commonly uses rollstock or film which it feeds to a drum that in turn passes it through the seal and cut heads. It can have other accessory modules like film folders and punches for special fitments on the bags themselves.

Balloon.- Term used for the effect that is created in the material that results from extruding plastic resins for making film sheets and tubular plastic rolls. The combined influence of the air injector and the puller rollers in the bag-making machine create a balloon-like shape in the material that emerges from the extrusion die.

Barrel.- Metal tube heated by resistance wires in which plastic resins are melted and then extruded through one or several feed screws housed inside it.

Barrier (oxygen).- An intrinsic property of packaging materials or laminated films that describes the amount of oxygen gas that can pass through them and come in contact with the contents of such packaging container. Also, the protective properties of many packaging materials or films vary considerably with the relative humidity present in the air, so this is a factor that needs to be specified in testing conditions. The common standard is 0, 60 or 100% relative humidity, and the units used to measure it are cubic centimeters per 100 square inches per 24 hours (cc/100 sq. in./24 hrs) / (cm3/100 in2/24 hr.), or cubic centimeters per square meter per 24 hours (cc/sq. m./24 hrs.) / (cm3/m2/24 hr.) under a pressure difference of 1 atmosphere.

Barrier (water vapor).- An intrinsic property of packaging materials or laminated films that describes the amount of moisture that can pass through them. It measures the efficacy of a material's water vapor barrier. The units used are grams per 100 square inches per 24 hours (g/100 sq. in./24 hrs) / (g/100 in2/24 hr.) or grams per square meter per 24 hours (g/sq. m./24 hrs.) / (g/m2/24 hr.).

Bi-oriented Polypropylene (BOPP).- Short for biaxially oriented polypropylene, a variety of polypropylene that has been especially treated so that all its molecules are oriented along the same axis, which gives it better physical properties and enhanced transparency, among others.

Blow molding.- Plastic manufacturing process whereby a resin is melted inside a barrel containing a feed screw and dropped by gravity through a die, forming a hollow tube called a "parison". When the parison reaches the desired size, it is clamped into a mold and air is blown into it. Air pressure then pushes the molten plastic out to match the mold's shape. Once the workpiece has cooled, the mold opens up and the finished product is ejected.

Bottom Load Bag / Pouch.- Bag or pouch with a seal and / or a zipper at the top and whose bottom is left open until it is filled with the product it is going to carry, making it look flawless and neat.

Bottom seal.- A term used to describe the lower part of a bag or pouch. This flat joint or straight closure across the bottom part of the bag (similar to a pillowcase) is used to create the strongest seal for heavy bags.

Closure.- Fitments used to open and close bags or pouches. For example, double sided tape, detach and seal strips, vacuum seals, etc.

Crimp seal.- A property of laminated film in which one of its layers is made with polyethylene, which, upon exposure to heat in an oven expands and contracts in an inhomogeneous way, creating a seal by deforming the film's structure into the shape of a very tight, wavy line.

Cold seal.- This is a term that describes the joining of sheets or laminated films through the use of a strip of pressure-sensitive tape, which seals the bag without having to use heat.

Corona treater.- Short for corona surface treatment device, this piece of equipment includes a high-voltage generator (30 Kv) that opens the surface pores of plastic films, mostly polyolefins, so that they become receptive to bonding with printing inks. coatings and adhesives.

Die.- This is the nozzle through which molten plastic is extruded out of feed screws contained inside the barrel. The shape and size of the die will determine the gauge and tube size of the bag / pouch to be made, and, if necessary, will also mold the bag's zipper.

Double-sided tape.- Tape that has an adhesive on both sides, covered by a liner. One of its sides is exposed and glued to the body of a lip bag / pouch. After the bag has been opened, the liner on the other side is removed and the adhesive is exposed. This way, the bag or pouch can be opened and closed multiple times by sticking its lip to the exposed adhesive tape.

ESD (acronym).- Stands for electrostatic sensitive device: Any product or component that is sensitive to electrostatic discharges that build up on non-conductors or semi-conductors. Also stands for electrostatic dissipative: Any product or material used to prevent or slowly conduct static charges away.

Ethylene.- A gaseous, colorless alkene obtained from oil and natural gas. Used in the manufacture of polyethylene, which is a material from which bags and plastic containers are made.

EVA (acronym).- ethylene-vinyl acetate, a copolymer of ethylene and vinyl acetate that is much softer and clearer than LDPE (low density polyethylene) and LLDPE (linear low density polyethylene) and has a lower melting temperature. It is used to enhance the mechanical properties of extruded plastics.

Extrusion.- One of the commonest plastic processing techniques, extrusion encompasses an ample variety of different applications such as films, tubes and pipes. It starts when a plastic resin is gradually melted and pumped into a die through a rotating device called a feed screw. The die will shape the molten plastic pushed by the feed screw. The extruded plastic is pulled out and cooled by a water bath. Once cooled, the extruded product is stored in spools for later processing.

EZ tear.- A tear strip attached to the inside of a bag / pouch with an exposed tip that can be pulled away to open the bag cleanly and easily by tearing the packaging material open when the strip is pulled. A common example of this type of closure is the plastic envelope that covers cigarette packs.

FDA (acronym).- The Food and Drug Administration is an American federal agency that regulates and supervises food safety standards, and in general, the safety standards of all products that come in contact with or are used in the vicinity of human beings.

Feed screw.- A rotating screw that is housed inside a barrel that is heated by resistance wires to melt and mix thermoplastic resins. A barrel may contain one or more feed screws at one time in order to improve mixing and efficiency in the formulation of plastic compounds.

Film extrusion.- This is similar to the previous process, except the die has the shape of a ring and the molten plastic coming out of it is expanded and blown upward by a high-pressure air current. The setting of the die and the speed of the air current will determine the gauge and width of the resulting plastic balloon. Later, puller rollers will spool the balloon or film sheet for later processing.

Fitment: Accessories or other complementary features such as strips, holes, labels, etc. that make a bag or pouch unique, different from others.

Flat Bag-. The most common type of bag, it can have two or three side seals, a folded bottom, or a bottom seal plus two side seals.

Flap.- Part of a bag / pouch, adjacent to the closure that is used for the thermal sealing of said bag or pouch.

Flexographic printing.- This is a printing process that utilizes a flexible relief plate. In other words, the printed areas of a design are higher than the non-printed areas. The printing plate is made with a photo-sensitive polymer (formerly it was made of vulcanized rubber), a very flexible material that can adapt to a wide variety of printing surfaces or substrates. Flexography is commonly used, for example, on corrugated cardboard and plastic substrates. It is similar to the way a rubber stamp works. This process uses fast-drying liquid inks, which allows for the printing of high volumes at very low cost.

Foam.- Resin that is injected with a gas in order to expand in volume through the creation of countless air bubbles inside it. This process provides said resin with cushioning, shock-absorbing as well as thermal insulation properties. Commonly foamed plastics include polyethylene (carpet padding) and polystyrene (Styrofoam).

Foil.- A thin aluminum sheet that is laminated or tri-laminated to a PET (polyethylene terephthalate) or Nylon substrate. It is mainly used to provide a superior oxygen barrier and an attenuating barrier for electromagnetic frequencies and electrostatic discharges.

Gauge.- Term used to describe the thickness of a plastic film or sheet, measured in thousands of an inch or mils (one mil = 0.001"), or microns. Film thicknesses may vary between 0.35 and 4.0 thousands of an inch, depending on the material used. The micron (μ) is used in the metric system. 25.4 microns equal 0.001 inches, and 1000 microns equal 1 mm.

Gusset.- A feature of bags or pouches that have side or bottom reinforcements. These folds on the sides or the bottom of a bag or pouch allow it to expand up to the limits determined by the closure type in order to comfortably accommodate variable volumes or adjust the shape of the bag to the shape of its contents. Bags or pouches fitted with gussets are measured in three dimensions: width x length x gusset (W x L x G); and so are reinforcements: wide x length x bottom gusset (W x L x G). This allows the bag or pouch to adjust to the shape of the container as well as to distribute the weight of the contents in a uniform manner within the bag. This style maximizes the bag's load capacity and minimizes the risk of leaks or spillage.

Hand hole.- A helical opening or a series of round holes designed to hold a bag or pouch in hand or by using the fingers

Hang hole.- A hole punched in the header of a bag or pouch so that it may be hung up for retail

Haul-off tower This is a structure in the shape of a tower with smooth rollers fitted on the top. These rollers close the extruded plastic balloon to give it a tubular shape. The haul-off tower has a certain specific height in order to give the product enough time to cool. Other devices can be fitted over this tower to cut, gusset or give the product any particular shape or treatment. Then, the plastic tube reaches the top of the structure and enters the corona treater station. Finally, at the end of the system, the puller rollers spool it away for further processing.

HDPE (acronym).- This acronym stands for High Density (0,95 to 0,965) Polyethylene. It has a greater rigidity, higher thermal resistance and better water vapor barrier properties than LDPE (low density polyethylene), but is much more opaque. It is a conventional type of plastic (non-biodegradable, recyclable) that is commonly used in one-use plastic bags.

Hopper.- Part of a bag making machine or a plastic molding machine where the plastic components are mixed and fed into the machine before being melted.

Hot seal.- High temperature joining of two materials, usually plastics. This kind of seal is not considered highly resistant, but is relatively inexpensive. It utilizes a metal filament (resistance), that is heated and melts and joins two sheets of plastic, which are then separated from one another by the pull of the bag making machine.

Hydrocarbon.- Chemical term to describe an organic compound composed entirely of carbon and hydrogen

Label.- Marker, tag; a piece of paper that is attached on a product to identify or describe it.

Lamination.- Process whereby two or more types of material, usually films, are assembled together by gluing and curing.

LDPE (acronym).- This stands for Low Density (0,90 to 0,92) Polyethylene, a transparent, highly elastic compound that is used in common plastic bags in gauges from 1 to 5 thousandths of an inch (mils).

Lip or Flap Bag / Pouch - Header Bag / Pouch.- A header, or a lip or flap is a band of excess material on either end of the bag or pouch that can have different uses. In the case of a header, it is a band of material on both sides of the pouch or bag that can be used as a surface on which labels can be glued or hand holes can be punched. A lip or flap is a band of materials on one side of the bag or pouch that can be used as a closure in bags that have a strip of double sided adhesive tape on the inner side of its surface. In thin laminated bags or pouches, headers can be crimped. See Crimp seal.

LLDPE (acronym).- This stands for Linear Low Density Polyethylene, a very elastic compound that is used together with other polyolefins to increase mechanical and low temperature resistance in other plastic materials.

L seal.- This seal style, whereby one of the sides and the bottom part of the bag are joined to their facing sides, is used for bags or pouches of disproportionate sizes which normally do not fit in the bag making machine.

Multi-Cavity Bag / Pouch.- A bag or pouch in whose body different areas have been sealed off, creating cavities in which two or more products can be inserted. This type of bag / pouch is frequently used instead of shipping trays.

Nonwoven.- A polypropylene-based fabric or textile not obtained by weaving. It is used to prevent scratches on delicate pieces as it does not leave stains on the surfaces on which it is applied.

Notch.- A die cut in the shape of a V that is made in finished bags or pouches for ease of opening. It is similar to a slit, but is bigger and more efficient.

Nylon - Polynylon.- These are two types of polyamide resins with high melting points and superior clearness and rigidity. The second one has a higher melting point and consequently better thermal resistance, but the first is easier to manufacture and is relatively inexpensive. Both have good flavor and aroma barrier properties, but poor water vapor barrier properties.

Opacity.- A term that is used to measure the impenetrability of pigmented plastic films (especially those colored white) to visible light and UV radiation. This is beneficial for photosensitive products or materials.

Opening force.- This is the quantity of pounds force that is needed to open a bag's seal. The measurement of opening force can be external or internal. The former relates to the force that has to be exerted by a consumer in order to open the product's packaging. Internal opening force is the air pressure needed for the bag or pouch containing the product to open from the inside out. The device that measures opening forces is called a tensometer.

PET - Polyester.- polyethylene terephthalate, ethylene terephthalate or polyethylenterephthlate, better known by its acronym PET, is the type of plastic most frequently used in containers for liquids and foods and textiles. It is a linear thermoplastic polymer with a high degree of crystalinity. Like other thermoplastic resins, PET can be processed by extrusion, injection molding, preform blow molding and thermoforming.

Photosensitivity.- A property of some materials that are affected by visible or other kinds of light. The most common commercial products that show marked photosensitivity are photographic film and photographic plates. There are packaging materials that can fully prevent the incidence of light on this kind of products.

Plastic injection molding.- This is a plastic manufacturing process whereby plastic resin is melted inside a barrel fitted with a feed screw, which then injects it into a mold which gives it the desired shape. After the plastic cools, the mold is opened and the finished product is removed.

Printing plate.- A smooth, flat and thin piece or metal or other material that has been prepared as a surface for reproducing text or images on another sheet of material, called the substrate.

Polyethylene.- Chemical compound of the polyolefin family formed by the joining of ethylene monomers in long chains, with very marked plastic and thermoplastic properties. It can be found mainly in low and high-density varieties. It is colorless, non-reactive with most kinds of foods and cannot be dissolved by non-aromatic hydrocarbons.

Polyethylene Foam (PEF).- Low density polyethylene that has been injected with air bubbles.

Polyethylene Foam - Laminated.- Polyethylene foam laminated to a thin, flat polyethylene film liner. This product is perfectly smooth, has a better appearance and can be printed. Laminated PEF does not create friction with the product being packaged and consequently does not scratch or break, which is not always the case with the non-laminated variety.

Polypropylene.- A propylene-based polymer with a high degree of transparency and mechanical resistance that is frequently used for making plastic copolymers and coextrudates.

Polystyrene.- Polystyrene is a versatile plastic that can be made rigid or in a foam version. Everyday use polystyrene is clear, hard and brittle, and has a relatively low melting point. Typical uses include protective wrapping, containers, lids, cups, bottles and plates. (Opportunities and challenges in plastic containers, February, 1992.)

Pouch Seal.- A thick thermal bond with a high degree of mechanical resistance, this is the most frequently used process for products made of laminated film with a polyethylene inner layer.

Pre-Cut.- A bag or pouch that has been previously perforated along a line across its header so that it can be opened easily and cleanly without undue tearing or deformation (commonly used in polyethylene bags).

Puller roller.- A device that is driven by a motor that spools the tubular roll coming from the haul-off tower.

Punching machine.- .- A piece of equipment or tool having sharp edges that is used for cutting or stamping a design through force or pressure. This tool is used for making various types of holes in bags or pouches.

Puncture resistance.- A puncture can occur when plastic is subjected to dynamic conditions like impacts. This property can give us an idea of how strong an impact a laminated film can resist before it breaks or it fails due to the force that its contents exert upon it.

Resistance wires.- Metal wires fitted around the barrel of a bag making machine in order to gradually heat the resins until they melt near the nozzle and the die. The number of wires and their temperature will depend on the type of resin and the kind or mixture desired.

Rotomolding. - Short for rotational molding; a plastic manufacturing process where resins are melted inside a mold that is spun at high speed. The centrifugal force caused by the rotational movement of the mold pushes the molten plastic towards the walls of the mold, which then takes the desired shape. This process is frequently used to make cisterns and water tanks.

Rounded corners.- A bag or pouch whose lower ends have been rounded for ease of insertion in a shipping box or final packaging.

Screen printing.- Screen printing or silkscreen printing is a printing technique that is used for the reproduction of documents or images on any kind of material or substrate through a mesh stretched over a frame. The transfer of ink onto the substrate is blocked in those areas that will remain blank on the printed surface by the use of an impermeable substance that coats the corresponding areas of the mesh, while it isn't in the uncoated areas.

Seal: Term used to describe the point or line at which the sides or one of the ends of a bag or pouch are joined together to finish the product. It may be hot or cold.

Sheet or flat roll.- Delivery of a material in sheets without any kind of thermal sealing or curing. Depending on the size of the finished stock, the material may be delivered as sheets or in rolls.

Shelf life.- The period of time that passes from the moment a product is packaged until it is used or consumed.

Side Gusset Bag / Pouch.- A bag or pouch that has gussets on both sides. A gusset is a fold that runs the whole length of the bag, including the horizontal seal at the bottom. It is commonly used in the packaging industry for products that will be normally shipped in square boxes.

Side seal.- This type of seal is applied on both sides of the bag / pouch, while the bottom part is folded and fitted with a zipper, if required.

Slit.- A straight cut made with a die or a punch on one of the sides of a bag in order to make it easier to open. It is similar, but not as efficient as a notch.

Stand up pouch.- This is the pouch style that is gusseted at the bottom, so it can support the product it contains without falling over. The pouch appears to be standing up on its base, which results in heightened esthetic appeal.

Style.- Particular design of a bag or pouch. For example, square bag, gusseted pouch, 2 seal bag, etc.

Tear Strip.- A strip of tape attached across the width of a bag / pouch, especially if said bag is made of elastic material, in order to make it possible to open it cleanly, without undue stretching or tearing. These tape strips are often fitted with notches or slits on one of their side ends in order to make it easier ("EZ tear") to detach the strip along a straight line all the way to the other side of the bag / pouch. These strips are perfect for types of packaging that hold fragile products that may not be damaged or mishandled in any way, like stationery, photographic film, etc.

Tensile strength.- This is the test that measures the physical response of a material that is subjected to traction forces. The objective is to find out about the material's resistance to tearing stresses as well as to measure its main mechanical properties.

Thermoforming.- Plastic manufacturing process that utilizes rolls of laminated film or plastic sheets as starting material. The starting material's size and gauge determining the finished product's thickness and size. The starting material is laid on a conveyor which passes through an oven where the plastic resins become soft enough to be molded. When the softened film or plastic sheets pass over the molds, a pressure box or high-pressure air are used to force it onto the mold. The softened plastic takes the mold's shape, and once it cools and hardens, the molded products are ejected and trimmed prior to shipping. Items most frequently made with this process include cups and disposable dishes.

Thermoplastic.- Plastic resin that can be melted repeatedly. It softens when heated and hardens upon cooling, being able to undergo this process many times. The thermoplastic resin family includes styrene polymers and copolymers, acrylics, cellulosic materials, polyethylenes, vinyls and Nylons.

Thickness (see Gauge).- A physically observable measurement of the density of the material used in making bags or pouches. The usual thickness measurement units are microns, thousandths of an inch (mils) and millimeters.

3 (three)-seal.- a bag or pouch in which 3 of its sides are sealed. This type of seal is often made to order if the bag making machine does not have that capability, or it is either more convenient or easier to make.

Tin tie.- Metal or plastic tape that is attached to the outside of a pouch in order to provide an attractive, airtight closure. The tin tie is then tightened snugly around the bag's folded flap. Gourmet coffee bags are often fitted with this kind of closure.

Tri-laminated - Metalized Bag / Pouch.- These are made with two or three film layers laminated together. They are most commonly used in packaging with outstanding superior oxygen and moisture barriers (very low OTR and WVTR) for products that require a shelf life of up to 6 months.

Tubular roll.- A strip of bags or pouches extruded directly from the bag making machine, without any cuts. May be gusseted or not and be sold by the linear foot or by weight in pounds or kilograms.

UVI (acronym).- This acronym stands for ultraviolet inhibitor. This property is imparted by an additive added to the formulation of plastic film, either because the film itself needs to be protected against this type of radiation, or the product to be packaged is especially sensitive to it.

Vacuum seal.- A packaging process whereby the air is removed from the inside of a bag or pouch in order to extend the shelf life of a food product. This operation is accomplished by means of a vacuum pump and is a conservation measure that is done to certain types of foods like meats, fish and produce in order to stop or slow the activity of aerobic bacteria contained in them. This operation can be made more efficient if the atmosphere inside the bag is modified by injecting an inert gas that displaces oxygen out of the product's container. Commonly, nitrogen is used as inert gas.

VCI (Vapor Corrosion Inhibitor).- This is an additive that is mixed in with plastic resins to impart enhanced protection against the corrosion of metals contained inside plastic packaging. This additive creates a kind of vapor that reacts against the action of oxidation on the surface of metals, thereby inactivating this process and acting at the same time as a drying and lubricating agent. The typical color of VCI-treated plastics is green, though they can also be found in yellow.

Vent holes.- A series of holes punched in a bag or pouch used to let the air out of the bag upon packaging the product in question. These fitments are very useful in large bags or pouches as they make the packaging process more efficient.

Virgin resin.- This term describes those thermoplastic resins that comply with high standards of purity and cleanliness (devoid of recycled materials). These resins are optimal as starting materials for high-quality lamination

Zip, zipper or seal top.- A resealable or reusable bag or pouch is that which is fitted with a pair of ribs across its width that interlock in male-female fashion with another pair of ribs on the facing side of the bag's body, creating a simple mechanism that allows a flexible bag or pouch to be repeatedly opened and closed. This fitment can be extruded (molded through the bag making machine's die) or attached to the bag later. In this case, the ziplock mechanism is extruded separately on a polyethylene base and attached by fusing it to the inside of the bag or pouch.

WRITING & READING PRODUCT CODES

METALIZED

EXTRUDED

HOW ARE BAGS MEASURED?

GAUGE (THICKNESS)
CONVERSION CHART