This article contains an in depth look at plastic baggies.
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A plastic baggie is a type of sack, container, or pouch made of an unwoven material that is exceptionally flexible and pliable made of a polymer. They are used to store food, electronics, pharmaceuticals, shipping, and retail displays for products. Plastic baggies have become a staple of society and a common form of container.
The wide use of plastic baggies is due to their versatility and low cost as well as their ability to be easily recycled multiple times. There is an endless number of uses for plastic baggies with the number of uses ranging into the billions and trillions. Although plastic had wide industrial use during World War II, plastic baggies did not find general use until the 1960s when a Swedish engineer introduced the concept.
Plastic baggies are lightweight, durable, and convenient, which makes them an ideal tool for transporting lightweight goods such as food from the grocery store. It is this characteristic that led to the rapid rise of their popularity.
During their initial introduction, plastic baggies were considered to be an environmental threat that had to be aggressively confronted. Over the years, modern science has developed methods and scientific techniques for taking the polymer materials and reprocessing them for further use, eliminating the fear of an environmental disaster. Additionally, public awareness and consciousness has increased as it pertains to plastic bags and the harm they can do.
Though baggies have an industrial and commercial use, they are commonly found in homes where they are used for storage. The normal size of plastic baggies is between one quart and a gallon. Most baggies are small and compact, with larger types available for industrial packaging and storage.
The construction of plastic baggies is very simple and consists of a single polymer. The manufacture of plastic baggies is as simple as their structure and includes the careful choice of a polymer material. Though there are several types of polymers, only a select few are used in the manufacture of plastic baggies.
Polymers are made from petroleum. When being used for the manufacture of plastic baggies, they are in a granular form or pellets. Color is added during the polymerization process.
The selection of the correct polymer is an essential step in plastic baggie manufacturing. Choosing the proper material is dependent on an understanding of the different types of polymers since each type has characteristics and properties that are beneficial for the final product. The four polymers commonly used in baggie manufacturing are polyethylenes, produced in densities of high, medium, low, and linear low.
Polyethylene is the most widely used polymer due to its excellent chemical and impact resistance, electrical properties, and low friction coefficient. In addition, it is lightweight, can easily be shaped and processed, and has zero moisture absorption. Polyethylene has a variable crystalline structure and is produced by the polymerization of the ethylene monomer. The chains for polyethylene molecules can be very long, up to as many as 500 subunits.
The chosen polyethylene material is mixed with a lower density polyethylene in a mixer to form a homogeneous material. The type of mixing process depends on the type of baggie that will be produced. The choice of mixer is based on the viscosity and shear level required for the thermoplastic application. Multi shaft mixers and planetary mixers are commonly used.
The plastic resin mixture is carefully melted under precisely controlled conditions until it becomes molten and pliable. The density and consistency of the resin mixture have to be sufficiently malleable to be able to be compressed and shaped. It is melted at a temperature between 350o F to 410o F. The melting process has to be carefully controlled such that the melted resin does not burn.
When the resin pellets are sufficiently pliable, they are extruded through a circular die. The die determines the thickness of the bags. Air is blown into the melted material to form a long inflated tube. When the molten blown material reaches the top of the tower, it is pinched off at one end and stretched and pulled to the required size and thickness.
As the inflated bubble of plastic stretches up in the extrusion process, it is allowed to gradually cool such that it maintains the proper thickness.
As the bubble rises, a set of rollers flatten it and move it from the top of the tower by a set of other rollers to collect rolls, as can be seen in the image below. The light blue lines represent the flattened polymer material being moved to the rolls at the bottom of the image, which are also blue.
Once the material is on the rolls, it is ready to be processed to form plastic baggies. A full roll of film weighs over 300 lbs. and can produce over 30,000 bags.
In the conversion department, the rolled film is unwrapped. Conversion is the actual making of the bags and is where they are shaped, formed, and sealed. Specialized machines complete the cutting process, and the excess film is collected for recycling. Special features and characteristics are also added, such as gussets, handles, and zipper seals.
Printing is added at one of two places, prior to conversion when the film is on the roll or after conversion. The ink used to print on the bags is a special mixture that is applied by rollers. If there is more than one color, each color is applied separately by a different roller.
Wicket bags are stacked plastic bags held together by a thin piece of metal, which is referred to as a wicket, much like the ones found in cricket. Having bags wicketed makes them easier and faster to dispense.
A specialty machine for the conversion process is a side seal machine that uses different attachments to create bottom gussets, inside or outside lips, punch handles, perforations, and applies tape for courier bags. The image below has examples of the different types of shapes that can be completed using a side seal machine.
Bottom seal machines remove the need to hand seal the bottoms of bags and are capable of sealing 200 bags per minute. A rolled web of printed film is fed into the machine, where it is cut and sealed.
T-shirt bag machines are specially designed for cutting and hot sealing the bottom of T-shirt bags. Any type of T-shirt bag can be produced with or without gussets and in varying widths and lengths. A key factor regarding T-shirt bag machines is their ability to process any type of polymer material. A second requirement is the placement of printing on the bag, which must be centered and precisely positioned.
In the conversion process, bags used to be cut by hand with a heated knife, which sealed the bag during the cutting process. As technology has progressed, cutting and sealing bags have been taken over by machines that work quicker and are more accurate.
Baggie cutting machines are controlled by a computer that has the dimensions of the bags input into its programming. The cutting speed is carefully controlled and can be adjusted for the size of the bag and type of material. A tracker assists in efficiently sealing the bags and cutting them to the perfect length.
There is a wide assortment of polymers that can be used to produce plastic baggies. The difficulty is in choosing the correct polymer to ensure that the bag that is produced is appropriate for the application for which it was designed. Every type of polymer offers characteristics and properties that meet the specific needs of certain applications.
Though there are many varieties of available polymers, in the case of plastic baggies, the polymer that is used the most is a version of polyethylene. Polypropylene is also used to manufacture plastic baggies due to its exceptional strength and endurance.
HDPE has all of the qualities to make it an excellent choice for making plastic baggies. It is lightweight, transparent, moisture and heat resistant, and has exceptional tensile strength. The United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA) have approved its use for food handling.
The federal approval of the HDPE material has expanded its use by food producers and restaurants. For this reason, HDPE plastic baggies are used to store food in homes and commercial enterprises. A major factor in the use of HDPE is its ability to be repurposed and recycled.
Each type of plastic has a symbol on the bag where it is a major part of the bag’s structure. The symbol for HDPE, as seen below, identifies HDPE and that it is a highly recyclable polymer.
The unique quality of MDPE is its clarity, though it is not as clear as low density polyethylene. The material made from MDPE is not very strong and does not stretch. It is used for carrying light loads and things that won’t cut through it. MDPE has a strong resistance to the effects of acids, oxidants, and reducing agents. Much like other polyethylene materials, it has low water absorbency.
When MDPE is heated, it melts. This particular property makes it ideal for recycling since it can be reheated, melted, molded, and reshaped multiple times without the degradation of its properties.
LDPE is a clear polyethylene that has moderate strength and stretch properties. It is a very versatile material popular for sealing its contents due to its low melting point. LDPE is very soft, pliable, and lightweight, with low temperature flexibility, toughness, and corrosion resistance. Its high impact resistance and chemical resistance makes it an ideal bag material for storing items at very low temperatures.
LDPE is recycled by being melted and formed into plastic sheets, which are sold to plastic manufacturers as raw material. There is a wide variety of places where LDPE can be dropped off for recycling from curbside pickup to grocery store drop off bins.
The symbol for LDPE can be seen below, which indicates its use as a manufacturing material.
LLDPE has a thinner gauge of plastic than LDPE but does not lose any of the strength of LDPE. Users can use it as a replacement for LDPE bags but not lose any of the quality of LDPE. It has unique melt flow properties. During extrusion, LLDPE remains more viscous. It has high tensile strength, impact resistance, and puncture resistance with excellent stretching flexibility. LLDPE makes it possible to produce thinner plastic film with tougher and more resilient profiles.
As with other polyethylene materials, LLDPE is easily recyclable for the production of other plastic products.
PP bags have exceptional strength and resistance to chemicals, as well as excellent endurance and long shelf life. PP bags are ideal for storing materials that may be in storage for long periods. They are clearer than polyethylene bags, making it easier to see the contents, and have been approved by the FDA and USDA.
Unlike polyethylene polymers, PP is produced from a propylene monomer and is a linear hydrocarbon resin. It is one of the least expensive plastics on the market. Due to its durability, strength, and lightweight, it is widely used to produce a wide variety of products, aside from plastic baggies.
Polypropylene is a low toxin and heat tolerant material and can be used for products that come in contact with foods since it does not leach harmful or dangerous chemicals. These particular properties are the reason that it is used for long term food storage. The symbol for PP can be seen below and is displayed on bags that have it as the main material.
A unique production process that uses PP is woven PP plastic bags, where the plastic PP film is drawn into tape and woven. The weaving process creates an exceptionally strong heavy duty fabric for the manufacture of plastic bags.
Plastic baggies have found a permanent place in society and are used for many purposes including storage, packing lunches, selling products, and protecting sensitive equipment. Their many uses have led to the development of a wide assortment of specialized baggies designed for a particular application.
As small and compact as baggies are, they can perform tasks better than any other form of soft side container. The essential feature that makes them so valuable is their durability and strength as well as their low cost.
The key to food safe bags is their durability and safety. The purpose for the storage of food is to preserve it for future use. To meet this requirement, food safe baggies must be durable enough to withstand exposure to the storage unit and safe enough not to contaminate the food. These two factors are essential. Convenience and easy access are other qualities necessary for food safe plastic baggies. Food safe baggies are one of the most used types of plastic baggies. They are made of clear plastic that has been heat sealed to block contamination from microorganisms.
Baggies with gussets are able to expand to allow for easy insertion of items. Gussets are slits along the sides, bottom, or sides and bottom of the bag. They lay flat until the bags are opened, and items are placed inside. Once opened, the bag will double or triple its width to match the items being placed in it.
There are endless uses for gusset bags due to their versatility and flexibility. They can store tools, food, clothing, and other items regardless of the size of the item. Their only limitation is their size. To accommodate various items, gusseted baggies come in as many sizes as they have uses.
The image below is a representation of a gusseted bag, which has a length, width, and depth.
Barrier bags are made of exceptionally sturdy material that is designed to protect the contents. They are made to protect against moisture, dirt, contaminants, and microorganisms as well as serve as a safety precaution for valuables. Barrier bags are made from a heavy duty polymer that is impact, puncture, and odor proof. In many cases, they are manufactured to fit the specifications of a particular industrial application.
Though barrier plastic baggies may be clear to display their contents, they can also be made in various colors as a method to code and categorize the materials in the bag.
The purpose of a biohazard baggie is to protect its contents and ensure the safety of those near to it. They have pre printed symbols that identify them as carrying hazardous materials. Specimen biohazard baggies have a pouch attached to place paperwork and protect the paperwork from the contents. Additionally, check boxes can be printed on the exterior for tracking, information, and processing the bag.
The key to food safe bags is their durability and safety. The purpose for the storage of food is to preserve it for future use. To meet this requirement, food safe baggies must be durable enough to withstand exposure to the storage unit and safe enough not to contaminate the food. These two factors are essential. Convenience and easy access are other qualities necessary for food safe plastic baggies.
Food safe baggies are one of the most used types of plastic baggies. They are made of clear plastic that has been heat sealed to block contamination from microorganisms.
Hanging or hang hole plastic baggies have a hole punched through the top of the bag in a flap that allows them to be hung on a peg or display. In most cases, hanging plastic baggies have a zip seal that is placed just below the hang hole. Bottom opened hanging plastic baggies have the hang hole at the bottom of the bag and hang upside down such that they can be opened to remove the contents and then resealed.
Header plastic baggies are a form of display bag that has a header seal with a hanging hole. They are used for retail sales and have information regarding the product printed in the header area. Header plastic baggies can be manufactured in any size to fit the needs of a product and are available in various colors. The header on the bag is normally one to two inches and, as with hang hole bags, the bag seal is just below the header.
Reclosable or resealable plastic baggies are made of LDPE plastic and are available in two types: seal and grip. They come in various thicknesses to meet the standards of the objects being stored, the storage unit’s temperature, and how long the bag will remain in storage.
Grip: Grip resealable baggies have a grip located at the top of the bag, which makes it easy to open and close the bag. Their ease of access has made them a staple of the medical industry for the storage of cotton and gauze swabs.
Seal: Seal plastic baggies have been popular for many years and can be easily found in lunchrooms. The zipper style seal can be engaged with the thumb and forefinger. Seal plastic baggies come in different colors. The colors are activated when the two portions of the seal are pressed together. Sealing the bag using the colored method indicates whether the bag is completely sealed, which serves as a safety measure.
Plastic baggies have an endless number of uses due to their durability and strength. From storing parts for an assembly to including something special in someone’s lunch, plastic baggies fill a wide assortment of needs and seem to be an essential tool. Though they have been given a bad reputation, society still relies on them as a valuable method for saving and storing various items as well as a means for shipping and sending information.
A key benefit of plastic baggies is the number of ways they can be used multiple times to serve multiple functions. This particular feature is what makes them different from similar containers.
A common use for plastic baggies is storage since they last a long time, maintain their seal, and can have any type of material placed in them. The use of plastic baggies as storage tools can be found in many locations in a home such as the kitchen, workshop, or playroom. Industrial uses for plastic baggies include a method for organizing small parts and tools as well as a way to send items between departments.
There are certain items when placed in a package may spread, break, or damage other items in the package. In those situations, it is important to have a method for controlling the unstable item and keep it safe. This can easily be accomplished with plastic baggies. Whether it is a jar of liquid or small pieces, plastic baggies can retain the contents and keep it contained.
Whether a document is being sent, being stored, or has historical significance, plastic baggies are used to protect it against atmospheric contamination, microbes, and moisture. Plastic baggies are used to keep photos, envelopes, precious greeting cards, and other written and printed material safe and secure. The tight seal on plastic baggies and their strong impenetrable construction makes them an ideal method for protecting and storing important documents.
An unusual use of plastic baggies to store documents has been developed by hunters. When hunting, the weather conditions can change quickly and expose their tags and license to damaging conditions. To protect their documents, they place them in a plastic bag for safe keeping.
Professional organizers and efficiency experts use small plastic baggies to group items during an organizing project. From unclassifiable items to miscellaneous pieces and parts, plastic baggies are an efficient and necessary method for putting stray items into a category. The convenience and accessibility of plastic baggies makes it easy to take a pile of loose items and organize them.
Plastic Baggies can act as a protective shield for items that can be harmful or dangerous such as medications, ammunition, sharp small tools, and powders. The sturdy protection provided by plastic baggies contains and controls unsafe items as well as highlights where they are placed. Placing unsafe items in a plastic baggie is one of their additional functions as an organizational tool.
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