Everything you need to know about plastic bags and their use.
You will learn:
Plastic bags are versatile, one-piece containers crafted from polymer-based materials, designed for holding, transporting, and packaging numerous items. Though they may appear delicate due to their thin design, plastic bags are actually durable, waterproof, and maintain their form under normal usage. They are predominantly fabricated using diverse plastic polymers, with polyethylene and polypropylene leading as the most prevalent choices.
The diversity among plastic bags stems from factors such as the materials employed, their dimensions, hues, closure mechanisms, and styling. Polyethylene bags vary in density—ranging from high-density, low-density, medium, to linear. Conversely, polypropylene bags are distinguished by their transparency, excellent tensile strength, as well as resistance to heat and chemicals.
The polymers used to create plastic bags originate from processed natural gas or refined crude oil. These materials are subjected to high pressure and heat to isolate pure polyethylene chains, which are subsequently polymerized to produce resin pellets. Adjustments in heat and pressure during this stage yield resin pellets of varying densities, enabling the fabrication of different styles and types of plastic bags.
The creation of various plastic bag types is heavily reliant on the choice of specific resin pellets for the extrusion process. Each type of plastic exhibits distinct features and qualities, meaning that while plastic bags might seem similar at first glance, each kind possesses unique strengths, thickness, and durability.
Plastic bags start as resin pellets made from pure plastic, which is extracted from crude oil or cracked natural gas. The plastic bag manufacturing process begins at the cracking plant, where naphtha (a byproduct of crude oil) or ethane (a natural gas liquid) is converted into ethylene. Ethylene is a crucial hydrocarbon used to produce a range of plastic products, including polyethylene plastic bags. Among these hydrocarbons, ethane is the less expensive and more environmentally favorable option for producing ethylene, which is why it is widely used in modern plastic bag production facilities.
Ethylene, which is produced as a gas during the cracking process, must be transformed into polyethylene resin through a process called polymerization. During polymerization, manufacturers apply pressure and catalysts to induce a chemical reaction between ethylene molecules, creating strong polymer chains. These chains provide the foundation for plastic’s durability, flexibility, and wide range of properties. Plastics engineers carefully manipulate these polymer chains to achieve specific physical and chemical characteristics in the plastic resins, optimizing for strength, transparency, and processability according to the intended application—whether for retail grocery bags, industrial liners, or food storage solutions.
Polyethylene, a versatile polymer consisting of long chains of ethylene monomers, is the most commonly used material for producing plastic bags. This polymer results from the reaction of ethylene molecules in the presence of a catalyst, which breaks the double bonds between carbon atoms and forms strong, flexible chains. Thanks to its low cost, excellent moisture resistance, and recyclable properties, polyethylene dominates the global plastic bag market for both single-use and reusable bag types.
Polypropylene is another important plastic derived from crude oil, first introduced in 1951 and refined for commercial and industrial applications by 1957. Like polyethylene, polypropylene is created from crude oil, from which the monomer propylene is extracted. Through a process known as chain growth polymerization, propylene monomers are transformed into the robust and versatile polymer polypropylene. Polypropylene plastic bags are valued in packaging due to their high resistance to fatigue, exceptional clarity, and ability to withstand higher temperatures than polyethylene bags.
During polypropylene production, propylene monomers are linked together to create a solid plastic material. To produce functional plastic bags, this polymer is blended with plasticizers, stabilizers, and fillers. The mixture is then melted, formed into resin pellets or bricks, and cooled for use in a variety of packaging applications ranging from retail shopping bags to heavy-duty industrial sacks that require additional strength and puncture resistance.
Plastic bag coloring can be achieved through various methods, depending on customer requirements, branding objectives, and the intended use of the plastic. The most common coloring techniques include masterbatch, cube blends, and precolored resin. Selecting the best method depends on whether bulk plastic bag production, custom plastic bag orders, or specialty plastic film products are being created.
Masterbatches, also known as color concentrates, are the most widely used and cost-effective method for coloring plastics in the bag manufacturing sector. This process involves blending concentrated pigments with polymer resin, then heating the mixture to ensure a thorough integration of color. Masterbatch technology allows plastic bag producers to create vibrant, consistent, and highly customizable colors to enhance branding and product identification.
Cube blending, or salt and pepper mixing, combines a masterbatch with polymers, ensuring precise control over the final color distribution. Cube blending preserves the original mechanical and barrier properties of the polymer, as it remains solid throughout the mixing process. Cube blends are ideal for orders where consistent performance and color are critical, such as food-grade plastic packaging or branded retail carrier bags.
Precoloring incorporates pigments directly into the plastic resin during polymerization, resulting in a resin that is ready-colored and consistent. Precolored resins are convenient for manufacturing runs that require strict color and performance characteristics, like high-visibility waste collection bags, colored shipping bags, or food-safe colored liners. This approach can help maintain efficiency and colorfastness across large production volumes.
The extrusion process is employed to create the plastic film used in plastic bags. It starts with heating plastic resin pellets—typically polyethylene or polypropylene—to temperatures exceeding 500°F, transforming them into a uniform molten liquid. The resin must become sufficiently pliable to be pushed through a circular die at the end of the extruder, creating continuous plastic film. This step is foundational for the blown film extrusion process, which is the industry standard in plastic bag manufacturing for producing both thin and heavy-duty films with consistent thickness and clarity.
Heating the resin to the correct melting point is crucial for shaping and forming plastic bags. Resin pellets are introduced into the extruder through the hopper, located at the top of the barrel above the auger. Early hoppers were simple cone-shaped structures that required manual loading of resin pellets, making the plastic bag manufacturing process labor-intensive and less efficient.
Today’s hoppers have evolved with technological advancements, featuring a variety of shapes and sophisticated feeding mechanisms that automate the resin loading process. This automation is critical in modern high-volume plastic bag manufacturing plants, reducing downtime and ensuring consistent feed rates for precise film quality and thickness control.
The extruder serves as the heating and mixing mechanism in the plastic bag manufacturing process. It utilizes a long tube called the barrel, inside which a helical screw (the auger) moves the resin pellets from the hopper toward the die. Heating elements along the barrel melt the plastic pellets into a homogenous molten liquid. Meticulous temperature control during extrusion is vital for achieving the correct film properties needed for applications such as food packaging, retail shopping bags, and specialty plastic liners. The molten resin is then pushed through the die, initiating the blown film process that gives plastic bags their signature shape and strength.
At the end of the extruder barrel, the molten plastic is forced through a circular die before entering the cooling tower. A screening or breaker plate sits in front of the die to remove any potential contaminants, ensuring the purity of the molten resin. Every step of this process impacts the final clarity, barrier properties, and strength of the resulting plastic bag material.
As the molten plastic resin progresses through the extruder barrel, pressure is applied to force it through the screen or breaker plate and into the die. The breaker plate removes contaminants and protects the die by withstanding high pressures generated during extrusion—a crucial quality control measure in the blown film plastic bag manufacturing process.
The die then directs the molten plastic into a cooling cylinder (either vertically or horizontally oriented), where the thickness of the bags and their width are determined. This process ensures the bags are seamless and free of holes or weak points. Adjusting the speed at which molten plastic flows through the die and into the cooling cylinder allows manufacturers to produce different gauges of plastic film, from ultra-thin grocery bags to thick, heavy-duty garbage bags and industrial packaging liners.
As the molten plastic resin exits the extruder, it passes through the die and breaker plate into the base of the cooling tower cylinder. Here, compressed air is introduced to inflate and shape the plastic—similar to inflating a large balloon. This process is essential for forming the tubular, continuous film required for most plastic bag applications, especially in high-volume blown film lines.
As the plastic tube is inflated with air, it travels upward through the cooling tower, cooling as it goes and taking on the precise dimensions of the finished plastic bags. The film's movement speed directly influences its final thickness: rapid expansion produces thinner, lighter bags ideal for produce or shopping, while slower expansion results in thicker, heavy-duty bags used for packaging, storage, and industrial applications.
The newly-formed film continues cooling as it rises to the nip rollers, which press the sides of the tube together and stretch the film both axially and radially. This process ensures uniform thickness, exceptional clarity, and the elimination of any air bubbles, blisters, or other imperfections—key factors for food packaging, retail, and specialty bag requirements.
The diameter of the plastic tube and the height of the cooling tower (usually between 25 and 35 feet) determine the bag’s width and the speed of the cooling process. This step is critical in producing consistent, high-quality plastic bag film rolls ready for printing, cutting, and conversion into finished bags.
Gussets are folds, pleats, or indentations added to the sides or bottom of a plastic bag to increase its volume while allowing it to lay flat for easy storage and packaging. In the cooling tower, boards embedded in the walls create these gussets by indenting the fully inflated plastic as it moves toward the nip rollers.
The gusset forms two overlapping rectangles, which are pressed together by the nip rollers. Side gussets are particularly common in plastic bag designs that require more storage capacity, such as shopping bags, garbage bags, and food service packaging. Proper gusseting is essential for producing more durable, versatile, and functional plastic bags suitable for a variety of uses and industries.
Nip rollers, positioned at the top of the cooling tower, provide the necessary traction, tension, and winding to transfer the completed bag material onto rollers for further processing. As the inflated plastic film cools, it crystallizes at the frost line, becoming firm enough to be flattened into lay-flat or collapsed tubing. Nip rollers are critical in pulling the cooled plastic film upward while ensuring uniform winding, which is essential for subsequent printing, cutting, and bag-making operations.
The rollers regulate the firmness of each plastic film roll by removing trapped air as the material exits the cooling tower. Properly engineered nip rollers minimize defects, produce tight rolls, and enable high-speed, automated plastic bag production—core requirements for serving retail, food service, and industrial packaging markets efficiently and reliably.
During the production process, polyethylene and polypropylene bag materials may be treated with several additives to enhance performance, safety, and durability. Typical plastic bag additives include:
The thickness (or gauge) of plastic bags is a key specification, determined by the application and performance requirements. Thickness is measured in mils, with one mil equal to one-thousandth of an inch (0.001"). Thicker bags generally provide greater strength and puncture resistance, ideal for heavy-duty or industrial packaging, while thinner gauges are sufficient for lightweight items or produce bags. Bag thickness can also be measured in microns (µ), the metric equivalent, with 0.05 mm equal to 50 µ. For example, a food storage bag might require 1.5 mils thickness, while a heavy-duty industrial liner may exceed 4 mils.
Choosing the correct bag thickness is crucial for balancing protection, cost, user convenience, and environmental impact. Thicker bags can be reused multiple times, contributing to sustainability and plastic waste reduction initiatives. Transparent, high-clarity films made with thinner gauges are important for retail product display and food freshness, while thicker, colored, or reinforced films serve shipping and hazardous materials handling needs.
| Mil Thickness | Thousandth of an Inch Thickness | Best For... |
| 1/2 mil | .0005" | Short-term use for lightweight products such as produce bags. A standard grocery store bag is ½ mil, while a dry cleaning bag is typically ¾ mil thick. |
| 3/4 mil | .00075" | |
| 1 mil | .001" | Storing, displaying, and shipping everyday items such as food, bakery goods, or clothing. Bread bags are often 1.5 mils thick. Trade show and retail boutique bags frequently use 2 mil film for enhanced tear resistance and reusability. |
| 1.5 mils | .0015" | |
| 2 mils | .002" | |
| 3 mils | .003" | Providing scuff protection and tear resistance during shipping, especially for heavy or abrasive items. Industrial pallet covers typically use 3 mil film, while construction bags and debris liners may be 4 mils or more. |
| 4 mils | .004" | |
| 5 mils | .005" |
The optimal gauge for a plastic bag is determined by three key factors:
Careful selection based on these criteria ensures the plastic bag meets industry regulations, user requirements, and sustainability goals. Many suppliers now offer custom bag sizes, recyclable or biodegradable plastic films, and personalized printing to cater to a diverse range of end users and industries.
Modern plastic bag factories employ strict quality control protocols—monitoring film uniformity, sealing strength, and bag dimensions—using automated inspection systems throughout production. Advances in recyclable plastics, biodegradable films, and reuse-focused design also increasingly shape plastic bag industry trends. Many manufacturers now offer eco-friendly stock and custom bags made from recycled polyethylene or with additives to facilitate decomposition, meeting growing demand for sustainable packaging solutions. When evaluating plastic bag suppliers or making purchasing decisions, consider factors like material recyclability, compliance with food safety standards, access to custom printing, and availability of certified compostable or degradable options to support your business’s environmental commitments.
Plastic bags are manufactured from polyethylene, which starts as ethylene derived from natural gas or oil. This ethylene undergoes a transformation into polymer form. Polyethylene is then modified to suit different applications and types of plastic bags.
Plastic materials are created from polymers, which are constructed from monomers. Polyethylene consists of long chains of carbon atoms bonded with hydrogen atoms. This polymer structure allows plastic to be easily adjusted into various densities and shapes.
HDPE is known for its strength and high tensile strength. It can endure temperatures up to 120°C or 248°F and exhibits resistance to various solvents. Its linear molecular structure results in a robust material capable of withstanding prolonged use.
LDPE plastics are characterized by their thickness, flexibility, and resistance to punctures and tears. Thickness is measured in mils, with one mil equating to one thousandth of an inch. A higher mil count indicates a thicker bag, with typical ranges from 0.9 mil for kitchen bags to up to 6.0 mil for heavy-duty contractor bags.
| Comparison of LDPE to HDPE | ||||||
|---|---|---|---|---|---|---|
| Recommended Uses | Recommended Location | Puncture Resistance | Tear Resistance | Measured In | Sample Products | |
| Low Density | Sharp Object, Including Glass and Wood, Contruction Debris, Irregular-shaped Items and Everyday Kitchen Trash. | Kitchen Contruction Site, Garage, Yard, Roll-out Trash Can | Excellent | Excellent | Mils | Kitchen Trash Bags, Outdoor Trash Can Liners, Retail Shopping Bags, Garment Bags, Lawn & Leaf Bags |
| High Density | Light-weight Trash Such As Tissues, Office and Restroom Waste and Shredded Paper | Offices, Restrooms, High-traffic Areas, Paper Shredders, Recycling Bin | Fair | Fair | Microns | Grocery Bags, Recycling Bags |
LLDPE bags, while similar to LDPE bags, offer enhanced strength and puncture resistance. They are commonly used for lighter gauge gusseted bags. LLDPE bags are more cost-effective and environmentally friendly compared to LDPE bags. They are produced through the copolymerization of ethylene with butene, hexene, and octene.
MDPE offers greater strength and rigidity while remaining flexible enough for easy processing. Its increased thickness makes it suitable for handle and loop bags. The higher density of MDPE enhances its resistance to shock, drops, and stress-cracking.
Metallocene is distinct from traditional monomers like ethylene, propylene, or vinyl acetate. Instead, it consists of particles of charged metal ions combined with carbon atoms. Metallocene maintains similar density standards to polyethylene, with lower densities being softer and higher densities offering greater resilience. During manufacturing, it is blended with LDPE and LLDPE to create a superior poly film that seals quickly and securely. However, the cost of metallocene is higher due to its blending with polyethylene.
Vinyl is made by combining chlorine and ethylene to produce ethylene dichloride, or EDC. The process for forming vinyl EDC involves creating vinyl chloride monomer (VCM), which is polymerized and turned into a PVC resin powder. The addition of modifiers and additives alter its physical properties. Vinyl is flexible, waterproof, durable, flame retardant, resistant to wear and tear, UV radiation, and stress. Its positive properties make it ideal for storing and preserving precious items.
Polypropylene is composed of long chains of propylene molecules, giving the material both flexibility and strength. It is highly resistant to fatigue and can endure repeated use without significant damage. With its low density, polypropylene is lightweight yet offers a high strength-to-weight ratio. Although polypropylene bags are versatile and can serve various purposes like other plastic bags, they are most commonly used for tote and shopping bags.
The variety of plastic bags is virtually limitless, expanding annually as new applications are discovered. They can come in many forms, including flat, gusseted, anti-static, postal-approved, protective hazard bags, and shrinkable types.
Flat plastic bags are characterized by their wide and long dimensions without depth. These bags can be sealed using heat, ties, staples, or tape, making them a versatile option for storing a range of items, from food to electronics.
Markable bags feature a white block designed for labeling the contents. This makes them ideal for organizing and storing small items, ensuring easy identification and access.
Resealable bags have a means for closing the bag that can include zip track or some form of slider zipper. Large versions can be used for storage, while smaller ones can be used for packing lunches.
Gusseted plastic bags have tucked in pleats on the sides so that they can expand when filled. Their gussets increase their volume and give them greater capacity without stretching or changing the shape of the bag. Gusseted plastic bags are similar to flat plastic bags in that they can be heat sealed, tied, stapled, or taped. They are sometimes referred to as flat bottom plastic bags due to the bottom that forms when the gussets are expanded. The special design of gusseted plastic bags makes it possible to use them for any type of application.
Anti-static plastic bags are equipped with a special additive that prevents static electrical charges, making them ideal for storing electronic components. These bags come in various colors and densities of plastic material to suit different needs.
Postal-approved bags are designed to be compatible with United States Postal Service (USPS) scanners to ensure smooth processing and avoid delays. These bags are manufactured to both protect their contents and meet USPS standards for efficient mail handling.
Biohazard bags are designed to protect workers from hazardous materials. These bags are clearly marked with the biohazard symbol and come in various colors such as clear, white, red, yellow, black, or blue, depending on their intended use. They must comply with standards set by the CDC, DOT, EPA, and OSHA for handling medical waste. Made from robust plastic, biohazard bags are resistant to punctures and tears, ensuring safe containment of dangerous substances.
Cleanroom requirements are very stringent and have to be met in order for the cleanroom to maintain its ISO classification. Bags for cleanrooms are designed to hold sensitive instruments and medical devices. The production of cleanroom bags requires the use of pure unused resin and not recycled plastics and must meet ISO 9 standards.
Wicketed bags are stacked on a wire wicket and secured with rubber washers or a clipboard header. They feature a 1.5-inch lip and starter notches for ease of use. These bags can include bottom gussets, butterfly vents, perforations, and resealable tape. The wicketed design allows for holding over 200 bags and can be customized to fit specific needs.
Shrink bags are used with shrink wrap machines to securely enclose items. The items are placed in the bag, which is then heated in the machine. The heat causes the bag to shrink tightly around the contents, creating a secure seal. This method is ideal for protecting and preserving sensitive items during storage or shipping.
VCI (Vapor Corrosion Inhibitor) bags are designed to protect ferrous metals from corrosion. These bags are typically clear, allowing for easy inspection of the metal inside. They work by creating a moisture-resistant barrier that prevents exposure to humidity, which can lead to corrosion. Yellow VCI bags are used for ferrous metals like iron, steel, and cast iron, while blue and clear VCI bags are intended for non-ferrous metals such as aluminum, copper, and brass. Metal parts stored in VCI bags remain dry and free from corrosion.
Content for a tamper evident bag is loaded at the bottom and heat sealed. Once the contents are inserted, the bag can only be opened by cutting or tearing a perforated tear strip. The purpose of tamper evident bags is to ensure the security of the contents and show someone receiving the bag whether it has been opened.
In recent years, plastic bags have faced significant criticism, prompting several countries and states to introduce legislation aimed at their reduction. Currently, the focus is on enhancing recycling efforts and minimizing plastic bag disposal in landfills.
Legislative measures have been implemented to decrease the prevalence of plastic bags in retail environments. These regulations aim to mitigate their environmental impact on oceans, rivers, lakes, forests, and wildlife habitats, while also easing the burden on waste management systems and landfills.
Proposed measures include broad recycling initiatives, outright bans, or bans with associated fees to deter the use of plastic bags.
Out of all 50 states, 18 have implemented legislation aimed at reducing or banning plastic bags, with California, Maine, and Delaware having the most stringent regulations. The accompanying graphic highlights states with strict legislation and bans, as well as those that have yet to take action.
In 2019 alone, over 95 pieces of legislation were introduced across various states to regulate and manage plastic bag use.
Most of these legislative efforts focus primarily on promoting recycling as a key environmental strategy.
In addition to state-level regulations, several cities have implemented their own bans or fees related to plastic bags. Notable examples include Boston, Chicago, Los Angeles, San Francisco, Seattle, Boulder (CO), Montgomery County (MD), New York City, Portland (MA), and Washington, D.C.
A customized plastic bag, poly bag, or pouch is a container made of thin, flexible plastic film, nonwoven fabric, or plastic textile tailored to meet a product's particular requirements. Chemicals, food, powders, ice, periodicals, and...
A mattress bag is a heavy duty plastic bag designed to protect a mattress from the elements, dirt, dust, moisture, damage, and debris. They come in a variety of sizes and shapes to meet the needs of any size mattress...
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...
Pallets are covered and protected with plastic pallet covers, commonly known as PPC, which are enormous gusseted poly bags used for storage and shipment. Pallets are found in storage facilities, shipyards, local businesses, warehouses, or...
A poly bag is a common shipping and packaging resource made of polymer material that is exceptionally durable, pliable, and customizable to fit any application. Made of polyethylene or polystyrene materials, poly bags are a precisely...
A plastic bag is a thin, flexible pouch made from plastic film, non-woven fabric, or plastic textiles. Also known as polybags or pouches, plastic bags are used for a variety of purposes, including containing and...
Evidence bags that cannot be tampered with are essential parts of any crime scene. These evidence bags are made of heavy-duty, leak-proof polyethylene that is tear- and puncture-resistant. They also have a very strong, sticky closing...
Pressure-sensitive adhesive tapes consist of a backing material film coated with an adhesive intended for relatively low-stress applications. Light pressure, usually done by the fingertips, is applied to initiate the binding. In the sticking process, the fluid properties...
A cardboard box is a shipping container made of thick heavy duty paper known as paperboard, which is more than 0.01 inch or 0.25 mm thick. The term cardboard is used as a generic descriptor for various types of solid firm papers used to produce boxes
Carpet tape is a double-sided tape designed for securing carpets or rugs to the floor. It's made of strong, durable, and adhesive material that can hold the carpet in place and prevent it from sliding or wrinkling. Carpet tape is used in
A corrugated box is a disposable container whose sides are made up of layers of material that include an inside layer, outer layer, and middle layer. The middle layer, between the outer and inner layers, is fluted, which are rigid wave shaped arches that provide cushioning...
One kind of pressure-sensitive self-adhesive tape is foam tape. It has one of several different backing materials and is made of foam. It may have adhesive on one or both sides. Foam tapes are, at their most basic level, tapes that are applied to uneven or
A mailing tube is a sturdy, solid, and durable cardboard container designed for shipping long slender devices and products or rolled up maps, banners, and posters. The indestructible exterior of mailing tubes...
Masking tape is pressure sensitive, thin and very adhesive, easy to tear paper that is used in various tasks ranging from masking off areas that are not to be painted or as insulation for electric wires among other...
Paper tubes consist of paper or paperboard sheet layers wound together to form strong, hollow, and usually cylindrical shapes. The paper layers are laminated or bonded together using adhesives. The wall thickness of the tube can vary depending on the number of layers wrapped during manufacturing...
A poster tube is a cylindrical, triangular, or rectangular hollow prism that is commonly used to transport rollable, unframed art, important documents, or long and slender materials. They also carry objects like...
PTFE stands for polytetrafluoroethylene and is a synthetic fluoropolymer used widely in many industries and many other applications. PTFE is also commonly referred to as thread seal tape, teflon tape, and plumber‘s tape...
A shipping tube is a long container used for mailing long items that are rolled or folded to fit in the tube. They are constructed of various types of materials with Kraft paper being the most common and widely...
A Sonotube® is a cardboard concrete forming tube made of waxed paper or lamination that is wound into a tube into which concrete is poured to create supports, columns, and supports for posts. Sonotube® is a registered trademark owned by SPC RESOURCES, INC...
A tape and label core is a thick durable tube that forms the center of a label or tape roll with the same shape as that of a toilet paper or paper towel core but is sturdier and more resilient. Although the shape of tape and...