From grocery stores to farmer’s markets, you see plastic bags just about everywhere you go. They help us get all our necessities from point A to point B! But have you ever wondered how they’re made?
Plastic bags go through all different processes before they end up in the stores. Let’s take a closer look into how plastic bags are made. It’s not as simple as you’d think!
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What Type of Plastic is Plastic Bags?
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Most plastic bags are made from polyethylene, specifically high-density polyethylene. Tons of small plastic pellets are put under high heat and pressure to liquefy the material before it’s cut, shaped into bags, and printed.
Polyethylene originally starts out as ethylene, which is a type of gas that is present in coal gas, natural gas, and crude oil. When ethylene is combined with a catalyst like benzyl peroxide, the result is the polyethylene material that we use to make plastic bags and other commercial packaging.
How Are Plastic Bags Made?
Plastic bags are made by a process called blown film extrusion. Polyethylene pellets are melted down, blown into a thin material, and manufactured into bags.
Here’s how plastic bags are made:
- Step One: Polyethylene pellets are put into a hopper.
- Step Two: The pellets undergo pressure and heat to liquefy the plastic.
- Step Three: Through a process called blown film extrusion, the liquified plastic is blown upward into a long tube shape.
- Step Four: The plastic tube starts to cool off, and giant rollers flatten the tube into one thin sheet of plastic.
- Step Five: The plastic is cut into its desired width.
- Step Six: Once the plastic is cut, it’s put onto one giant roll of plastic.
- Step Seven: Next, the plastic is printed with an alcohol-based ink.
- Step Eight: The plastic is then formed into its desired bag shape.
- Step Nine: A large punch punctures each bag at the top, which creates the handles.
- Step Ten: The edges of the bag are heat sealed by pressing two identically shaped plastic pieces together.
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Step 1 
Pouring the Plastic
Tons of small polyethylene pellets are put into a giant hopper. The exact amount of pellets added depends on how many bags are being made.
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Step 2 
Melting the Plastic
Once inside the hopper, the polyethylene pellets undergo high heat and pressure. This causes the pellets to melt into a liquid state.
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Step 3 
Blown Film Extrusion
The liquified plastic is blown upward in a giant tube shape through a process called blown film extrusion. This is when liquified plastic is inflated with air, creating a large plastic tube.
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Step 4 
Flattening the Tube
After the plastic tube has cooled, giant rollers compress it into one large sheet of plastic.
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Step 5 
Cutting the Plastic
The plastic is then cut into its desired width by two razors placed on each side of the plastic sheet. The excess plastic is discarded and reused for smaller packaging needs.
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Step 6 
Rolling the Plastic
The plastic sheet is put onto a large roll so it can be easily transported to the next step of the manufacturing process.
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Step 7 
Customizing the Bags
The plastic gets printed with alcohol-based ink. A grocery store, restaurant, or any other business will send in their logo or design. From there, it will get printed on the bags in bulk.
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Step 8 
Shaping the Plastic
The plastic sheets are fed through a mechanical roller that shapes the bottom and sides of the bag with a spinning disc.
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Step 9 
Cutting the Holes
The bag handles are created with a large hole punch. The punch stamps through each layer of plastic so consumers can easily carry their bags.
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Step 10 
Sealing the Bag
Two identically shaped plastic pieces are pressed together, and the edges are heat sealed. This binds the sides of the bag together so items can be put inside!
Which Plastic Bags Are the Strongest?
Plastic bags made from High Density Polyethylene (HDPE) are the strongest. The material is flexible, water-resistant, and strong. In fact, it can hold up to 50 pounds!
Here’s what an average plastic bag can hold:
Textbook + Laptop + A Two-Liter Bottle of Soda
A Bag of Potatoes + Medium-Sized Bag of Dog Food + One Bottle of Wine
3 Gallons of Milk + A Bag of Sugar + A Pineapple
Disclaimer: The information above is for entertainment purposes only. Weight capacity will vary from bag to bag, and proper care should be taken when transporting your own items.
Plastic bags are stronger than they look! While you probably shouldn’t use one to carry your most prized possessions, they’re a simple way to carry around your necessities.
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Where Are Plastic Bags Manufactured?
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Plastic bags are manufactured all over the world, but most locations are in the United States, Australia, and Germany. Since the manufacturing process has many steps and requires industrial equipment, most facilities are rather large.
Most of the manufacturing for plastic bags is automated. Through a series of belts, rollers, and cutting tools, plastic sheets get formed into the bags we know and love for carrying our groceries and other goods. Precision is key when it comes to creating consistent sizes and materials. The best way to ensure a high level of precision is by using automated processes to create the bags. That’s why plastic bags are made by machines and not by hand!
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Can You Print on Plastic Bags?
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You can definitely print on plastic bags! The printing process is typically done by a promotional products distributor or bag manufacturer. Most bag imprints are grocery store logos, catchy phrases, or recognizable slogans.
Advertising with plastic bags can increase brand recall and inspire future purchases. Customers tend to reuse these bags as well, which means your logo continues to get seen over and over again!
Why Did Grocery Stores Switch to Plastic Bags?
Grocery stores switched to plastic bags because they are cheaper than paper bags. Plastic grocery bags also have handles, which makes them easier to carry. Back in the day, paper bags didn’t offer handles. This meant customers couldn’t buy very much as the bags were difficult to carry!
When plastic grocery bags became popular in the United States, it was also believed that they were better for the environment than paper bags. Paper bags required the chopping down of trees, and plastic bags were thought to alleviate the burden on the environment at the time.
What Are the Properties of Plastic Bags?
Plastic bags are convenient for a ton of reasons. Between their flexibility and their strength, they are a great way to carry the items you need to transport from one place to the other!
Here are the properties of plastic bags:
Flexible
Plastic bags are made of a flexible material that allows for some wiggle room. Since the walls of plastic bags aren’t rigid, they can fit all kinds of items!
Strong
On average, plastic bags can hold up to 50 pounds. Strength is what makes plastic bags such a great option for grocery stores. They can fit all kinds of groceries like cartons of orange juice and canned soup!
Water-Resistant
Are you carrying your groceries from your car in a rainstorm? Good thing you’ve got plastic bags! They are naturally water-resistant, which keeps your groceries dry.
Affordable
Plastic bags cost less than paper bags. This makes them a great choice for small business owners who are budget-conscious.
The Bottom Line
No matter which way you spin it, it takes a ton of work to create plastic bags. Luckily, there are all kinds of specialized tools and pieces of equipment out there to make the process efficient. Next time you see a plastic bag, you’ll think about all the steps it took before it reached your hands!
References
How It’s Made Plastic bags [Video file]. (2015, August 5). Retrieved June 1, 2020, from https://www.youtube.com/watch?v=aQ4O8MMDuH8
Monnier, M. (2019, December 31). Shoppers Call on Target to Stop Using Disposable Plastic Shopping Bags. Retrieved June 04, 2020, from,
https://www.apartmenttherapy.com/target-plastic-bag-petition-36701174
Paxton, R. (2019, March 02). How to Make Polyethylene. Retrieved June 04, 2020, from
https://sciencing.com/make-polyethylene-10029798.html
Plastic bag manufacturing process [Video file]. (2016, May 3). Retrieved June 4, 2020, from
https://www.youtube.com/watch?v=oHCF58LJUBg
Polyethylene or Polypropylene Resin Pellets Wholesale. (n.d.). Retrieved June 03, 2020, from
https://plasticpellets4fun.com/pages/polyethylene-or-polypropylene-resin
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