Plastic Bottles

Plastic Bottles

Chapter 1: Plastic Bottles and their Types of Manufacturing Techniques

This chapter will discuss what plastic bottles are and the types of manufacturing techniques.

What are Plastic Bottles?

Plastic bottles are bottles made of high or low-density plastic, such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polycarbonate (PC), or polyvinyl chloride (PVC). Each of the materials mentioned has a distinct function, which includes:

  • PET: a type of plastic that may be used to carry water and refreshments on the go.
  • PE: a stiff plastic bottle material that is also used to make squeeze bottles.
  • PP: a plastic that is used to make pharmaceutical bottles (pills)
  • PC: a material that is used to create refillable and reusable containers.
  • PVC: a durable material used for products that require long-term storage

Types of Manufacturing Techniques for Plastic Bottles

Apart from the general blow molding, other techniques bring about the formation of bottles like reheat and blow molding, co-extrusion blow molding, and injection molding.

These techniques will be detailed below:

Co-Extrusion Blow Molding

Multi-layered bottles are produced through co-extrusion blow molding. The layers are extruded together in the parison and fused into the final bottle. The Co-extrusion technique can be used to accomplish cosmetic effects such as adding soft-touch matte without needing an additional spraying procedure or preserving PCR on the outside layer of the bottle while using virgin material on the inside to safeguard the formula. This method can also be used to extend the barrier qualities of bottles in the same manner that it is used for tubes.


Extrusion Blow Molding

The parison forms vertically in the extrusion blow molding process. The wall thickness is controlled by adjusting the orifice size through which the parison extrudes. It then closes the mold over the parison as it hangs and transfers it to the blow molding station. This is where the bottle is made, as previously highlighted in the second phase of the RBM process. The problem of non-uniformity of the hanging parison is solved by varying the wall thickness. The weight of the formed portion would otherwise extend the hot and still-forming area above it. As the parison forms, the wall thickness increases to achieve a consistent thickness across the formation.

Injection Molding

Injection-molded bottles are uncommon, although the technique may be utilized to mold a particular purpose when extremely tight tolerances are necessary. Plastic is pumped into a closed mold between the cavity and core inserts during injection molding. The part cools as the pressure pulls the plastic into the hollow. The mold opens, releasing the final portion. Ejecting the part from the injection mold would require too much labor and expenditure for a narrow-mouthed container, such as a bottle. This is why injection-molded bottles are uncommon, and blown bottles are more common. If the wall is straight, or if the application requires threading on both the inside and outside of the neck, an injection molded "bottle" could be possible.

Reheat and Blow Molding

This procedure consists of two steps of the standard Reheat and Blow Machine (RBM) bottle production process.

  1. Injection Blow Molding

For the manufacture of hollow plastic products, the injection blow molding (IBM) process is employed. Injection blow molding is a three-stage process. Melted plastic is pumped into a mold cavity to create a preform parison during the first stage. The preform is formed like a test tube, but it has a molded screw finish on top. The preform is subsequently sent to the second stage of blow molding. To inflate a preform against a cold mold chamber, the air is pumped through a core pin. After that, the container is moved to the third station for ejection.


Processes can be executed in two ways i.e. one-step injection molding process; and two-step injection molding process. These happen when:

  • Melted polymer is initially injected into the final shape of a cold mold container. It is then released, resulting in a one-step injection molding process.
  • At the first stage, the melted plastic is injected into a mold, producing a preform. The cold preform is then transferred to another machine, enclosed in a mold, heated, stretched with a pin to the necessary length, and blown into the proper mold shape. This is called a two-step injection molding process.
  1. Stretch Blow Molding

The injection blow molding process serves as the foundation for stretch blow molding. This involves molding a preformed parison before transferring it to a blow molding chamber. To orient and align the molecules, the parison is stretched biaxially during blow molding. The container's gas barrier, stiffness, clarity, and impact strength are all improved because of this orientation. Containers can thus be lighter as a result. PET and polypropylene are examples of stretch blow molding resins.


Chapter 2: Plastic Bottle Design

As previously mentioned, plastic bottles are often composed of four materials: PET, PP, PC, and PE, which are sometimes known as Low-Density Polythene (LDPE) or High-Density Polythene (HDPE).

  • HDPE is the most common plastic used in bottle manufacturing. They are manufactured using either injection or extrusion blow molding.
V1-HDPE Plastic


The material is cost-effective, impact-resistant, and compatible with a wide range of chemicals, including acids and caustics (corrosive elements that bind compounds). It has good moisture insulative properties. It is typically offered in FDA-approved food grade. Aromatic hydrocarbons are incompatible with HDPE. It is also suitable for milk bottles and liquid cleaning product bottles. HDPE is naturally transparent and flexible. When color is added to HDPE, it becomes opaque, which adds weight to the bottle and makes it more rigid. While HDPE offers excellent protection at temperatures over the freezing point, it cannot be used with goods that are filled at temperatures above 70 degrees.

  • LDPE plastic has a comparable appearance and properties to HDPE; however, it is less rigid and generally less chemically resistant. The primary application of LDPE is compression. Although LDPE is more expensive than HDPE, when made in color or natural, it produces a shiny bottle. Because LDPE is amorphous and HDPE is crystalline, LDPE has more flexibility and HDPE has more firmness. Polyethylene is costlier than polypropylene, which is the most affordable thermoplastic, even though the two have many applications in common.

The following section will go through each of these five materials in depth.

PET: Polyethylene Terephthalate

By reacting petroleum hydrocarbons with ethylene glycol and terephthalic acid, a thermoplastic polymer is created. The polymer might be opaque or transparent depending on the particular material makeup. Polymerization is used in the production process, which results in long molecular chains that can later be used to build PET bottles.


During polymerization, two types of contaminants are typically formed i.e. diethylene glycol and acetaldehyde. Although diethylene glycol is normally not created in sufficient quantities to harm PET, acetaldehyde can be produced during polymerization and during the bottle production process. A high concentration of acetaldehyde in PET used during bottle manufacturing might give the beverage inside an off taste. After the plastic has been created, the PET bottle production stage begins. To verify that the plastic is safe for usage, many post-manufacturing tests are performed. These tests confirm that the bottles are not permeable to carbon dioxide, especially in the case of soda bottles. Shatter resistance, transparency, thickness, gloss, and pressure resistance of the PETs should be monitored.

PP: Polypropylene

Polypropylene resin is a low-density polymer that is usually opaque and has good thermoforming and injection molding properties. It competes largely with polyethylene for bottle applications and can be made transparent for see-through uses, whereas polyethylene can only be made translucent. Polypropylene cannot compete with the optical purity of polymers like polycarbonate, yet it performs admirably.


It is ideal for extrusion and molding applications such as blow molding due to its low viscosity at melt temperatures. Although PP has great chemical resistance, it has poor impact resistance at low temperatures. At low temperatures, oriented PP has higher impact resistance. The PP is generally colored and has a lustrous surface.

PC: Polycarbonate

Polycarbonates are synthesized by polymerizing bisphenol A (C15H16O2) and phosgene (COCl2). Because it is more expensive than other bottle-making polymers, it is generally used in high-end reusable bottles such as nursing bottles or those found on water coolers or in lab settings.


The material has exceptional optical qualities and strength, making it appropriate for bottles that display their contents with the transparency of glass but must also withstand repeated and occasionally severe handling. The material is autoclavable, and unlike the preceding materials, this one is sterilizable. It is excellent for the use of reusable bottles due to its high quality and low cost. It is the preferred material for baby bottles. It is used for milk packaging in countries like Germany and Austria. They are durable, which huge retailers would highly regard as less risk, less loss. It should be mentioned, however, that BPA, an ingredient of polycarbonate and a byproduct of its polymerization, is suspected to be harmful.

PS: Polystyrene

Polystyrene plastic is a transparent thermoplastic that can be found as both a solid plastic and a rigid foam material. Polystyrene plastic is typically used in a variety of consumer products, especially for commercial packaging. A well-known polystyrene foam product “styrofoam” has been invented in the industry. The material is controversial amongst environmental groups due to it being slow to biodegrade and is increasingly present as outdoor litter (particularly in the form of foam floating in waterways and the ocean). The solid plastic form of polystyrene is commonly used in medical device applications like test tubes or in everyday items like smoke detector housing and often in food containers. Polystyrene foam is used most often as a packing material.


Styrofoam is also used for disposable tableware from many restaurants. Polystyrene is very inert and thus would not easily react with either acidic or basic solutions. Thus, polystyrene can last long in the natural environment posing as a litter hazard. One of the disadvantages is that the material is usually thrown away after only being used for a brief time. However, Polystyrene can rapidly dissolve when exposed to chlorinated substances or other hydrocarbon substances.

PVC: Polyvinyl Chloride

One of the most widely utilized thermoplastic polymers globally is Polyvinyl Chloride (PVC), next to only a few more widely used plastics like PET and PP. It is a naturally white and exceedingly brittle plastic. PVC is manufactured in two primary forms, which are:

  • rigid polymer (rPVC) or unplasticized polymer (uPVC), and
  • flexible plastic.

PVC is distinguished by its stiff yet brittle structure in its most basic form. Rigid PVC can be used in a variety of industries, including plumbing, sewage, and agriculture. Due to the use of plasticizers such as phthalates, flexible, plasticized, or standard PVC is softer and more bendable than uPVC (e.g., diisononyl phthalate or DINP). Flexible PVC has been used in construction as an insulator on electrical lines or in flooring residences, clinics, educational institutions, and other areas where a hygienic environment is essential. In some circumstances, PVC can be a good substitute for rubber. Rigid PVC, usually known as "vinyl," is used in construction as a pipe for plumbing and siding. The "schedule" of PVC pipe is a term that is frequently used (e.g., Schedule 40 or Schedule 80). Wall thickness, pressure rating, and color are all significant changes across the schedules.


The following are some of the most important features of Polyvinyl Chloride (PVC):

  • It has a high density in contrast to other polymers
  • Economically, PVC is widely available and inexpensive
  • Another advantage is its high durability
  • Sturdy PVC has high strength and stiffness

PVC, in both its rigid and flexible form, can be applied in a variety of sectors. Rigid PVC has a high density, making it very rigid and robust. It is also widely available and inexpensive, which, when paired with the long-lasting properties of most plastics, makes it an obvious choice for many industrial applications such as a building. PVC is a highly durable and lightweight material that is ideal for construction, plumbing, and other industrial applications. Furthermore, the material's high chlorine content makes it fire-resistant, which is why it has become so popular in a variety of industries. Although PVC provides numerous benefits that make it a desirable material to deal with, there are still some considerations to take. When utilizing PVC, the following disadvantages persist:

  • The thermal stability of polyvinyl chloride is low.
  • PVC releases poisonous gases when exposed to or melted in fire. Often, chemicals that can stabilize PVC at extreme temperatures are added during production.

Chapter 3: Applications and Advantages of Plastic Bottles

Plastic as a material is used across multiple sectors, and so are plastic bottles. Plastic bottles are mainly used in packaging products such as:

  • Water
  • Cooking oil
  • Soft beverages
  • Milk
  • Ink
  • Shampoo
  • And many more…

These can be sized in bottles ranging from extremely small to extremely big carboys.

Advantages of Plastic Bottles

As much as the use of plastic bottles across industries may have its own disadvantages, like the need to use large amounts of fossil fuels in manufacturing, the numerous benefits outweigh the drawbacks. It is advantageous because of attributes such as:

Reusable Material

PET, including other bottle material types, are easily recycled after their initial usage. They can be remade into a variety of secondary goods. Some beverage bottles and nonfood containers are also made from recycled plastic. Plastic bottles' small weight reduces the cost of transporting recyclables to recycling centers.


Colors and Shapes

Plastic products are easy to shape into a variety of bottle forms, which improves their appearance and usefulness. Some varieties of plastic bottles, for example, include inbuilt handles, measuring indications, and pouring lips. Furthermore, plastics can range from clear to any shade or color, whether translucent or opaque. This makes products and branding easily identifiable by sight. Thus, plastic bottles do not need painting since the coloring substance is mixed into the plastic resin. It is not prone to rub or wash off.


Savings on Energy

Plastic bottles are lighter than glass bottles, which saves energy and money when shipping products. Plastic bottles require less energy to produce than glass bottles because plastics are soft and have relatively low melting temperatures.

Tough and Secure

Unlike glass containers, plastic bottles are robust and sturdy. When dropped, they do not shatter into sharp fragments. This makes products and packaging safe to handle. Plastics have important physical features such as toughness and chemical resistance because they are polymers (large molecules formed by connecting numerous small molecules). Bottles and containers made from plastic are impervious to leaks and bursts, preserving both the contents and the outer transportation containers.

Chapter 4: Recycling of Plastic Bottles

As much as plastic bottles can have a variety of attributes, such as being compact and easy to grip yet sturdy and difficult to break, their after-use needs to be addressed. How they get disposed of, reused, or recycled has a significant impact on the environment and cost-saving.


The Danger of Plastic Bottles to the Environment

Throughout the world today, over 60 million water bottles are discarded every day, and it can take up to 700 years for a single plastic bottle to biodegrade. These bottles clog up landfills and need landfill space to bury the non-recyclable waste. Plastic waste has various negative consequences for the ecosystem. As plastic degrades, toxins are released into the water and air, posing a health risk to humans, plants, and animals. To address these issues, individuals have collaborated to create a procedure for recycling plastic bottles and converting them into other useful goods such as clothing, furniture, fences, and new plastic bottles, bags, and containers.


The Process of Recycling Plastic

Recycling is divided into numerous phases. Bottles must be collected from homes, businesses, and other sites first. The plastic bottles must then be separated from the metal, glass, and other objects that people discard in recycling bins. Plastic bottles are also classed based on the type of plastic used to make them. Following that, any food, drink, or chemical residue in the bottles is removed.


Furthermore, the bottles are pulverized into flakes and shredded. They are then melted and formed into small pellets about the size of a grain of rice. The pellets are packaged and sold to companies that can melt them down and transform them into a variety of goods. When considered, many of the plastic toys, tools, electronic devices, and other plastic goods are made from recycled plastic.

Why to Recycle

There are numerous reasons why plastic bottles should be recycled. For starters, recycling minimizes pollution caused by the chemicals used to manufacture these bottles. Recycling also reduces the amount of rubbish sent into landfills, allowing the garbage to take up less space.

The bulk of the waste is disposed of in landfills. It could need up to 500 years to disintegrate and decompose but could leach pollutants into the water and soil. Around 165 million tons of plastic rubbish lies floating in the oceans, posing a health and safety threat to marine life.

Micro-plastics are minuscule particles smaller than five millimeters in length produced from cosmetics, fabrics, or the breakdown of larger pieces that can be eaten by marine wildlife. They also contribute an additional 8.8 million tons to the oceans each year. Recycling also employs people who collect recyclable items and work in facilities that convert them into new materials. Recycling is important for both the economy and the environment, and it is easy to do.

Why Can’t All Plastics be Recycled?

Plastic has become widely used due to its inexpensive cost and ability to be manufactured with a wide range of properties. Only a small part of the plastic rubbish is recycled since there are various varieties of plastic with different chemical compositions, and recycled plastics might be polluted by mixing types. Paper and ink, for example, contaminate plastic waste.

Plastic is manufactured by combining smaller molecules into a big chain-like molecule, frequently with extra components added to give it specific properties, from petroleum or natural gas. It is time-consuming to separate many of the plastics from other recyclables, as well as differentiating the different plastic types from one another. There has been no simple solution to this so far. Some, like phthalates and bisphenol A, are potentially harmful to one's health.


Plastic production accounts for 4% of global oil production, both as High-Density raw material and as an energy source in the manufacturing process. These polymers contain fossil fuel energy and have a higher energy value than coal and wood. Dumping so many of them in Landfills is not only a waste of a valuable resource that could be used to generate electricity, heat, or fuel, but it is also a waste of a valuable resource.

Plastics are strong but lightweight, resistant to chemical, UV, bacterial degradation, and thermal and electrically conducting.

What the Chasing Arrows Symbols Mean

A chasing arrows symbol, or resin code, does not necessarily mean that a plastic container is recyclable. Most plastic containers are marked with the chasing arrows symbol number one through seven in the center.


The chemical compound used to create that plastic container is indicated by the number inside the arrows. The sign, unfortunately, does not imply that the plastic container can be recycled.

Inside the chasing arrow symbols, there are seven resin codes. These are:

  1. PET (Polyethylene Terephthalate) is in pop and water bottles. This can be recycled.
  2. HDPE (High Density Polyethylene) is an opaque plastic that is commonly seen in bottles containing laundry detergent and milk. Most of them can be recycled.
  3. PVC (Polyvinyl Chloride) is found in plastic pipes, shrink wrap.
  4. LDPE (Low-Density Polyethylene) is found in plastic wrap, produce bags, and plastic bags.
  5. PP (Polypropylene) can be used to make yogurt tubs and ketchup bottles.
  6. PS (Polystyrene) is present in egg boxes made of Styrofoam.
  7. Other is a group that comprises food containers (clamshells), polycarbonate used in sports bottles, and bio-based plastic used in compostable food containers, among other resins.

How Plastic of Each Resin Code is Handled

Most cities collect type 1 and 2 plastics, as well as PET and HDPE resin bottles. These are created from a blow-molding procedure. The remaining plastics numbered 3 through 7, which are created using an injection molding or stamp molding technique, contain additives. These plastics, which require distinct recycling procedures and a different end market, are not commonly collected.

The markets for plastics with numbers 1 and 2 are stable and plentiful. At this time, the markets for the other plastics are sporadic and inconsistent. For those markets, it is cheaper and easier to start with new plastic than gathering enough of the correct type (right color, no additives, no inks, and so on) than starting with recycled plastic. Plastics numbered 3 through 7 are frequently collected at the curb and must be removed at a recycling center, which is expensive, and disposed of somewhere. It is significantly easier and less expensive for residents to reuse or properly dispose of these containers.

How Residents can Help

To reduce trash and make room in the recycling trucks, residents can flatten plastic bottles. Residents can also assist by utilizing reusable containers, choosing products with fewer packaging, shopping in bulk, purchasing products made from post-consumer recycled materials. This goes along with only recycling resin numbers 1 and number 2 plastics (bottles) with the other recyclable materials in the recycling bins.

Reduced usage of plastics, as well as reuse and recycling whenever possible, remain the greatest solutions for the plastic problem. More rules that prohibit the use of plastic bags, impose bottle deposits, and boost recycling would be beneficial. However, millions of tons of plastic waste remain in landfills across the country. Technologies that can use this waste as a resource can help to clean up the environment, reduce the reliance on oil, reduce the use of non-renewable natural materials, reduce greenhouse gas emissions, and produce energy.


Plastic bottles are bottles made of high or low-density plastic, such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polycarbonate (PC), or polyvinyl chloride (PVC). Each of the materials mentioned has a distinct function, which includes:

  • PET: a type of plastic that may be used to carry water and refreshments on the go.
  • PE: a stiff plastic bottle material that is also used to make squeeze bottles.
  • PP: a plastic that is used to make pharmaceutical bottles (pills)
  • PC: a material that is used to create refillable and reusable containers.
  • PVC: a durable material used for products that require long-term storage

It is essential to align the choice of a plastic bottle with the best suited manufacturing technique. Apart from the general blow molding, other techniques are used to form bottles like reheat and blow molding, co-extrusion blow molding, and injection molding.

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