What is the difference between PP and PE film?

Polyethylene and polypropylene are two of the most common plastics used in the food packaging industry. On the surface they seem very similar, however, they each have certain well-defined characteristics and functions. Do you know the difference between them?

Today we are going to look at the characteristics of each of these polymers to help you understand the 5 differences between polypropylene and polyethylene food packaging.

POLYETHYLENE AND POLYPROPYLENE: GENERAL CHARACTERISTICS

When we talked about plastics identification codes, we explained that polyethylene is classified as number 2 – HDPE: High–density polyethylene — and number 4 – LDPE: Low-density polyethylene. Polyethylene is a polymer made of ethylene, and depending on how it polymerises, the properties of polyethylene change.

Polypropylene, however, is classified as number 5 – PP. It is also a plastic polymer, but its monomer is propylene, which is easily produced and has a high degree of purity.

THE DIFFERENCES BETWEEN POLYETHYLENE AND POLYPROPYLENE FOOD PACKAGING

1. CHEMICAL AND HEAT RESISTANCE

• High temperatures: polypropylene withstands high temperatures better than polyethylene. While the first remains in perfect condition between 140ºC and 170ºC, the highest temperature the latter can withstand is between 105ºC and 115ºC
• Low temperatures: in this case, polyethylene is more resistant at low temperatures, maintaining its characteristics as low as -80ºC. Polypropylene only preserves its properties above 0ºC.
• Chemical resistance: in spite of the fact polyethylene has a better resistance to wear and tear, it is polypropylene that stands out for its high resistance to abrasive acids, this being one of the main differences between the two plastics.

2. FLEXIBILITY

Polyethylene is a very elastic material that stretches easily, making it the perfect material for food packaging. Polypropylene  is much less flexible, although it is notably more difficult to break. Depending on the orientation the plastic is given – BOPP or OPP –, it will have a greater or lesser degree of flexibility.

3. LIGHTNESS AND COLOUR

Polypropylene is a much more lightweight material than polyethylene. Regarding colour, in its natural form the first is a translucid white, while polyethylene is colourless. Different industrial extrusion processes are used to develop the best features for the packaging industry, in other words, better transparency, tearability, pierceability, etc.

4. RECYCLABILITY

Polypropylene and polyethylene food packaging is easy to recycle, as both materials are thermoplastics. This means that they melt when exposed to heat processes and can be moulded repeatedly. In the specific case of these two plastics, they can be given a new use after recycling. Polyethylene is the more widely recycled of the two, however.

5.   USES IN FOOD PACKAGING

The different features of both plastics mean their uses as food packaging are often very different. Let’s look at some examples:

• Microwaveable packaging: thanks to its resistance to high temperatures, polypropylene is perfect for microwaveable packaging.
• High hot-tack: food packaging with high hot-tack, or resistance to heat sealing, is perfect for packaging nuts, rice, and sauces. It is principally made of biaxially-oriented polypropylene.
• Polypropylene is a good material to use for heat treatments, such as sterilisation and pasteurisation, as it withstands both treatments perfectly. However, polyethylene can only withstand pasteurisation.

OTHER USES OF POLYPROPYLENE AND POLYETHYLENE

Polyethylene and polypropylene can both be used for purposes other than food packaging:

• Insulation: the special polypropylene film PP FLOC is principally used as insulation for car-interior parts, as well as for doors and windows.
• Plastic bags: polyethylene is one of the most commonly used materials in plastic bags. These may be shopping bags, bin bags, etc.
• Adhesive tape: most adhesive tapes are made from polypropylene because it is particularly strong.
• Toys: high-density polyethylene is commonly used to make children’s toys.
• Storage boxes: stackable plastic storage boxes are generally made from polypropylene because it is tough and resistant to abrasion.
• Agricultural use: greenhouses, geothermal blankets (normally hybrids of PE and PP).

If you would like more information on the different uses of these plastics, please visit our webpage or contact us, we will be happy to answer all your queries!

Polymer plastics are ideal for a wide range of packaging applications because of their barrier qualities, which help keep items fresh, avoid contamination, and extend shelf life. Polymer plastic containers, for example, are especially common in manufacturing facilities. They are large molecules that share standard recurring structural units called monomers. These monomers are covalently linked together to create a polymer.

They have a high molecular weight and are made by a synthesis process known as polymerization. Polymers are classified into two broad categories based on their synthesis processes. Due to other methods, they may be generated if the monomers have double bonds between their carbon atoms. When two monomers are united in various polymerization operations, a tiny molecule such as water is eliminated. These polymers are referred to as condensation polymers. Polymers exhibit considerable differences in physical and chemical characteristics compared to their monomers.

Additionally, their properties may vary based on how many repeating units are in the polymer. Polymers are abundant in nature and play an essential role. Companies use synthetic polymers for various reasons. Polyethylene, polypropylene, PVC, nylon, and Bakelite are the primary examples of synthetic polymers. When synthesizing synthetic polymers, the process must be precise to produce the desired output consistently. Understanding their distinctions and how to utilize them is critical. Thus, you need to understand their differences and appropriate use.

Polyethylene’s Structure and Chemical Properties

Polyethylene is a polymer composed of ethylene molecules consisting of two carbon alkane units [-CH2CH2-]. It is a thermoplastic polymer. The majority of its physical features are molecular weight dependent. The most prevalent varieties are High-Density Polyethylene (HDPE), Medium-Density Polyethylene (MDPE), and Low-Density Polyethylene (LDPE). Additionally, they are well-known for their chemical resistance as they do not react with strong acids or bases upon exposure. Polyethylene is a chemically inert and transparent material which implies that, unlike a transparent material, it allows light to flow through but does not create images.

Co-polymerization of ethylene is possible, but it compromises its purity. However, polyethylene is less susceptible to co-polymerization than other polymers. As a result, ensuring its purity is often more expensive. There have been significant environmental worries about polyethylene because it does not naturally disintegrate unless treated. Nevertheless, other approaches have been devised and are being used to address this problem. Polyethylene is currently produced using sugar cane, wheat grain, and sugar beet to mitigate its impact on the environment.

Applications
Polyethylene is the most common thermoplastic consumer good, with many uses. The following are some of the more frequent applications:

• It is certified for food packaging because of its resistance to water absorption.
• Plastic’s strength and stress resistance are well suited for consumer items such as buckets and bins.
• Due to their high tensile strength, they make excellent packaging materials that are durable and long-lasting.

Polypropylene’s Chemical Properties and Applications

Polypropylene is another thermoplastic polymer that is stiffer than polyethylene. Polypropylene comprises propylene monomer units composed of three-carbon alkane units [–CH2(CH3)CH2]. Due to its rigidity, it is often utilized in manufacturing molded material. Propylene is often copolymerized with ethylene molecules to increase its elasticity. Ethylene propylene rubber, to be precise. Although polypropylene is less transparent than polyethylene, it may be translucent by removing the color.

Polypropylene is also classified according to its molecular weight. However, most polypropylenes have a density in between that of High-Density Polyethylene and that of Low-Density Polyethylene. When exposed to light, it undergoes chain disintegration, resulting in oxidation processes and the formation of free radicals, raising further concerns about health and its safety in the environment.

Uses and Applications
MDI corrugated plastic solutions use polypropylene frequently in making corrugated plastic containers for transport, inter-facility good transfer and warehouse bins for storage. Polypropylene reusable boxes, sheets, hopper bins, custom containers are often used during in-plant storage and stacking, inside hot or cold processing facilities, and while transporting or displaying.

Polypropylene

• Provides convenient stacking & nesting
• Made of food-grade, high-density plastic
• Delivers protection & reduces damage
• Provides reusability & in return cost savings
• Offers moisture control & optional fumigation holes

Polypropylene Pros and Cons

Polypropylene is an excellent injection molding material. Apart from its typical plastic applications, polypropylene excels in fiber applications, which expands its range of applications beyond injection molding to include packaging materials for hopper bins, boxes, sheets, rolls, and custom applications that need rigid dividers. As with any other polymer, polypropylene has several benefits and limitations that make it more appropriate for some applications than others.

Pros

• It’s a less costly material.
• It’s very resistant to moisture.
• It possesses high flexural strength because of its semi-crystalline nature.
• It has good chemical resistance over a wide range of bases and acids.
• It contains good fatigue resistance, thus having a good impact strength.
• It’s resistant to electricity and is, therefore, an excellent electrical insulator.
• It is more easily repaired from damage.

Cons

• Its high thermal expansion coefficient precludes it from being used in high-temperature applications.
• It is photodegradable by ultraviolet light.
• It has a low resistance to chlorinated solvents and aromatics.
• It is difficult to paint due to its weak adhesion capabilities.
• It is very flammable.
• It is susceptible to oxidation.

Despite its flaws, polypropylene is an excellent material. It has a unique combination of characteristics not found in any other material, making it an ideal option for various tasks.

Polyethylene Pros and Cons

Polyethylene is the world’s most widely used plastic to make shopping bags, toys, and shampoo bottles. MDI is an expert at manufacturing and extruding poytheylene to create double and single faced rolls / sheets, trays, totes, bins and boxes.  Polyethylene benefits and cons include the following:

Pros
Polyethylene has several advantages, so it has been used to manufacture various plastic items.

• Polyethylene is durable and water-resistant, making it last longer when exposed to the elements compared to other polymers.
• Although its strength and hardness are low, it is very malleable and has a high impact strength, making it stretch rather than shatter.
• Depending on its, it can be almost transparent to opaque.
• While polyethylene is an excellent electrical insulator, it may get electrostatically charged.
• Its low density makes it suitable for packaging.
• Polyethylene can be recycled into other products.
• Its heat-resistant properties enable it to be used in high and low temperatures.

Cons
Despite its widespread use, polyethylene has a few drawbacks that may dissuade manufacturers and consumers from its utility.

• • It takes a long time to degrade and may remain in landfills for decades.
  • Polyethylene is mainly derived from petroleum or natural gas, with limited resources.
  • Producing polyethylene consumes a significant amount of energy and results in considerable carbon dioxide emissions, a greenhouse gas that contributes to global warming and climate change.
  • The recycling process is complex and may take a long time.

Differences Between Polypropylene and Polyethylene

Polyethylene and polypropylene are plastics composed of polymers. Most polymers may be broken down into discrete components that serve as the polymer’s building blocks; these single units are monomers. Polyethylene’s monomer unit is ethylene, while polypropylene’s monomer unit is propylene. The primary distinction between polyethylene and polypropylene is that polyethylene is produced by polymerizing ethylene monomer units, while polypropylene is produced by polymerizing propylene monomer units.

Which Is the Best Polymer Between Polyethylene and Propylene?

Polyethylene and propylene plastics provide comparable advantages. Along with being very pliable, they are also moderately impact-resistant, which means that strength is not a worry when using these polymers. Additionally, both polymers are heat resistant and have minimal toxicity to people. Their low toxicity is another consideration if you use plastic for food and beverage containers.

Finally, each of these plastics is recyclable, which may be advantageous for environmentally aware businesses involved in producing many temporary things, such as food containers and signage. There are several benefits to utilizing these plastic materials that firms should consider before final selection.

At MDI, we design and customize plastic containers that ensure more efficiency, durability, and cost-saving solutions across various industries and businesses ranging from small firms to fortune 500 companies. Contact us today to make the most use of your money when investing in any plastic.