What is Polypropylene Material? | Types of PP Material | Fundamental properties of Polypropylene | Advantages | Disadvantages | How To Recycle PP?

What is Polypropylene Material?

Polypropylene, better known as PP, is a crystalline thermoplastic made up of a blend of different polypropylene monomers. It is known for its toughness and rigidness. Being resistant to many external factors makes Polypropylene one of the most used thermoplastics in the plastic manufacturing industry.

PP is broadly utilized in producing many different kinds of products in various industries throughout the world.

People wouldn’t even realize that most of the products they’re using in their day-to-day lives are produced by Polypropylene plastic.

According to a study conducted by Fortune Business Insights, the global polypropylene industry’s size stood at USD 78.22 Billion in 2019 and is projected for profitable growth with reaching USD 105.49 Billion by the year 2027.

Types of PP Material and Their Key Benefits – 

There are two major types of polypropylene available in the global market called Homopolymers and Copolymers.

1. Polypropylene Homopolymer:

It is the most extensively utilized general-purpose grade polypropylene type. It contains a propylene monomer in a semi-crystalline form.

The major applications are seen in textiles, packaging, pipes, healthcare, and electrical industries.

2. Polypropylene Copolymer:

This Polypropylene family is divided into multiple random copolymers and block polymers. The family is created after polymerizing propane and ethane.

Also Read – Compression Molding Process – A Detailed Guide | Thermosets Composite Compression Molding | Types of Compression Molding | Molds Used for Compression Molding | Advantages | Disadvantages | Applications

• Polypropylene Random Copolymer – 

This variation of PP material is produced by polymerizing ethane and propane. The ethane units take about 6% of the total mass, accommodated randomly within the polypropylene chains.

These polymers have fantastic optical clearance and decant flexibility, making them suitable for producing visual products and products requiring significant physical presence.

•  Polypropylene Block Copolymer – 

This polypropylene is more rigid and less fragile compared to the random copolymer. That’s because of the higher ethane content of 5% to 15%. The co-monomer are arranged in regular blocks.

Because of high rigidness, these polymers are highly suitable for heavyweight industries like transportation and logistics.

• Impact Copolymer 
• Expanded Polypropylene
• Polypropylene Terpolymer
• Polypropylene, High Melt Strength 

Impact Copolymer:

Impact copolymer is a combination of Propylene Homopolymer and Propylene Random Copolymer. The ethylene content is super high, at 45% to 65%.

Mainly utilized in manufacturing components requiring tremendous impact resistance. Thus, it is highly suitable and heavily used in automotive and electrical applications.

Expanded Polypropylene:

This PP material has a foam-like structure and appearance with very low density. The foam-like design makes it attractive to produce 3D polymer foam products.

It has an impressive higher strength-to-weight ratio, thermal conductivity, great impact resistance, water, and chemical resistance.

Expanded polypropylene is mainly used in construction, electrical, automobiles, and consumer goods.

Polypropylene Terpolymer:

Polypropylene terpolymer is comprised of 3 chemicals: propylene segments, monomers ethylene, and co-polymer.

It has remarkable transparent properties and reduced crystalline uniformity, making it the right choice for sealing film and related applications.

Polypropylene, High Melt Strength:

It is what it sounds like. This polypropylene material blends melt strength and expandability fantastically. It has good chemical resistance and a slew of excellent mechanical properties, making it quite fitting to produce soft, low-density foams, food packaging, automobile, and construction verticals.

Fundamental Properties of Polypropylene – 

Polypropylene is a low-density, lightweight polymer. In fact, it is one of the lightest commercially available polymers out there. Thus making it suitable for lightweight product applications. Below I have shown the typical properties of polypropylene.

• Homopolymer: 0.904 – 0.908 g/cm³
• Random Copolymer: 0.904 – 0.908 g/cm³
• Impact Copolymer: 0.898 – 0.900 g/cm³
• For homopolymer, the melting goes up to 160 – 165°C. And for Copolymer, it’s 135 – 159°C.
• High flammability is also one of the highlight properties of the PP material.
• Chemical resistance varies for all the chemicals. It provides fantastic resistance with diluted acids, alcohol, and bases—comparatively lower but still good resistance for aliphatic hydrocarbons, ketones, esters, and aldehydes.

Also Read – What is PEEK Material? | Properties of PEEK | Limitations of PEEK | How PEEK is Manufactured? | Applications of PEEK

PP Processing Conditions – 

PP material is one of the most versatile thermoplastic processes to work with. It can be processed with virtually all the methods quite efficiently. First, however, we will discuss Injection and Extrusion molding.

Injection Molding:

Without any doubt, Injection Molding is the most compatible process for polypropylene. Products like Household items, agriculture products, healthcare items, toys, vending machines components, electrical boxes, automotive products, etc.

• First of all, Dying is not important if storage is done well.
• Mold Temp. – 10-80°C
• Melt Temp. – 200-300°C
• Mold shrinkage is mostly present, varying between 1.5 ad 3%. The main factors affecting shrinkage are the processing conditions, polymer physics, and the finality of the part produced.

Extrusion Molding:

Extrusion molding is also well-known for processing polypropylene. The second best after injection molding can be utilized to manufacture products like plastic bottles, containers, household items, wires, pipes, etc.

• Compression Ratio: 3:1
• Melt temperature: 200-300°C
• Cylinder Temperatures: 180-205°C
• (221-230°F) , for regrinding

Advantages of PP material – 

• Water-resistance is one of the key benefits of polypropylene, which makes it impenetrable. A quality that is extremely useful in industrial and medical applications.
• Good fatigue resistance also makes it eligible to be used in many products like live hinging and shampoo lits where in which any sort of bending is not allowed.
• Resistance to biological conditions like retrogression, fungi, algae, and bacteria.
• High electricity resistance is another quite handy benefit of polypropylene as that makes it compatible for manufacturing electrical components.
• Polypropylene is very inexpensive compared to other thermoplastic materials like PET, PS, LDPE.
• PP is completely recyclable, making it even more inexpensive to process without hurting the environment.

How To Recycle PP?

That’s the biggest question of the hour.

The PP recycling begins with getting rid of the contaminants present in the plastic wastage, which needs to recycle. To do that, the plastic material should be melt at 250°C followed by removing residual molecules using vacuum and solidification at 140°C.

The recycled PP will be mixed with 100% virgin PP with a ratio of 50/50. The main challenge faced by Polypropylene recycling is the amount of actually recycled plastic used for making products is very low, as it completely depends on the consumption.

However, it has still been used extensively in manufacturing products as it doesn’t have any huge effect on the environment. The toxicity effect for the material is considerably low.

The main recycled PP applications are brooms, ice scrapers, signals, battery cables, battery cases.

Disadvantages of PP material –

• High flammability
• Suspectable to oxidation
• Below par bonding properties
• Suspectable to UV degradation
• Low resistance to chlorinated solvents and aromatics

Applications of Polypropylene – 

As we’ve already discussed earlier, Polypropylene is a highly used thermoplastic material with various handy material properties. It is widely used in many sectors.

• Automotive Industries 
• Medical Applications 
• Industrial Applications 
• Fibers and Fabrics 
• Consumer Goods 

ALSO READ – What is Injection Molding Wastage? | Remedies to Reduce Plastic Waste

1. Automotive Industries:

Polypropylene’s supreme moldability, resistance to bending, and outstanding mechanical properties like chemical resistance and decent wearability make it perfect for manufacturing automotive parts.

Main Applications include instrumental panels and door trims, fender lines, battery cases, boxes, trays, etc.

2. Medical Applications:

Polypropylene has a huge influence in the medical industry because of its dozens of applications. High chemical and bacterial resistance is the main reason for that immense influence.

Additionally, Medical Grade PP demonstrates decent stream sterilization.

The most common application is medical syringes ( Polyproylene has the leading market share for needles ). Other critical applications include specimen bottles, diagnostic devices, food trays, pans, medical vials, Petri dishes, pill containers, etc.

3. Industrial Applications:

Industrial applications are a major chunk of polypropylene processing. Properties like corrosion resistance and good tensile strength play a key role for PP to be used extensively in industrial applications.

Polypropylene sheets are used to manufacture products like tanks, sheets, pipes, packaging, etc.

4. Fibers and Fabrics:

PP fibers and fabrics are utilized in many products like tapes, strapping, bulk filament, staple fibers, spun-bond, etc.

PP products are also considered fitting for marine applications because of good water resistance.

5. Consumer Goods:

PP materials are often used in the consumer goods sector to manufacture products like Luggage, toys, furniture, etc. It is also used for packaging materials for fruits, veggies, and meats.

History of Polypropylene – 

The story of the origination of polypropylene materials is quite interesting in its own way. The first commercially available polypropylene enzyme was found in 1954 by an Italian chemist named Guilio Natta and his assistant Paolo Chini.

At that time, they were associated with a company named Montecatini Company (now Montedison SpA). They used multiple catalysts invented by another noted German chemist Karl Ziegler for synthesizing polyethylene.

Natta and Zieglar won a global price in chemistry for their invention in the year 1963.

The commercial production of polypropylene was started in 1957 by a Hoechst AG in West Germany (now in Germany).

Commercial production really kicked off in the early 1980s when a more stable version of the material was available in the free market. Japanese Mitsui Petrochemical Industries, Ltd developed it.

The Future of Polypropylene –

Source: MRFR analysis

According to research conducted by a notable research organization called Polaris Research, the global polypropylene market will reach USD 120.11 Billion by 2026.

However, the research was done in 2018, which means before the Covid-19 pandemic stuck and hugely changed our lives. The overall market size will possibly decrease PP and the entire plastics processing industry because of a slowdown in global economic activity.

PP Plastic has major applications in the Agriculture, packaging, and automobile industry, which is said to keep the momentum going. Furthermore, additional incremental revenue can come from the pharma industry, which prefers PP material for packaging applications.

The dominant position for PP processing is held by the Asia-pacific region and will continue to lead the table for a long time.

Final Thoughts – 

Polypropylene material can be extremely crucial for both buyers and manufacturers to improve productivity, save time, boost profits, and doing out bit to save the environment. In addition, the material’s outstanding properties make it easy for manufacturers to make good quality products.

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