Everything You Need To Know About Polypropylene Plastic

If you’re looking for a tough, versatile plastic that can be used in a variety of applications, then polypropylene is the material for you. This type of plastic is made from propylene, a hydrocarbon that is derived from natural gas or petroleum. It has many desirable properties, including resistance to heat and chemicals. In this blog post, we will discuss the basics of polypropylene plastic and its many uses!

What is Polypropylene Plastic?

PP Injection Molding

Polypropylene plastic is a type of thermoplastic polymer that is produced by the polymerization of propylene. It is a strong, lightweight material with excellent chemical resistance and a wide range of temperature stability. Polypropylene plastics are also resistant to abrasion, have low water absorption properties, and can be easily colored or formed into any shape.

Property Of Polypropylene Plastic

Polypropylene plastic is renowned for its toughness, stability, and flexibility. It has excellent chemical resistance and is resistant to most acids, bases, and organic solvents. It also has a good dielectric performance and can be molded into any desired shape with ease. Polypropylene plastic also has high impact strength, low permeability to gases and water vapor, and excellent insulating properties. It has a wide range of applications, from medical to engineering.

Property Value
Technical Name Polypropylene (PP)
Chemical Formula (C3H6)n
Appearance Colorless, Odorless, Translucence, Translucent
Melting Point 189 ℃
Injection Mold Temperature 32 - 66 ℃
Heat Deflection emperature 100 ℃
Density 0.89 - 0.91 g/cm³
Tensile Strength 32 MPa
Flexural Strength 41 MPa
Elongation At Yield 8 %
Elongation At Break 70 %
Shore Hardness (D) 72
Specific Gravityh 0.91
Shrink Rate 1.5 - 2.0 %

How Polypropylene Plastic is Made?

Injection molding materials

Polypropylene plastic is produced through a process called polymerization. This is when molecules of propylene are made to “react” with each other, forming chains of polymers. These chains can then be formed into a wide variety of shapes and sizes.

The process methods used to produce polypropylene in the world are mainly divided into the following categories: solvent method, solution method, liquid phase bulk method (including liquid phase gas phase combination), and gas phase bulk method. The characteristics of each process are described as follows:

Solvent Polymerization

The catalyst is dissolved in the solvent, and then propylene monomer is added to it, and a polymerization reaction occurs. The product produced by this method has good dispersibility and uniform particle size distribution.

  • (1) The propylene monomer is dissolved in an inert liquid solvent (such as hexane), solvent polymerization is carried out under the action of the catalyst, and the polymer is suspended in the solvent in a solid granulated state, and the kettle-type stirring reactor is used;
  • (2) There is a deashing and solvent recovery process, the process is long, more complex, equipment investment, and high energy consumption. But the production is easy to control, the product quality is good;
  • (3) Polypropylene particles were separated by centrifugal filtration method and then boiled and dried by air flow and extruded for granulation.

Solution Polymerization:

The solvent is used to dissolve the catalyst, and then the propylene monomer is added to it for polymerization. The advantages are that the product has good dispersibility and uniform particle size distribution, which can save energy consumption in processing.

  • (1) Using high-boiling straight-chain hydrocarbon as a solvent, operating at a temperature higher than the melting point of polypropylene, all the polymer dissolved in the solvent showed homogeneous distribution;
  • (2) High-temperature gas extraction method to vaporize the solvent to obtain molten polypropylene, and then extruded granulation to obtain granulated products;

Liquid phase bulk method:

molding materials

The monomer is heated to a molten state, and the catalyst is added to react with the monomer directly in the reactor. The advantages of this method are that it can obtain high-molecular polypropylene, has low energy consumption, and short processing time.

  • (1) The raw material propylene monomer was heated to a molten state, and the catalyst was added to it;
  • (2) The monomer was polymerized in the reactor, and after its molecular weight reached a predetermined value, it was cooled by circulating water outside the wall of the reaction vessel, and then extruded for granulation.

Gas Phase Bulk Method:

The propylene monomer is heated to a gaseous state, and the catalyst is added for polymerization. This method has low energy consumption.

  • (1) The propylene monomer was heated to a gasified state and fed into the reactor;
  • (2) The catalyst was added, then it reacted with the monomer in a gas-phase reaction, and finally cooled by a circulating water jacket to obtain a polypropylene powder.

The Benefits Of Polypropylene Material

Plastic Molding

Strength: Polypropylene is incredibly durable and strong, making it a great choice for applications that require strength and durability.

Durability: Polypropylene is highly resistant to abrasion, meaning it will not easily tear or wear down over time.

Cost-Effective: Polypropylene material is cost-effective due to its strength and durability.u

Versatility: Polypropylene is highly versatile and can be used in a wide variety of applications, making it an ideal choice for many projects or products.

Resistance to Oils and Acids: Polypropylene material is resistant to oils and acids, making it perfect for containers that need to hold liquids or powders.

Fatigue resistance: Polypropylene is highly resistant to fatigue, meaning it can withstand repeated stress without breaking down over time.

Recyclable: Polypropylene is an eco-friendly material as it can be recycled, helping to reduce your environmental impact.

Polypropylene Processing

Injection Molding Polypropylene:

PP Materials

Polypropylene is a very useful plastic for injection molding and is typically available for this purpose in the form of pellets. Polypropylene is easy to mold despite its semi-crystalline nature, and it flows very well because of its low melt viscosity.

CNC Machining Polypropylene:

PP CNC Machining

CNC machining is an efficient and precise way to cut polypropylene parts. It can be used on a variety of materials, including polypropylene. CNC machines are highly accurate and able to create intricate designs with minimal waste.

Blow Molding Polypropylene:

PP Molding Parts

Blow molding is a process used to create hollow shapes from polypropylene material. The process involves inflating molten polypropylene into a mold, and then cooling it until solidified. This method is often used to create large objects like bottles, buckets, or jugs.

Vacuum Forming Polypropylene:

Vacuum forming is a process used to shape polypropylene material into desired shapes. It involves heating the plastic until it is soft and then using vacuum pressure to form it into the desired shape. The benefits of this process include speed, accuracy, and cost-effectiveness.

Applications Of Polypropylene Plastic

Polypropylene is a versatile plastic that can be used in many industries and applications. It can be used to make packaging, textiles, home goods, automotive components, the construction Industry, medical equipment, and much more.


Polypropylene is often used in food packaging as it is lightweight yet durable and able to keep food items safe and fresh. It can also be used to make bottles, jars, tubs, and other containers for storing liquids or powders. Its ability to resist oils, acids, and solvents makes it perfect for holding potentially hazardous materials.


Polypropylene is also used in the textile industry due to its durability, strength, and resistance to abrasion. It is often used to make carpets, rugs, synthetic leather, and clothing items. Polypropylene fabrics are lightweight, breathable, and quick-drying – perfect for activewear or outdoor activities. They can also be dyed or printed in a variety of colors and patterns.

Home Goods:

Polypropylene is ideal for home goods such as furniture, food containers, plastic bottles, curtains, window treatments, storage containers, and more. It is strong enough to hold up to daily wear and tear but soft enough to be comfortable. Polypropylene is also resistant to staining caused by oils or dirt, making it an ideal choice for busy households.

Automotive Components:

Polypropylene has good mechanical properties, and it can be directly manufactured or modified to manufacture various mechanical equipment parts, such as manufacturing industrial pipes, agricultural water pipes, motor fans, infrastructure templates, etc. Modified polypropylene can be molded into the bumper, scratch strip, car steering wheel, dashboard, and interior decoration, greatly reducing body weight to achieve the purpose of energy saving.

Construction Industry:

Polypropylene fiber is the lightest of all chemical fibers, with high strength, good toughness, good chemical resistance, and microbial resistance and low price, with glass fiber, reinforced modified or with rubber, SBS-modified polypropylene is used in a large number of building templates after foaming polypropylene can be used to make decorative materials.

Electronic Components:

Polypropylene has superior electrical insulation properties, so it is widely used in the manufacture of electronic components such as capacitors and insulating sheets. In addition, its low water absorption rate makes it the ideal material for high-voltage switchgear because it can keep its shape even when exposed to moisture or humidity.

Medical Equipment:

Polypropylene is used to manufacture many medical devices such as stethoscopes, plastic containers, catheters, syringes, surgical instruments, and prostheses due to its strength and durability. Polypropylene can also be sterilized with heat or chemicals, making it ideal for medical applications.

These are just a few of the many applications of polypropylene plastic. With its durability, strength, and versatility, it is sure to be a great choice for any project or product.

Polypropylene Plastic Injection Molding With Aria Manufacturing

Our polypropylene plastic injection molding process uses a heated plastic material that is injected into a custom mold. This process is highly efficient, and cost-effective, and allows us to create complex shapes quickly and with precision. We use advanced techniques such as hot runner systems and multi-component molding to ensure the best possible results for your project needs.

At Aria Manufacturing, we strive to provide you with the highest quality polypropylene plastic injection molding services. Our knowledgeable team is here to help you create the perfect products for your unique application needs. Contact us today to learn more about how our services can benefit you and your project!


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.