Polypropylene Injection Molding we simple say PP injection molding, compare to Polypropylene, PP is more easy, Polypropylene is a thermoplastic polymer used in a wide array of applications. It’s produced in a process called chain-growth polymerization, and it is formed from propylene which is it monomer. It was discovered by Italian scientist back in the 1950’s

It has the following characteristics;

  • It has a high melting and boiling point so it is used in the production of microwave containers.
  • It does not react with bases, acids, water or detergents.PP injection molding
  • It’s resistant to cracking and stress even in flexing positions.
  • It’s very durable.

It’s used in the following ways;

  • Making of yoghurt containers
  • Making of medicine bottles.
  • It’s used in plastic films.


Injection moulding on the other hand is the process of producing parts by injecting molten material into a mold. It can be done with the following materials; metal, plastic, glass, confections and elastomers.

Polypropylene injection molding therefore is the injection of molten polypropylene into a mold. The purpose of the molding is to create more complex forms of polypropylene which cannot be made if it was in its original form.

Injection molding is the most modern form of plastic manufacturing despite the fact it was discovered long ago. It’s done by a machine called an Injection Molding Machine.


  • Die casting
  • Metal Injection Molding
  • Thin wall injection molding.
  • Injection molding of liquid silicon rubber.
  • Reaction injection molding.


  1. You first come up with a design you would like developed, this can be done with modern software called CAD (Computer Aided Design), and examples of such software are Solid Works, which is mainly used by Engineers to design their prototypes.
  2. You will then design the mold, molds which can be designed from various materials like steel, aluminum or a beryllium-copper Alloy.
  3. The final stage is the manufacturing process. Which is done by the injection moulding machine and the process is repeated numerous times to come up with thousands if not millions of the final product.

PP injection molding partsThe best temperature for the process of molding to take place is in between a temperature of 450-500F. In order for it to melt it requires a temperature 25 degrees more that the molding temperature.


  1. Due to the high pressure used to mold it, it’s possible to add detailed features to the mold more easily as compared to other materials used in the injection molding process.
  2. Once it’s designed, it can be easily manufactured as compared to other molding materials which require much more work before the manufacturing process making it a highly efficient material for the job.
  3. It has more strength as compared to other materials this is mostly because of the material polypropylene which is very durable.
  4. One can use other types of plastics when manufacturing.
  5. The molding process is done using mechanized robots hence, due to all this automation it has reduced the cost of manufacture.
  6. Compare to PC, PA or ABS injection moulding, PP injection molding is less cost, that is other reason why most of them use PP injection molding parts.


  1. Due to the high melting point of the plastic, it’s very hard to maximize on the molding potential of the material.
  2. The polypropylene is corrosive when exposed to chlorinate solvents hence poses a high risk for the consumers.
  3. It cannot be easily painted hence difficult to improve color design.