Polypropylene Injection Molding we simple say PP injection molding, compare to Polypropylene, PP is easier to say, 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 its monomer. It was discovered by Italian scientist back in the 1950’s

Polypropylene (PP) is a thermoplastic polymer that is widely used in a variety of applications. It has the following characteristics;

  1. Lightweight: PP has a low density, making it a lightweight material that is easy to handle and transport.
  2. High strength: PP is a strong and durable material that can withstand impact and wear.
  3. Flexible: PP is a flexible material that can be bent and shaped without breaking.
  4. Resistant to chemicals and solvents: PP is resistant to many chemicals and solvents, making it suitable for use in harsh environments.
  5. Resistant to moisture: PP is resistant to moisture and can be used in damp or wet environments.
  6. Resistant to high temperatures: PP can withstand temperatures up to 150°C (302°F) which makes it suitable for many industrial applications.
  7. Good electrical insulation: PP is a good electrical insulator and can be used in electrical equipment.
  8. Good fatigue resistance: PP has good fatigue resistance and can be used in applications that require repeated bending or flexing.
  9. Good dimensional stability: PP has good dimensional stability and maintains its shape over time.
  10. Recyclable: PP is a recyclable material, which is beneficial for the environment.
  11. Low flammability: PP has a low flammability and will self-extinguish when exposed to a flame.
  12. Good chemical resistance: PP is resistant to many chemicals, including acids, bases and organic solvents.
  13. Good UV resistance: PP can add some UV resistance agent so that will have very good UV resistance, making it suitable for outdoor use.

Applications PP plastic injection molding parts

There are many goods that can be produced using PP plastic injection molded parts, some examples include:

  1. Automotive parts: PP is often used to make parts for automobiles such as battery trays, interior trim, and door panels.
  2. Household goods: PP is a popular material for manufacturing household goods such as storage containers, laundry baskets, and kitchenware.
  3. Medical equipment: PP is commonly used in the medical field for parts such as syringe barrels, test tube holders, and medical trays.
  4. Industrial components: PP is used to make a wide range of industrial components such as gears, bearings, and valves.
  5. Packaging materials: PP is used to make a variety of packaging materials such as bottles, jars, and cups.
  6. Electrical equipment: PP is used to make parts for electrical equipment such as switches, connectors, and circuit breakers.
  7. Furniture: PP is used to make furniture such as office chairs, tables, and storage cabinets.
  8. Toys: PP is a popular material for manufacturing toys such as action figures, dolls, and building blocks.
  9. Consumer electronics: PP is used to make parts for consumer electronics such as phone cases, laptop covers, and tablet covers.
  10. Agriculture equipment: PP is used to make parts for agriculture equipment such as gears, bearings, and valves.
  11. Logistics equipment: PP is used to make parts for logistics equipment such as pallets, crates, and containers.
  12. Sports equipment: PP is used to make parts for sports equipment such as helmet, racket, and other sports related gears.
  13. Textile: PP is used to make parts for textile industry such as gears, bearings, and valves.PP injection molding


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. The process can be used to produce a wide variety of parts, including containers, automotive components, medical devices, and toys. Injection molding is a fast and efficient way to produce large quantities of identical plastic parts with tight tolerances.

Polypropylene injection molding, therefore, is the injection of molten polypropylene into a plastic 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.



  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 of 25 degrees more than the molding temperature.


There are several advantages of using PP plastic injection molding for manufacturing plastic parts:

  1. High production efficiency: Injection molding allows for high-volume production of identical parts in a short amount of time.
  2. Cost-effective:
  3. Compare to PC, PA or ABS injection moulding, PP injection molding parts are less cost, that is another reason why most of them use PP injection molding parts.
  4. Versatility: PP is a versatile material that can be used in a wide variety of applications, and injection molding can produce parts in a wide range of shapes and sizes.
  5. High dimensional accuracy: Injection molding allows for tight tolerances and high dimensional accuracy, which is important for parts that need to fit together or function properly.
  6. Good surface finish: Injection molding can produce parts with a smooth surface finish that requires minimal post-processing.
  7. Good chemical resistance: PP is resistant to many chemicals and solvents, making it suitable for use in harsh environments.
  8. Good impact resistance: PP is a strong and durable material that can withstand impact and wear.
  9. Lightweight: PP is a lightweight material which is easy to handle and transport, making it suitable for a variety of applications.
  10. Recyclable: PP is a recyclable material, which is beneficial for the environment.
  11. Good thermal resistance: PP can be used at high temperatures which makes it suitable for many industrial applications.


While PP injection molding has many advantages, there are also some disadvantages to consider:

  1. High initial investment: Injection molding equipment and tooling can be expensive, especially for complex or large parts, once you need injection molding service, find a molding supplier will be better option.
  2. Limited to specific shapes and sizes: Injection molding is best suited for parts with simple geometries and uniform wall thicknesses.
  3. Limited to thermoplastic materials: Injection molding can only be used with thermoplastic materials, which limits the types of materials that can be used.
  4. Material waste: Some material is wasted during the injection molding process, especially during the start-up and shut-down of production runs.
  5. Long lead time: The lead time for making the mold and tooling can take up to several weeks or even months.
  6. Not suitable for small production runs: Injection molding is not cost-effective for small production runs no matter you work with PP or other plastics injection molding parts.
  7. High energy consumption: The process requires high energy consumption, which can increase production costs.
  8. Quality control: Quality control issues can arise if the parts are not produced under the right conditions, such as temperature and pressure.
  9. Surface finish limitations: Injection molding may produce parts with surface finish limitations, especially on highly detailed or textured parts.
  10. Some shrinkage: The injection molding process can cause some shrinkage of the parts, which can affect the dimensions and fit of the final product, PP plastic injection molded parts is much more easy to have sink marks comparing to other materials.

Dongguan Sincere Tech Co., Ltd. is a professional plastic mold/molding company, offer custom injection molding service to worldwide, material we can work including, PP, PC, PA66, ABS, PMMA, PPSU, PPS, ASA, TPE, TPU, PET, PS, etc,

If you have a project that needs custom plastic injection molding service, you are welcome to contact us, we will send you the best price and save your 40% mold cost.