Polypropylene Injection Molding

Whether you need durable components or lightweight designs, our polypropylene injection molding services deliver precision, consistency, and quality to meet your production demands.

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Erye Offer Polypropylene Injection Molding Service to Specific to Your Needs!

Polypropylene (PP) is widely used in various industries due to its light weight, durability, and chemical resistance. We offer cost-effective and reliable PP injection molding solutions to meet your high performance and quality standards.

Advanced Molding Capabilities: Precision molding for both simple and complex PP parts.
Custom Material Options: Includes reinforced and impact-modified PP grades.
In-House Tooling: Faster turnaround with optimized mold designs.
Secondary Services: Assembly, surface finishing, and package customization.

Injection Molded Polypropylene Design Guidelines

Polypropylene is relatively easy to mold. But still requires careful consideration of its high flexibility, low density and checmical resistance. Below are key design recommendations to optimize performance and manufacturability.

Item	Description
Wall Thickness	Maintain uniform wall thickness to prevent warping and sink marks. Typical range is 0.5 mm to 5 mm, depending on part size and function.
Draft Angles	Include draft angles of 1-2 degrees on vertical surfaces to ensure easy part ejection from the mold.
Ribs and Bosses	Design ribs with a thickness of 50-60% of the nominal wall thickness to avoid sink marks; ensure bosses are properly supported (e.g., with ribs) to maintain structural integrity.
Radii and Fillets	Use radii and fillets with a minimum radius of 0.5 mm to reduce stress concentrations and improve mold flow during injection process.
Shrinkage Considerations	Polypropylene (PP) has a relatively high shrinkage rate of 1.0% to 2.5%. To control tolerances and maintain dimensional stability, the shrinkage rate must be taken into consideration.
Living Hinges	PP's flexibility allows for living hinges, but the hinge thickness should be 0.25–0.5 mm for durability.
Stiffening Features	For large or flat parts, add ribs or other stiffening elements to prevent warping, especially given PP’s higher shrinkage tendencies.

Key Properies of PP Molding Material

Polypropylene (PP) properties can vary significantly depending on the specific grade (homopolymer, copolymer, etc.) and any additives used. Here's a general overview of key properties with typical data.

Property	Value/Range	Description
Density	0.898 - 0.908g/cm³	Varies slightly between homopolymer and copolymer.
Melting Point	Homopolymer: 160 - 165°C; Copolymer: 135 - 159°C	Copolymer has a lower melting point.
Tensile Strength (Yield)	20 - 40 MPa	Range reflects variations in PP types.
Elongation at Break	15 - 700%	Wide range due to different PP formulations.
Flexural Modulus	1.1 - 1.6 GPa	Reflects stiffness; higher for homopolymer.
Water Absorption (24 hrs)	<0.01%	PP is highly hydrophobic.
Heat Deflection Temperature (HDT)	50-60°C	HDT A (1.8 MPa)

Key Considerations:

Homopolymer vs. Copolymer:
- Homopolymer PP is generally stiffer and stronger.
- Copolymer PP offers better impact resistance, especially at low temperatures.
Additives: Fillers like glass fibers or talc can significantly enhance PP’s mechanical properties.
Temperature: PP’s properties can change with temperature, and it’s not well-suited for high-temperature applications

Start PP Molding Project

Get high-quality PP injection molded parts! Contact with Erye to request a quote!

Features of PP Injection Molding

Advantages

Cost and Efficiency

PP is relatively inexpensive compared to many engineering plastics, it is an economical option for mass production.

Low Density & Lightweight

One of the lowest densities among common plastics, PP molding parts are typically lightweight, reducing material weight in applications such as packaging and automobiles.

Good Electrical Insulation

Naturally provides strong resistance to electricity, making it useful for housings and electrical components.

Recyclable

Easy to recycle, which lowers material costs and it is more sustainable and cost-efficient in circular use.

Safe for Food Contact

Many PP grades are certified for direct contact with food and drink, making it common in packaging and kitchenware

Limitations

Lower Strength and Stiffness

Compared to engineering plastics like nylon or ABS, PP has relatively low mechanical strength and rigidity.

Poor Heat Resistance

Standard PP softens at relatively low temperatures (around 100–120 °C), which limits its use in high-temperature applications.

Shrinkage and Warpage

PP tends to shrink and warp more than some other plastics, which can complicate precision molding.

Poor Bonding and Painting

Its low surface energy makes it difficult to glue, paint, or print on without surface treatments.

Case Study

Case Study of PP Injection Molding Car Parts

Learn how we helped an automotive client develop a custom injection mold for a car relay box cover. From material selection to mold design, we delivered a complete solution for automotive industry!

PP Injection Molding Applications

Packaging

Food containers
Bottle caps and closures
Medicine bottles
Storage boxes and bins
Cosmetic packaging (lids, jars)

Automotive

Battery cases
Interior trim parts (door panels, dashboards)
Fluid reservoirs (washer fluid, coolant)
Air ducts and housings

Medical

Syringe barrels
Specimen containers
Medical device housings
Pipette tips
Diagnostic test cassettes

Industrial

Chemical storage tanks
Battery cases
Industrial containers
Pipe fittings
Material handling trays

Additonal Options for Polypropylene Parts