PP Injection Molding – Ultimate FAQs

Injection molding is one of the best ways to manufacture plastic products because injection molding offers a number of advantages over other processes. Injection molding comprises melting and injecting the mixture of polymer resin and additives into a closed mold cavity where it solidifies by cooling.This article contains frequently asked questions, get started.

What is The Molding Polypropylene?

Polypropylene/PP injection molding material is the most commonly used packaging material in the world. It is available in a wide variety of shapes and sizes, and can be custom made to help ensure its versatility. It features a wide range of applications that include packaging of consumer products, plastic components for such industries as the automotive industry.

Polypropylene Injection Molding Process

Plastic Injection molding can be done in an open mold, which has temperature control and automated filling features, and a closed mold, where the cavity is completely heated. Such processes vary based on material flow rate and melt temperature. Also, the thickness of the wall is determined by whether one-shot or multi-shot processes are used. The consumption rate can be related to how many shots are used during one cycle. In general, PP injection molding is performed through reciprocating movement into the cavity of the mold at a constant speed of a few meters per second until reaching the desired melt pressure point.

PP injection molding caps

PP Injection Molding Temperature

Injection molding temperature plays an important role in quality of the part. Best results are obtained when polypropylene is molded at cylinder temperatures ranging from 400- 570°F. Cylinder temperatures should be 25-50°F higher than the minimum temperature required to fill the part, but not over 570°F. In most cases, molding temperatures will be in the 400-525°F range.

PP Injection Price/ Polypropylene Injection Molding Cost

There are a few ways to answer this question and it really depends on the part you’re trying to make. The short answer: plastic injection molding cost anywhere from $100 for a 3D printed low-volume injection mold to $100,000+ for a complex multi-cavity steel mold for high-volume production. However, as these costs get distributed among hundreds or thousands of parts, injection molding is an ideal process to mass-produce plastic parts affordably.

Why is Polypropylene Good for Injection Moulding?

Polypropylene is generally considered to be the most responsive thermoplastic to injection speed and pressure. It sets up quickly in the mold, enabling molders to attain high production rates. This combination of performance properties gives polypropylene a position in the injection molding field that is unique among thermoplastics.

Polypropylene is a premium thermoplastic with excellent melt flow and toughness properties. This combination of outstanding material properties gives polypropylene the ability to be easily molded, processed and manufactured into a wide range of products.

How Many Types of PP Plastic Are There?

Polypropylene is a synthetic polymer, so it can be made in many different compositions and textures. Some are transparent while others are opaque, with different glosses and degrees of stiffness. The most common forms are homopolymers and copolymers.


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