How to choose the right polypropylene grade for your appliaition

Introduction

Choosing the right grade of polypropylene according to the application is a huge and complex task, especially when you do not have material specifications or similar polypropylene application data.Although product literature is not difficult to obtain, the amount of information on the data sheet may lead to new problems, especially for molders and extruders who lack polypropylene experience.

So far, there is no fixed method suitable for the selection of polypropylene materials, but our discussion in the blog post will provide some references in your material selection process.

When choosing the right polypropylene grade, there are four key factors that must be considered, and we will show them one by one in the blog post. In this blog post, we will discuss the impact of the use of polypropylene materials in the selection of materials.

Preliminary selection of polypropylene grade

At present, there are homopolymers, random copolymers and block copolymers on the market, and it is rare that they replace other products without sacrificing their own performance. Therefore, it is easiest to select the appropriate polypropylene product according to the first performance of each product type.

For most applications, choosing between these features can determine which type of polypropylene to use. Once determined, other criteria can be listed according to needs, and then sorted by importance.

How to choose the correct polypropylene grade for your application according to the production process of plastic products.

The process will determine the choice of appropriate MFR. Production processes that require high melt strength, such as blow molding, blown film extrusion, profile extrusion,etc., Suitable for polypropylene grades with high molecular weight and low MFR.

Injection molding allows greater freedom of choice due to its inherent process characteristics, so low melt viscosity polypropylene with wide-area MFR is an ideal choice. Generally speaking, high-speed, thin-wall, and molding applications require a higher MFR level, while thick-walled, functional parts prefer a lower MFR level. The impact performance of block copolymers is controlled by MFR to a certain extent. Under the same other conditions, the lower the MFR level, the better the impact performance. However, other factors, such as composition and number of blocks, affect these same properties. Products with narrow molecular weight distribution obtained by controlling rheology or high-activity catalysts have less warpage, more uniform mold shrinkage and better stretching, but lower melt strength.

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