Usefulness of Polypropylene Films

PP film is among the leading materials today used for flexible packaging as well as industrial applications. Two important forms of polypropylene films include:

Cast Polypropylene Film

Cast polypropylene commonly known as CPP and widely known for its versatility.

·         Super resistance to tears & puncture

·         Greater transparency and better heat resistance at high temperatures.

·         Excellent moisture and atmospheric barriers

·         High permeability to water vapor

Biaxially Oriented Polypropylene Film

Biaxially oriented polypropylene film (BOPP) is stretched in both transversal and longitudinal directions, producing molecular chain orientation in two directions.

·         Orientation increases tensile strength and stiffness

·         Good puncture and flex crack resistance over wide range of temperatures

·         Have excellent gloss and high transparency can be glossy, clear, opaque, matte or metalized

·         Efficient barrier against oxygen and moisture

PP vs. PE – Selecting the Suitable Polymer
Though Polyethylene and Polypropylene are similar in physical properties but here are key points to consider to select the polymer suitable to your needs.

Polypropylene Processing Conditions

Polypropylene can be processed virtually by all processing methods. The most typical processing methods include: Injection Molding, Extrusion, Blow Molding and General-Purpose Extrusion.

1.      Injection Molding

o    Melt temperature: 200-300°C

o    Mold temperature: 10-80°C

o    Drying is not necessary if stored properly

o    High mold temperature will improve brilliance and appearance of the part

o    Mold shrinkage lies between 1.5 and 3%, depending on processing conditions, rheology of the polymer and thickness of the final piece

2.      Extrusion (tubes, blow and cast films, cables, etc.)

o    Melt temperature: 200-300°C

o    Compression Ratio: 3:1

o    Cylinder Temperatures: 180-205°C

o    Pre-Drying: No, 3 hours at 105-110°C (221-230°F) for regrind

3.      Blow molding

4.      Compression molding

5.      Rotational molding

6.      Injection blow molding

7.      Extrusion Blow Molding

8.      Injection stretch blow molding

9.      General-Purpose Extrusion

Expanded Polypropylene (EPP) may be molded in a specialized process. Being an ideal material for injection molding process, it is majorly used for batch and continuous production.

3D Printing with Polypropylene
As a tough, fatigue resistant and durable polymer, PP is ideal for low strength applications. Due to its semi-crystalline structure and heavy warping, it is currently difficult to use polypropylene for 3D Printing processes.

Today, several manufacturers have optimized PP properties or even created blends with improved toughness making it suitable for 3D Printing applications. Hence, it is recommended to thoroughly refer to documentation provided by supplier for printing temperature, printing bed, etc., while 3D Printing with polypropylene...

Polypropylene is suitable for:

·         Complex models

·         Prototypes

·         Small series of components, and

·         Functional models

Is PP toxic? How to recycle PP?

All plastics have a ‘Resin Identification Code/ Plastic Recycling Code’ based on the type of resin used. PP’s resin identification code is 5.

PP is 100% recyclable. Automobile battery cases, signal lights, battery cables, brooms, brushes, ice scrapers, etc., are few examples which can be made from recycled polypropylene (rPP).

The PP recycling process mainly includes melting of waste plastic to 250°C to get rid of contaminants followed by removal of residual molecules under vacuum and solidification at nearly 140°C. This recycled PP can be blended with virgin PP at a rate upto 50%. The main challenge in PP recycling is related to its amount consumed – currently nearly 1% PP bottles are recycled as compared to 98% recycling rate of PET & HDPE bottles together.