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BorECO™ High Modulus PP (PP-HM) for sewer applications

Introduction

Polypropylene has an excellent track record after more than 30 years of service for non-pressure sewage and drainage applications. The inherent material properties and their development, energy and cost efficiency, pipe design and ease of manufacture and installation have contributed to this success. The traditional cornerstones of the requirements profile such as impact resistance, stiffness and chemical resistance are increasingly being supplemented by demands for purity, sustainability and recyclability. Consequently, the continuous development seen in both material and pipe design has brought additional benefits to pipe producers and end users and is contributing to a more sustainable environment.

The first generation of PP with higher modulus PP was introduced in 1998 and provided a major step forward with an optimized balance of the stiffness-impact properties. A few years later, this product was improved and an E-modulus of 1700 MPa was achieved, representing the first PP-HM to meet the requirements set in the modified EN1852 standard in 2002 (which was adjusted based on the development of this new class of polypropylenes). The journey has continued and recently, the next generation PP for underground drainage and sewage has been introduced. It presents the first and unique 2000 MPa PP-HM from Borealis – BorECO™ BA2000, achieved without the use of fillers, meeting and exceeding the requirements set in the recently - again - modified EN1852.

 

What is High Modulus PP (PP-HM)?

High-Modulus PP is a material with increased stiffness while keeping a good impact performance, allows for further down-gauging of the pipes, thus making a significant contribution to sustainability, thanks to less material consumption, lower pipe weight, lower transportation costs and faster installation.

51With regard to the amount of material used for underground drainage and sewerage, PP pipe systems have the lowest weight per meter pipe of all conventional and standardised materials for the application.

The nominal weight per meter of a solid wall DN200 mm conventional PP-B pipe is 4.65 kg and a corresponding PP-HM 2000 MPa weighs 3.77 kg/meter. For a concrete pipe with the same diameter the weight is around 55 kg per meter, i.e. approximately 15 times heavier!

 

The stiffness (modulus) and impact strength of BorECO™ HM-PP materials is maximised in the following ways:

 

  1. by increasing the crystallinity level of the semi-crystalline polypropylene material
  2. by nucleating the crystals in order to obtain many small crystals rather than few large crystals
  3. by optimizing the level of the comonomer/EPR phase contained in the PP.
  4. by obtaining a fine dispersion of the comonomer/EPR phase in the PP

 

crystal

Non-nucleated PP crystal structure

structure

Crystalline structure of BorECO™ PP

 

The ideal material therefore for such an application is one which exhibits the combination of the having a low density (or high specific volume) and a high stiffness.

The following table compares these characteristic data for the most commonly used plastics material in non-pressure sewer applications.

 

 

Material Density (kg/m³) Specific volume (m³/ton) Tensile modulus (MPa)
BorECO™ PP 900 1,10 up to 2000
Standard PP(-B) 900 1,10 1300
HDPE 960 1,04 1000
PVC 1400 0,71 2500

 

 

The following table demonstrates clearly what the combination of low density (high specific volume) of the material in combination with the high stiffness of the High Modulus PP materials means in terms of the meter weight of waste water pipes.

table

 

Conclusion

The PP polymer development has supported the progress of plastics pipes both for solid wall and for structured-wall pipe systems and will continue to do so in the years to come, because we believe that there is still a high potential for development and optimisation in the areas of material- and compound development and in pipe design. It is well known that the development of PP-B and the high-modulus PP have contributed to an increased use and geographical spread of PP pipe systems. Future developments are expected concerning improvements in processability, and thus even further reduction of pipe weight per meter, and naturally to proceed in building on the sustainability benefits and lifetime expectancy with plastics pipes systems are the focus of development work.

The continuous efforts in PP development have also induced the development of new pipe designs such as the spirally wound pipe. The results of processing trials using the Krah spiral winding process together with BorECO™ PP materials, have revealed that this innovative pipe manufacturing process and this innovative material almost give the impression that they were invented for each other.

 

Contact

 

James McGoldrick
Application Development + Technical Service Engineer
Tel +43 732 6981-5157
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Borealis Polyolefine GmbH
St. Peter Strasse 25
4021 Linz
Austria
Martin Lackner
Application Marketing Manager
Tel +43 1 22400-396
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Borealis AG
IZD Tower
Wagramer Strasse 17-19
Vienna
Austria