Sewage pipes, from cast iron to multi-layer polyolefin silent grade
Nowadays, it is important in buildings that the sewage systems be as silent as possible, especially in cases such as discharge of kitchen appliances. For many years, cast iron pipes and fittings have served successfully, due to their large density which provides sufficient sound attenuation. New building designs, however, do not tolerate heavy cast iron pipes and
prefer plastic replacements. A practical approach tried earlier to overcome the weakness of plastics in sound attenuation was to increase pipe’s thickness, which increased pipe weight
and installation difficulties. Introducing mineral fillers in plastic pipes was the next approach employed which resulted in thinner pipes with reasonable level of sound transmission. However, this was achieved at the cost of mechanical properties, especially impact strength. More recently, multi-layer pipe technology was developed to improve mechanical properties of pipes while maintaining the sound attenuation characteristics of filled PP. Although this technology has made a great success; impact strength of manufactured pipes is still unsatisfactory because of the inherent properties of filled PP.
ParsaNano silent formulations are materials of choice for pipe manufacturers who look for the benefits of low weight and easy to work with plastic pipes along with the sound attenuation and excellent mechanical properties. Figures 1 and 2 illustrate the advantages of ParsaNano silent grades in comparison with traditional cast iron and neat PP pipes.
Figure 1. Comparison of sound level in four different materials used in sewage pipes. The red line shows the maximum sound level in buildings recommended by The Association of German Engineers (VDI) guideline No. 4100.
Figure 2. Significant weight saving in sewage pipes made of ParsaNano.
ParsaNano, an innovative solution
Engineered bimodal size distribution of mineral particles (micro and nano-sized) has enabled ParsaNano to provide amazing improvement in both mechanical and sound insulation properties. Combining ParsaNano material and multi-layer technology, manufacturers can reduce pipe thickness and therefore pipe weight (compared to thick wall silent pipes), while having a great insulation and mechanical properties. These pipes are excellent from aesthetic point of view as well. Figure 3 shows the structure of a multi-layer pipe made by ParsaNano.
Figure 3. Structure of a three-layer sewage pipe showing incorporation of ParsaNano in the middle layer which is covered by two thin external and internal PP layers.
Figure 4. Superior mechanical properties of ParsaNano compared to the conventional filled PP.
Figure 4 represents the advantages of ParsaNano compared to conventional filled PP in terms of mechanical properties. As mentioned earlier and also seen in this figure, ParsaNano provides much higher (about 80%) impact strength compared to its conventional counterparts. This benefit which is very much desired for pipe manufacturers comes from the great potential of this material to undergo plastic deformation and thus, absorb energy prior to fracture. Figure 5 illustrates the significant plastic dilation of the polymer matrix around micron-size
minerals which are induced by the nano particles incorporated.
Figure 5. SEM micrographs taken from fracture surfaces of (a) ParsaNano and (b) conventional filled PP.
Mechanism of sound attenuation
Noise produced by water flow in a pipeline travels to the outside and this phenomenon is called structure-borne noise which depends on both micro and macro-structure of the pipe material. Sound insulation depends on three physical properties of material including its surface mass, its stiffness and its damping capability. The surface mass (surface density) and the stiffness of a material play role in sound shielding by means of scattering the incident wave. Damping characteristic of a material, however, is important in absorbing the energy of the sound wave.
Efforts have been made to improve the sound-proofing quality of the plastic pipes and attentions have been shifted towards the mineral filled plastic pipes for a better soundinsulation performance. The mineral filler can attenuate sound by scattering the incident waves through both increasing the surface density andthe stiffness of the material. Incorporation of
nano particles in ParsaNano improves the sound attenuation property of the material since these particles act as sound scattering obstacles and further reflect the incident waves. Figure 6 provides a schematic representation of the sound attenuation mechanism in a three-layer pipe made based on ParsaNano material.
ParsaNano materials are specifically developed to improve the performance of solid wall pipes for underground non-pressure sewerage. Besides, with ParsaNano high modulus PP grades demands of pipe industry for ease of production would be satisfied. ParsaNano is built on the well-established properties of PP to deliver high:
- impact strength
- elastic modulus
- abrasion and stress crack resistance, even at low temperatures
- corrosion and chemical resistance
- flexibility and structural integrity to accommodate ground
- movements without breaking
- temperature resistance at 60°C – short-term up to 90°C.
Pipes made with ParsaNano have several advantages, including:
- excellent impact strength combined with
- high ring stiffness,
- low pipe weight per unit length,
- increased pipe design freedom,
- safer pipe handling and easier installation, and
- long-term durability.