Hello and welcome to this blog post. Today we discuss how we can reduce the global warming potential (GWP) of engineering thermoplastics with the focus on Polybutylene terephthalate (PBT). Also we discuss how to reduce the GWP of Polyphenylene sulfide (PPS) by applying a replacement strategy. In another post we discussed the PPS GWP reduction in more detail.
Effective ways to reduce the global warming potential (GWP) of thermoplastics
One way is to replace a high GWP polymer by a lower GWP one, and have at the same time a cost benefit as well as no reduction in performance. An example of this is the suggestion of material manufacturer Polyplastics to replace PPS components in the EV battery cooling system by low-cost long-glass fiber PP or POM [5]. PP has a GWP of 1.63 kg CO2 eq and POM has a GWP of 3.2 kg CO2 eq. Those are much lower compared to PPS with 5.46 kg CO2 eq or even higher in some cases. Reason which makes this change possible is that long-life coolants (LLC) for cooling batteries in EVs is maxim 100°C and for most time between 60 to 80°C, allowing PP and POM to take over this job. In this example we have a cost, and lower GWP advantage and keeping the needed performance. In addition, if one would like to keep the PPS and still lower the Carbon footprint, an effective way is to use recycled glass fibers. In detail we discussed this approach here.
Another way to reduce the GWP of an existing polymer is to use recycling methods. This approach we discuss next.
Using PET-bottles to reduce GWP of PBT
It is possible to exchange fossil based raw material by post-consumer (PCR) PET bottle waste as feedstock in order to reduce the GWP of PBT. In our example, 60 wt% PCR PET bottles were up-cycled to a higher engineering PET which shows almost the same properties as a PBT resin based on 100% fossil feedstock. The carbon footprint could be reduced by 49% compared to the fossil based PBT. Table 1 compares the properties of the standard PBT and low GWP PBT and Figure 1 shows the GWP reduction achieved with this up-cycled product.
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| Figure 1: comparing the cradle-to-gate CO2 footprint of PBT and low-GWP PBT [1]. |
Table 1: Overview properties of PBT and low-GWP PBT [1].
| Properties | PBT (Valox) | PBT low GWP (Valox iQ) |
|---|---|---|
| Tensile strength at yield (MPa) | 54 | 50 |
| Flexural stress at 5% strain (MPa) | 85 | 82 |
| Flexural modulus (MPa) | 2500 | 2460 |
| Notched Izod, 23°C (J/m) | 35 | 35 |
| Specific gravity | 1.31 | 1.31 |
| Tc (°C) | 164 | 170 |
| Tm (°C) | 225 | 220 |
| HDT, 0.45 MPa (°C) | 155 | 150 |
Conclusions
Considering the GWP during your material selection journey is becoming more and more easier since material manufacturers start to up-cycle and recycle their products. Also, based on requirements, new low GWP and low cost materials can be used for traditional engineering and high performance polymer applications.
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[1] https://www.researchgate.net/figure/58_tbl2_298399814
[2] https://www.researchgate.net/publication/298399814_Environmental_Benefits_of_post-consumer_recycled_PET_based_Valox_iQ_resin_vs_Valox_resin_using_Life_Cycle_Assessment_Approach
[3] https://www.findoutaboutplastics.com/2022/01/global-warming-potential-gwp-vs-thermal.html
[4] https://www.findoutaboutplastics.com/2021/12/eco-profiles-of-polymer-resins-global.html
[5] https://www.plasticstoday.com/automotive-and-mobility/ev-cooling-components-can-be-molded-less-heat-resistant-plastics
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