How SABIC developed a prototype solid-state water meter made from amorphous Noryl PPO to break into this industry
We were recently approached by SABIC about ongoing work to make an entry with Noryl PPO into the ultrasonic and/or electromagnetic water meter business, dominated today by metals (brass – 70-80%) or high-end fiberglass. reinforced semi-crystalline thermoplastics (GF). These are often over-engineered for the applications, but work and give OEMs confidence that they will last 10-12 years before a replacement is needed.
The company has developed a prototype that can achieve the level of mechanical performance required in such complex injection molded parts through the successful “marriage” of material, design and processing technology. Additionally, they claim that using their GF Noryl in this application results in cost savings of 15%-20% over in-place thermoplastics and >50% for metal. In addition, the expected life of these water meters is 12 to 15 years. Find out how SABIC researchers answered this editor’s questions about why they undertook this project and how they approached it.
Photo credit: SABIC
Q: What prompted SABIC to initiate this work?
SABIC has been active with its Noryl PPO in the field of water management for decades, particularly in applications in contact with potable water, including standard water meters (i.e. volumetric or mechanical).
With the emergence of new types of water meters (solid-state water meters such as ultrasonic or electromagnetic flowmeters), we have seen yet another area of application where the use of our materials could be beneficial.
These types of meters are growing in popularity because they are more accurate and often have a longer lifespan than mechanical / volumetric water meters (meaning a higher return on investment for utility companies). As a result, this market segment is growing rapidly (in some cases >10% CAGR) and there is strong demand across all regions/clusters.
Currently, the materials of choice in place are brass or thermoplastic resins such as GF PPA, GF PPS and GF nylon 12, all of which are premium semi-crystalline materials. thermoplastics or even brass with amorphous Noryl PPO were of great interest to us. As a result, we decided to take a different approach to demonstrating to customers that our GF Noryl PPO resins can do the job and provide additional value, such as parts savings, over in-place materials.
Q: Has anyone ever considered Noryl PPO for these commercial applications?
Glass-filled PPO resins such as Noryl WM330G or FE1630PW resins have already been considered by major OEMs in this field, but as a direct solution, they could not meet the requirements of very demanding applications, especially with regard to relates to fatigue/fluctuating pressure (e.g. water hammer and sine wave pressure resistance at cold water temperatures).
Since these customers felt that Noryl resin was not strong enough, they were also hesitant to develop new parts/designs with Noryl PPO in mind. Therefore, we decided to develop our own prototype by taking advantage of our experience and advanced (anisotropic) modeling capabilities to design a solid-state water meter (i.e. a tube of flow) that would meet the stringent requirements of OEMs and convince them to use Noryl resin.
SABIC researchers took the following approach:
▪ Select 5-6 commercially available solid-state water meters on the market and perform a disassembly of each to understand the main components, principle of operation, part design and (existing) materials used.
▪ I spoke to several OEMs and Key Opinion Leaders in this field to understand their specific needs and requirements for this application, particularly with regards to long-term mechanical properties such as fatigue, burst and creep rupture.
▪ Based on the above, they designed/developed their own prototype to meet these requirements based on advanced simulation capabilities leveraging proprietary data
Q: How did Noryl stack up against existing high performance engineering resins used for this application:
As mentioned earlier, since Noryl is an amorphous resin, fatigue performance can be an issue. In order to meet part/OEM requirements, we had to focus on developing a balanced/optimized part and tool design. The influence of processing parameters has been studied for the long-term performance of the application to ensure optimal molding.
We positioned a 30% GF Noryl PPO (i.e. Noryl WM330G) as an offset to the 40% GF PPA or GF PPS or 50% nylon GF12. The overall strength of Noryl resin is good dimensional stability in contact with water and temperature; good resistance to drinking water over long periods; and very low water absorption with no change in properties due to water absorption. Noryl resin also exhibits good resistance to constant pressure (creep rupture). Also, it demonstrates easy processing. Also, it is not well known that Noryl has excellent antibacterial growth properties. In addition, the low density of the material is attractive from a cost point of view.
Q: Can you detail the main results?
After developing a prototype and cutting the tools, we molded water meters (i.e. flow tubes) from different materials, including Noryl WM330G resin, to compare their performance. The first and most important step was to convince the OEMs that our materials are capable of meeting the threshold requirements. In some cases, extra care was needed to get the processing conditions/parameters right to get the best performance, but ultimately we were able to show that 30% GF Noryl resin can meet the threshold requirements.
Since these parts are being installed on existing infrastructure where unexpected stresses could arise (i.e. due to pipe misalignment or simply the way these meters were installed), we had to perform additional internal testing to prove Noryl WM330G resin would not fail due to improper installation. . Successfully executed tests were for bending of the water meter (i.e. flow tube), pulling it in opposite directions (i.e. similar to tensile bar test ) and also testing the strength of the threaded connection with a torque test.
We have shared the results with several OEMs and they have been positively impressed with the work and the significant performance improvements that have resulted from simply making the right design decisions for the part and tool (design) and optimizing the working conditions. processing. Several of them have tried Noryl resin since then and will consider it for future projects, especially where they have more design freedom as current tools are designed for semi-crystalline materials.
During this time, SABIC researchers elaborated further on the key challenges and how they overcame them. One of the biggest lessons learned was how optimizing processing/injection molding parameters, but also certain mold design decisions (eg hot or cold runner) can significantly improve part performance. Noryl is amorphous and therefore the strength of the weld line is its Achilles heel. To get the best part performance, and therefore create strong weld lines while avoiding voids, they aimed to:
▪ Higher melting temperature: 330 C/626 F (vs 290 C/554 F-310 C/590 F on datasheet)
▪ Higher mold temperature: 120 C/248 F (vs 100 C/212 F on datasheet)
▪ Higher packing pressures: 900 bar (eg not ~60% injection pressure, now ~250%)
▪ Longer wrapping times: e.g. 30 seconds (should not be a limiting factor)
▪ Hot Runners vs. Cold Runners: Hot runners prevent premature freezing of the door and therefore longer and more effective seal pressure can be applied to prevent voids forming during cooling. In the case of a cold channel, a sufficiently large core is needed.
▪ We often find that the packaging pressure is too low and the packaging times are too short. Packaging shouldn’t be a limiting factor; wrapping and cooling must occur simultaneously for the entire cycle time. Note that gate freezing (with cold runner) may prevent sufficient compaction times.
▪ Recommended setup process:
1. 99% filling without pressure
2. Determine the appropriate injection speed
3. Set the appropriate packing pressure and time
The above improvements helped the SABIC team fill the part better (i.e. 99% of hypothetical mass) and reduce voids that could lead to failures and improve mechanical performance requirements, such as bursting and fatigue.
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