Suggestions for multilayer piping
Outer layer: Polyamide (PA) 612 resin | Inner layer: Modified PPE resin
For pipes of water-cooling systems in electric and fuel-cell vehicles (FCVs) operating below 135°C, we recommend a two-layer pipe structure consisting of an inner layer of XYRON™ modified PPE resin with an outer layer of LEONA™ PA612 resin. This combination, illustrated in the schematic diagram below, offers good bending properties, low elution, and long-life coolant (LLC) resistance.
Resin pipes with inner layers made from XYRON™ modified PPE resin offer the following advantages:
- Bending properties：
Minimal springback reduces processing time and cost. In addition, the reduced risk of interference with other components offers greater freedom in layout design.
- Low elution：
Low ion elution ensures minimal variation in the electrical conductivity of coolants. This reduces the risk of vehicle fires due to coolant leakage, and helps to reduce the frequency with which ion-exchange resins in FCVs must be replaced.
- LLC resistance：
Inner layers offer the same superior LLC resistance provided by PP-based resin pipes.
- Pressure resistance：
Modified PPE resins offer excellent pressure resistance at high temperatures (80, 135°C), and enable pipes to be made with thinner walls to reduce weight.
Advantage 1: Bending properties
For components of vehicle cooling systems, whose layout must be carefully designed to satisfy stringent space requirements, good bending properties are essential. Here we compare the bending properties of multilayer pipes made from two pairs of materials: (1) an inner layer of XYRON™ modified PPE resin with an outer layer of LEONA™ PA612 resin, and (2) an inner layer of PP resin with an outer layer of PA612 resin.
Whereas the PP/PA612 component exhibits significant deformation at high temperatures due to springback of the right-angle bend, the XYRON™/LEONA™ component exhibits a dramatic reduction in springback angle. This helps cut processing time and cost and minimizes risks of interference with other components, offering greater freedom in layout design.
Advantage 2: Low elution
The electrically insulating or conducting properties of coolant liquids are a subject of growing concern in thermal-management systems for BEVs. Higher-conductivity coolants pose a greater risk of vehicle fires due to coolant leakage in BEVs, while in FCVs the voltage of the FC stack may lead to electrical breakdown of the entire cooling system. To preserve the insulating properties and electrical conductivity of coolants in BEVs and FCVs, the pipes conveying these coolants must be made from materials exhibiting low elution of various ionic species.
Here we compare the elution properties of the materials we recommend for resin pipes—XYRON™ modified PPE resins and LEONA™ PA612 resins—to those of commercially-available PA612, PA12, and PP resins. For each material, we immersed a material sample in purified water at 95°C and measured the total organic carbon (TOC) and conductivity due to eluted ions. As shown in the figure, the results of these tests confirmed that pipes with a XYRON™ inner layer exhibit dramatic reductions in both TOC and conductivity compared to PA612 and PA12.
This promises reduced risk of vehicle fires due to coolant leakage and less frequent replacement of ion-exchange resins in FCVs.
Further results of this comparison, and a discussion of the methods used to characterize pipe features, may be found in the following document. Please contact us to ask any questions or discuss any concerns regarding this material.