In an injection-molding magnetic compound, the binder is the matrix that carries the magnetic filler — and it decides how the granules behave in your press and how the part survives in the field. Ruiyi compounds run on three thermoplastics: PA6, PA12 and PPS. The PA-vs-PPS choice is the one engineers ask about most, because it touches moisture, temperature and cost at once.
Moisture: the nylon problem
Nylons absorb water — PA6 more, PA12 noticeably less. Absorbed moisture plasticizes the matrix: dimensions drift, and magnetic and mechanical properties shift with ambient humidity. For a sensor target or an encoder ring that must hold a pole signature over years, that drift matters. PA12's lower moisture uptake is exactly why it exists in the portfolio, and PPS is essentially non-hygroscopic: it absorbs well under 0.1%, which is why it dominates under-hood and wet-environment designs.
Temperature: mind the barrel limit
Every Ruiyi compound sheet carries an explicit processing ceiling: nylon (PA) compounds must not exceed a barrel temperature of 280 °C, while PPS compounds are rated to 330 °C. The same ordering holds in service — PPS retains stiffness and dielectric properties well past where nylons soften, which is why PPS-binder compounds cluster in automotive motor applications close to heat sources.
| Property | PA6 | PA12 | PPS |
|---|---|---|---|
| Moisture uptake | High | Low | Negligible (<0.1%) |
| Max barrel temp (Ruiyi sheets) | 280 °C | 280 °C | 330 °C |
| Continuous service temp | ~100–120 °C | ~100–120 °C | ~200 °C+ |
| Mechanical character | Toughest of the nylons here | Good toughness, best dimensional stability of the PAs | Stiff, dimensionally exact, more brittle |
| Chemical resistance | Good | Good | Excellent (fuels, solvents, salts) |
| Relative cost | Lowest | Mid | Highest |
Indicative values for orientation — each grade's official window is on its TDS.
What the grades actually show
The pattern is visible in the published data. Take the RY-16 performance series: the PA12 version lists tensile strength ≥50 MPa, while the PPS version (RY-16-FS) drops to ≥30 MPa — PPS parts are stiffer and more heat-resistant but give up nylon's toughness. Magnetic performance stays in a similar band across binders at equal filler loading, so the binder decision is mostly an engineering decision, not a magnetic one.
On the rare-earth side the same split exists: isotropic NdFeB runs in both PA12 (ten published grades) and PPS (eight grades), with anisotropic NdFeB in each. Use the series filter in the grade finder to pull every grade of a binder family into one view and compare them directly.
Choosing in practice
- Consumer appliances, office equipment, dry interiors: PA6 delivers the lowest cost with excellent toughness.
- Sensors, encoders, anything with a dimensional or pole-precision spec across humidity: PA12.
- Under-hood motors, fuel and fluid contact, reflow-adjacent processes, sustained >150 °C: PPS.
- Unsure between two specific grades? Put them in the comparison tool and check the mechanical table side by side.