Overview
ISO 4076:2025 - Polyphenylsulfone (PPSU) - specifies minimum expected strength (hoop stress) for injection‑moulded PPSU fittings as a function of time and temperature. It defines generic reference lines (mathematical curves) for long‑term hydrostatic strength to be used in design calculations, establishes extrapolation limits for life‑time predictions, and gives procedures to demonstrate conformance. The reference lines are intended as generic guidance (not grade‑ or supplier‑specific).
Key topics and requirements
- Reference equation (applicable 10 °C–135 °C):
log10 t = A + B/T + C log10 σ + (D/T) log10 σ
For PPSU the document gives numerical coefficients: A = −64.495, B = 31 700.557, C = 28.281, D = −15 573.347 (T in K, t in hours, σ in MPa).
- Extrapolation limits: minimum allowable extrapolation times are established (based on experimental data at 110 °C and Arrhenius behaviour with an activation energy of 110 kJ/mol). Table 1 provides limits (e.g., ≤60 °C → 100 years).
- Tabulated expected strengths: Table 2 lists calculated hoop strength values for common temperatures and service times (examples: at 20 °C - 1 year: 39.6 MPa; 100 years: 32.9 MPa).
- Conformance testing (Annex A): materials evaluated per ISO 9080/ISO 1167; testing temperatures include 20 °C, 60–70 °C, 95 °C and 110–135 °C. At least 97.5% of test results must lie on or above the reference lines.
- Design & wall thickness (Annex B): principles for deriving S values and minimum wall thicknesses relative to application classes, design pressures and service coefficients (uses Miner’s rule and ISO 10508 guidance).
Applications and who uses it
ISO 4076:2025 is useful for:
- PPSU fittings manufacturers for component design and wall‑thickness calculations.
- Design engineers and specifiers of hot/cold water piping systems who need time‑temperature strength data.
- Materials suppliers and R&D teams validating PPSU grades for plumbing applications.
- Testing laboratories and conformity assessors using ISO 9080 / ISO 1167 test methods to demonstrate compliance.
- Certification bodies and standards committees harmonizing piping system design for buildings and industrial fluid transport.
Practical uses include lifetime predictions, dimensioning of injection‑moulded fittings, product certification, and comparing materials for hot‑water plumbing applications.
Related standards
Keywords: ISO 4076:2025, PPSU, polyphenylsulfone, expected strength, reference lines, injection moulded fittings, long‑term hydrostatic strength, extrapolation limits, ISO 9080, hoop stress.
