3D architecture and anisotropic mechanical performance of commercial oriented PVC pressure pipes

Although oriented PVC (OPVC) pipes achieve high-pressure performance through hoop expansion, the quantitative relationships between three-dimensional architecture and mechanical anisotropy in real pipe walls has not been fully quantified. In this study, a commercial OPVC pipe was analysed by comparing oriented and adjacent non-oriented segments extracted from the same product, thereby eliminating formulation and thermal-history variability. A plane-resolved sampling strategy combined with Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and synchrotron X-ray diffraction was used to characterise orientation-induced changes in the amorphous and crystalline phases, and to correlate them with multiscale mechanical testing (tensile, flexural and Charpy impact) performed along well-defined directions. Synchrotron diffraction provides direct evidence of orientation-dependent crystallite reorganisation, revealing strong anisotropy that cannot be captured from a single sampling direction. DSC results show a slight increase in glass transition temperature together with a reduction in melting enthalpy after orientation, consistent with restricted segmental mobility and partial loss of crystalline order. SEM observations reveal an orientation-induced laminar architecture together with filler–matrix debonding. Mechanical testing demonstrates pronounced anisotropy governed by the alignment between the applied stress field and the hoop-oriented architecture. Configurations in which deformation or fracture intersects the oriented structure exhibit higher strength and impact energy, whereas off-axis configurations show reduced efficiency. Overall, this work provides a reproducible experimental framework for relating process-induced architecture to anisotropic thermo-mechanical performance in OPVC pipe walls, supporting testing-based benchmarking and design-relevant performance assessment. • Synchrotron XRD reveals plane-dependent crystallite reorganisation in OPVC pipes. • Plane-resolved sampling directly probes 3D anisotropy in real OPVC pipe walls. • SEM reveals laminar wall architecture and particle–matrix debonding. • Mechanical anisotropy follows stress/crack alignment with hoop orientation.