Curtain walls are attached to framing with screws, so screw pullout force is critical. Measured comparison (screw diameter 4.2mm, embedment depth 15mm, core density uniformly 100 kg/m³):
- PET: 450 N
- PVC: 620 N
- PU: 280 N
- XPS (not applicable – strips easily)
PVC’s excellence comes from its toughness, allowing threads to bite securely. PET is also good, but PU and XPS, due to brittleness or softness, easily strip. Engineering measures: embed plastic expansion anchors (nylon or polypropylene) in PU or XPS panels, increasing pullout force to over 800 N. Curtain wall codes require individual fixing point capacity ≥1.2 kN, so through-bolts with backing plates or pre-embedded nut mechanical connections must be used.
