ISO 2507-1:1995

Overview

ISO 2507-1:1995 specifies a general test method for determining the Vicat softening temperature (VST) of thermoplastics pipes and fittings. It adapts method B of ISO 306 for components in tubular form rather than sheets, defining how to measure the temperature at which a standard indenter under a force of 50 N ± 1 N penetrates 1 mm into a test piece while temperature increases at a controlled rate. The standard applies only to thermoplastic materials for which a rapid softening point can be observed and is not suitable for crystalline or semi‑crystalline polymers.

Key Topics and Requirements

• Principle: Measure the temperature at which the indenter reaches 1.00 mm ± 0.01 mm penetration; this temperature is reported as the VST in °C.
• Load and indenter: Standard indenter (cylindrical cross‑section ≈ 1 mm²) with total thrust 50 N ± 1 N.
• Heating rate: Temperature rise in the heating medium controlled at 50 °C/h ± 5 °C/h; uniformity checked at 6‑minute intervals.
• Apparatus: Rigid frame and rod, load‑carrying plate, micrometer dial gauge (0.01 mm resolution), immersion heating bath or air circulation oven, thermometer (±0.5 °C accuracy).
• Test piece preparation:
  • Segments of pipe/fitting rings with width 10–20 mm and length ≈ 50 mm (or specified socket lengths for fittings).
  • Wall thickness >6 mm: machine outer surface to 4 mm; 2.4–6 mm: test as is;