Thermoplastics Pipes and Fittings - Vicat Softening Temperature - Part 2: Test Conditions for Unplasticized Poly(Vinyl Chloride) (PVC-U) or Chlorinated Poly(Vinyl Chloride) (PVC-C) Pipes and Fittings and for High Impact Resistance Poly(Vinyl Chloride) (PVC-HI) Pipes