Information on the most widely used ASTM standards within the materials testing industry
ISO 2505 Thermoplastic Pipes Longitudinal Reversion Test (PF Heat Reversion Test)
The longitudinal Reversion rate of pipe materials refers to the percentage change in length of thermoplastic pipe materials under specific temperatures, used to assess the thermal contraction properties of the material. The measurement method is based on the national standard ISO 2505, GB/T 6671-2001, (TCVN 6148 standard equivlent with ISO 2505). which is mainly divided into two types: liquid bath test (Method A) and air oven test (Method B).
Definition and Standard
The longitudinal retraction rate is an indicator of the shrinkage performance of thermoplastic pipe materials along the length direction when heated. It is calculated by measuring the change in distance between the marked lines before and after heating.

Testing Methods
Method A (Liquid Bath Test): The sample is immersed in an inert liquid (such as glycerin or silicone oil) at 150±2°C. The insulation time is calculated based on the wall thickness (usually 1 min/mm). After cooling, the change in length is measured. This method is suitable for small-diameter pipes.
Method B (Air Oven Test): The sample is placed horizontally in an oven, with the temperature set according to the material type (e.g., 150±2°C for PVC, 110±2°C for PP). The time is also calculated based on the wall thickness, and after cooling, the length is measured.
This method is suitable for all pipe materials; large-diameter pipes need to be cut into four pieces for testing. Influencing FactorsThe longitudinal retraction rate is mainly influenced by the type of material, processing technology (such as extrusion speed and cooling rate), and wall thickness. UPVC pipes must be strictly controlled within standard limits (usually ≤5%) to ensure stability in use.
Equipment: Longitudinal Reversion Tester (PF Heat Reversion Test Apparatus) for testing Pipes made from Unplasticized Polyvinyl Chloride Polymer ( Thermoplastic material).
The longitudinal shrinkage rate of the PE water supply pipe is determined by placing a specimen of specified length in a heating medium at a given temperature for a certain period of time, and measuring the distance between the marked lines before and after heating, expressed as the percentage change in length relative to the original length.

Sample preparation
Sampling: Cut at least 200mm of pipe section from the pipe as a sample.
Marking: Use a marking tool to evenly mark two circular markings on the sample that are 100mm apart, ensuring that one marking is at least 10mm away from the end. www.unitedtest.com
Pre treatment: The sample needs to be placed in an environment of (23 ± 2) ℃ for at least 2 hours to reach temperature equilibrium.
Testing procedure
Heating treatment: Place the sample in an oven set at 150 ℃ and maintain it for sufficient time (usually 1 hour) to fully heat the sample.
Cooling: After heating, remove the sample and let it cool naturally to room temperature (23 ± 2) ℃, or follow specific standard requirements.
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