Fibre Physics
Hygroscopic materials absorb water vapour from the surrounding atmosphere until the rate of absorption equals the rate of evaporation. In textile testing, moisture regain equilibrium is the point at which the fabric sample neither gains nor loses weight in a controlled environment. This state is highly dependent on the relative humidity and temperature of the testing room.
The equilibrium must be reached before any physical property measurements begin, ensuring consistent data across different laboratories.
Laboratory Conditioning
Standard atmosphere for textile testing requires twenty degrees Celsius and sixty-five percent relative humidity. To ensure the samples reach this stable state, they are pre-conditioned at a low humidity to ensure they approach equilibrium by absorbing moisture. This approach prevents hysteresis effects from affecting the final weight.
The conditioning period ranges from four to twenty-four hours.
Testing Process
Weighings of the sample are conducted at regular intervals to confirm that no further mass change occurs. If the difference between two weighings is less than zero point one percent, the sample has reached its stable point. This confirmation is crucial for accurate tensile strength tests.
Commercial Weight
Commercial transactions of raw fibres and yarns rely on these standardized moisture values to calculate the invoice weight of shipments. Since water is heavy, buyers do not want to pay for excess water, and sellers cannot afford to lose weight through dry fibers. This financial factor makes precise humidity control the most important operational parameter in commercial textile labs.
