Dew-Retted Heilongjiang Flax against Imported Water-Retted Bales
Dew-retted Heilongjiang flax provides cost savings for medium counts, while imported water-retted bales deliver the fineness needed for yarn counts above Nm 50.
Pressley Clamp Testing
Strength Measurement
Mechanical method for measuring the breaking strength of a flat bundle of fibers under tension determines the commercial value of a flax crop. Executing pressley clamp testing involves securing a prepared ribbon of fibers between two metal jaws and applying force until failure. The result is recorded as the amount of weight required to break a specific mass of fiber.
Laboratory Procedure
Technicians must carefully align the fibers to ensure they are parallel and free of tangles before tightening the device. Since pressley clamp testing uses a zero gauge or a small 1.5 millimetre gap, it isolates the strength of the fibers from the influence of twist. Atmospheric humidity must be controlled to prevent moisture from skewing the results.
This test is repeated multiple times to find an average. Reliability depends on the precise calibration of the spring balance and the consistent application of clamping pressure.
Quality Threshold
Spinning mills use these results to determine if a batch of flax can withstand the high tensions of wet-spinning frames. If the force recorded during pressley clamp testing falls below the buyer specification, the material is downgraded for use in coarser yarns. High-quality linen requires a strong foundation.