Fibre quality characterization of water-retted Indianlinseed (Linum usitatissimumvar. RLC 92)

Introduction

Fibre fineness, length, bundle strength, and diameter are widely regarded as the key processing properties that determine the suitability of extracted bast fibre for textile spinning, yarn production, or composite reinforcement (Norton et al., 2006) [1] . These properties are influenced jointly by the genotype of the plant, the agronomic conditions under which it is grown, and the retting and mechanical extraction method used to isolate the fibre from the stem (Norton et al., 2006; Goudenhooft et al., 2019) [2,1] . While the physical and mechanical properties of dedicated fibre-flax have been extensively characterised, comparatively little quantitative data exist for the bast fibre obtained from Indian dual-purpose linseed genotypes, which are cultivated mainly for oil but whose straw represents a potentially valuable, currently under-utilised by-product (Husain et al., 2009) [3] . The present study characterises the physical and mechanical properties of textile-grade fibre extracted from the dual-purpose linseed variety RLC 92 through water retting and mechanical scutching-hackling, and situates these results within the range of values reported for flax and linseed bast fibre in the wider literature.

Materials and methods

Fibre source

The fibre characterised in this study was obtained from dual-purpose linseed (variety RLC 92) straw processed by seven-day water retting, sun drying, mechanical scutching, and manual hackling, as detailed in a companion process study on the extraction and yield of this fibre. The clean, hackled long-line fibre fraction was used for the physical and mechanical property testing reported here.

Testing methods

Fibre fineness was assessed by an in-house method and expressed in denier, using a torsion balance following sample preparation and dye marking. Fibre length was measured in accordance with ASTM D5103 using a black plate and calibrated ruler. Bundle fibre strength and elongation were determined in accordance with ASTM D1445 using a Stelometer. Fibre diameter was determined by a microscopic method. All tests were carried out at the Northern India Textile Research Association (NITRA), Ghaziabad. Mean values and coefficients of variation (CV %) were computed from the test replications using Microsoft Excel.

Results

Fibre fineness

The average fineness of the extracted fibre, assessed by the in-house denier method, was 55.50 denier, with a coefficient of variation of 14.53% (Table 1).

Fibre length

Fibre length, measured according to ASTM D5103, averaged 282.36 mm, with a coefficient of variation of 31.38%. The minimum and maximum fibre lengths recorded were 125.0 mm and 533.0 mm, respectively (Table 2).

Bundle fibre strength

Bundle fibre strength, tested according to ASTM D1445, gave a tenacity of 70.38 g/tex, a mean breaking load of 4575 gf, a coefficient of variation of breaking load of 22.16%, and an elongation of 2.0% (Table 3).

Fibre diameter

Fibre diameter, determined by the microscopic method, averaged 63.23 μm, with a coefficient variation of 76.98% (Table 4).

Discussion

The fineness value obtained (55.50 denier, CV 14.53%) indicates a moderately fine, reasonably uniform technical fibre bundle. Fineness in bast fibres is known to be influenced jointly by cultivar and growing-season conditions, with drier growing seasons and favourable agronomic management generally producing finer, more uniform fibre (Norton et al., 2006) [1] ; the present value is consistent with fibre of adequate fineness for blending applications. The relatively high coefficient of variation observed for fibre length (31.38%) reflects the inherent heterogeneity of technical bast fibre, which is composed of bundles of elementary fibres of unequal length rather than a single continuous filament (Angulu & Gusovius, 2024) [4] . The average length of 282.36 mm, and the wide spread between the minimum (125.0 mm) and maximum (533.0 mm) values, are of a similar order of magnitude to the weighted average fibre lengths of 100-550 mm reported for retted and non-retted flax fibre fractions, with retted fibre consistently showing greater average length than non-retted fibre (Nair et al., 2013) [5] . This spread is also consistent with the expectation that hackling separates the fibre population into a long-line fraction and a shorter tow fraction rather than a single uniform length class (Manian et al., 2021) [6] . The measured tenacity (70.38 g/tex) and low elongation (2.0%) are characteristic of bast fibre as a stiff, high-strength material with limited extensibility. Retting quality has been shown to directly affect these mechanical properties, with the breaking force of properly retted fibre exceeding that of non-retted fibre, since adequate removal of pectic and non-cellulosic binding material through retting improves rather than weakens tensile performance (Nair et al., 2013) [5] . The comparatively low elongation obtained here is consistent with a wellretted, low-extensibility fibre suitable for spinning. The measured average diameter of 63.23 μm is substantially larger than the elementary (single-cell) flax fibre diameter of approximately 20 μm commonly reported in the composite-reinforcement literature (Goudenhooft et al., 2019) [2] , indicating that the present measurement reflects a technical fibre bundle comprising several elementary fibres bound together, rather than an individual ultimate fibre cell. The very high coefficient of variation for diameter (76.98%), compared with the markedly lower CV for fineness (14.53%), is consistent with this interpretation: technical bundles vary considerably in the number of elementary fibres they contain along their length, whereas fineness, expressed on a linear-density basis, averages out much of this bundle-to-bundle variability (Goudenhooft et al., 2019; Angulu et al., 2024) [4,2] . Taken together, the fineness, length, and strength characteristics obtained for RLC 92 fibre in this study fall within ranges reported as suitable for spinning bast fibre either alone or in blends with other fibres such as cotton (Martin et al., 2014), supporting the potential of this under-utilised Indian linseed genotype as a textile fibre resource.

Conclusion

The bast fibre extracted from dual-purpose Indian linseed (RLC 92) through water retting and mechanical scutching-hackling exhibited a fineness of 55.50 denier, a length of 282.36 mm, a bundle tenacity of 70.38 g/tex with 2.0% elongation, and a diameter of 63.23 μm. These values are broadly comparable with previously reported physical and mechanical properties of flax and linseed bast fibre, confirming that the extracted fibre possesses fineness, strength, and length characteristics adequate for further textile processing. The findings support the potential of this under-utilised Indian linseed genotype as a viable raw material for blended yarn spinning and other textile applications.

References

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8. How to cite this article: Singh V, Pandey R, Dubey R, Sakshi, Yadav A, Mishra M. Fibre quality characterization of water-retted Indian linseed (Linum usitatissimum var. RLC 92). International Journal of Agriculture Extension and Social Development. 2026;9(9):773-775. doi: https://www.doi.org/10.33 545/26180723.2026.v9.i9j.4267