Characterisation of heterogeneous Dorper fleece and comparative performance of Dorper and Merino felted textiles

Interest in circular material use has increased attention to animal-fibre by-products that fall outside apparel-quality classifications. Dorper waste wool has been converted into thermal and acoustic insulation, showing that a low-value fleece can retain useful nonwoven performance (Patnaik et al., 2015). Such materials should therefore be evaluated against both intended product requirements and conventional wool grades.

The Dorper is a South African meat breed rather than a specialised wool breed (Cloete et al., 2000). Hair-type, wool-type and intermediate coverings occur and the breed standard describes the preferred covering as a short, loose and light mixture of hair and wool (Dorper Sheep Breeders’ Society of South Africa, 2015). Dorper fleece should therefore be evaluated as a potentially heterogeneous fibre source.

Published textile research on Dorper fibre is limited. Patnaik et al. (2015) produced needle-punched insulation from Dorper waste wool but treated the material as a bulk fibre category. The relationship between wool–hair heterogeneity in unseparated Dorper fleece and the quantitative performance of a wet felt has not been established, nor has a direct comparison with Merino felt produced under matched conditions.

Fibre morphology alone cannot establish finished-textile performance. Diameter, length, crimp, cuticular structure and medullation affect fibre migration and entanglement during felting, but material suitability must be assessed based on the resulting textile (McGregor and Schlink, 2014; Raja et al., 2013). Measuring the felt, therefore, enables fibre-level observations to be considered alongside product-level properties.

This study characterises the constituent fibre populations of Dorper fleece and evaluates a 100% Dorper felt manufactured without deliberate wool–hair separation, compared with a separate 100% Merino felt produced under matched conditions. Fibre morphology and physical characteristics are related to the structural, mechanical, moisture-transfer and thermal properties of the felts, thereby assessing Dorper fleece as a value-added textile resource.

The Dorper is primarily a meat breed, and its fleece has limited commercial importance as an apparel raw material (Cloete et al., 2000). Patnaik et al. (2015), for example, described the Dorper fibre used in their investigation of insulation materials as waste wool. More broadly, the literature on waste-wool valorisation identifies opportunities for using low-value wool fibres in insulation, composites, sorbent materials and other technical products, as well as for extracting keratin for higher-value applications (Sun et al., 2023). This supports evaluating underused fleece according to its performance in alternative textile structures rather than exclusively against apparel-wool quality criteria.

The Dorper breed standard describes the preferred covering as a short, loose and light mixture of hair and wool (Dorper Sheep Breeders’ Society of South Africa, 2015). Sheep coverings can contain wool, hair, kemp and intermediate fibres (Ryder and Stephenson, 1968; Ryder, 1983). For textile evaluation, these may be grouped pragmatically as finer, crimped wool fibres and coarser, often medullated hair-type fibres. A bulk mean fibre diameter cannot adequately describe such constituent fibre populations.

Textile evidence specific to Dorper fibre remains scarce. Existing nonwoven research establishes that Dorper waste wool can be processed as a bulk material (Patnaik et al., 2015), but does not resolve the constituent wool and hair populations within an unseparated fleece. Characterisation of these populations is therefore necessary before bulk measurements can be interpreted in relation to processing behaviour and textile performance.

Wool is a hierarchical keratin fibre whose properties arise from its multi-scale protein architecture, internal cellular organisation and cuticular surface. Its processing behaviour depends on fibre diameter and diameter distribution, length, crimp, cross-sectional shape, medullation and cuticle-scale geometry (Botha and Hunter, 2010; Datta et al., 2023). These interacting characteristics influence fibre flexibility, cohesion, bulk and thermal behaviour; technical suitability cannot therefore be inferred from mean fibre diameter alone.

Merino wool provides an established comparative material because its relatively fine diameter and pronounced crimp promote fibre flexibility, cohesion and bulk (Botha and Hunter, 2010). Felting behaviour is not, however, governed by fineness alone. Chaudri and Whiteley (1970) found that crimp form was a major determinant of the felting rate of loose wool and that its effect interacted with directional friction, crimp frequency and fibre diameter. Liu and Wang (2007) similarly demonstrated that fibre length had a pronounced influence on felting propensity, while fibre diameter and cuticle-scale characteristics also contributed to the extent of entanglement. These findings confirm that felting must be interpreted through the combined effects of fibre dimensions and morphology.

During wet felting, moisture and mechanical action promote progressive fibre migration and entanglement. Directional friction arising from the orientation of the cuticle scales contributes to preferential rootward migration, while fibre length, diameter, crimp, scale geometry, elasticity and medullation modify the response (Chaudri and Whiteley, 1970; Liu and Wang, 2007; McGregor and Schlink, 2014). Raja et al. (2013) reported lower feltability for coarse, highly medullated wool than for medium-fine wool, demonstrating that consolidation depends on interacting fibre characteristics rather than the presence of cuticle scales alone.

Research on coarse, medullated and low-value wool demonstrates that fibres unsuitable for apparel can still provide functional performance in non-woven products. Sun et al. (2023) distinguish between the direct utilisation of waste-wool fibres in applications such as insulation, composites and sorbent materials and the extraction of keratin for regenerated or functional products. Direct conversion into a non-woven structure is particularly relevant where the preservation of the original fibre form and reduced preparatory processing are desirable.

Raja et al. (2013) produced technical felt after partially removing kemp and blending coarse wool with medium-fine wool. A 60:40 coarse-to-fine wool blend was identified as suitable for the technical felts developed in that study. Although the work confirmed the technical potential of coarse wool, it did not evaluate an unseparated heterogeneous fleece without a fine-wool carrier.

Patnaik et al. (2015) manufactured needle-punched thermal and acoustic insulation from 100% Dorper waste wool, establishing that the fibre could form a functional non-woven structure. However, the material was treated as a single bulk population, and needle punching produces consolidation through the action of barbed needles rather than the directional fibre migration involved in wet felting.

Other studies provide further evidence for the technical utilisation of low-value wool. El Wazna et al. (2019) produced needle-punched non-wovens from acrylic and wool waste and reported thermal conductivity values comparable with those of conventional insulation materials. Kobiela-Mendrek et al. (2022) manufactured felts from coarse mountain-sheep wool for sound absorption and found that performance was strongly dependent on felt thickness. These findings demonstrate that coarse and waste wool can contribute to functional non-wovens, while also showing that performance depends on the architecture and dimensions of the resulting textile rather than fibre identity alone.

Felt performance is determined by the combined effects of fibre properties and the architecture established during manufacture, including fibre orientation, entanglement, mass per unit area, thickness, fibre volume fraction and porosity. Kistamah et al. (2017) demonstrated substantial differences in mechanical and thermophysical properties among woven, felted and non-woven fabrics. Similarly, dos Santos et al. (2022) evaluated wool felt through mechanical, morphological, flammability and microbiological testing, illustrating the importance of characterising the finished material rather than inferring performance from fibre morphology. For lofty non-wovens, thickness can be a dominant determinant of steady-state thermal and water-vapour resistance and should be considered before differences are attributed to fibre type (Naylor et al., 2017).

Existing studies have therefore used different bonding routes, modified the starting material or evaluated properties unrelated to wet-felt formation. Evidence remains limited concerning wet felt manufactured from unseparated Dorper fleece and the relationship between its constituent fibre populations and the physical, mechanical and transport properties of the resulting material.

Greasy fleece collected immediately after shearing from 20 Dorper and 20 Merino sheep was pooled separately by breed. Merino wool was used as the reference material. Each pooled fleece lot was scoured and carded before being divided into five portions from which five replicate felt panels were manufactured. The panels, therefore, represented felting replicates produced from the same composite fibre lot.

The Dorper fleece was processed as a heterogeneous material without deliberate separation of its constituent wool and hair fibre populations prior to scouring, carding or felt manufacture. Dorper wool and hair fibres were manually selected solely for fibre-level morphological and physical characterisation. Dorper and Merino materials were processed separately and were not blended.

Longitudinal surfaces and cross-sections of raw and scoured Dorper wool and hair fibres were examined using a JSM-7800F field-emission scanning electron microscope (JEOL, Tokyo, Japan). Fibres were mounted on conductive carbon tape, sputter-coated with gold–palladium and examined at an accelerating voltage of 5 kV and a working distance of 10 mm. Longitudinal micrographs were used to characterise the cuticle-scale pattern and scale-edge morphology.

For cross-sectional examination, fibre bundles were drawn through an aperture in a rigid metal plate and cut flush using a microtome blade. The prepared bundles were mounted vertically and examined to determine cross-sectional shape and the presence or absence of a medulla. Magnifications and scale bars are provided in the corresponding plate captions.

The bulk mean fibre diameters of the heterogeneous Dorper fleece and Merino wool were measured separately using an Airflow apparatus in accordance with IWTO-28-2013. Mean fibre length was determined in accordance with IWTO-17-04.

Crimp frequency was determined manually using raw, relaxed fibres. The number of complete crimp waves within a 25 mm fibre length was counted and converted to crimps per centimetre. Ten fibres were assessed for each fibre population: Merino wool, Dorper wool and Dorper hair (n = 10 per group).

The Dorper and Merino fleece lots were scoured separately using woolwash FS 80/90 at a concentration of 4.5% v/v, following a laboratory-scale procedure in accordance with ASTM D584-10. The scoured fibres were rinsed and air-dried on mesh racks for 24 h at room temperature away from direct sunlight.

The dried fibres were carded separately using a laboratory roller card to open and individualise them, forming a relatively uniform carded web. Some loosely held short fibres and residual vegetable matter were removed during carding; however, no deliberate separation of the Dorper wool and hair fibre populations was undertaken.

Five replicate felt panels were manufactured from each composite fibre lot using a mechanical wet-felting machine. For each panel, four carded webs, each weighing 62 g, were cross-laid at 90° to the preceding web over a 900 × 900 mm template. The fibre assembly had a total initial mass of 248 g and a nominal initial mass per unit area of approximately 306 g/m².

Each fibre assembly was wetted with 2 L of aqueous felting liquor containing 4.5% Woolwash FS 80/90. The assembly was positioned between textured bubble wrap and perforated rubber cover sheets in the felting machine. Mechanical agitation was applied for four 20-min cycles, yielding a total felting time of 80 min. The developing felt was reoriented and inverted after each cycle to promote multi-directional fibre migration and consolidation. The finished panels were rinsed in tap water and dried flat on perforated racks at room temperature.

The same fibre mass, web arrangement, felting liquor concentration, liquor volume, agitation time and drying conditions were used for the Dorper and Merino panels.

Specimens were conditioned for 24 h at 20 ± 2°C and 65 ± 4% relative humidity before testing. Specimens were obtained from each of the five replicate panels per material. When multiple specimens or readings were obtained from a single panel, they were averaged to yield a single panel-level value.

Felt thickness was measured using a textile thickness gauge in accordance with BS 2544. A presser-foot pressure of 2.0 kPa was applied over an area of 2,000 mm². Ten measurements were obtained at distributed positions across each panel and averaged to yield a single panel-level value.

Bulk density (⁠$ρbulk$⁠, $g/cm3$⁠) was calculated for each panel from the measured specimen mass per unit area and conditioned thickness. The fibre volume fraction (⁠$Vf$⁠) and nominal porosity (⁠$P$⁠) were subsequently determined assuming a solid keratin fibre density (⁠$ρfibre$⁠) of $1.31 g/cm3$⁠:

Bending length and flexural rigidity were determined using the cantilever method with a Shirley Stiffness Tester in accordance with ASTM D1388. Specimens measuring 150 × 20 mm were tested from both faces and both ends. The measurements were averaged to obtain one representative value for each independently manufactured felt panel. Flexural rigidity was reported in mN·m.

Moisture regain was determined using the oven-drying method specified in ASTM D1576-90. Conditioned specimens were weighed, dried at 105 ± 2°C to constant mass and reweighed to the nearest 0.005 g. Moisture regain was calculated as:

where M_c is the conditioned mass, and M_d is the oven-dry mass.

Tensile behaviour was evaluated using an Instron constant-rate-of-extension universal testing machine and a strip method adapted from ISO/SANS 13934-1. Specimens measuring 250 × 60 mm were cut from representative positions, avoiding visible defects and local variations in Web uniformity. Testing was conducted using a gauge length of 100 mm and a crosshead speed of 100 mm/min. Maximum load at rupture and displacement at maximum load were recorded in newtons and millimetres, respectively.

Relative water-vapour permeability and thermal resistance were measured using a PERMETEST instrument (Sensora, Liberec, Czech Republic). Specimens measuring 120 × 120 mm, with an active diameter of 80 mm, were examined under isothermal conditions at an airflow velocity of 1.0 m/s. Measurements were performed in accordance with the instrument procedure referenced in ISO 11092. Relative water-vapour permeability (p _wv) was reported as a percentage and thermal resistance (R_ct) in m²·K/W.

Fibre-characterisation and felt-performance data were analysed separately. Results are reported as means. Bulk mean fibre diameter and fibre length were compared between the composite Dorper and Merino fibre lots using one-way analysis of variance (ANOVA). Crimp frequency was compared among Merino wool, Dorper wool and Dorper hair using one-way ANOVA. Following a significant overall ANOVA, Tukey’s honestly significant difference test was used for pairwise comparisons. Statistical significance was accepted at p  < 0.05.

For each felt property, measurements obtained from specimens or locations within the same panel were averaged to produce one panel-level value. The panel means for the Dorper and Merino felts were compared using separate one-way ANOVAs, with five independently manufactured panels per material (n = 5). Because these panels represent manufacturing replicates derived from a single composite batch per breed rather than independent biological replicates, the statistical inference demonstrates the repeatability of the laboratory felting process for these specific pooled lots. The results cannot be broadly generalised to capture the full biological variation across the Dorper breed without multi-lot, multi-farm or multi-seasonal sampling. Statistical significance was accepted at p  < 0.05.

Dorper wool fibres exhibited an overlapping cuticular scale structure in the raw and scoured states [Figure 1(a)–(d)].

Surface deposits on the raw fibres partly obscured the scale edges, whereas the scoured fibres displayed clearer scale definition, consistent with the removal of grease and other surface contaminants during scouring (Bhavsar et al., 2023). Localised surface irregularities were also observed, although the micrographs do not establish whether these originated before or during processing.

Figure 2 provides a comparative representation of the cuticular morphology of scoured Merino wool, Dorper wool and Dorper hair. The Merino wool displayed comparatively prominent scale edges, whereas the scale edges of Dorper wool appeared less pronounced. Dorper hair exhibited a relatively low-relief cuticular surface. Because Dorper hair required a lower magnification owing to its greater fibre dimensions, and because scale dimensions were not quantified, these observations represent qualitative morphological differences rather than direct measurements of scale height or frequency.

The raw and scoured Dorper hair micrographs provide further evidence of its relatively low-relief cuticular morphology (Figure 3). Surface deposits were visible on areas of the raw fibres, whereas the cuticle outlines were more readily discernible after scouring. Because the raw and scoured fibres were examined at different magnifications and scale dimensions were not measured, no quantitative inference concerning changes in cuticular geometry was made. Cuticle-scale geometry contributes to directional friction and fibre migration during felting; however, scale height, scale frequency and directional friction were not measured in the present study (Chaudri and Whiteley, 1970; McGregor and Schlink, 2014).

Cross-sectional micrographs distinguished non-medullated wool fibres from medullated hair fibres within the Dorper fleece (Figures 4–6). The images describe cross-sectional form and medullation qualitatively and do not constitute a statistical comparison of fibre diameter.

Dorper wool fibres displayed predominantly circular cross-sections without visible medullation (Figure 4), consistent with conventional wool morphology (Kadolph and Marcketti, 2017).

Dorper hair fibres exhibited irregular cross-sectional profiles and continuous medullation [Figures 5 and 6(a)–(d)].

A medulla introduces air-containing spaces within the fibre and can influence density and optical behaviour (Lewis and Rippon, 2013). The present images establish their presence but do not quantify the medullary fraction or its independent contribution to thermal performance.

Medullated fibres can contribute to harsh handling and non-uniform colouration in apparel wool (Lewis and Rippon, 2013). In a non-woven, however, medullation and coarseness should be evaluated through their effects on web formation, bulk and product performance rather than treated as disqualifying features in isolation.

Bulk mean fibre diameter did not differ significantly between the heterogeneous Dorper fleece (22.44 ± 1.01 µm) and Merino wool (21.70 ± 0.57 µm; p = 0.059), whereas Merino wool had a significantly greater mean fibre length (66.07 ± 2.28 mm) than Dorper fleece (43.50 ± 2.52 mm; p  < 0.001) (Table 1).

The larger standard deviation for Dorper fleece reflects greater variation among the replicate Airflow measurements; it does not represent the fibre-diameter distribution within the fleece. The Airflow method provides a bulk mean fibre diameter and neither measures the individual-fibre diameter distribution nor distinguishes between the wool and hair populations within a heterogeneous fleece (Botha and Hunter, 2010). Consequently, the comparable bulk mean fibre diameters should not be interpreted as evidence that Dorper fleece is uniform or structurally equivalent to Merino wool.

Interpretation of the Dorper Airflow result also requires caution because the measurement principle assumes an approximately constant fibre density. Fibre density decreases as the degree of medullation increases (Merrick et al., 1998); therefore, the medullated hair population may have affected the Airflow-derived mean fibre diameter relative to that obtained using an individual-fibre optical method. The direction and magnitude of this potential effect were not determined in the present study. Future research should combine individual-fibre diameter analysis with a validated optical or microscopic assessment of medullation to quantify the diameter distributions and relative proportions of the constituent fibre populations (Lupton and Pfeiffer, 1998).

The greater mean fibre length of Merino wool may have promoted greater fibre overlap and entanglement within the carded web, as fibre length influences the felting propensity of animal fibres (Liu and Wang, 2007). Nevertheless, fibre length acts in combination with fibre diameter, crimp, cuticular morphology, medullation and processing conditions. It should therefore be considered one contributor to the differences between the Dorper and Merino felt structures rather than an independent explanation of their performance.

Crimp frequency differed significantly among the three fibre groups (one-way ANOVA, p  < 0.001; Table 2). Merino wool had the highest mean crimp frequency (11.28 ± 1.19 crimps/cm), compared with Dorper wool (8.48 ± 0.96 crimps/cm) and Dorper hair (7.48 ± 0.92 crimps/cm). Tukey’s honestly significant difference test showed that Merino wool differed significantly from both Dorper fibre populations, whereas no significant difference was found between Dorper wool and Dorper hair.

Crimp configuration also differed qualitatively (Figure 7): Dorper wool appeared helical, whereas Merino wool and Dorper hair were predominantly sinusoidal. Crimp can influence packing, cohesion and fibre mobility (McGregor and Schlink, 2014), but configuration was classified visually. Its contribution cannot therefore be separated from fibre length, diameter, medullation, cuticular morphology and processing conditions.

The structural and mechanical properties of the machine-manufactured felts are presented in Table 3. All measured properties differed significantly between the Dorper and Merino felts (p  < 0.001).

Dorper felt was thicker than Merino felt (4.80 vs 3.16 mm), had a lower bulk density (0.064 vs 0.097 g/cm³), a lower fibre volume fraction (4.87 vs 7.40%) and a higher nominal porosity (95.13 vs 92.60%). Dorper felt also had a greater bending length (4.52 vs 3.86 cm), flexural rigidity (0.34 vs 0.19 mN·m) and displacement at maximum load (104.41 vs 95.10 mm), whereas Merino felt exhibited a greater maximum load at rupture (196.61 vs 179.00 N). All differences were significant at p  < 0.001 (Table 3). The greater bending length and flexural rigidity of Dorper felt indicate greater resistance to bending. Kistamah et al. (2017) similarly demonstrated that stiffness and related mechanical properties differ considerably among felted, woven and non-woven structures. In the present study, the bending response was strongly associated with greater thickness and lower bulk density in the Dorper felt and also reflected the potential contribution of its coarser, medullated fibres. Because bending stiffness depends on both intrinsic fibre properties and fabric architecture, the effects of fibre type cannot be completely isolated from those of overall thickness and internal packing consolidation.

Maximum load at rupture and displacement at maximum load represent different aspects of tensile behaviour and should be interpreted separately. Dos Santos et al. (2022) likewise distinguished between tensile resistance and elongation when evaluating wool felt, reporting different comparative responses for these properties. In the present study, the greater maximum load at rupture of Merino felt indicates superior resistance to rupture under the specified test conditions, whereas the greater displacement of Dorper felt indicates that it underwent more deformation before reaching maximum load. The results, therefore, do not establish the overall mechanical superiority of either material; instead, they demonstrate distinct deformation and failure responses.

These observed tensile behaviours are directly linked to differences in fabric architecture, bulk density, interfibre cohesion and the degree of consolidation developed during wet felting. The lower bulk density and higher nominal porosity of the Dorper felt reflect a less densely consolidated internal network. This loftier, more open matrix permitted greater initial structural deformation and internal fibre sliding, explaining its greater displacement at maximum load. Conversely, the higher fibre volume fraction and tighter packing of the Merino felt increased both interfibre friction and the number of contact points per unit volume. The greater fibre length and crimp frequency of Merino wool further promoted fibre overlap and entangling, yielding a more cohesive matrix capable of sustaining higher tensile loads before rupture. While these mechanisms align directly with the structural metrics, they remain structure-based interpretations of the physical data rather than directly observed causal relationships.

The moisture-related and thermal properties of the machine-manufactured felts are presented in Table 4. Moisture regain was comparable for Merino and Dorper felt (13.63 and 13.04%, respectively; p = 0.676). Merino felt exhibited significantly greater relative water-vapour permeability than Dorper felt (30.4 vs 20.3%; p  < 0.001), whereas Dorper felt exhibited significantly greater thermal resistance (0.1233 vs 0.0979 m²·K/W; p  < 0.001).

Comparable moisture regain indicates similar equilibrium moisture sorption under the specified conditioning conditions. Moisture regain primarily reflects water sorption within accessible regions of keratin and is independent of inter-fibre macro-porosity or liquid water retained between fibres.

The lower relative water-vapour permeability and greater thermal resistance of Dorper felt align directly with its greater thickness, lower bulk density and higher nominal porosity (Table 3). Increasing fabric thickness extends the tortuous diffusion path for water vapour molecules, while lower bulk density increases the total volume of stagnant air entrapped within the fibrous matrix. Similar thickness- and porosity-dependent relationships have been reported for the thermal and water-vapour transport of lofty non-wovens (Naylor et al., 2017).

Thermal transport through a non-woven structure is governed by conduction through solid keratin fibres and static air entrapped within the pore volume. Siddiqui et al. (2018) demonstrated that fibre volume fraction and entrapped static air contribute substantially to effective thermal conductivity and thermal resistance in non-wovens. El Wazna et al. (2019) also reported competitive thermal-insulation performance for needle-punched non-wovens containing wool waste, while Kistamah et al. (2017) showed that thermophysical performance varies with material composition and fabric structure.

In the present study, the superior thermal resistance of Dorper is driven by its low bulk density, lower fibre volume fraction and high structural porosity, which together maximise stagnant-air entrapment while minimising solid-fibre conductive heat pathways. Furthermore, the internal medullary air voids within the coarse Dorper hair fibres provide supplementary intra-fibre air entrapment alongside the inter-fibre matrix porosity. Consequently, the thermophysical response represents a combined effect of fabric-architecture and fibre-morphology, where high matrix porosity and thickness restrict convective heat loss while reducing relative water-vapour diffusion.

Although bulk mean fibre diameter did not differ significantly between the materials, Dorper fleece contained morphologically distinct wool and hair populations. The hair fibres were medullated and differed from the wool fibres in their cuticular and cross-sectional morphology. Merino wool had greater fibre length and a higher crimp frequency than the Dorper fibre populations. The similar bulk mean fibre diameters therefore concealed important differences in fibre composition and morphology.

Dorper felt combined greater thickness and bending stiffness with greater displacement at maximum load, whereas the thinner Merino felt sustained a greater maximum load at rupture. These responses are consistent with different degrees of fibre migration, overlap and consolidation. The importance of fibre length, crimp and directional friction in felt formation is well established (Chaudri and Whiteley, 1970; Liu and Wang, 2007). Nevertheless, because fibre orientation and the internal pore structure were not directly characterised, the effects of individual fibre characteristics cannot be completely isolated from those of the resulting fabric architecture.

The transport results were similarly influenced by structure. Dorper felt was thicker, more thermally resistant and less permeable to water vapour. Its greater thickness, lower bulk density, lower fibre volume fraction and higher nominal porosity were consistent with a more open, air-containing structure that may have contributed to these differences (Naylor et al., 2017). However, pore size, pore distribution and fibre orientation were not directly characterised. Moisture regain was comparable despite the differences in fibre composition.

Unseparated Dorper fleece was successfully converted into wet felt without blending with Merino wool or deliberately removing the hair component. Waste-wool research identifies insulation and non-woven products as potentially useful valorisation routes for low-value fibres (El Wazna et al., 2019; Sun et al., 2023). Coarse-wool felt has also shown potential in acoustic applications, although its performance was strongly dependent on material thickness (Kobiela-Mendrek et al., 2022). The thickness, bending stiffness and thermal resistance measured in the present study therefore support further investigation of Dorper felt for insulating layers and semi-rigid non-woven components.

These applications should remain candidate uses rather than confirmed end uses. Application-focused studies of wool felt have included tensile, laundering, flammability, microbiological and serviceability evaluations (dos Santos et al., 2022). Further assessment of Dorper felt should therefore include abrasion resistance, dimensional durability, flammability, acoustic performance and behaviour under relevant service conditions.

Unlike Merino wool, which is traded as an established textile commodity with regularly reported market indicators, no comparable formal market indicator could be identified for Dorper fleece. For context, the South African all-Merino indicator was R253.46/kg clean wool at the opening sale of the 2026/2027 season (Cape Wools SA, 2026). Dorper sheep are primarily produced for meat, and their heterogeneous hair–wool covering has limited established commercial value as a textile raw material (Cloete et al., 2000; Dorper Sheep Breeders’ Society of South Africa, 2015). Dorper fleece may therefore represent an underused, low-value fibre resource rather than a conventional wool commodity, offering potential as a low-value raw material source for non-woven applications. However, low raw material value does not necessarily translate into low overall production cost, as collection, scouring, carding and subsequent processing requirements must also be considered.

Processing the fleece without deliberate fibre separation could reduce preparatory operations and retain a greater proportion of the available material, thereby influencing processing costs and material yield. However, comparative trials using unseparated fleece and separated wool and hair fractions are required to determine whether improvements in uniformity or performance would justify the additional processing involved. Industrial-scale processing trials, yield measurements and formal environmental and economic assessments are therefore required before the commercial viability of Dorper felt can be established.

This study linked fibre-level characterisation of heterogeneous Dorper fleece with the properties of wet felt manufactured from the unseparated material. Dorper fleece contained non-medullated wool and medullated hair populations with distinct cuticular, cross-sectional and crimp characteristics; Merino wool had greater fibre length and crimp frequency.

The unseparated fleece formed a coherent felt without Merino blending. Relative to Merino felt, Dorper felt was thicker and stiffer, showed greater displacement at maximum load and thermal resistance and showed lower maximum load at rupture and relative water-vapour permeability. Moisture regain was comparable. The results demonstrate a material-level performance difference but do not isolate fibre morphology from felt thickness and architecture.

A primary limitation of this study is that the raw fleeces were pooled prior to panel manufacture; consequently, the five panels evaluated per material represent technical manufacturing replicates from a single composite lot rather than true biological replicates. While the findings confirm the repeatability and feasibility of the laboratory wet-felting process for the evaluated lot, they cannot be broadly generalised to represent the wider biological variation across the Dorper breed. Density, porosity and fibre orientation were not quantified and manufacture was laboratory-scale. Further work should sample independent fleeces, quantify felt architecture, compare unseparated and separated fractions and evaluate industrial processing, end-use performance and economic and environmental feasibility.

No external funding was received for this research.

The data supporting the findings of this study are available from the corresponding author upon reasonable request.