Preliminary examination of the effects of relative humidity on the fracture morphology of cotton flat bundles

Abstract

A preliminary examination of the effects of relative humidity (RH) of three testing conditions on cotton fiber fracture morphology is presented herein. In addition, measurements of fiber moisture content, stelometer cotton flat bundle strength and elongation were collected at the three testing conditions. A general trend is observed for moisture content, strength and elongations measurements; testing in conditions with higher RH generally resulted in a progressive increase in moisture content, strength and elongation values. The morphology of broken fibers was also affected by the testing conditions. Fibers broken at high RH (i.e. 70 ± 2°F and 80 ± 2% RH) showed a more frayed fracture where microfibril separation, a fracture pattern that suggests independent microfibril failure, was evident. In contrast, at standard conditions (i.e. 70 ± 2°F and 65 ± 2%), fiber fractures were more granular (clean fractures), a reflection of a more unilateral breaking action. At low RH (i.e. 70 ± 2°F and 50 ± 2%), fiber fractures exhibited a distorted granular pattern, with extended fracture breaks that did not exhibit microfibril separation. Our preliminary findings are of relevance to post-harvest moisture control efforts currently employed in industry and may contribute to larger efforts to understand the effects of the fracture and damage observed in cotton fiber properties.

Keywords

Cotton tenacity elongation moisture AFIS HVI fiber fracture relative humidity

Cotton fibers readily exchange moisture content with their surrounding atmosphere. As water exchange progresses, the physical properties of the fiber are significantly altered.^1–3 Girth, strength, elongation and electric conductivity are among a few of the cotton fiber properties that change with differing moisture content.^1,2,4 Gains in strength are particularly noteworthy, since the strength of most synthetic fibers is not significantly changed by changes in atmospheric moisture.¹ Cotton is primarily composed of cellulose polymers that are organized in a collection of porous amorphous regions and tightly packed crystalline regions.² Current understanding indicates that incorporated moisture interacts with cavities in the amorphous region.⁵ Water-cellulose interactions release internal polymer stresses by reorganizing the network of hydrogen bonds in the amorphous cellulose regions.^5,6 As a result, cellulose sheets in the cotton fibers can withstand applied loads independent of other sheets and, thus, exhibit increased strength.

Maintaining control on cotton moisture content is crucial in preserving fiber quality during post-harvest cotton handling. For example, the reduced strength of seed cotton with low moisture content can lead to increased fiber breakage during ginning.⁷ Increased breakage, in turn, results in fibers of reduced length and commercial value.³ Studies on the morphology of broken fibers provide insight into what occurs during fiber fracture.^8,9 Tensile loads tend to untwist the helically organized microfibrils that form a cotton fiber. These breaks tend to occur where reversal points of microfibril arrangement are found.⁵ The effect of atmospheric moisture on the fracture morphology of broken fibers has been previously investigated.⁹ At standard conditions cotton fiber breaks have been described as sharp or even, an indication of moderate interactions between the microfibrils that form the cotton fibers. At 100% relative humidity (RH), fiber breaks were described as tattered or frayed, with separation of the microfibrils visible. Fractures performed in a vacuum and at 0% RH, showed great similarity to fractures that occurred at standard conditions, but with fracture points that were not as clean or granular. In only comparing fractures of fibers broken at standard conditions with fractures produced at extremes in moisture conditions (i.e. 0% and 100% RH), these experiments left unanswered the question of whether the observed moisture effects on cotton fiber fractures would be present at more typical environmental conditions like those found at a gin, or in non-standard laboratory conditions.

Our study seeks to further explore the effect of RH on cotton fiber fracture morphology. A better understanding of the effect of conditions more commonly found during cotton post-harvest handling would provide more practical insight. The work presented herein is divided into three parts. In the first part, a standard characterization of six cotton cultivars using commercially employed instruments (USTER HVI-1000 and USTER AFIS PRO) was performed. This characterization reveals if the morphology of fiber fractures is significantly affected by fiber properties. In the second part, fiber strength and elongation measurements were collected at three environmental conditions for the same cotton varieties, and a non-statistical comparison on the effect of moisture on stelometer measurements was performed. A stelometer was selected in this initial study since the instrument could be easily moved into a humidity-controlled glove box and because testing would produce fiber samples that were broken at different environmental conditions. The third part of this investigation explored the relationship between moisture content and the way a fiber behaves as it breaks. Broken fibers were examined with scanning electron microscopy (SEM) for differences in broken fiber morphology.

Materials and methods

Cotton samples

Six cotton varieties were chosen for this study. Varieties were selected based on their wide range of percent elongation and strength when measured by high volume instrument (HVI) testing (HVI strength ranged from 24.7 to 38.9 g/tex, and elongation ranged from 4.0 to 6.4%). Three of the cotton varieties were purchased from the Agricultural Marketing Service of the United States Department of Agriculture as International Calibration Cotton Standards (ICCS). The remaining varieties were used in recent studies at the Southern Regional Research Center (SRRC-ARS-USDA, New Orleans, USA). Two of the cotton varieties were grown in 2005, while the remaining variety, an international cotton from Australia, was grown in 2006.

Fiber testing

Cotton varieties were tested with an USTER HVI-1000 (USTER Technologies; Raleigh, NC, USA) to assess their elongation, breaking strength, micronaire and length uniformity (5 replicates for each sample). An USTER AFIS PRO unit was used to test for maturity ratio and fineness (5 replicates for each sample). All tests were performed at the SRRC-ARS-USDA. Prior to the measurements, the cotton samples were equilibrated for at least 24 hours at 70 ± 2°F and 65 ± 2% RH.

Subsamples from each cotton variety (5 g) were used to determine fiber strength and elongation, as measured with a stelometer, and moisture content at three environmental conditions. To prepare each sample, approximately 0.5 g of fiber was hand-combed until the fibers were mostly parallel. Each sample was then passed through a fine comb to remove excess fiber and to ensure that the fibers remained aligned. The resulting sample (∼ 0.06 mg) was secured in a Pressley clamp with a 1/8 inch gauge spacer. Samples were then tested on the stelometer following the ASTM D-1445-90 method.¹⁰ Five samples for each cotton variety were examined at each selected environmental conditions. Tests were performed at standard conditions (see above), at high RH (i.e., 70 ± 2°F and 80 ± 2% RH) and at low RH (i.e., 70 ± 2°F and 50 ± 2%). These conditions were chosen as representative of extremes that might be found in facilities that handle cotton post-harvest. Subsamples were stored at standard conditions, and then allowed to equilibrate to the testing conditions for at least 24 hours. Subsamples for high RH studies were not exposed to low RH environmental conditions, and vice versa. Testing was conducted in a medium-sized (50” × 24” × 24”) atmosphere controlled glove box (Coy laboratories; Grass Lake, Michigan, USA). The glove box RH was altered to reach the desired RH and constantly monitored with calibrated devices. The temperature was maintained at 70 ± 2°F; temperature fluctuations were reduced by cycling the glove box atmosphere through a chilled water bath from time to time. Moisture content for the samples at each testing condition was determined following the ASTM oven-drying standard method.¹¹

The effects of moisture on the morphology of broken cotton fibers were determined by examining samples with a LEO Gemini SEM (FEI; Hillsboro, OR, USA). Following stelometer testing, broken fiber samples were mounted on a SEM stub and coated with a gold/palladium coat. Each sample was examined for changes in fracture morphology that resulted from the stelometer tensile test. Areas near sites of fiber failure were examined at higher magnification.

Results and discussion

HVI and advance fiber information system (AFIS) analysis

An HVI instrument was used to assess the elongation, breaking strength, micronaire and length uniformity of the selected cotton varieties. These fiber properties, determined at standard conditions, are summarized in Table 1. As expected, HVI results showed a wide range of strength and elongation values. Cotton III fibers exhibited the highest strength (38.9 g/tex); however, fibers from cotton IV, V and I (32.5, 31.4 and 31.1 g/tex, respectively) can also be classified as very strong if USDA cotton classifications¹² are followed (i.e. strength higher than 3 g/tex). In contrast, cotton VI exhibits borderline strong fibers (29.3 g/tex), and cotton II has intermediate strength fibers (24.7 g/tex). In terms of elongation, cotton I exhibited the highest elongation percentage at 6.4%. Other varieties exhibited moderate (cotton II and VI; 5.9 and 5.3%, respectively) or low (cotton V, III and IV; 4.8, 4.6 and 4.0%, respectively) elongations.

Table 1.

Average fiber properties as measured by high volume instrument (HVI) testing

Cotton	Cultivar	Micronaire	UHML mm	UI [%]	Strength [g/tex]	Elongation [%]
I	C39STD	Average	3.41	29.1	83.5	31.1	6.4
I	C39STD	STDV	0.01	0.3	0.6	1.8	0.2
II	L2STD	Average	4.58	28.5	80.2	24.7	5.9
II	L2STD	STDV	0.02	0.3	0.5	0.4	0.3
III	M1STD	Average	3.12	32.6	83.4	38.9	4.6
III	M1STD	STDV	0.03	0.1	0.4	1.4	0.2
IV	FM960MS	Average	4.15	28.1	82.2	32.5	4.0
IV	FM960MS	STDV	0.07	0.3	0.6	1.1	0.2
V	DP488MS	Average	4.28	30.0	82.5	31.4	4.8
V	DP488MS	STDV	0.02	0.4	1.4	0.9	0.2
VI	Australia2	Average	4.64	28.6	81.5	29.3	5.3
VI	Australia2	STDV	0.05	0.5	0.7	0.3	0.4

UHML: upper half mean length; UI: uniformity index; STDV; standard deviation.

The range of HVI-determined micronaire values, which are a function of maturity and fineness, was also diverse. Three cotton varieties, cotton III, I and IV (3.12, 3.41 and 4.15, respectively), ranked within the low micronaire range (below 4.2 according to USDA classifications).¹² In addition, cotton V, II and VI (4.28, 4.58 and 4.64, respectively) exhibit micronaire values in the moderate to high range. HVI analysis also provided a measure of the uniformity index (UI) of the cotton varieties. The UI, essentially a percent ratio between the mean length and the upper half mean length of the fibers, provides an indication of the uniformity in length distribution of the sampled fibers and of the amount of short fiber content (SFC). All cotton varieties exhibited average or high UIs¹² (values ranged between 80.2 and 83.5%); with cotton II and VI exhibiting the lowest indexes (80.2 and 81.5%, respectively).

The maturity, fineness, length and SFC of the cotton varieties under standard conditions were also analyzed (Table 2). All varieties can be classified as mature (maturity ratio >0.85 according to USDA classifications),¹² with cotton IV exhibiting the highest maturity (0.95) and cotton I having the lowest (0.86). Fiber fineness ranged between 134.0 and 172.2 mtex, with cotton II having the coarsest fibers and cotton III having the finest. As expected, there seems to be a relationship between the micronaire and fineness values of the cotton samples. Cotton II and III exhibit the highest percent of SFC (28.9 and 27.7% by number; 10.3 and 9.2% by weight). The high SFC for cotton II correlates well with its length uniformity as determined by HVI; however, in the UI measurement, cotton III exhibited one of the highest length uniformities.

Table 2.

Average fiber properties as measured by advance fiber information system (AFIS)

Cotton	MFL (by number) mm	SFC (by number) %	MFL (by weight) mm	SFC (by weight) %	Fineness mtex	Maturity ratio
I	Average	20.6	24.1	25.4	8.6	140.4	0.86
I	STDV	0.5	1.5	0.5	0.7	0.9	0.01
II	Average	19.6	28.9	24.9	10.3	172.2	0.91
II	STDV	0.3	0.7	0.3	0.3	0.5	0.01
III	Average	21.08	27.7	27.43	9.2	134.0	0.88
III	STDV	0.05	2.4	0.05	1.1	1.6	0.01
IV	Average	21.1	20.3	25.15	7.1	161.6	0.95
IV	STDV	0.5	1.7	0.01	0.7	4.2	0.02
V	Average	22.61	19.2	26.92	6.3	168.2	0.93
V	STDV	0.08	2.1	0.08	1.1	2.6	0.01
VI	Average	21.08	21.4	25.40	7.30	170.8	0.94
VI	STDV	0.05	1.7	0.01	0.08	3.3	0.01

MFL: mean fiber length; SFC: short fiber content; STDV: standard deviation.

Following HVI and AFIS characterization, we can give broad classifications to the examined cottons. Cotton III is a strong but low maturity fiber when compared to the other examined varieties. Its low elongation (HVI measurement) is surprising given its strength. Cotton I, is slightly weaker than cotton III, but has a similar maturity ratio. Cotton IV has very mature and moderately strong fibers, in contrast to cotton II, which has weak, relatively immature fibers.

Stelometer and moisture content tests

A stelometer was used to examine the breaking strength and elongation, at 1/8” gauge length, of all six cotton varieties. In a stelometer flat bundle test, a small bundle of cotton fibers, combed until the fibers are parallel, is placed between two securing clamps. The clamps are then placed in the instrument, which then measures the amount of force required to separate the fibers to the point of breakage/failure. The strength of the fiber, often reported as stelometer tenacity, can be calculated by dividing the force required for breakage by the mass of the fiber sample. For this study, initial stelometer measurements were performed at standard conditions and corrected to readings with ones from the ICCS (Figure 1). While stelometer measurements confirmed cotton III as the strongest cotton (29.8 g/tex), strength measurements with a stelometer differ significantly from the related HVI measurement (38.9 g/tex with HVI; a 27% difference). Such discrepancies have been previously reported.^13–15

Figure 1.

Strength measurements for six cotton varieties as measured with a stelometer at various atmospheric conditions.

Notably, strength measurements with the three ICCS standards used in this study corresponded well with their stated values. Cotton I, II and III exhibited strengths of 25.1, 16.8 and 29.8 g/tex, respectively, which compared well to their stated standard strength values, 25.0, 18.0 and 30.8 g/tex, respectively. Four cotton varieties exhibited similar strength: cotton V, I, IV and VI (26.3, 25.1, 24.7 and 24.6 g/tex, respectively). Cotton II exhibited the weakest fibers with 16.8 g/tex. However, the percent error for some of the measurements was significant (>5%). At standard conditions cotton II and VI presented the highest percent error (10% and 15%, respectively), perhaps due to the lower UI of these cotton varieties.

Stelometer elongation measurements did not match with HVI measurements performed at standard conditions (Figure 2). Cotton I showed the largest elongation (7.1%), followed by cotton III, VI, II, V and IV. Notably, elongation measurements for the cotton standards, cotton II and III (5.3% and 6.1%, respectively) compared well with stated values (5.6% and 6.4%, respectively) for these calibration samples. These findings suggest that the discrepancy in elongation values is due to inherent differences of the instruments used for the measurements. HVI elongation measurements are based on optical measurements and are not calibrated against standards, whereas stelometry relies on a moving pendulum to measure elongation at the point of bundle break and is calibrated against standards. These principles might explain the somewhat low elongation value found for cotton III with HVI.

Figure 2.

Elongation measurements for six cotton varieties as measured with a stelometer at various atmospheric conditions.

Moisture content determinations were performed following the ASTM oven-drying method.¹¹ Moisture content ranged between 6.75% and 7.43%. The strongest cotton examined (cotton III) also showed the highest moisture content (7.43%), while the opposite held for the weakest cotton (cotton II, 6.75% moisture content). The remaining four cotton varieties showed similar moisture content (7.03% for cotton I, 6.84% for cotton IV, 6.97% for cotton V and 6.92% for cotton VI).

Stelometer measurements were also performed at non-standard conditions. Since many cotton fiber properties change with varying RH, temperature and moisture content, non-standard conditions can complicate instrument calibration and, more importantly, correction against a cotton standard. There is also the possibility of the instrument mechanical function differing with varying atmospheric conditions. Thus, for the purpose of this study, we aimed to develop a non-statistical comparison for which we could observe trends related to the effects of RH on strength and elongation measurements obtained with a stelometer.

Strength measurements at non-standard conditions with a stelometer differed at the various atmospheric conditions tested (Figure 1). At high RH, all cotton varieties exhibited increases in strength values when compared to measurements at standard conditions. Cotton III exhibited the highest strength, 32.1 g/tex, followed by cotton I, IV, V and VI (28.1, 27.3, 25.6 and 24.2 g/tex, respectively). Cotton II showed the lowest strength, 18.1 g/tex. However, we note that the error associated with some of these measurements is higher than the difference in strength measurements between tests at standard conditions and elevated RH. All increases in small bundle strength were accompanied by an increase in moisture content. These results compare to previous examinations on the effect of moisture content on cotton strength.^16,17 Further, greater gains in moisture content typically resulted in larger gains in strength. For example, cotton I showed the highest moisture content with 8.90%, a 27% gain in moisture content and a 12% gain in strength. The moisture content of cotton III increased to 8.84%, a 19% percent increase that accompanied a 7.7% increase in strength. At elevated RH, cotton III had 8.8% moisture content, followed by cotton V, VI, IV and II (8.8, 8.7, 8.68 and 8.41%, respectively).

At low RH, strength and moisture content measurements decreased. Once again, cotton III exhibited the highest strength, 28.4 g/tex, followed by cotton IV, I, V and VI (24.6, 24.5, 22.8 and 22.1 g/tex, respectively). Cotton II showed the lowest strength, 15.6 g/tex. Notably, strength measurements for cotton IV were only slightly different from the measurements at standard conditions. Still, measurements for this cotton variety showed a high percent error (9%), possibly due to measurement variability resulting from operator error. All samples showed a decrease in moisture content when compared to samples at standard conditions. Cotton III showed the highest moisture content at 5.81%, a 22% decrease. Cotton II showed the lowest moisture content at 5.35%, a 21% decrease. Cotton IV, which showed minimal decrease in strength at low RH (compared to standard conditions), showed 5.66% moisture content, a 17% decrease in moisture content. Other cotton varieties showed similar decreases in moisture content (Figure 3).

Figure 3.

Moisture content measurements for six cotton varieties as measured with a stelometer at various atmospheric conditions.

Elongation measurements at various RH levels show a trend that mirrors strength measurements; elongation measurements tend to increase with increasing RH levels (Figure 2). For example, cotton I, which showed the highest elongation at standard RH (7.1%), elongated 7.9% at high RH. In contrast, at low RH, cotton I elongated 6.3%. The biggest increase in elongation measurement was observed with cotton V, which elongated 5.1% at standard conditions, but showed 6.6% elongation at high RH (a 29% increase in elongation). The observed trends in strength and elongation measurements might reflect variations in fiber properties produced by changes in atmospheric RH; however, the accuracy of our determinations requires further testing. Calibration with a standard whose strength at non-standard conditions is known seems a requirement for validating measurements. These and other considerations will be implemented in future studies. Independent of the accuracy of the stelometer strength and elongation measurements, flat bundles of fibers were broken at differing environmental conditions. An examination of the different fiber fractures should still provide for a method of comparing the effect of testing environmental conditions on the fracture morphology of the fibers.

Fiber fracture

A variety of fiber fractures were observed for all the collected stelometer samples. Representative SEM micrographs of fractured flat fiber bundles are shown in Figures 4, 5 and 6. Strength measurements for each flat bundle sample produced a collection of broken fibers. Since not all fibers in the flat bundle break or elongate uniformly, a variety of fiber fractures are expected. Micrographs were selected to represent the most typical fractures observed in the fiber bundles. Cotton fractures following tensile tests at standard conditions reflect the structure and organization of the fiber (Figure 4). Cotton fibers are composed of a number of helically-wound microfibrils that form hollow tubes. When the cotton fiber is dried, the hollow tube collapses and forms a kidney-like structure.¹ During tensile strength testing, the fiber helix attempts to unwind to relieve stress. Weak points along the fiber break and start an axial separation (seen for cotton IV, Figure 4(d)) of the microfibrils.^8, ⁹ At standard conditions most of the fiber breaks are sharp or even (i.e. breaks at the same level). Sharp fiber breakage suggests moderate microfibril interactions, which leads to simultaneous breakage of the microfibrils.⁹ Two of the cotton varieties showed non-uniform breaks (cotton III and VI, Figure 4(c) and (d)). These extended breaks might result from the higher strength of these two varieties. Cotton II (Figure 4(b)), the weakest fiber, breaks in a sharp form and exhibits thin microfibril sheets that are characteristic of weaker or less mature fibers.⁸ While slight fiber surface damage (cracks) can be observed for cotton III, IV and V (Figure 4(c) to (e), respectively), the damage could have resulted from the SEM sample preparation.

Figure 4.

Cotton fiber morphology following stelometer tensile tests at standard conditions. Fracture damage is highlighted for cotton II and V. Microfibril axial separation is highlighted for cotton IV.

Figure 5.

Cotton fiber morphology following stelometer tensile tests at elevated RH. Fracture damage is highlighted for cotton IV. The directions of various microfibrils in cotton V are highlighted (to contrast with Figure 6(e)).

Figure 6.

Cotton fiber morphology following stelometer tensile tests at reduced RH and temperature levels. Surface fracture damage is highlighted for cotton II and IV. The direction of microfibrils in cotton V is highlighted (to contrast with Figure 5(e)).

Long, frayed fiber breaks are observed for cotton samples submitted to stelometer tests at high RH (Figure 5). The increase in RH and accompanying increase in fiber water content reduces the interaction between the microfibrils,⁵ resulting in the microfibrils breaking independently during the tensile test.⁹ Frayed fiber breaks are readily observed for cotton II, III and IV (Figure 5(b) to (d)). However, the extensive microfibril separation observed for cotton V is more typical of wet (100% RH) cotton fibers subjected to tensile loads.⁹ The helical organization of the cotton microfibrils is particularly prominent in the micrograph of cotton III (Figure 5(c)). The fracture for cotton III is not parallel to the length of the fiber; instead a small inward angle is observed. Given that the fibers are stronger at higher RH, a higher force has to be applied to break them. Thus, fibers have to unravel more from their helical organization before fracturing. The resulting fractures tend to show the results of tensile stress as weathered ruptures. We note that thin microfibril sheets are observed along failure points of cotton II (Figure 5(b)). In contrast, microfibrils for the stronger cotton V appear to be thicker (Figure 5(e)). The frayed surface of these cotton fibers complicates observing the fiber surface damage. But in general terms, the morphology of these fiber fractures is similar to those reported for wet cotton fibers. Some fibers exhibit surface cracks that extend far away from the point of failure, but as with samples at standard conditions, this type of damage could have been caused during the SEM sample preparation.

At reduced humidity, fibers exhibit distorted granular breaks (Figure 6), that is, breaks that are extended from the point of fracture, but without exhibiting the sheer stress and helical unraveling observed at high RH. Similar extended fractures were observed for cotton III and VI (Figure 4(c) and (f)) at standard conditions, yet that fiber morphology was attributed to the higher strength of those cottons. In contrast, at low RH, all fibers showed a decreased strength (see above). Instead, the extended fractures at low RH are likely due to the increased brittleness of the fibers. This brittleness results in more fracture points, but, unlike the sample fractures at elevated RH, independent microfibril fracture separations are not observed. Cotton V samples provide a good comparison. At high RH (Figure 5(e)), as described above, the fracture shows significant microfibril separation. More so, the microfibrils appear to be pointing at different directions, an indication that they fractured independently. In contrast, at low RH (Figure 6(e)), the microfibrils, while still visible, are aligned, in close proximity while directed in the same direction. Thinner microfibril sheets are still observed for cotton II (Figure 6(e), when compared to 5(e)).

Conclusions

The aim of this study was to explore the effect of the moisture content of three testing environments (low and elevated RH and standard conditions) on cotton fiber fracture morphology. Strength, moisture content and elongation measurements were also performed at these conditions. General trends were observed. Notably, examinations at the elevated RH (i.e. 70 ± 2°F and 80 ± 2%) resulted in increased strength, moisture content and elongation values, when compared to measurements at standard conditions (i.e. 70 ± 2°F and 65 ± 2%) or reduced humidity condition (i.e. 70 ± 2°F and 50 ± 2%). SEM micrographs showed that fiber failure morphology is affected by the RH of the testing environment. Fibers broken at high RH demonstrated more independent fracture for the microfibrils and, thus, appeared frayed. These observations were similar to the reported examinations of fiber fractures of wet cotton (100% RH).^8,9 In contrast, fibers were more granular or even in their fractures at standard conditions. Notably, fibers broken at 50% RH exhibited extended fractures that were not accompanied by microfibril separation, likely a result of fiber brittleness at low RH. Independent of testing conditions, differences could be observed between the fractures of weak and strong fibers, with the weaker fiber often displaying thinner microfibrils. The observed fiber fracture trends might affect the way seed cotton and cotton fibers are treated post-harvest.

Moisture control in post-harvest cotton processing facilities is gaining significant attention in today’s cotton industry; yet, examination of fiber fractures of processed fibers is not a focus of current research. While the rate of tensile load also plays a significant role in the morphology of fiber fractures, our findings suggest that cotton fiber processing at low RH might result in more extensive fiber damage. However, the resulting effect of the fiber fractures we observed on other cotton properties, like length, is not clear and should be explored. Hence, future studies of fiber fractures on various processed fibers and the effect of these fractures on commercial fiber properties will follow this initial study.

Footnotes

Acknowledgements

The authors acknowledge the assistance provided by Jeannine Moraitis, Clare Kappel, Corey Harris and Crista Madison of SRRC-ARS-USDA for performing the analyses. We also thank Chris Delhom and Olga Richard of SRRC-ARS-USDA and Ivan Dickson of the LSU Cotton Fiber Lab for providing key stelometer training and Dr. Omar Green, Dr. Matt Tarver and Samira Musah for providing helpful manuscript comments.

Funding

This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

Disclaimer

The use of a company or product name is solely for the purpose of providing specific information and does not imply approval or recommendation by the United States Department of Agriculture to the exclusion of others.

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