With the growing popularity of eco-friendly and sustainable textiles, a paradigm shift is observed in selection of high end use health and hygiene products. Cotton nonwovens treated with bioactive extract from the herb T. chebula could have a positive cradle to grave impact. The energy and time efficient manufacturing along ease of recyclability and biodegradability improves the cotton nonwovens Life Cycle Assessment (LAC) implication. Application of the aqueous extract of T. chebula rich in tannins and other antimicrobial agents provides an effective environment friendly finish. It improved the fibre’s, UV protection abilities, light fastness and perspiration fastness along with antimicrobial properties.
The health and hygiene sector has seen a large growth spurt ever since the invention of cellulosic nonwoven fabrics. It is perceived that the global market for nonwoven fabrics will see a steady growth from USD 40.5 million in 2020 to USD 53.5 billion by 2025 K/S . Nonwovens can provide good bacterial barrier textiles, as seen by the vast use of face masks and PPE kits in today’s COVID-19 scenario. It is therefore not surprising that cellulosic fibres are one of the top contenders in the ever expending field of nonwovens. The application of speciality finishes to them further provides good antimicrobial properties, ultra-violet protection, high absorption etc. But to meet the demand of these high end use products they are coated with chemicals that include inorganic salts, iodophors, phenols and thiophenols, formaldehyde derivatives and amines [2, 3], which may not always be ideal.
Simultaneously, cotton as a natural fibre with its well known properties of absorption, breathability, strength is fast becoming the fibre of choice within an aware and discerning market. When constructed by the nonwoven process, it leads to further reduction in time and energy. Its eco-friendly end of product lifecycle is an added advantage. Making it a cheap viable option for a number of skin friendly health and hygiene products, which can be further enhanced with the use of environmentally friendly antimicrobial treatments.
Figure 1. Terminalia chebula (Harda)
The application of Terminalia chebula (T. chebula) commonly known as Harda in the Indian Sub-continent provides the potential to create a sustainable finishing treatment, (Figure 1). Extracts of T. chebula are known to contain polyphenols and ellagitannins. The presence of 30-35 % tannin, thus enables the retention of colouring matter permanently post washing . Harda also plays a role in the inhibition of bacterial growth on textiles. Its high tannin content binds the enzymes and proteins that make up the cell wall structure of micro-organisms thereby restricting its growth .
The process of uniform dyeing with natural plant extracts on woven cotton fabrics usually involves constant stirring and agitation for extended time frames. This cannot be practiced on nonwoven fabrics as it would result in disturbance of its physical structure. Literature on the dyeing and fixation of nonwoven fabrics with natural dyes is scarce.
The aim of this paper therefore is to report the potential benefits of Terminalia chebula fruit extract as a “green” agent and its application, optimization and evaluation on cotton nonwoven fabrics of varying GSM’s.
2. Materials and Methods
T. chebula dried powder was procured from Adiv Pure Natural, Mumbai, India.
Cotton nonwoven, needle punched fabric of 100 GSM and 200 GSM were purchased from Tata Mills, Mumbai.
All chemicals used were laboratory grade.
Methods of aqueous extraction
For the three extraction methods mentioned below 10 grams of T. chebula powder along with 100 ml distilled water was heated for one hour.
- Open bath extraction: The powdered herb mixed in distilled water was heated and constantly stirred in an open bath.
- Reflux Method of extraction: The chebula powder was refluxed in a round bottom flask attached to a water jacketed condenser. This allowed for the condensation of vapours back into the flask.
- Rota Dyer: Vigorous agitation and constant temperature were used for extraction in a rota dyer
The extract obtained was filtered and subjected to 10 minutes of centrifugation at 3000 revolutions per minute. It was followed by filtration using a Grade 2 sintered glass crucible. A pure aqueous extract of T. chebula was then obtained.
Fabric treatment with obtained extract
Padding of the nonwovens was carried out on a vertical two-bowl pneumatic padding mangle at concentrations of 20% and squeeze rollers were set to achieve 80% wet pick-up. It was followed by fixation either by drying or steaming at varying temperatures and time intervals to optimize the process. After optimization all further samples were dried at 120oC for 3 minutes.
2.3. Evaluations and Tests performed
a. Wavelength of maximum absorption: For measurement of wave length of maximum absorption the extract was analysed through a UV-VIS 8500, UV-visible spectrometer of Hitachi, Japan. Once the (λmax) was determined it was used as a fixed point to analyse color concentration levels of all the three extracts diluted to identical levels.
b. Colour strength properties of dyed cotton nonwovens:
Colour characteristic measurements
A Rayscan SpectraScan 5100+ equipped with reflectance accessories was used to analyse the dyed samples. The K/S values were determined using the formula: K/S=(1-R)2/2R, wherein;
K is Absorption coefficient, S is Scattering coefficient and R is reflectance at complete opacity. An average of 4 reflectance measurements were noted each from four different sample areas.
Colour space values
The Spectra flash® SF 300 was used to evaluate the dyed nonwovens CIELAB colour space (L*, a*, b* and H*) values. This enabled understanding of tonal variations achieved on the samples, (Where L* corresponds to brightness, a* to red-green coordinates and b* to yellow-blue coordinates).
c. Colour fastness properties
Colour fastness to light- The ISO 105: B02:1994 was used for assessing light fastness. Assessment was done using the blue wool scale. The rating ranged from 1-8, (Where 1 is poor, 2-fair, 3-moderate, 4-good, 5-better, 6-very good, 7-best and 8 is excellent).
Colour Fastness to Perspiration– Test method used was ISO 105:E04. The colour change of sample and the staining of the undyed samples were assessed using a grey scale.
d. Ultraviolet Protection Factor- The (AS/NZ) 4399:1996. UPF ratings were noted in the range of 290-400 nm. The classes were identified as 15-24 (Good), 25-39 (Very Good), 40 and above (Excellent).
e. Antibacterial properties- The AATCC Test Method 100-2004 (AATCC technical manual, 2007) was used. To determine antibacterial effectiveness of the dyed cotton nonwovens. Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus) were used as inoculants. The reduction in bacterial colonies was estimated by the equation R=100 (B-A)/B, wherein
R=% reduction of bacterial count
A= Bacterial colonies recovered from treated specimens incubated for 24 hr contact period.
B= Bacterial colonies recovered from untreated specimens immediately after inoculation (as “0” contact time).
3. Results and Discussion
3.1 Identification of wavelength of maximum absorption
Figure 2. UV-Visible absorption spectrum of aqueous extract from T. chebula
The extracts from all three processes contain flavonoids observed by a broad band formed between 340-385 nm as shown in Figure 1. A typical UV-Visible spectra of flavonoids includes Band A that lies in the range of 310nm -350nm indicating flavones and Band B that lies in the 350nm-385nm range indicating the flavonoid subgroups . A sharp peak displayed at 365.50nm in the graph also ascertains presence of flavonols as the major constituent in the aqueous extract (Figure 2).
3.2 Comparative study of the three aqueous extraction methods
The extract obtained from the reflux method was observed to give the highest concentration at 0.6304. Followed by 0.5260 for Rota dyer method and minimum being 0.3419 for the open bath method. The optical density values were compared at 365.50nm. The reason could be the constant evaporation and condensation of the distilled water washing the herbal powder and promoting maximum extraction during refluxing.
3.3 Colour characteristics of cotton nonwovens pad-dyed with chebula aqueous extract
In order to optimise extract fixation method on 200 GSM cotton nonwovens. The aqueous extract was initially padded with 20% concentration followed by fixation either through drying (D) or steaming (S). Effect of varying temperatures on K/S values of pad-dyed dried and pad-dyed steamed 200 GSM cotton nonwovens with initial time of 3 minutes are noted in Table 1. The highest K/S values were observed for cottons steamed and dried at 100° C. Overall reduction by 40% in K/S values was observed in the steamed nonwovens. On the other hand the dried samples displayed an encouraging rise by 22% while increasing temperature from 90° C to 100° C. No dramatic increase was observed with further increase in temperature.
But with respect to colour coordinates all L*, a*, b* values are within the 70-100 range, thus indicating bright shades with deep tones of yellow. The dried samples exhibit redder tones as compared to the greener shades displayed in the steamed samples.
|Table 1. Effect of temperature on K/S values of steamed or dried 200 GSM cotton nonwovens|
|Fixation Process||Temp. (° C)||L*||a*||b*||K/S|
|Note: Fixation time 3 mins|
The K/S values of 100 GSM cotton nonwoven samples pad-dyed dried and pad-dyed steamed at varying time intervals are noted in Table 2. All “L” values indicate that an overall bright shade with prominent tones of yellow was achieved. With steamed samples displaying highest results.
|Table 2. Effect of temperature on K/S values of dried and steamed 100 GSM cotton nonwovens|
|Fixation Process||Time, mins||L*||a*||b*||K/S|
|Note: Fixation temperature 120° C|
3.4 Fastness Properties
Colour fastness to washing
Colour fastness to washing was used to decide the optimization of the fixation methods for the aqueous extract padded samples. The results for varying temperatures and time intervals are noted in Table 3 and Table 4.
|Table 3. Assessment of wash fastness of treated samples using various temperatures|
|Fixation Method||Temp. (0 C)||CC||SC||SW|
|Note: Fixation time – 3 mins,
CC= Change in colour,
SC= Staining in cotton,
SW= Staining in wool
Studies on cotton indicate that the wash fastness of a dye is influenced by the rate of diffusion and state of dye particle inside the fibre .
The effect of varying fixation methods and temperatures on te wash fastness of the cotton nonwovens have been recorded in Table 3. They conclude that a samples dried at 120° C offer optimum fixation benefits. Woollen adjacent fabrics displayed lower staining ratings as the protein fibres affinity to natural dye is higher compared to cellulosic fibres.
|Table 4. Assessment of wash fastness of treated samples using various time intervals|
|Fixation Method||Time, mins||CC||SC||SW|
|Note: CC= Change in colour,
SC= Staining in cotton,
SW= Staining in wool
The effect of varying time intervals and fixation methods on wash fastness properties of the nonwovens have been noted in Table 4. Both steamed and dried samples showed marked improvement in colour change values with increase in time to 3 minutes. Negligible change was observed with further increase in temperatures.
Colour fastness to light
After selection of the pad-dye-dry fixation method for the extract treated sample at 120oC for 3 minutes the samples were tested for light fastness. Reviews of materials dyed with extracts rich in tannins have claimed to have good light fastness properties and stand well against photochemical oxidation . In Table 5. similar results are reflected for 100 GSM and 200 GSM cotton nonwovens. The higher results achieved by 200 GSM fabrics could be attributed to greater penetration and aggregation of dye molecules due to the fibre arrangement and porosity of the fabric.
Colour fastness to perspiration
The samples of both GSM’s are nearly similar in results on treatment with acidic solution. Results of treatment with alkaline solutions are better for 100 GSM as compared with 200 GSM cotton nonwovens as noted in Table 5.
|Table 5. Assessment of light and perspiration fastness of cotton nonwovens dyed with T. chebula.|
|GSM of sample||Conc. (%)||Light fastness||Perspiration fastness|
|Acidic solution||Alkaline solution|
|Note: CC= Change in colour, SC= Staining in cotton, SW= Staining in wool|
3.5 Ultraviolet Protective Factor
A very small portion of the solar spectrum is made of UV rays, however they cause severe damage on living organisms such as skin carcinoma, malignant melanomas, accelerated skin ageing, cataract (etc) . The effect of UV transmittance on undyed 200 GSM cotton nonwovens is good as compared to 100 GSM. On application of T.chebula aqueous extract all samples including 100 GSM nonwovens displayed immediate improvement and were found to have excellent readings above 50+.
3.6 Antimicrobial properties
T.chebula is a herb with multiple medicinal values. The presence of gallic acid and its ethyl esters, egallic acid, ethanedionic acid and a number of other bioactive compounds have been recorded . The antimicrobial effect against both S. aureus and E.coli was maximum in 200 GSM samples treated with 40% concentration extract. Table 6. The samples showed good results against gram negative bacterial colonies which is similar to results reported in other studies [11, 12]. This could be because the gram negative bacterium is essentially composed of lippo polysaccharides (LPS) that reduces accumulation of antibacterial agents on the cell membranes. The presence of the above mentioned bioactive compounds in T.chebula prove effective in causing leakage in the cell membrane, thus reduction in the colony forming units, (CFU’s).
|Table 6. Effect on antibacterial properties of T.chebula extracts, (30% conc) on cotton nonwovens|
|Cotton Nonwoven||Conc, (%)||Bacterial Reduction, (%)|
|S. aureus||E. coli|
The successful application of aqueous T.chebula extract on cotton nonwoven fabrics by the pad-dye-dry process shows encouraging results. Cotton being the favoured choice of an aware customer can be enriched with the use of the herb to reach its full potential. The enhanced antibacterial properties, excellent Ultraviolet protection, good light and perspiration fastness it offers, is the need of the hour. This would help promote cotton nonwoven fabric treated with plant derived bioactive components as an viable environment friendly option in the field of health and hygiene.
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