In the current study, an acrylic acid grafted bamboo rayon fabric was utilized as a substrate to immobilize ZnO nanoparticles. The bamboo rayon-ZnO nanoparticles composite was prepared by the treatment of swollen grafted fabric with ZnCl2 followed by conversion of Zn2+ ions into ZnO nanoparticles. The modified product was characterized and then evaluated for antibacterial activity against gram-positive and gram-negative bacteria as well as durability of their antibacterial activity after washing. The product showed antibacterial activity against both types of bacteria which was found to be durable till 40 washes. The modified material also showed improved UV protection. The product can be claimed as semidurable multifunctional textile material.
With increase in awareness about health and the requirement of protection, a number of functional properties are expected from textile materials. Textiles can be colonized by microbes which can result in adverse effects both on textiles and users. Apart from this the UV protection is becoming one of the desirable properties as textiles act as barrier layer between human body and the environment and can protect human body from harmful effects on skin of UV light if finished properly. Bamboo, a lignocellulosic material, belonging to the grass family
The grafted fibres especially from hydrophilic monomer like acrylic acid adsorb metal ions from the solution and also swell in contact with water. Hence they offer suitable substrate to immobilize the nanoparticles and to form nanoparticles composites. Incorporation of metal nanoparticles into polymer matrix has been reported by various researchers. Silver nanoparticles have been incorporated into poly(N-vinylpyrrolidone) (PVP) nanofibers using two distinct methods [
The deployment of different nanoparticles on grafted bamboo rayon has been reported earlier from our laboratory [
The bamboo rayon yarn was knitted to make fabric (single jersey, gsm-133.28, WPI-36, CPI-38) which was then scoured using NaOH (4% owf) and soda ash (1% owf). The scoured fabric was used for grafting. All chemicals (ZnCl2, NaOH, K2S2O8, and acrylic acid) used were of laboratory grade.
Grafting of acrylic acid onto bamboo rayon was carried out as per the procedure reported in our earlier research paper [
When grafted bamboo rayon sample was put in water, it swells to some extent due to the hydrophilic nature of acrylic acid as well as bamboo rayon. The grafted fabric was further treated with ZnCl2, where the adsorption of zinc ions takes place and the adsorption mechanism can be viewed as complex formation of zinc ions with carboxylic groups. When the swollen fabric containing Zn2+ ions was put in sodium hydroxide solution and cured, the ions are converted to ZnO nanoparticles and distributed almost uniformly throughout the network.
The grafted bamboo rayon fabric was characterized in order to validate grafting. The optimization of the grafting reaction was earlier reported from our laboratory [
FTIR spectra of fibres.
Figure
TGA of bamboo rayon, AA-g-BR, and nanoZnO
However, beyond 350°C, the loss in weight was slowed down and finally at 450°C, weight loss values observed were 96.81% for ungrafted, 90.13% for AA-g-BR, and 80.95% for nanoZnO
The surface morphology of the nanoZnO
SEM photographs of ungrafted (a) bamboo rayon, AA-g-BR (b), and nanoZnO
The change in appearance of modified fabrics due to nanoZnO formation was measured (refer to Table
Colour values of composite fabric (nanoZnO·AA-g-BR).
Sr. |
Nature of sample | ZnCl2 conc. |
Bending length |
K/S | L* | a* | b* |
---|---|---|---|---|---|---|---|
1 | Ungrafted | 0 | 2.35 | 0.2229 | 82.59 | −0.84 | 8.42 |
2 | AA-g-BR | 0.25 | 2.70 | 0.2000 | 88.72 | 0.64 | 8.84 |
3 | AA-g BR | 0.5 | 2.75 | 0.3055 | 85.22 | 0.57 | 9.90 |
4 | AA-g BR | 1.0 | 2.75 | 0.3143 | 82.94 | 0.52 | 7.90 |
L*, a* and b* are the colour co-ordinates.
The K/S values were of very small order, indicating negligible change in appearance of the fabric. ZnO nanoparticles are white in colour and hence offer the advantage in terms of minimal change in appearance. The bending length increased after modification indicating the increase in stiffness of modified bamboo rayon. However, the increase in bending length with the concentration of ZnCl2 was insignificant.
The quantitative antibacterial assessment was made using AATCC-100 (2004) test method and the results are presented in Tables
Effect of ZnCl2 concentration on antibacterial properties of nanoZnO·AA-g-BR.
Sr. |
Nature of sample | ZnCl2 conc. |
Bacterial reduction (%) | |
---|---|---|---|---|
|
|
|||
1 | Ungrafted | 0 | N | N |
2 | AA-g-BR | 0 | 35.52 | 30.35 |
3 | AA-g-BR | 0.25 | 88.60 | 89.78 |
4 | AA-g-BR | 0.5 | 100 | 98.13 |
5 | AA-g-BR | 1.0 | 100 | 99.56 |
N: negligible.
Durability of the antibacterial properties of ungrafted and grafted samples loaded with nanoZnO (0.5%).
Sr. number | Number of washes | Bacterial reduction (%) | |||
---|---|---|---|---|---|
Ungrafted | Grafted | ||||
|
|
|
|
||
1 | 0 | 87.52 | 87.90 | 100 | 98.13 |
2 | 5 | 41.95 | 43.10 | 92.88 | 90.04 |
3 | 10 | 18.25 | 19.10 | 82.19 | 82.93 |
4 | 20 | — | — | 78.63 | 79.02 |
5 | 40 | — | — | 71.36 | 72.98 |
6 | 50 | — | — | 56.98 | 60.18 |
The bamboo rayon fabric showed no antibacterial activity against both
In case of ZnO nanoparticle containing ungrafted bamboo rayon, the unwashed sample showed excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. However, the antibacterial activity was reduced drastically after subsequent washing showing only 50% reduction after 5 washes. The nanoZnO
The UV protection of the modified fabrics was evaluated and the results are summarized in Table
Durability of the ultraviolet protection of nanoZnO·AA-g-BR (0.5%).
Sr. number | Number of washes | Calculated UPF |
---|---|---|
1 |
|
106 |
2 |
|
75 |
3 |
|
55 |
4 |
|
46 |
5 |
|
21 |
Bamboo Rayon-ZnO nanoparticles composites were successfully prepared using acrylic acid grafted bamboo rayon substrate. The acrylic acid graft chains were responsible for immobilization of ZnO nanoparticles. Due to this type of anchoring the modified product displayed efficient and durable antibacterial activity and semidurable UV protection.
The authors do not have any stake in Datacolor International or AATCC and their names appear in the paper purely in coincidental and academic nature. Their reference is made to indicate standard equipment and test method made use of in this work and in no way it advocates these brands.
The authors gratefully acknowledge University Grants Commission (UGC-SAP) India for the research fellowship.