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Preparation and properties of low fibrillated antibacterial Lyocell fiber
⁎Corresponding author. dongzhh11@163.com (Chaohong Dong)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Abstract
In the process of Lyocell fiber-forming, nano zinc oxide was added to prepare the fabric with antibacterial function. The chemical structure and crystal structure of the fabric were analyzed by Fourier transform infrared spectroscopy and X-ray diffraction, which show that the chemical structure of the fiber was not significantly changed, however the crystallinity decreased obviously. The thermogravimetric test results show that the thermal stability of the fabric doped with nano-ZnO is not affected. The results of the physical and mechanical properties of the fabric show that the Lyocell fabric has better wear resistance, the bursting strength decreases by about 20% compared with the fabric before doping, and the whiteness of the fabric increases. Lyocell fabric has a good killing effect on microorganisms, and the antibacterial rate of staphylococcus aureus and Escherichia coli can reach 97%. Finally, the dyeing experiments show that the effect of ZnO on the dyeing property of the fiber is limited, which is controlled in the range that can not be recognized by human eyes. It must be mentioned that the idea and novelty of this paper were adding nano ZnO in dry-jet wet spinning process to prepare ZnO-Lyocell, and increase some physical and chemical properties of lyocell, and the role of nano ZnO was like a doping material, which providing the fiber with long-lasting antibacterial properties.
Keywords
Lyocell
Nano zinc oxide
Antibacterial
Dyeing
Low fibrillation
1 Introduction
Lyocell is a kind of regenerated cellulose fiber newly developed in the 1990s, with renewable trees, bamboo, and straw as raw materials, non-toxic tasteless N-methyl morpholine oxide (NMMO) as solvents, spun by a dry-jet wet spinning process (Fink et al., 2001). Compared with traditional regenerated cellulose fibers, the Lyocell fibers production process is green and environmentally friendly, does not produce waste gas and harmful gases, has the characteristics of sustainable use and recycling. Lyocell fiber has the advantages of soft feel, high comfort, simple dyeing process, and high colorfastness (Sarkar and Vora, 2011; Sharma et al., 2019, Sayyed et al., 2019; Zhang et al., 2018), at the same time, the product also can achieve microbial degradation in the natural environment, which is expected to fundamentally solve the major problems of sustainable development of the textile industry (Jiang et al., 2020; Parajuli et al., 2021; Yang et al., 2021).
As society pay more and more attention to health and hygiene, the antibacterial performance also become one of the fabrics’ additional functions (Adams and Walls, 2020; Gao and Cranston, 2008). In the process of using fiber products will come into contact with a variety of bacteria, mold, and other microorganisms. These microorganisms in the appropriate external conditions will grow rapidly, and produce odor at the same time will spread disease (Wang et al., 2017). However, the fact that Lyocell fiber itself does not have antibacterial properties, which limits its development and high-end application fields. To meet the needs of different levels of consumers, the development of antibacterial Lyocell fiber has become an inevitable trend (Kjea and Hzb, 2015; Ristíc et al., 2011; Uddin, 2015).
Nowadays, there are three different ways to prepare antibacterial Lyocell fibers: physical blending, chemical reaction, and post-treatment. The physical blending method is directly adding antibacterial agents into the spinning dope, which due to the remarkable acceptance towards organic or inorganic functional additives when cellulose physical dissolved in NMMO (Kulpinski, 2005; Melle et al., 2006), which can be utilized to produce antibacterial Lyocell fiber. The hydroxyl groups on cellulose can provide reactive sites for reactive antibacterial agent, which can be oxidized to carboxyl groups (Gao and Edgar, 2019; Saito et al., 2007), then the antibacterial fibers can be obtained by chemical grafting (Najmeh et al., 2022), Schiff base reactions and other chemical reactions. Although the Chemical reaction methods can be used, and may obtain fibers with long-lasting antimicrobial properties, it appears rather difficult to realize from the technological view. Lyocell fiber also can obtain antibacterial properties through post-treatment methods, such as physical coating, filling or impregnation process etc. (Borsa, 2012; Liu et al., 2018; Meng, 2016). The post-treatment method has the advantages of simplicity, convenience, flexibilityand low cost, but the durability can be an issue.
Antibacterial agents are mainly divided into organic antibacterial agents and inorganic antibacterial agents: organic antibacterial agents have good antibacterial properties, but their heat resistance and stability are lower than inorganic antibacterial agents (Fang et al., 2006; Li et al., 2008), the decomposition products and volatiles are toxic and are prone to drug resistance (Cohen, 1992; Xu et al., 2013) and other shortcomings, and their use is limited to a certain extent. Inorganic antibacterial materials have attracted more and more attention due to their advantages of good heat resistance, stability, drug resistance, broad-spectrum antibacterial, long validity period and low toxicity (Simoncic and Tomsic, 2010; Jana et al., 2019). In addition, some people study biological extracts as antimicrobial agents, such as chitosan (Svjetlana et al., 2009), animal keratin (Matine et al., 2022), plant extracts (Eisvand et al., 2020), etc., it is possible to lead a new direction of development. At present, inorganic antibacterial materials are mainly divided into metal ion inorganic antibacterial materials and photocatalytic inorganic antibacterial materials. Metal ion inorganic antibacterial material is mainly an antibacterial material prepared by loading metal ions with strong antibacterial activity such as Ag+, Zn2+, Cu2+ onto the substrate (Román et al., 2020; Smiechowicz et al., 2011; Smiechowicz et al., 2018; Mahboubeh et al., 2022). Photocatalytic antibacterial materials are mainly antibacterial materials containing TiO2 and ZnO substances. These materials are mainly generated by light, and the electrons and holes generated by light can react with hydroxyl groups or adsorbed O2 on the surface of the material to form free radicals, such as “·OH” and “·O2–”. These free radicals will attack the bacterial cell membrane and further kill the bacteria to achieve the purpose of bacteriostasis (Alswat et al., 2017). Previous studies have shown that ZnO is more likely to generate reactive oxygen species than other oxide nanomaterials (Tam et al., 2008; Zhang et al., 2013). The antibacterial properties of zinc oxide have a significant relationship with its specific surface area. When the particle size of ZnO is in the nanometer scale, it can provide a surface area with high antibacterial activity, and the fine size does not have a large impact on the mechanical properties of the substrate. Nano-zinc oxide has great research potential as a fabric antibacterial agent (K. Catherine Siriya Pushpa, 2015; Ciolek et al., 2019; Chen et al., 2019; Sharma et al., 2016).
In this study, Lyocell fiber was doped with nano zinc oxide to prepare environment-friendly and safe high-end antibacterial fabrics. The chemical structure and crystal structure of the fabric were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The apparent morphology and element distribution of the fabric before and after the doping were compared and the thermal stability of the sample was analyzed by thermogravimetric test (TG). The physical and mechanical properties of the fabric, such as friction resistance, breaking strength, and whiteness, were tested. The antibacterial performance test results show that the nano ZnO-Lyocell fabric has a good killing effect on bacteria, and the dyeing results show that the dyeing properties of ZnO-Lyocell fabrics are lower than that of the control Lyocell fabrics, but they can still achieve satisfactory color effects.
2 Experimental
2.1 Materials
NMMO (50 wt%) and nano ZnO were obtained from Shanghai Macklin Biochemical Co., Ltd (China), and the particle size of nano ZnO is 30 ± 10 nm. Wood pulp (DP = 820 and 97.9 % α-cellulose) dispersing agent and stabilizer were supplied by Shandong Jinyingli New Material Technology CO., Ltd., China.
2.2 Preparation of antibacterial loycell fabrics
Nano zinc oxide antibacterial agent was mixed with dispersant and stabilizer to prepare antibacterial agent dispersion solution. In the process of preparing the Lyocell fiber spinning solution by mixing pulp and solvent, the antibacterial agent dispersion solution was added to it, and the antibacterial Lyocell fiber was prepared by the dry-jet wet spinning method at a certain temperature. The cellulose content in the spinning solution is 11 % (w%), and the addition of nano-zinc oxide is 5 % (w% of cellulose). During the spinning process, the spinning speed was 20 m/min, the number of spinneret holes was 20,000, the spinneret hole diameter was 120 µm, the air gap length was 20 mm, and the coagulation bath was 25 % NMMO solution. Finally, the antibacterial Lyocell fiber was obtained after cleaning, drying, and oiling. Subsequently, the lyocell fiber was twisted into tight Siro with the count of 40 S, and woven into a fabric with a density of 80 g/m2 by a double-knit circular machine, which was named as ZnO-Lyocell fabric. The lyocell fabric without nano-zinc oxide is produced by the same spinning and weaving process and is named control Lyocell fabric, which means all of the technologies are same, except without nanoparticles. The schematic diagram of ZnO-Lyocell fabric preparation process was shown in Fig. 1.
Schematic diagram of preparation process of ZnO-Lyocell fiber.
2.3 ZnO-Lyocell fabric dyeing process
First, 5 g of ZnO-Lyocell fabric was weighed for use, and 0.1 g of reactive dye (2 %. owf) was dissolved in 150 g of deionized water to obtain a dye solution. When the dye solution was heated to 40 °C, the ZnO-Lyocell fabric was immersed, and the bath ratio is 1:30. After the fabric was immersed in the dye solution for 10 min, sodium sulfate was added. The total amount of sodium sulfate added was 70 g/L, and it was added every 10 min, and one-third (3.5 g) of the total amount of sodium sulfate was added each time. After all the sodium sulfate was added, the temperature was kept constant for 10 min, and then the dye solution was heated to 60 °C at a heating rate of 1 °C/min. Then keep the temperature constant, and start adding sodium carbonate, the amount of sodium carbonate is 10 g/L, and each addition is a quarter of the total amount, and the interval between each addition is 10 min. After the addition of sodium carbonate, the temperature was continued for 10 min, and the dyeing process was completed. The fabrics are then washed in hot water, soaping and cold water. The concentration of soap liquid is 2 g/L. Finally, the dyed-ZnO-Lyocell fabric was obtained by drying. The dyed-Lyocell fabric was prepared in the same dyeing process.
2.4 Characterization
The chemical structure and crystal structure of Lyocell fabric and ZnO-Lyocell fabric were analyzed by a Nicolet iS 50 FT-IR spectrometer (Thermo Fisher Scientific, USA)and XRD (Dandong Haoyuan Instrument Co. Ltd, China) respectively. The particle size of nano ZnO was analyzed by Laser Particle Size Analyzer (PSA) with a Bettersize3000Plus (Dandong Better Instrument Co. Ltd, China). The surface morphology of the nano ZnO, dope with nano ZnO, control Lyocell and ZnO-Lyocell fabrics was observed by the JSM-6010LA SEM apparatus (Nippon Electronics Co). The type and content of elements on the surface of samples were assessed with JEOL-6300F energy dispersive spectrometer (EDS). Thermal degradation of samples was analyzed by thermogravimetric test (TG) using an HTG-1 thermal. The breaking strength of the fiber was analyzed by vibroskop400 single fiber strength tester. According to the test standard T/CCFA01026-2016, the wet abrasion number of the fiber was tested by WAT25 wet friction tester. A Multifunctional electronic fabric strength tester (Nantong Hongda Experimental Instrument Co., Ltd) was used to measure the bursting strength of the control Lyocell fabrics and ZnO-Lyocell fabrics. The pilling performance of fabrics was tested by a YG401H-9 Martindale wear tester (Quanzhou Meibang Instrument Co., Ltd). The WSB-V intelligent whiteness test instrument (Zhejiang Top Yunnong Technology Co., Ltd) was used to evaluate the whiteness index values of control Lyocell fabrics and ZnO-Lyocell fabrics. The antibacterial activity of ZnO-Lyocell fabric and dyed-ZnO-Lyocell fabric against E. coli and S. aureus was tested by FZ/T 73023-2006, which is a quantitative antibacterial test method.
3 Results and discussion
3.1 Chemical structure and crystal structure of fabric
The chemical structure of Lyocell fabric and ZnO-Lyocell fabric were analyzed by FTIR in the wavenumber range of 500–4000 cm−1, and crystal structure of the samples were analyzed by XRD with an accelerating voltage of 36 kV and a current of 20 mA (k = 0.154 nm) respectively. The spectrum obtained from the test results is shown in Fig. 2. In Fig. 2(a), there is no significant change between the infrared spectrum of Lyocell-fabric and ZnO-Lyocell fabric, which have typical infrared spectrum characteristics of cellulose fiber. The characteristic peak at 3323 cm−1 is generated by the stretching vibration of –OH on cellulose, and the peak at 2900 cm−1 is attributed to the stretching vibration of the C–H bond (Saleh et al., 2017; Yassine et al., 2016). The characteristic peak at 1636 cm−1 is caused by the water absorbed by the cellulose fabric, the absorption peaks at 1160 and 980 cm−1 are attributed to the stretching vibration of -C-O-C-, and the absorption peak at 1010 cm−1 is caused by CH2-CH2 (Amin et al., 2012). In addition, the lattice structure differences of control Lyocell fabrics and ZnO-Lyocell fabrics were compared and analyzed by X-ray diffraction, as shown in Fig. 2. b. The diffraction peak at 12.48° is attributed to the (1 –1 0) crystal plane, while the diffraction peak at 20.36° and 21.12° is caused by the (1 1 0) and (0 2 0) crystal plane (Sayyed et al., 2020; Zheng et al., 2017). The diffraction peak intensity of Lyocell fabric decreases obviously after being doped with nano-ZnO, indicating that nano-ZnO reduces the crystallinity of cellulose. It is probably because of the addition of nano-ZnO, the macromolecular chains in the fiber are arranged loosely and the amorphous region is increased, which leads to the decrease of crystallinity. The crystal information of nano-zinc oxide is masked by cellulose, and no obvious information can be seen in the XRD spectrum. The decrease of crystallinity will lead to the decrease of mechanical properties.
FTIR spectra (a) and XRD diffraction patterns (b) of control Lyocell and ZnO-Lyocell.
3.2 Apparent morphology and elemental analysis
Fig. 3 indicates the morphology of nano ZnO and the dope with ZnO by field emission scanning electron microscope. As seen in Fig. 3 (a), the particles are uniform and nearly round. The particle size of nano ZnO was analyzed by PSA, the result is D10 = 24.9, D50 = 30.8, D90 = 38.2, the nanoparticles of ZnO have an average diameter of about 31.2 nm. In Fig. 3 (b), it shows the nanoparticles are well dispersed in the dope and rarely agglomerate.
The SEM photo of control nano ZnO (a) and ZnO in dope (b).
The apparent morphology and surface element distribution of control Lyocell fiber and ZnO-Lyocell fiber were observed and compared by scanning electron microscope (SEM) and supporting energy dispersion X-ray spectrum (EDS). Digital photos and element content are shown in Fig. 4. The microscopic surface of control Lyocell fiber is smooth and almost free of protrusions and impurities. The ZnO-Lyocell fibers have a relatively rough surface with uniform and tiny bumps, which probably because part of the zinc oxide particles on the fiber surface. The elemental analysis results show that only C and O elements are visible on the surface of the control Lyocell fibers, while Lyocell fibers with nano-zinc oxide added during production can see a small amount of zinc in addition to carbon and oxygen. This results show that the uniform particles on the fiber surface are zinc oxide, and most of the zinc oxide is in the fiber. Nano-ZnO exposed on the fiber surface plays an important role in inhibiting bacterial growth. With the use of fiber products, the zinc oxide inside the fiber gradually exposed, providing the fiber with long-lasting antibacterial properties.
The apparent morphology and element distribution of control Lyocell and ZnO-Lyocell.
3.3 Thermal degradation behaviors
The thermal stability of control Lyocell fabrics and ZnO-Lyocell fabrics was compared by thermogravimetric analysis under air and nitrogen atmosphere respectively, at 50–700 °C with a heating rate of 10 °C/min−1. The thermal degradation curves and data are summarized in Fig. 5 and Table 1. It can be seen from the thermogravimetric curve that the thermal stability and thermal oxidation stability of ZnO-Lyocell fabrics are not significantly different from that of the control Lyocell fabrics, which may be due to the low content of nano-zinc oxide. In the air atmosphere, the initial degradation temperature and the maximum degradation rate of the fabrics before and after doping with nano-ZnO are the same, and the residual amount of the two fabrics is similar at 700 °C. However, in nitrogen atmosphere, the initial degradation temperature (T10%) was slightly increased, but the difference was not obvious, and the amount of carbon residue was significantly increased compared with that in air atmosphere.
Thermogravimetric curves of control Lyocell and ZnO-Lyocell in air (a) and nitrogen (b).
| Sample name | Atmosphere | T10% (℃) | Tmax (℃) | Residue at 700 ℃ (%) |
|---|---|---|---|---|
| Control Lyocell | air | 306 | 351 | 0.9 |
| ZnO-Lyocell | 312 | 348 | 0.8 | |
| Control Lyocell | N2 | 295 | 356 | 5.1 |
| ZnO-Lyocell | 320 | 362 | 5.4 |
3.4 Fiber breaking strength and degree of fibrillation
The breaking strength and degree of fibrillation of the fiber were measured by single fiber strength tester and wet friction tester respectively. The diameter of the test sample is 10 cm. After five tests, the average value is taken to obtain the bursting strength of the sample. The results are shown in Fig. 6. The higher the content of ZnO in the fiber, the lower the breaking strength of the fiber. On the other hand, the wet abrasion number of the fiber increase at first,which means the decrease of fibrillation, when the content of ZnO exceeds 5 %, the wet abration number decreases rapidly. This is because the crystallinity of the Lyocell fiber itself is relatively high, so the longitudinal strength of the Lyocell fiber is high, making the Lyocell fiber have high breaking strength, but the lateral connection between the microcrystals inside the fiber is weak, under the condition of wet expansion or alkali wet expansion and mechanical external force, the microfibril is easy to break from the side, which leads to the formation of fibril (Zhang et al., 2005; Nicolai et al., 1999; Mi Kyong Yoo et al., 2015). The crystallinity of the fibers decreased after the addition of ZnO, which was verified by XRD results (Fig. 2 b). Therefore, the breaking strength of the fibers decreased. Nano-ZnO, the hard particle, add in dope can increase the adhesion with lyocell fiber, which improved the ability to resist deformation in the process of friction and wear, so the friction coefffcient of the ZnO-Lyocell increased with the incorporation of Nano-ZnO. On the other hand, when the wear surface was deformed due to shear force, Nano-ZnO particles beared part of the load, which can reduce the deformation, and prevent the generation and propagation of cracks on the fiber effectively (Ting et al., 2022; Li et al., 2001). Therefore, the degree of fibrillation of the ZnOLyocell is lower than control Lyocell. However, due to the excessive incorporation of nanoparticles, the dispersion of ZnO in the spinning dope getting worse, which leaded to the poor spinnability of the dope, many defects were easily formed in the fiber, which leaded to the increase of fibrillation and decrease of breaking strength. Therefore, the preferred content of ZnO in the antibacterial fiber is 4–5 %.
Breaking strength and Wet abrasion number of Zno-Lyocell fiber.
3.5 Friction performance
The surface fuzzing and pilling performance of Lyocell fabrics doped with nano zinc oxide were tested by the modified Martindale method. The diameter of the test sample is 14 cm. Under the load pressure of 9 kPa, the abrasive (sample with a diameter of 10 cm) moves according to the trajectory for one cycle, which is called one friction, and the duration of one friction is about 1 s. According to the test standard GB/T 4802.2-2008, friction tests of Lyocell fabrics were conducted for 0, 125, 500, 1000, and 2000 times respectively. The picture only shows the sample pictures without friction and after 1000 and 2000 frictions. After 125 and 500 rubs, the visible standing fibers on the fabric surface increased, and the hair bulb was almost not seen. After 1000 times of friction, there are a small number of hairballs on the fabric surface (Fig. 7 b). When the number of friction increases to 2000 times, the hairballs on the fabric surface become more obvious and the number of hairballs also increases. Compared with the standard comparison card, the pilling performance rating of ZnO-Lyocell fabrics can reach grade 4–5 after 1000 times of friction, and also can reach grade 4 after 2000 times of friction. But a little number of hairballs come out on the control Lyocell fabrics after 500 frictions, and more hairballs than ZnO-Lyocell fabrics after 1000 and 2000 frictions, therefore the pilling performance rating of control Lyocell fabrics is half grade lower. In contrast, a little number of hairballs come out on the control Lyocell fabrics after 500 frictions, the pilling performance rating reach grade 4–5, and reach grade 4 after 1000 times of friction. The results show that the Lyocell fabrics doped with nano zinc oxide have better wear resistance, which is consistent to the result of section 3.4.
Digital photos of ZnO-Lyocell fabric surfaces after 0, 1000, 2000 rubs.
3.6 Mechanical properties and whiteness of fabric
The bursting strength of Lyocell fabrics before and after doping nano zinc oxide was tested by a multi-functional electronic fabric strength tester, and the whiteness of the sample was tested by a fabrics whiteness tester, the results are shown in Fig. 8. The bursting strength of control Lyocell fabric is 433 N. The bursting strength of the fabric is reduced to 346 N after doped with nano-ZnO, which is 20 % lower than that of the control fabric, within the acceptable range. This may be because the addition of nano-ZnO destroys the crystallization zone of Lyocell fiber, and the crystallinity decreases, which is consistent with the XRD results. Furthermore, the whiteness of ZnO-Lyocell fabrics was slightly increased, 74 % from 69 % of the control Lyocell fabrics.
Bursting strength and whiteness of control Lyocell fabric and ZnO-Lyocell fabric.
3.7 Antibacterial properties
The antibacterial properties of ZnO-Lyocell fabric and dyed-ZnO-Lyocell fabric were tested by the bacteriostatic rate method. In this study, Staphylococcus aureus was selected as a gram-positive bacterial and Escherichia coli selected as gram-negative bacteria, the growth of these two kinds of bacteria is investigated to investigate the anti-bacterial property of samples. The data are summarized in Table 2. The antibacterial test results showed that ZnO-Lyocell fabric showed an bacteriostasis rate of 80 % against Escherichia coli, and 97 % against Staphylococcus aureus. After dyeing, the fabric had an average bacteriostasis rate of 97 % against Escherichia coli, and 95 % against Staphylococcus aureus. Nano zinc oxide is generally regarded as a safe material for humans and animals because of its ease of preparation and low cost. The antibacterial mechanism of ZnO can generally be divided into two parts: the first is the release of Zn2+ ions. The gradual release of Zn2+ may destroy the cell membrane structure and render the bacteria useless. The second method is photocatalysis, under light conditions, zinc oxide will generate electrons and electron holes, in the environment will contact with H2O and O2 to generate O2–, OH– and H2O2, etc. These highly reactive substances react with the components of the bacteria, thus affecting their activity.
| Microbial species | Bacterial concentration (cfu/mL) | Antibacterial rate (%) | |||
|---|---|---|---|---|---|
| Control Lyocell | ZnO-Lyocell | Dyed-ZnO-Lyocell | ZnO-Lyocell | Dyed-ZnO-Lyocell | |
| E. coli | 1.0 × 107 | 2.0 × 106 | 2.9 × 105 | 80 | 97 |
| S. aureus | 9.9 × 106 | 2.9 × 105 | 6.0 × 105 | 97 | 95 |
3.8 Dyeing performance
The dyeing properties of ZnO-Lyocell fabrics were tested with reactive red CDR, reactive yellow P-FG, and reactive blue SPE. The dyeing results are shown in Fig. 9 and Table 3. It can be seen from Table 3 that compared with control Lyocell fabric, the K/S value of ZnO-Lyocell fabrics have decreased, which means that the dyeing property of Lyocell fabric decreases after doping nano-zno, which probably because the addition of zinc oxide hindered the absorption of dyes by the fibers. The dyed fabrics all have small Delta-E (Color difference) values, indicating that the fabrics have better leveling performance. The Delta-E value of the ZnO-Lyocell fabrics dyed by reactive red CDR is higher than that of control Lyocell fabric, while the DE value of the fabric dyed by reactive yellow P-FG and reactive blue SPE is decreased. No matter which dye is used, the Delta-E value of the fabric is less than 0.5, and the human eye cannot observe an obvious color difference. The test results of rubbing fastness show that the dry rubbing fastness of the control Lyocell fabric and the ZnO-Lyocell fabric dyed with three dyes can reach level 5, while the wet rubbing fastness is slightly different. The wet rubbing fastness of blue ZnO-Lyocell fabric was improved compared with that of control-Lyocell fabric, reaching grade 4–5, which may be related to the lower dyeing depth. Therefore, due to the low addation of zinc oxide, the effect on the dyeing property of the fiber is limited, which is controlled in the range that can not be recognized by human eyes.
Digital photograph of ZnO-Lyocell fabric dyed with reactive dyes.
| Samples | Color | Dyeing performance | Color fastness to rubbing |
|||||
|---|---|---|---|---|---|---|---|---|
| K/S | L | a | b | Delta-E | dry | wet | ||
| Control Lyocell fabric | red | 11.98 | 43.53 | 57.80 | 0.68 | 0.18 | 5 | 4 |
| yellow | 9.82 | 82.72 | 6.68 | 86.42 | 0.24 | 5 | 4–5 | |
| blue | 16.92 | 32.50 | 4.16 | −41.69 | 0.25 | 5 | 4 | |
| ZnO-Lyocell fabric | red | 9.53 | 45.48 | 57.22 | −0.77 | 0.24 | 5 | 4 |
| yellow | 8.82 | 84.46 | 7.28 | 87.33 | 0.17 | 5 | 4–5 | |
| blue | 12.57 | 35.84 | 2.29 | −40.51 | 0.17 | 5 | 4–5 | |
4 Conclusion
Lyocell fabric with antibacterial effect was prepared by doping nano zinc oxide. The chemical structure of the fabric was not significantly changed which proved by FTIR results. However, X-ray diffraction test results showed that the crystallinity of Lyocell fabric decreased significantly. Corresponding to the decrease in crystallinity, the bursting strength of the ZnO-Lyocell fabric decreased from 433.1 N to 345.9 N, and the strength lost about 20 %. However, the control Lyocell fabric itself has high bursting strength, and the strength loss of the ZnO-Lyocell fabric is within an acceptable range. Thermogravimetric test showed that the thermal stability of Lyocell fabric was not significantly affected by doping nano-ZnO. ZnO-Lyocell fabrics have good friction resistance, and the pilling performance of the fabric is still above grade 4 after being rubbed 2000 times by Martindale wear tester. The antibacterial results showed that the ZnO-Lyocell fabrics showed good antibacterial performance with 80 % and 97 % inhibition rates against Escherichia coli and Staphylococcus aureus, respectively. After dyeing, the antibacterial activity of the fabric against Escherichia coli was significantly increased from 80 % to 97 %, while the antibacterial activity against Staphylococcus aureus had little change. The results of dyeing experiments show that under the same process, the dyeing depth of nano-zinc oxide lyocell fabrics is lower than that of control lyocell fabrics, but both have good levelness. In industrial production, the amount of dye should be appropriately increased to obtain satisfactory color depth.
Funding
This research was supported by the State Key Laboratory of Bio-Fibers and Eco-Textiles, Qingdao University (ZDKT202110).
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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