1 Introduction

Environmental contamination is one of the most serious issues confronting the planet in the twenty-first century. With the COVID-19 pandemic, the rapid expansion in the use of single-use products, particularly face masks, have resulted in the creation of plastic waste and environmental pollution. Face masks mostly consist of polymers or derivatives of plastic, with larger concentrations of polyethylene (PE) and polypropylene (PP), as well as other polymeric materials, such as polystyrene (PS), nylon, polyurethane (PU), and polyester (PET) [1]. Due to concerns about environmental pollution, some of the specifications for future advanced materials have changed, and it is now necessary to design sustainable goods while also considering the biodegradability and renewability of the employed materials. Bioplastic polybutylene succinate (PBS) is made by polycondensing 1,4-butanediol and succinic acid. Succinic acid can be produced from renewable feedstocks, such as starch, sucrose, or glucose through microbial fermentation. Petroleum-based feedstocks are utilized to synthesize 1,4-butanediol. It is an aliphatic polyester with flexibility, melt processability, and chemical resistance. It is often used and discarded in daily life and has qualities such as PE and PP. It may also be combined with other bioplastics to enhance their qualities and is used for packaging, biodegradable bags, and mulching films. PBS is, therefore, a substance that has promise for replacing synthetic plastics and reducing the build-up of plastic waste. PBS can be decomposed by hydrolysis or enzymatic oxidation into water and carbon dioxide [2,3,4].

Smaller fiber sizes enhance the porosity and specific surface area to the volume-ratio filter of the medium, which efficiently allows air molecules to pass through the filter. This is especially true for nanofibers between 200 and 60 nm in diameter, as the slip effect promotes aerodynamic slip and reduces the risk of air molecules crashing into the nanofibers. Air filters produced with biobased materials, including cellulose acetate (CA) [5], poly(vinyl alcohol) (PVA) [6], poly(lactide) (PLA) [7], poly(ethylene terephthalate)(PET)/silk fibroin [8], chitosan [9] developed by electrospinning method. They are considered environmentally sustainable and popular in the scientific community. Electrospinning is easy and cheap to set up for research purposes. However, electrospinning systems need to use high-voltage electrostatic field support, making them unsafe and requiring more devices. SBS is a relatively new technology for producing fibers with diameters ranging from the micro to the nanoscale that uses a compressed gas or air and a spinning matrix comprised of concentric nozzles. Since conductivity is not necessary, the application range of the polymer solution is broadened. The SBS technique is also safer and uses fewer devices because it does not need high-voltage electrostatic field assistance [10,11,12].

Many researchers are interested in producing PBS-based nanomaterials for applications such as wound dressing, medication delivery, scaffolding, and separators. Jeong et al. investigated the fiber electrospinnability of PBS polymers with different solvent mixtures [13]. Liu et al. researched the effect of different concentrations and different needle orifices on PBS fiber morphology by the electrospinning method [14]. Zhang et al. developed PBS/wollastonite/apatite composite scaffolds for tissue engineering by electrospinning [15]. Tian et al. created antimicrobial electrospun PBS fiber mats using PVP-capped silver nanoparticles [16]. Klairutsamee et al. researched the effect of solvents and different organic salts on PBS fiber morphology by electrospinning [17]. Llorens et al. produced a polyethylene glycol/PBS scaffold by coaxial electrospinning and investigated its biocompatibility and drug release behavior [18]. Cooper et al. reported the influence of a co-solvent system of chloroform/N,N-dimethylformamide and chloroform/dimethyl sulfoxide on PBS fiber electrospinnability [19]. Kurokawa et al. used PBS polymer to improve the mechanical properties of CA nanofibers by forming CA/PBS composites [20]. Guidotti et al. fabricated regenerated wool keratin-PBS nanofibrous mats for drug delivery and cells culture [21]. Gavende et al. created PBS electrospun nanofiber scaffolds for the biomimetic structure [22]. Ostheller et al. investigated melt-electrospun PBS fiber for bacterial filtration efficiency [23]. In these studies, production rates were generally restricted to between 0.5 and 5 mL/h. Recently, Bang et al. developed an oil/water separation by making comparative production with PBS polymer using both electrospinning and SBS methods [24]. Bang et al. showed that SBS technology is 28 times more productive than electrospinning. However, the usability of PBS nanofibers for air filtration has not been investigated.

The goal of this work is to manufacture a biodegradable filter using a PBS polymer solution via the SBS method, and to analyse its physical characteristics, morphological appearance, and filtration performance (Fig. 1). In addition, the degradation behavior of PBS nanofibrous webs was compared with the commercial PP meltblown filter. The study suggested that it should be feasible to a develop high-performance PBS-based nanofiber filter using the SBS approach. The efficiency and safety of the SBS approach and the potential for employing PBS nanofibers in materials research are both clarified by these findings.

Fig. 1
figure 1

Illustration of the PBS nanofibrous N95 respiratory filters fabrication by solution-blow spinning production

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2 Materials and method

2.1 Materials

Commercial PBS (a bio-based and biodegradable resin, FZ71PB®, melting point 115 °C, density 1.26 g/cm3 and melt flow index MFI [190 °C, 2.16 kg], 22 g/10 min) was supplied by PTT MCC Biochem Company Ltd. (Thailand). The chemicals used in this study were chloroform, ethanol, and sodium hydroxide (NaOH) from Merck & Co. and used as received. The commercial N95 mask was bought from the local market.

2.2 Production of PBS Solution-Blown Filter

PBS solutions with 8, 9, and 10 wt% concentrations were prepared by dissolving in mixed solvents of chloroform and ethanol 3:1 (v/v) and continuously stirred at 400 rpm (ISOLAB GmbH, Germany) for 6 h. The biodegradable webs were fabricated in a lab-scale solution-blow spinning machine (AREKA Group Ltd., Turkey) with the prepared solutions. The schematic of the solution blow spinning machine was illustrated in Fig. 1. The PBS solutions were placed in a plastic syringe tube and fed through a metal nozzle with a 22-gauge blunt-tip needle. In these experiments, the distance between the nozzle and the drum collector, the drum speed, the air pressure, and the feeding rate were fixed and the parameters were 30 cm, 100 rpm, 3 bar, and 60 mL/h, respectively. The PBS webs were collected on the nonwovens with the help of a vacuum-assisted, drum collector (circumference = 30 cm). The samples were left in the oven at 40℃ for 6 h to remove residual solvents. The substrate of nonwovens with a basis weight of 30 g/m2 was distinguished by an insignificant pressure drop of 5 Pa and a filtering efficiency (300 nm particles) of 6.61% at a flow rate of 85 L/min. The effectiveness and airflow resistance of PBS filters as developed should not be significantly impacted by the nonwovens support layer. All solution preparation and spinning operation was performed in a room temperature environment (temperature = 22 ± 2 °C and relative humidity = 45 ± 5%). All samples were dried in an oven (FN400P, Nuve, Turkey) at 50 °C for 24 h to remove the residual solvent.

2.3 Characterizations and Measurements

The morphologies of PBS nanowebs were observed with a scanning electron microscope (SEM; Tescan Vega 3 Czech), after gold/palladium-sputter coating. One hundred measurements were taken from different points on the fibers in the SEM picture of each sample using ImageJ software to determine the average fiber diameter and standard deviation.

A digital thickness gauge for nonwovens was used to measure the thickness of the PBS nanowebs (Loyka 5318, Loyka Instruments, Turkey) at ten points. The samples were kept in a conditioned environment at 20 ± 2 °C and 65 ± 4% humidity for 24 h before measurement and then tested in the same environment. The average and standard deviation of the findings were the reported values.

The unit mass of the PBS nanowebs was scaled using a digital balance (KERN Sohn GmbH, Germany). Three samples with a 100 cm2 area were taken from each type of material and, their weights were measured. The mean value and standard deviation per square meter weight were calculated.

An evaluation of the air permeability of the fabric was done to determine how much air could be passed through the textiles. The PBS nanowebs were placed in a Prowhite air permeability tester II (PRO-SER LTD, Turkey) and used to measure air permeability. During the test, a pressure of 100 Pa was applied to the area of 20 cm2 (ISO 9237). The samples were kept in a conditioned environment at 20 ± 2 °C and 65 ± 4% humidity for 24 h before measurement and then tested in the same environment. Five measurements were done for each group. The average and standard deviation of the findings were the reported values.

The mechanical properties of the PBS nanowebs were measured with a testing machine (Instron 5944, USA). The nanofibrous webs were cut into rectangular-shaped samples (10 × 2 cm2) with an initial grip separation of 50 mm and a cross-head speed of 10 mm/min. The samples were kept in a conditioned environment at 20 ± 2 °C and 65 ± 4% humidity for 24 h before measurement and then tested in the same environment. Three measurements were done for each group. The average and standard deviation of the findings were the reported values.

TSI Certitest® Automated Air Filter Tester Model 8130A model air filter tester was used to measure the filtration efficiency of PBS nano webs. It could generate solid NaCl particles with a median diameter of 0.26 μm. The aerosol particles were fed with a flow rate of 85 L/min through the nanofibrous filters with 100 cm2 of the test area, after which the difference in particle concentration between upstream and downstream was measured. The samples were kept in a conditioned environment at 20 ± 2 °C and 65 ± 4% humidity for 24 h, before measurement and then tested in the same environment. The filtration efficiency test was performed in three different parts of the sample for each sample tested to ensure that the test was homogeneous. The filtration efficiency (η) was calculated using η = (Ci − Cf)/Ci, where Ci and Cf are the initial and final pollutant concentrations, respectively. The quality factor values were calculated using these parameters. The quality factor (QF) was determined by the equation QF =  − ln (1 − η)/ΔP, where ΔP and η are the pressure drop and filtration efficiency of the webs, respectively.

The packing density (α) of nanowebs was calculated using α = (W/ρf × Z) × 100, where W is the basic weight of the nanowebs, ρf is the density of the polymer and has a value of 1.26 g/cm3 for PBS, and Z is the thickness of the nanowebs.

After 3 h of degassing at 100 °C, the specific surface area and pore volume of nanowebs were calculated using the NOVA touch 4LX (Quantachrome TouchWin, USA) method.

2.4 Hydrolytic Degradation

The PBS nanowebs (cut into ~ 2 × 2 cm squares) were immersed in 1N NaOH solution at 25 °C for 3, 6, 12, 18 and 24 h, respectively. The PBS nanowebs were weighed. The samples were collected after a set period and rinsed with distilled water before being dried to a constant weight in a vacuum oven at 50 °C. The degree of degradation was determined from the weight loss [22]. The degradation degree was calculated using (%) = (W0 − Wt)/W0 × 100, where W0 is the initial weight of PBS nanofiber and Wt is the weight of PBS nanofibers after hydrolysis. The specimens were observed through SEM.

2.5 Statistical Analysis

Statistical analyses and one-way analysis of variance (ANOVA) were performed using Minitab 16. ρ values less than 0.05 have a statistically significant impact on the response of the experimental, according to the 95% confidence interval.

3 Results and Discussion

3.1 Morphological Appearance of PBS Nanofibrous Webs

One of the key factors in effectively producing SBS fibers is the solution concentration [25, 26]. First, different nanofibers using different PBS concentrations were produced, and their SEM is displayed in Fig. 2. Figure 3a shows that most fiber diameters varied from 60 to 392 nm at lower solution concentrations of 8 wt%, with an average diameter of 224 nm. The fiber diameter distribution was 38–390 nm, with an average diameter of 199 nm at 9 wt concentration, Fig. 3b). When the concentration was increased to 10 wt. %, the range of fiber diameters was widened to 38–813 nm, with a 315 nm average diameter.

Fig. 2
figure 2

SEM images of the PBS samples produced with a 8 wt%, b 9 wt%, and c 10 wt%

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Fig. 3
figure 3

a Box-plot and b fiber diameter distribution of PBS nanofibrous webs

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The PBS nanofibers that were produced possessed average fiber in the range of 199 and 315 nm. The smaller diameter fibers were formed from 9 wt% of PBS solution, as evidenced by the boxplot of each sample in Fig. 3a, which is displayed. The diameter of the fibers increased when 10 wt% PBS solution was used. The normal distribution curves of the fiber diameters from various concentrations are shown in Fig. 3b. In contrast, with increased polymer concentrations, lower polymer concentrations led to a distribution curve with a stronger amplitude and a narrower size range. Smaller standard deviations, which were seen in the curves using 9 wt% PBS, are indicated by narrower curves with higher frequency peaks. A larger standard deviation that is linked to higher polymer concentrations may be directly related to the rise in surface tension and changes in the viscoelastic characteristics of the solution [10, 27]. By boosting the concentration, the fiber synthesis was enhanced, and their shape was more clearly defined. The increased viscosity at high concentrations is attributable to increased resistance, and the resistance of the polymer chains to the drag effects of the high-velocity gas flow results in the formation of nanofibers that have larger diameters. Additionally, the remarkable doubling phenomenon of filaments showed itself, most likely as a result of interaction with solution jets before solvent evaporation [28, 29]. This has been observed frequently in previous studies and is defined as a characteristic feature of solution-blown fibers.

According to several reports, decreasing the diameter of the fiber can greatly increase the surface area and hence the filtering effectiveness [7, 8]. Therefore, the 9 wt% concentration with the mean of the finest fiber diameter was chosen and productions were carried out at three different times (15, 30, and 60 min) for further studies. Three samples were obtained for SBS: PBS15, PBS30, and PBS60.

3.2 Physical Properties of PBS Nanofibrous Webs

Fabric weight is an essential property that must be controlled during the production process; for example, it is important not to produce fabric that is heavier than necessary. The most popular material for facemasks is PP nonwoven, which has a weight of 20–35 g/m2 [30]. The weight and thickness values of the PBS nanofibers are listed in Table 1. As might be predicted, the collecting time had a considerable impact on the nanofibers' weights and thicknesses, which ranged from 15 to 60 min. The weights of the produced samples were between 8.7 and 43.4 g/m2. The produced samples ranged in thickness from 89.9 to 309.1 mm. According to research done by Matuvalecius and co-workers under various settings, fiber thickness, and weight are influenced by the collecting time as well as by other factors such as polymer concentration, ratio of solvents, tip-to-collector distance, and voltage [31]. The differences in thickness were caused by the increase in collecting time from 15 to 60 min as all manufacturing parameters were held constant in this investigation. The lowest thickness and weight of fibers were produced for Sample PBS15, which had a collection duration of 15 min, as shown in Table 1. Nonetheless, the fiber thickness and weight collected were at their maximum for 60 min with the longest collection duration. According to Guibo and colleagues, the thickness of the produced fiber layer (density of fibers under the substrate) increases with longer electrospinning processing times, while decreasing average pore size [32].

Table 1 The properties of the PBS nanofibrous webs
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Permeability is a clue to the "breathability" of a face mask. The amount of gas that an object or material allows to move through it is known as air permeability. This mostly depends on the weight, thickness, and porosity of the fabric. The air permeability of the samples ranged 256.4 and 44.4 mm/s (Table 1.). Results for air permeability indicate that as weight increases, air permeability decreases. According to Epps and Leonas, increasing weight, particularly for nonwoven textiles, reduces air permeability, which is valid for our investigation [33]. In conclusion, PBS15 is the sample with the greatest air permeability, whereas Sample PBS60 has the lowest air permeability. Low air permeability is a characteristic that improves mask effectiveness, according to previous research [34]. This observation may be explained by lengthening the production process; in our sample, the increased mass of the layers per unit area resulted in lower air permeability.

Filtration performance is affected by fiber morphology, fiber diameter, weight and thickness, and is also related to packing density. The density of the nanofiber packing changes with spinning time. The more nanofibers that can be coated on the substrate, the longer the spinning time. As a result, the basis weight of the nanofibers increases with spinning time. It is natural to assume that as the spinning duration increases, so will the packing density and thickness of the nanofiber layer [35]. The range of packing density of the samples was between 7.7 and 11.8% (Table 1). The packing density increased, as expected, from Samples PBS15 to PBS30, but it decreased slightly from Samples PBS30 to PBS60. Because of the low repeatability of nanofibrous materials, layer density and packing analyses are quite complex [36], and it is thought that this may explain this difference.

The properties of the material that can sustain applied stress may be used to determine tensile strength. The mechanical characteristics of the nanofiber mats and the fiber density are connected. As fiber density increased, Young's modulus decreased, dropping from 0.35 MPa for webs for Sample PBS15 to 0.11 MPa for solution-blown samples spun for 60 min (Table 1). The tensile strength increased as the fiber density increased. Webs in Sample PBS15 had a tensile strength of 0.13 MPa, whereas those in Sample PBS60 had a tensile value of 0.22 MPa (Table 1.). Samples that were solution-blown spun for 15 min showed an elongation of 20.3%, while those that were webs for 30 min showed an elongation of 30.3%. For network web interactions to occur, fiber–fiber interactions must first take place, which results in correlations between tensile strength, and elongation with increasing fiber density [37]. Compared to sparsely packed fiber samples, these enhancements in mechanical characteristics were claimed to be related to decreases in pore sizes. The impact of nanofiber mat thickness on mechanical characteristics has been examined in several kinds of research. It has been demonstrated that when polycaprolactone (PCL) mat thickness increased from 0.02 mm (5.6 MPa) to 0.03 mm (12.8 MPa), the tensile strength more than doubled [38]. Increased fiber packing density and fiber-to-fiber contacts may be responsible for the improved mechanical properties of tensile strength and elongation seen in denser samples [37, 38]. The elongation at break indicates the flexibility of the material. Many factors affect the elongation of the nanofiber layer, including nanofiber elasticity and the number of entanglements in the nano-scaled nonwoven structure related to layer thickness [39]. The elongation increased from Samples PBS15 to PBS30 but decreased slightly from Samples PBS30 to PBS60. This can be attributed to the fact that with the increased thickness, the nanowebs fibers tend to be straighter, which reduces slippage and increases fracture between fibers in fiber stretching of nanowebs, resulting in lower elongation and a slightly higher tensile strength.

3.3 Filtration Performance of PBS Nanofibrous Webs

The SBS process involves several factors that require tight control to prepare filter media [36]. It is necessary for the combination of all elements to be beneficial, preferably a good arrangement between fiber diameter, pressure drop, permeability, thickness, and porosity since each isolated feature of a filter medium does not ensure high efficiency. The quality factor (QF) is widely used to evaluate the overall effectiveness of filter media since it combines the influence of collection efficiency (including the global collection efficiency for particles whose diameter varies from 7 to 300 nm) and pressure drop [40, 41].

The association between the filtration effectiveness of the Samples PBS15, PBS30, and PBS60 and the basis weight of the webs is illustrated in Fig. 4a. The filtration efficiency was 66.07, 95.26, and 99.09% for the Samples PBS15, PBS30, and PBS60, respectively, for the web weights of 8.7, 19.3, and 43.4 g/m2. Increasing the manufacturing time and increasing the basis weight of the webs, it appears that the filtration efficiency was boosted. This is because it causes the internal nanofibers to overlap, thereby increasing the probability that small particles will be collected by the web. Typically, filtration efficiency increased significantly, from 8.7 to 19.3 g/m2 to basis weight. Due to the narrower air gaps produced by the denser structure, Sample PBS60 had a clearly greater filtering efficiency than Samples PBS30 and PBS15. The large specific surface area of the branching nanofiber webs increased the effective contact area between the fibers and the target particles (the van der Waals attractive forces), which enhanced the capture of particles [40, 41]. According to National Institute of Occupational Safety and Health (NIOSH) regulations, N95 masks have a minimum of 95% filtration effectiveness and a pressure drop (Δp) below 343 Pa (35 mm H2O). The particles used in these tests were 0.3 μm NaCl particles with a volumetric flow rate of 85 L/min [42]. The filtration performance of Samples PBS30 and PBS60 was analogous to the N95 standard. The basis weight necessary pressure decreases for samples PBS15, PBS30, and PBS60 is shown in Fig. 4b. The pressure drop was 68, 251, and 368 Pa for the Samples PBS15, PBS30, and PBS60, respectively, for the web weights of 8.7, 19.3, and 43.4 g/m2. Like earlier research, the correlation between basis weight and pressure drop was relatively linear, since adding more nanofibers to webs increases their basis weight, which leads to increasing air resistance [43,44,45,46,47,48]. Due to the existence of fiber branches and the tiny air spaces between them, Sample PBS60 had a larger pressure drop than Samples PBS30 and PBS15 with the same base weight. While Sample PBS15 could not provide the filtration required for the N95 standard, Sample PBS60 could not fulfill the pressure drop required for the N95. It was determined that the Sample PBS30 complies with the standard with filtration and pressure drops.

Fig. 4
figure 4

Performance of the PBS nanofibrous webs; a filtration efficiency versus various basis weights, and b pressure drop versus various basis weight

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The benefit-to-cost ratio of filtering efficiency to pressure drop is known as QF. This experiential link makes it clear that a greater QF calls for better filtering efficiency and reduced pressure drop. As a result, high QF and superior efficiency are crucial for improving the performance of the filtering system. The QF values of samples were found as 1.60, 1.22 and 1.31 × 10–2 Pa–1 for Samples PBS15, PBS30 and PBS60, respectively. Although Sample PBS15 has a better quality factor than Samples PBS30 and PBS60, its filtration performance is lower. As the QF assesses the efficiency against the pressure drop ratio, this fact may be connected to the significant pressure drop demonstrated in the filtering tests. Most aerosol particles can be prevented because the basis weight (membrane mass per unit area) increases in proportion to the basis weight. Comparing the results to certain filter media described in the literature can help clarify the findings. Akduman obtained similar quality factor media of 1.03 × 10–2 Pa−1 for 85 L/min flow rate for electrospun cellulose acetate nanofibers [47]. Arican and contributors presented a quality factor of 1.11 × 10–2 Pa−1 for N95 respiratory filters for centrifugally spun gelatin nanofibers [49]. The filter media produced in this study possessed a slightly higher QF than the outcomes documented in the literature.

In the end, the result conforming to the N95 standard was obtained from the Sample PBS30: a pressure drop of 251 Pa, a filtration efficiency of 95.26%, and a quality factor of 1.22 × 10–2 Pa−1. Productivity and industrial applications will benefit from the suggested SBS method for PBS nanofiber fabrication.

It can be observed that the filtration efficiency of Sample PBS30 is very close to the N95 filter (Table 2.). However, the pressure drop of Sample PBS30 was significantly greater than that of the filter purchased (76 Pa). These phenomena can be attributed to the nano-size fiber diameter and through-pore size of the membranes. In addition, the QF of Sample PBS30 was lower than the filter (4.17 × 10–2 Pa−1). A preliminary study of PBS nanowebs as air filters was performed N95 standard, and this study investigated some performance properties required for their use as textile materials. Further research should include a decrease in pressure drop and reusability of PBS nanowebs to establish their practical application.

Table 2 Filtration performance of PBS nanowebs and commercial N95
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3.4 Degradation Performance of PBS Nanofibrous Webs

The degradation performance of nanofibrous webs in Sample PBS30 was tested in NaOH solution and the purchased commercial PP meltblown filter (33 g/m2) was employed as the control group. After 24 h, very little fiber remained intact (Fig. 5c SEM images at 24 h). The surface of the fibers became coarser as the degradation progressed, and the fibers eventually broke down and turned into chunks. While the commercial PP meltblown filter showed no change, Fig. 5b, the PBS nanofibrous webs degraded very quickly under the same degradation conditions, Fig. 5c. Weight loss was observed for up to 3 h (~ 10%) but was less dynamic; there was minimal indication of alterations in nanofiber morphologies. Within 24 h (~ 87%), the PBS polymer had changed to oligomer and then hydrolyzed to monomer.

Fig. 5
figure 5

a Images of sample PBS30, b images of commercial PP meltblown filter, c SEM images of the Sample PBS30 after hydrolytic degradation in a 1 N NaOH solution for 3 h, 6 h, 12 h, 18 h, and 24 h, and d the degradation rate (%) of sample PBS30

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According to the degradation testing findings, the nanofibrous webs of Sample PBS30 degraded well. This would decrease environmental pollution following the fundamental principles of sustainable development when compared to standard PP meltblown filters.

3.5 Surface Area and Porosity Analysis of PBS Nanofibrous Webs

The surface area, pore volume, and pore size of the produced materials are critical properties for efficient filtration. Brunauer–Emmett–Teller (BET) theory, the specific surface area (SBET) was determined using multi-point adsorption data from the linear segment of the N2 adsorption isotherms. The BET surface area of the Sample PBS30 was 13.35 m2/g, which indicated an obvious increase in the relevant surface area compared to other electrospun nanofibers membranes in similar research [50]. Figure 6a depicts the multi-point adsorption of Sample PBS30. Figure 6b depicts the desorption of the Barrett–Joyner–Halenda (BJH). An average pore radius of 1.71 nm was measured. In addition, the pore volume of the Sample PBS30 was 0.021 cc/g. The N2 adsorption–desorption isotherms of Sample PBS30 is shown in Fig. 6c.

Fig. 6
figure 6

Investigation of surface area and porosity for Sample PBS30; a multi-point adsorption, b BJH desorption and c N2 isotherm

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4 Conclusions

The production of environmentally friendly alternatives for non-biodegradable plastics derived from petroleum and their use as effective environmental filter materials is promising. In this light, the present work produced biodegradable PBS nanofibrous membranes using the SBS method for N95 respirators. The average fiber diameters of PBS nanofibers ranged between 199 and 315 nm. As might be predicted, increasing the manufacturing period resulted in heavier samples that were also less permeable to air. The ultimate tensile strength significantly increased as the PBS fiber density increased. Shorter fiber lengths between fiber-to-fiber junctions, which hinder the capacity of the fibers to re-organize in alignment with increasing strain, may have contributed to a decrease in Young's modulus. The PBS filter exhibited a filtration efficiency of > 95% and a pressure drop of < 343 Pa provided to the commercial N95 filter. BET analysis demonstrates the nanoporosity of the PBS fibers, opening a wide range of possible uses. As a result, this work offers a novel approach to producing PBS nanofibers and presents a unique model for highly effective nanofiber filters.

Considering the fast degradability of PBS nanofibrous webs, it is expected that biodegradable PBS fibers will be very useful for disposable facemasks for submicron particles, protective fabrics, and wipes, and will be able to replace the non-biodegradable fibers currently used in these applications.