Blend of Fibres to Improve the Mechanical Properties of Needle-Punched Nonwovens for PM2.5 Air Filtration

Blend of Fibres to Improve the Mechanical Properties of


INTRODUCTION
Blending different types of fibres has been a common practice in the production of needle-punched nonwoven fabrics.Blending allows for the combination of different fibre properties to achieve the desired characteristics in the final product [1][2][3][4].Fibre blend plays a crucial role in determining the mechanical properties of needle-punched nonwovens [5][6][7].By carefully selecting and blending different types of fibres, it is possible to enhance specific properties such as tensile strength, tear strength, burst strength, abrasion resistance, and flexibility, thus tailoring the nonwoven fabric for various applications and performance requirements [1,4,[8][9][10][11][12][13][14][15].
The fibre blend composition affects the tensile and tear strength of a needle-punched nonwoven by determining the inter-fibre bonding within the nonwoven structure [5,16,17].By combining different types of fibres with varying characteristics, such as high-strength fibres and low-strength fibres, the overall tensile strength of the fabric can be enhanced or tailored to meet specific requirements.Certain fibres, such as high-tenacity fibres or fibres with good interlocking properties, can enhance tear resistance when blended appropriately.The fibre blend composition impacts burst strength by influencing the fabric's structural integrity and resistance to internal pressure [5,18,19].Blending fibres with high tensile strength and good cohesion can improve the burst strength of needle-punched nonwovens.The fibre blend composition affects abrasion resistance by determining the fabric's surface properties, fibre strength, and inter-fibre cohesion [20][21][22].Blending fibres with high abrasion resistance or adding abrasion-resistant finishes can enhance the overall durability of the nonwoven fabric.Fibre blend composition plays a role in determining the flexibility of needle-punched nonwovens [23,24].By combining fibres with different bending properties or using fibres with good flexibility characteristics, the fabric's flexibility can be improved or modified.Different scholars at different times have studied the development, properties, and parameter effects of needle-punched nonwoven fabric for different application areas.Some of the studies done on needlepunched nonwoven are presented in Table 1.The mechanical properties of needle-punched nonwoven materials play a crucial role in determining their filtration behaviour [13,25].However, these properties come with certain limitations that can impact the overall performance of the material in filtration applications.Needle-punched nonwovens have limitations in tensile strength, especially if the fibres used are not inherently strong or if the needling process doesn't impart sufficient inter-fibre bonding.Roy and Ishtiaque [26,27] also noticed that higher punching and higher feeder speeds also give a higher number of breakages which results in lower tensile strength.Lower tensile strength can result in reduced https://doi.org/10.31881/TLR.2024.004durability, leading to potential issues during handling, installation, or exposure to airflows.It may also affect the integrity of the filter over time.
Needle-punched nonwovens may have limitations in resistance to bursting under certain conditions [19,28].The resistance to bursting is a crucial aspect of the material's integrity during air filtration.Fibre breakage during manufacturing weakens the overall structure, compromising the nonwoven's ability to resist bursting when exposed to increased pressure during air filtration.Polyester / Nylon / Kevlar structural effect and property [30] Polyester / Palm mechanical and ageing performances [31] polyester (HPET) / PP mechanical properties [5] polyester / Bamboo thermal resistance and the bursting strength [32] Recycled-PET / Kapok thermal resistance and air permeability [33] Polyester/viscose air permeability [34] Polyester/cotton scraps to wrap preserved fruit [35] PET / Areca building insulation applications [3] PLA/PP/Glass, PLA/PP/Hemp, PLA/Glass/Hemp, PP/Glass/ Hemp noise-control performance [36,37] PP/carbon electromagnetic shielding effectiveness [38] Carbon /Polypropylene mechanical Properties [39] PLA/TCF, PLA/flax, PLA/hemp, PP/TCF, PP/flax, PP/hemp mechanical property (Triumfetta cordifolia fibre (TCF)) [40] Jute / PP sound reduction, water absorbency, thermal resistance and air permeability [41][42][43] Kapok/PP Thermal Resistance [44] PP / Bamboo / PET, PP / Banana / PET, PP / Hemp / PET acoustic properties [45] PP / Nettle oil spill cleanup applications [2] Polyphenylene sulfide (PPS) PM2.5 filtration property, chemical resistance [46], [47] Polytetrafluoroethylene / PPS Air filtration property [48] Needle-punched nonwovens may have limitations in resistance to abrasion, which can be a concern in applications where the filter comes into contact with particulate matter or experiences friction [49].Poor abrasion resistance can lead to the shedding of fibres, compromising the filter's efficiency and potentially https://doi.org/10.31881/TLR.2024.004 introducing particulate matter into the filtered air.The flexural rigidity of needle-punched nonwovens may be limited, especially if the fibres are not sufficiently stiff or if the structure lacks the necessary rigidity [49].In applications where maintaining a specific shape or preventing sagging is crucial, limitations in flexural rigidity may lead to challenges in maintaining the desired filter geometry.
The nobility of this research work lies in the artful synthesis achieved through the blending of five distinct fibres.Among many fibres used for the Blending fibres allows for tailoring the nonwoven material to be compatible with specific contaminants present in the air.This is important in applications where the filter needs to address diverse pollutants or contaminants.Blending fibres also allow for cost optimization by using a combination of more affordable fibres with those that provide specific performance benefits.This approach helps achieve the desired filtration properties without compromising on cost-effectiveness.However, the literature is silent about the effect of using up to five fibres on the physical and mechanical properties of needle-punched nonwovens.In the present work, an attempt has been made to evaluate the effect on the mechanical properties of five fibre blend needle-punched nonwoven fabric by varying the web arrangement.

Sample preparation
The production line at Nonwoven Research Laboratories at the College of Textiles, Donghua University, China was used to produce the needle-punched nonwoven samples.

Nonwoven Web Preparation and Web Laying
PAN, PET, PLA, PP and PPS were opened and blended manually with equal proportions.Then the manually blended fibres were processed on the carding machine by keeping the feed roller, cylinder and doffer speeds constant.The fibre mass was placed evenly on the lattice of the carding machine.Carding is a drylaid web formation technique with further opening, cleaning, blending, and fibre alignment.The feed basis weight of fibres was the same at 100 g for all single webs https://doi.org/10.31881/TLR.2024.004

Needle Punching
The final webs were passed through in two consecutive machines.Sample webs were punched by preneedling and final needling punch looms with a constant feeding speed, delivery speed, punch density and needle penetration depth as shown in Figure 3.In the first stage, after the laying of fibre webs into 3D fluffy layers, the web from carding was fed into a pre-needling punching loom to entangled six layers by using a conveyor and roller feeding system.It was a preliminary 3D web to compact slightly the fluffy mass of fibre webs by entangling the fibres.Pre-needling is used to minimize the thickness of the web.

Standard Test Methods
All the tests followed a standard method, with all samples pre-conditioned for 24 hours at 20 ± 2°C and 65% relative humidity.

SEM Analysis
The scanning electron microscopy (SEM) was done with a Flex-SEM 1000, (SU1000, Hitachi Ltd. Japan).A gold layer using a vacuum sputter coater was used to coat all needle-punched fabric samples before analysis.SEM examined the morphology of fibres used and nonwoven fabric samples.

FTIR Test
The American Nicolet TM 5700 FT-IR spectrometer was used to carry out the Fourier transform infrared spectroscopy (FTIR) test.Based on the Attenuated Total Reflection (ATR) approach, spectra between 400 and 5000 cm -1 have been generated.FTIR tests were done at different areas of sample nonwovens and checked the uniformity and proper distribution of fibres during blending.

Thickness
The test was carried out according to the relevant provisions of GB/T 3820-1997 and ISO 5084:1996.
Thickness gauge, capable of registering the distance between the bearing surface of the presser foot and the reference plate (to an accuracy of 0.01 mm).

GSM
The nonwoven fabric GSM was calculated as per ASTM 6242 standards, i.e., mass per unit area (areal density in grams per square meter).The specimen of the size 10 X 10 cm was cut randomly from different places and weighted in electronic balance with an accuracy of 0.001 g and an average of 10 readings was taken.https://doi.org/10.31881/TLR.2024.004

Density
Nonwoven fabric density, or bulk density, is the weight per unit volume of the nonwoven fabric (kg/m 3 ).
It is determined by the following formula: Where: D: Fabric density (kg/m 3 ); GSM: gram per square meter; T: thickness (mm)

Tensile Strength and Elongation
Constant-rate-of-extension (CRE) testing machine was used to carry out the test.The maximum force a nonwoven material can bear when it is stretched is known as its tensile strength.At the point of rupture, elongation at break or final elongation is represented as a percentage.The test was conducted in accordance with the pertinent GB/T 3923.1-2013 and ISO 13934-1:2013 standards.Until it ruptured, a fabric test specimen with the required dimensions was expanded steadily.Records are the maximum force, the elongation at maximum force, and, if necessary, the force and elongation at rupture.

Bursting Strength
Constant-rate-of-extension (CRE) testing machine was used to carry out the test.The nonwoven fabric is concurrently stretched in both directions at the same time when it is subjected to bursting force, and the cloth typically fails in the direction where its elongation is lowest.External stresses on nonwoven textiles can cause them to burst instead of rupture due to tensile stress.The test was carried out according to the relevant provisions of GB/T 19976-2005.A fabric was securely clamped in the ring sample holder of the fixed base.A polished steel ball traversing at a fixed speed was pressed against the specimen until failure occurred.The force required to cause failure was recorded as the bursting strength.

Tear Strength
Constant-rate-of-extension (CRE) testing machine was used to carry out the test.The test was carried out according to the relevant provisions of GB/T 3917.recorded.The tear force was calculated from the force peaks of the autographic trace, or online by the electronic device.

Stiffness
Fabric stiffness was done based on ASTM D1388-96(2002) standard test method.The specimen was placed on the flat surface as a cantilever beam with a uniform load, and it was driven to move uniformly along the length direction by a driving mechanism.The inclined plane detection line contacted the sample when it was pushed out from the working platform and bent and sagged due to its weight.The extended length L was measured, and the bending length is also called the overhanging stiffness and the bending stiffness.According to the principle that the greater the bending stiffness, the harder it is to bend, it is used as a test index to evaluate the stiffness of the tested material.

Abrasion Resistance
The abrasion resistance test was done based on the GB/T48021-1997 standard test method for the stiffness of fabrics.The abrasion resistance of the samples was tested to have an idea about how the fabrics' rubbing properties would be.The number of abrasion cycles per specimen was 5000, the rotational speed was 56±0.6 rpm, the face diameter of the specimen was 32 mm, the specimen holder diameter was 38 mm and the pressure used was 12 kPa.Then the abrasion resistance is expressed based on the weight loss due to rubbing and calculated as follows: Where: Wl: weight loss (%); Wb: Weight before abrasion (g); Wf: Weight after abrasion (g)

Filtration Testing
Filtration efficiency and pressure drop were examined using a U-Test automatic digital tester (Model: F003, Uti Intelligent Technology Co., Ltd., Suzhou, China) to assess dust filter ability.According to the ISO 29463 assessment system standard, NaCl particles of PM2.5 were introduced to the filtering system at a constant air pressure flow rate of 32 l/min to stimulate dust.The tests were evaluated at 20 °C and 45% relative humidity.The moisture content of the fabric was determined using the ISO 939 standard.Then, filtration efficiency and dust holding capacity were calculated by the following formulas: [53] https://doi.org/10.31881/TLR.2024.004 Where: Fe: Filtration efficiency (%); Dc: Dust collected; Df: Dust fed

Scanning Electron Microscopy
Scanning electron microscopy (SEM) displayed the surface morphological structures of fibre used and needle-punched nonwoven fabrics.As depicted in Figure 4 (a-e), the image analysis revealed fibre crimp, which is added on synthetic fibre to improve the cohesion, bulkiness and web management before consolidation or bonding.The appearance and fineness of the fibre are also observed in Figure 4. SEM of the surface and crosssectional view of needle-punched nonwoven fabrics are also shown in Figure 4 (f-h).The surface morphology of all fabrics is almost the same, whereas the cross-section view of the fabrics is different.In Figure 4 (f) sample N0, web laying was done in the machine direction (indicated by yellow line) and cross direction (indicated by red broken line) alternatively, so that the fibre surface is viewed in the longitudinal and fibres cross-section is viewed cross direction.The red line in a horizontal direction indicates the path of the needle and the direction of fibre alignment is changed due to up and up-and-down movement of the needle.In Figure 4 (g) sample N1, web laying was done in the machine direction (indicated by a yellow line) so that fibres were favourably lined up in the machine direction.Like N0, the red line in a horizontal direction indicates the path of the needle throughout the thickness of the fabric.In Figure 4 (g) sample N2, six webs were pre-needled individually on each side before and laid down in a parallel manner one on top of the other so that the joint places between individual webs are visible in the cross-section view (indicated by the yellow line).Unlike N0 and N1, the path of the needle throughout the thickness of the fabric is not continuous due to the pre-needling effect in the case of N2 (indicated by a red ellipse).The vibration of the CH2, CH3, and CH bonds in the PET structure resulted in FTIR spectra of PET fibres having peaks at about 2900 cm -1 .In the chemical structure of PET, the conjugated ester group was identified by the stretching of the C=O bond at a peak of 1715 cm -1 .C=C stretching, attributed to benzene vibration, was seen at a peak 1050 cm -1 wavelength.1780 and 1680 cm -1 for the C=O stretch and 3600-3000 cm -1 for the O-H stretch are the regions of interest for PLA.The maxima in the graph that correspond to the PLA's C=O stretching and C-O-C stretching are located at around 1750 and 1180 cm -1 , respectively.https://doi.org/10.31881/TLR.2024.004and 1072 cm -1 were attributed to S-C6H4-S's C-S bond stretching, while those at 1572, 1470, and 1385 cm - 1 were assigned to S-C6H4-S's benzene ring stretching.The C-H bending modes were ascribed to the peaks at 1008 and 804 cm -1 .

Physical Properties
From Table 4, N2 shows a greater fabric thickness.This is because of pre needling, the fibre is not pressed down during the final needling.The individual pre-needled webs create voids when laid down together, resulting in a higher thickness for the final nonwoven compared to the others.On the other side, N0 shows a lower thickness.The individual webs are laid down at a right angle on top of the others alternatively.
The fibres are aligned in both machine and cross direction.Due to this the web is not exposed to tension and is drafted in the machine's direction because of the delivery rollers.Similarly, it is drafted in the cross direction due to the pressing of the top needle plate.So that the fibres are forced to go downward with the needle resulting in a reduced thickness.N1 shows a lower thickness than N2 and a higher thickness https://doi.org/10.31881/TLR.2024.004than N0.There are no voids between the webs, so it is pressed more and results in less thickness than N2.
However, there is a tendency to draft due to the parallel arrangement of all webs in the nonwoven structure, so N1 shows a slightly higher thickness than N0.The GSM of N0 is higher than N1 and N2.This is because there is less drafting, and all the fibres are entangled together in their position.In this case, a more compacted and dense fabric can be produced, leading to less thickness, higher GSM, and greater fabric density.On the other hand, N2 shows less GSM.This is because the web was drafted two times during the pre-needing and final needling.So that high thickness, less GSM and density of nonwoven fabric is achieved.A certain web weight produces less fabric weight when there is a greater needling density.The drafting and spreading of fibres during punching, which increases with the number of needles, is what causes the decrease in fabric weight.The web is drawn through the needling zone between the bed plate and the stripper plate, resulting in an increase in length that may contribute to the decrease in fabric weight.When the needles are removed, they tend to pull the fibres back up, and the forces of recovery cause the web to spread.
Even with the same blend ratio, the different fibre lay directions and pre-needling processes in cross-laid, parallel-laid, and parallel-laid pre-needled needle-punched fabrics can lead to variations in GSM due to changes in fibre distribution, needle penetration, and overall fabric density.In the cross-laid fabric, fibres may be arranged in a more interlocked or crisscross pattern during the carding and web-laying process.
Needles might penetrate the fabric at different angles due to the crisscrossing fibres, affecting the depth of entanglement, and potentially influencing GSM.This arrangement could result in a denser and more compact fabric structure, leading to a higher GSM.In the parallel-laid fabric, fibres are aligned more in the same direction, which might lead to a less dense structure compared to the cross-laid fabric.Needles might follow the same paths depending on the initial fibre alignment, potentially leading to more drafted fibre webs.This could result in a lower GSM as there may be more open spaces or voids within the fabric.
In parallel Laid Pre-Needled Fabric, pre-needling involves partial entanglement of fibres before the final https://doi.org/10.31881/TLR.2024.004 needling process.This pre-needling could lead to more drafted fibre webs because of passing through the machine multiple times, affecting the overall fabric density and GSM.A higher fibre packing density generally indicates a more compact and closely packed arrangement of fibres.

Bursting Strength and Bursting Stretch
The bursting properties of sample needle-punched nonwovens are presented in Figure 6.The bursting strength of N0 is higher than the others.This is due to the perpendicular arrangement of the webs.The fibres are arranged in both directions so that the fabric can resist the bursting load applied in all directions.
The other reason is that N0 has the highest density of the others, which means the fibres are entangled and create a strong cohesion force between them.So that they can resist the bursting load.Similarly, to resist the highest bursting load the fabric stretched more.N0 exhibits a moderate tensile strength attributed to the perpendicular arrangement of webs.In the machine direction, N0 demonstrates lower tensile strength than N1 but higher than N2.This lower strength in the machine direction compared to N1 is due to half of the fibres being oriented in the crossdirection.Notably, the decision not to pre-needle N0 results in reduced fibre breakage, contributing to a higher tensile strength in the machine direction compared to N2.Even with N0, tensile strength in the machine direction is higher because of the sliding of the fibres and resulting draft in the cross direction during needling, the tensile strength is also reduced relatively.N2 shows the highest braking elongation in the machine direction.This is due to the slippage of the pre-needle web layers because the entanglement https://doi.org/10.31881/TLR.2024.004 between the pre-needle webs is less.When the webs are pre-needled, the number of non-entangled fibres is minimized.So for the final needling, the entanglement of the fibres between the webs is less.N1 shows less breaking elongation in the machine direction.When the tensile load is applied parallel to the axis of the fibres, the effect of the load is distributed on the length and has less elongation.N0 shows less elongation than N2 and higher elongations than N1.The proportional arrangement of fibre webs in both directions reduces the elongation in the machine direction.But as compared to N1, N2 elongates more because less number of fibres are aligned in the direction.

Stiffness and Abrasion Resistance
The stiffness and abrasion resistance of sample needle-punched nonwovens are presented in Figure 8.
The fabric stiffness of N0 is expected to be influenced by the cross-web arrangement and high fabric density.N0 exhibits the highest fabric stiffness, attributed to its cross-web arrangement and high fabric density.Cross-web arrangement contributes to anisotropic properties, potentially impacting stiffness in both machine and cross directions.High fabric density generally leads to increased stiffness due to a more compact structure.The significant stiffness values in both machine and cross directions suggest a rigid and dense structure, making it well-suited for applications requiring robust mechanical properties.The fabric abrasion resistance analysis highlights the impact of arrangement, fabric density, and preneedling on the ability of needle-punched nonwoven fabrics to resist wear and abrasion.N0 exhibits the highest abrasion resistance among the three samples.The combination of cross-web arrangement and high fabric density contributes to a robust structure that withstands abrasion effectively, making it suitable for applications requiring high durability.N1 demonstrates moderate abrasion resistance, influenced by the parallel arrangement and a medium fabric density.N2 shows relatively lower abrasion resistance compared to N0 but slightly higher than N1.The pre-needling, parallel arrangement and less fabric density contribute to a fabric that can still withstand abrasion well, offering a balance between flexibility and durability.N2, with pre-needling and parallel arrangement, provides a good balance between flexibility and abrasion resistance.However, the difference is not significant between the samples.All samples show good abrasion resistance.This is because of the fibre strength, excellent cohesion between the fibres and high entanglement of the fibres, providing options tailored to specific durability requirements.https://doi.org/10.31881/TLR.2024.004

Tear Strength
The tear strength values provided in Figure 9 for different needle-punched nonwoven air filters (N0, N1, and N2) in both directions provide insights into their mechanical properties.The arrangement of fibres significantly influences tear strength.In the machine direction N0, arranged in a cross-web configuration, has the highest tear strength among the three filters.This is due to the presence of fibres in the cross direction resisting the nonwoven from tearing.N1, arranged in a parallel configuration, exhibits a slightly lower tear strength compared to N0.This is because of the presence of fewer fibres arranged in the cross direction and it is easy to slip in the direction of applied force.N2, pre-needled and parallel arranged, demonstrates the lowest tear strength among the three, attributed to the absence of fibres arranged in the cross direction and the breakage of fibres during pre-needling.In the cross direction N0, arranged in a cross-web configuration, has a measurable and less tear strength than N1 and N2.N1 and N2, both arranged in a parallel configuration, did not tear under the testing conditions in the cross direction due to the presence of many fibres in the machine direction to resist the nonwoven from tearing.Fabric properties, including density, arrangement, porosity, and air permeability, are essential in optimizing the performance of nonwoven fabrics for filtration applications.The balanced blending of diverse fibres further contributes to achieving the desired filtration efficiency while maintaining acceptable pressure drop levels.The filtration efficiency results reveal consistently high performance across all samples above 98%, indicating their excellent performance in capturing airborne PM2.5 particles with low-pressure drops.

Statistical Comparison Test Results between Samples
The summarized test results of the needle-punched nonwoven fabric in


Sig equals 1 indicates that the difference of the means is significant at 0.05 level.


Sig equals 0 indicates that the difference of the means is not significant at 0.05 level.

CONCLUSION
The blending of diverse fibres stands as a cornerstone in the production of needle-punched nonwoven fabrics, offering a pathway to tailor mechanical properties for optimal performance.The careful Manufactured Needle punched samples also provide a filtration efficiency of PM2.5 of more than 98% and a very low-pressure drop of 66.69-75.80Pa.The combination of these fibres not only optimized particle capture and pressure drop but also underscored a visionary approach in materials science.Needle- -needling before and laid down in a parallel manner one on top of the other For each sample, six webs were prepared in the blend ratio shown in and immediately after carding, the carded webs were laid down in different manners to produce three samples of needle-punched nonwoven.The final webs are prepared by laying individual webs in the order indicated in Figure2.To further increase final web homogeneity for samples N1 and N2, web laying was carried out in the machine direction without altering the main fibre orientation.Fibres were predominately oriented in the longitudinal (machine) direction, making the final web anisotropic.As it is indicated in Table3under remarks, In the case of N0, Six carding webs laid down at a right angle alternatively one on top of the other before needling.In Figure2, the red ➡ indicates the machine direction during carding, while blue ➡ indicates the machine direction during needling.About the needle punching machine, the six webs in the case of N0 are cross-laid at the right angle one from the other alternatively.It's a combination of parallel and cross.The carding parameters considered for the preparation of sample webs are feeder speed (0.77 rpm), cylinder speed (280 rpm) and doffer speed (7.01 rpm).

Figure 3 .
Figure 3. Needle punching process of the samples

2 -
2009 and ISO 13937-2:2000.A rectangular test specimen was cut in the centre of the shorter edge to form a trouser shape.The legs of the trousers were gripped in the clamps of a recording tensile testing machine to form a straight line and pulled in the direction of the cut to tear the fabric.The force to continue the tear over a specified distance was https://doi.org/10.31881/TLR.2024.004

Figure 4 .
Figure 4. SEM of fibres used and surface morphology of blended fibre needle-punched fabric

Figure 5 1 ,
Figure 5 shows the FTIR result of blended fibre needle-punched nonwoven fabric and the chemical structure of fibres.PAN fibres' FTIR spectra show a variety of peaks attributable to the presence of CH2, CN, C=O, and C-H bonds.The C-H bonds in CH, CH2 and CH3 have a relationship to the absorption peaks between 2926 and 2935 cm -1 .Another peak is seen between 2243 and 2246 cm -1 , and it is connected to the presence of nitrile (C-N) bonds, proving the existence of the nitrile group in the polyacrylonitrile chain.The presence of comonomers causes the absorption peaks in the ranges of 1730-1737 cm -1 and 1170 cm - 1 , which are connected to C=O or C-O bonds.Resonant C-O bonds are associated with absorption in the 1593-1628 cm -1 region.

Figure 5 .
Figure 5. a) FTIR result of blended fibre needle punched nonwoven fabric, b) Chemical structure of fibres

Figure 6 .
Figure 6.Bursting properties of sample needle punched nonwovens

Figure 7 .
Figure 7. Tensile properties of sample needle punched nonwovens

Figure 8 .
Figure 8. Stiffness and abrasion resistance of sample needle-punched nonwovens

Figure 9 .
Figure 9. Tear strength of sample needle punched nonwovens consideration of fibre composition plays a pivotal role in determining crucial attributes such as tensile strength, tear resistance, burst strength, abrasion resistance, and flexibility.Recognizing the inherent limitations in mechanical properties is imperative, especially as they directly impact the filtration behaviour of needle-punched nonwovens.Challenges such as reduced tensile strength may pose durability concerns during handling, while limitations in abrasion resistance can compromise the overall efficiency by contributing to fibre shedding.The sample laid down at the right angle provided better mechanical properties; like tensile of 769.69 N, bursting of 1480.15N, stiffness of 2516.84 mN.mm, abrasion resistance of up to 100%) and filtration efficiency of more than 98%.Whereas, samples laid down in parallel and pre-needled webs provided moderate mechanical properties and a filtration efficiency of more than 98%.The pressure drop of the samples in all cases was 66.69-75.80Pa and possible to say it was very low.Furthermore, this innovative synthesis of PAN, PET, PLA, PP, and PPS fibres marks a pioneering stride in filtration technology, promising advancements in efficiency, durability, and versatility.The unique properties offered by each fibre contribute to the development of an advanced filtration structure.

Table 1 .
Fibres, their blends and study properties of some needle-punched nonwovens production of needle-punched nonwovens Polyacrylonitrile (PAN), Polyester (PET), Polylactic acid (PLA), Polypropylene (PP) and Polyphenylene sulphide (PPS) are selected for this research work, i.e. the nobility of this research work.This innovative approach reflects a commitment to elevating the standards of nonwoven material design for air filtration.By intricately combining fibres with diverse characteristics, this research seeks to pioneer a new paradigm in filtration [62][63][64][65]ng to enhance efficiency, durability, and versatility.The deliberate fusion of five fibres embodies a dedication to precision and optimization, showcasing a thoughtful and forward-thinking strategy in the pursuit of creating advanced needle-punched nonwoven fabrics.This noble endeavour not only signifies a significant leap forward in materials science but also underscores a genuine commitment to addressing the multifaceted challenges of air filtration with ingenuity and excellence.PAN[50][51][52][53]fibres offer excellent strength and thermal stability.They can enhance the dimensional stability and durability of the nonwoven fabric.PAN fibres are known for their good resistance to chemicals and abrasion.PET[54][55][56][57]fibres are widely used in nonwoven applications due to their high tensile strength and excellent resilience.They provide good resistance to stretching and shrinkage.PET fibres offer high durability and are resistant to moisture, mildew, and most chemicals.PLA[58][59][60][61]fibres are derived from renewable resources, making them environmentally friendly.They offer good comfort, softness, and breathability.PLA fibres are biodegradable and have a lower carbon footprint compared to synthetic fibres.PP[62][63][64][65]fibres are lightweight and have high tensile strength.They

Table 3 .
Combinations of blending ratio

Table 4 .
Physical properties of sample needle punched nonwovens

Table 5
N1 (arranged in a parallel fashion) and N2 (pre-needled and parallel arranged) have a lower density.Interestingly, the filtration efficiency data (98.41%,98.12%,and 98.10% for N0, N1, and N2, respectively) indicates that fabric density alone does not dictate filtration performance.While N0 has the highest density, N1 and N2, with lower densities, demonstrate comparable filtration efficiencies.Air permeability, a measure of how easily air passes through a fabric, shows a trend of increasing values from N0 to N2.Higher air permeability is associated with lower pressure drop, indicating that the parallel arrangement in N1 and N2 facilitates efficient airflow.The pressure drop values (75.80 Pa, 68.12 Pa, and 66.69 Pa for N0, N1, and N2, respectively) corroborate this observation, emphasizing the influence of fabric structure on airflow resistance.This trend suggests that the parallel arrangement and pre-needling techniques contribute to a more favourable airflow resistance, resulting in lower pressure drops compared to the cross-web arrangement.Porosity, which represents the void space within a fabric, follows a similar trend as air permeability, increasing from N0 to N2.The higher porosity in N2 aligns with its lower pressure drop and enhanced airflow characteristics.
for different needle-punched nonwoven air filters (N0, N1, and N2) indicate the percentage of PM2.5 captured by the filters during air filtration and pressure drop.The fabric density of N0 (arranged in a cross-web pattern) is the highest among the samples.In https://doi.org/10.31881/TLR.2024.004contrast,

Table 5 .
Filtration efficiency and pressure drop of needle-punched nonwoven samples

Table 6
samples show that the mechanical properties of N0 are better than N1 and N2.The effects of web arrangement and pre-needling are statistically significant on the physical and mechanical properties of https://doi.org/10.31881/TLR.2024.004needle-punchednonwovensamples.The mean comparison between samples in physical and mechanical properties is indicated by the Tukey test.The pressure drop, thickness and bursting stretch mean difference between samples N0 and N1 is not significant at 0.05 level.This shows that the cross and parallel web arrangement does not affect the pressure drop, thickness and bursting stretch of needlepunched samples.The GSM, fabric density, bursting strength, tear strength in machine direction, abrasion resistance, pressure drop and filtration efficiency mean difference between N1 and N2 is not significant at 0.05 level.This indicates that the parallel arrangement of webs whether pre-needled or not has no effect on GSM, fabric density, bursting strength, tear strength in machine direction, abrasion resistance, pressure drop and filtration efficiency of samples.The abrasion resistance means the difference between N0-N2 is not significant at 0.05 level.This shows that cross-web arrangement and pre-needled parallel web arrangement have no difference in the effect of abrasion resistance of the samples.As depicted in Table6, a statistically significant distinction (p-value ⩽ 0.05) in Filtration Efficiency % (p=0.000)among the samples was noted at a 0.05 significance level.

Table 6 .
Tested properties comparison between samples value < 0.05 indicates that the difference of the means is significant at 0.05 level. P-