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Abstract

Insulation offers thermal comfort by blocking the heat flow across the walls of buildings and drastically reduces the cost associated with energy consumed in maintaining temperature inside the buildings. Commercial insulating materials such as fiberglass, polystyrene, and polyurethane foams, although demonstrating long serviceability, are associated with several limitations including non-biodegradability. This study hence presents the development of biodegradable multilayer nonwoven fabrics based on natural fibers for thermal insulation as a sustainable alternative to synthetic non-biodegradable polymers. The nonwoven fabrics of kapok, jute, and banana with thicknesses ranging between 5 and 15 mm were produced by needle punching. The developed needle punched nonwoven fabrics were attached together in different fiber combinations to produce multilayered fabrics. The nonwoven fabrics were investigated for thickness, areal density, porosity, and thermal properties like heat flux, thermal resistance, and thermal conductivity. The relatively low thermal conductivity of kapok, jute, and banana fibers, and presence of air pockets in the needle punched nonwoven fabrics, all together governed the development of a sustainable fibrous assembly for thermal insulation of buildings. The results confirmed that kapok, jute, and banana fiber based nonwoven fabrics can be successfully used as an alternative to conventional non-biodegradable thermal insulating materials.

Keywords

Heat Flux Needle Punching Nonwoven Fabric Thermal Insulation Thermal Resistance

Introduction

Naturally, heat flows from hot to cool regions, and depending on the extent of heat transfer through the material and ventilation, the temperature converges to an equilibrium. Thermal insulation of buildings maintains the indoor temperatures and reduces energy expenses; for that purpose the roof and walls of buildings exposed to the environment are insulated.¹ Insulation is an energy-saving strategy that reduces heat loss from buildings in cold weather and prevents the inside temperature from increasing due to higher outside temperatures during hot weather.² Cold climates generally demand higher requirements of thermal insulation for preventing heat loss (infiltration, ventilation, and radiation) from buildings compared to warm or hot climates.³ Insulation lowers the energy requirements for heating and cooling of the building and thus saves energy and also increases the comfort level. Different types of insulating materials are used for the insulation of floors, walls, and roofs which may be used inside or outside, for example, the use of insulating panels.^4,5 Cavity walls filled with polyurethane foams are also a common strategy for the insulation of homes and buildings. It is expected that the insulating material in service must handle the seasonal and day-to-day changes in temperature along with other characteristics like durability, stability in severe weathering conditions, non-flammability, etc.

For thermal insulation of buildings, wall insulation is used in different forms which creates an envelope around the structure and reduces the heat transmission caused by radiation, conduction, and convection.^6,7 The formation of an envelope around the structure prevents the exchange of heat (thermal energy) across the walls of the buildings due to a difference in temperature, hence, it maintains the temperature and provides comfort. Insulating materials possess heat-blocking ability through free spaces or porosity filled with air (gas) pockets. Since air has low thermal conductivity as compared to liquids and solids and low density as well, air is the most preferred choice for thermal insulations to prevent heat loss across the buildings. Over the years, several materials such as polystyrene and polyurethane foams, glass wool, fibrous materials based on virgin and/or recycled wool, cellulose, and polyester have been the most common examples for preventing the heat losses through conduction and convection.^6–11 Bright aluminum films are also used for the reflective insulation of buildings.¹²

Synthetic materials like fiberglass and glass wool cause itchiness, skin redness, and respiratory problems and may be carcinogenic, whereas synthetic polymers like polystyrene, polyurethane, and poly(ethylene terephthalate) based materials are non-biodegradable. Further, polyurethane foams predominantly used as a material for thermal insulation possess high risks of fire.¹³ Hence, there is a continuous need for alternative ecofriendly materials for thermal insulation.¹⁴ Therefore, naturally occurring fibers are gaining significant attention which are often agricultural by-products or agricultural wastes. Interestingly, natural fibers have low thermal conductivityies of up to 0.035 W/mK and better acoustic performance.¹⁵ Further, higher moisture levels do not significantly alter the thermal insulation properties of natural fibers and their combination with synthetic binders improves the thermal insulation performance.^16,17 Biodegradability, reduced emissions of greenhouse gases, and non-carcinogenicity are the prime inherent advantages of natural fiber-based insulating materials. In this respect, the use of cellulosic fibers which are abundantly available in nature have also been reported for thermal insulation of buildings. The use of neat and chemically modified cotton fibers, crop-straws, hemp, cotton/polyester blends, kapok, jute, and banana have been reported for this purpose.^18–20

Jute fiber, which is primarily used for packaging applications, has gained special attention over the years and is the second largest fiber consumed following cotton. Studies pertaining to jute fiber-reinforced composites and blends with other natural and synthetic fibers and jute nonwoven fabrics confirm the potential suitability of jute fiber for thermal insulation.^21–24 Needle punched nonwovens prepared from woollenized jute and wool demonstrated better thermal insulation properties than woollenized jute and polypropylene, and woollenized jute and acrylic. The effect of fabric weight and needle punch density on the thermal properties of jute-polypropylene nonwovens has also been studied.²⁵ Similarly, materials based on kapok and banana fibers and their blends with other fibers have been proven to be effective candidates for thermal insulation.^26–30 Certainly, the versatility of the needle punching technique to design and develop nonwoven materials with tailor-made properties for different applications including thermal insulation has been investigated. Although studies on nonwoven fabrics of natural fibers, that is, kapok, jute, and banana, for thermal insulation are available, studies focusing on the effect of the structural properties of needle punched multilayered nonwoven fabrics of these fibers on thermal insulation performance have rarely been reported. Therefore, the present study aims to investigate the thermal insulation performance of multilayered needle punched nonwoven fabrics of kapok, banana, and jute. The influence of fiber properties and structural properties of needle punched nonwoven fabric on the thermal insulation performance were studied.

Materials and Methods

The kapok, banana, and jute fibers used to prepare the needle punched nonwoven fabrics were generously supplied from Coimbatore, India. Table 1 summarizes the specification of kapok, banana, and jute fibers and Figure 1 (scanning electron microscopy, SEM) depicts the morphological structure of kapok fiber. SEM was performed on an Evo-18, Carl Ziess, Germany using the gold sputtered kapok fibers.

Table 1.

Properties of kapok, banana, and jute fibers.

Property	Kapok	Jute	Banana
Fiber density (g/cm³)	0.29	1.48	0.75–0.95
Average diameter (μm)	20.5	0.035–0.14	80–250
Average length (mm)	20	50–300	1000–5000
Fineness (denier)	0.4–0.6	6–50	27–135
Thermal conductivity (W/mK)	0.035	0.056	0.044

Figure 1.

SEM image of kapok fiber.

Preparation of Needle Punched Nonwoven Fabrics

The fiber samples of kapok, banana, and jute were firstly opened manually to maximum possible extent and the impurities like vegetable matters and trash were separated. The preparation of needle punched nonwoven kapok fabric is shown in Figure 2. For preparing the needle punched nonwoven fabric of kapok, 50 g fibers were fed to carding machine (Trytex) where the carding machine parameters were speed of feed roller 0.83 rpm, speed of cylinder 298.9 rpm, and speed of delivery roller 3.92 rpm. The developed carded web was then fed to Trytex needle punching machine to produce needle punched nonwoven fabrics with thickness of 5, 10, and 15 mm. The needle punching machine parameters were as follows: number of needles 1328, distance between two needles 6 mm, number of punches per min 50, feed rate 25 mm/stroke, and penetration depth 2 mm. The needle punched nonwoven fabrics of banana and jute fibers were also prepared using the same methodology, where the jute and banana fibers were firstly opened manually, cut to an average length of 6 cm, and then cleaned using a Shirley trash analyzer. The parameters of the needle punching machine for jute and banana fibers were needle gage 42, feed rate 5.2 m/min, penetration depth 2 mm, and delivery speed 7.3 m/min. The developed needle punched nonwoven fabrics of kapok, banana, and jute were designated as KX, BX, and JX, respectively. Accordingly, sample designation K5 represents the needle punched nonwoven kapok fibric with a thickness of 5 mm.

Figure 2.

Preparation of needle punched nonwoven kapok fabric: (a) fiber feeding in carding machine, (b) carded web, (c) Trytex needle punching machine, and (d) needle punched nonwoven.

Preparation of Multilayered Nonwoven Needle Punched Fabrics

To develop the multilayered nonwoven fabrics, two to three layers of prepared needle punched nonwoven fabrics with thickness of 5 mm were arranged side-by-side and stitched at all the four corners to prepare multilayered needle punched nonwovens fabrics. The multilayered nonwoven fabrics were designated according to the number of layers and type of needle punched nonwoven fabric used. For example, sample designation KK represents a two-layered nonwoven fabric prepared having two individual layers of needle punched nonwoven kapok fabric, each of 5 mm thickness. Similarly, sample designation KKK represents a three-layered nonwoven fabric prepared by joining three individual layers of needle punched nonwoven kapok fabrics each of 5 mm thickness. In case of three-layered nonwoven fabrics, the three layers were identified as top (to be in contact with the wall surface to be insulated), middle (core), and bottom layer (to be in contact with the external environment), and the thermal properties were investigated accordingly.

Characterization

The thickness of needle punched nonwoven fabrics was measured using the digital thickness gage following the EN-ISO-9073-2; 95 standard and the average value of 10 measurements is reported. The areal density (g/m²) of needle punched nonwoven fabric was measured according to ASTM D-3776 method. The porosity of needle punched nonwoven fabrics was measured using equation (1), where the density of fiber and fabric is in g/cm³. The air permeability of needle punched nonwoven fabrics is measured using the air permeability tester (YG461E-I) with a sample size of 10 cm² at an air pressure of 125 Pa. The thermal conductivity, thermal resistance, and heat flux of needle punched nonwoven fabrics were measured using Alambeta thermal tester (Sensora Tech, Czech Republic) with the test parameters sample diameter (10 cm), base plate temperature (18.9°C), top plate temperature (28.9°C), and number of cycles (5–10 times).

Porosity of needle punched nonwoven fabric (%) = \frac{(F i b r e d e n s i t y - F a b r i c d e n s i t y) \times 100}{F i b r e d e n s i t y}

(1)

Results and Discussion

Natural fibers like kapok, jute, and banana have been gaining attention for designing and developing value added and functional materials through their amalgamation with nonwoven preparation techniques like needle punching. Needle punching is known for its versatility due to its applicability to both natural and synthetic fibers of varying average length and producing nonwovens of varying properties as per the intended application. Hence, in the present study, the needle punching technique was chosen to prepare the nonwoven fabrics of kapok, jute, and banana fibers to be assessed for the thermal insulation application.

Needle Punched Nonwoven Fabrics

Needle punched nonwoven fabrics of kapok, jute, and banana fibers with varying thickness of 5, 10, and 15 mm were prepared with two different needle punch densities, 120 and 180. The single and multilayered needle punched nonwoven fabrics of kapok, jute, and banana are shown in the Figure 3. The physical properties of needle punched nonwoven fabrics are presented in Table 2 and Figure 4. All the needle punched nonwoven fabrics had smooth surface, and uniform fiber distribution and even thickness. Although the needle punched nonwoven fabrics were produced with similar thicknesses, little difference in their areal density was observed, hence, the porosity of these nonwoven fabrics also differed accordingly. The small difference in areal density was mainly associated with the difference in fiber density, since the fiber volume fraction was kept similar in all the nonwoven fabrics. The multilayered needle punched nonwoven fabrics were prepared by assembling the individual nonwoven fabrics of kapok, jute, and banana, each having a thickness of 5 mm. The assembled individual nonwoven fabric layers were stitched at all the four corners to impart structural integrity and better surface contact. The physical and thermal properties of needle punched nonwoven fabrics prepared using the needle punched density of 120 and 180 punches/cm² as such and compressed under a load of 5 kg for 48 h were assessed, and the values are presented in Figure 4. It was observed that when the needle punch density was increased from 120 to 180 punch/cm², the thickness of needle punched fabrics reduced marginally. The reduced fabric thickness on the other hand increased the areal density relatively. The application of compressive load of 5 kg on needle punched fabrics resulted in the compaction of nonwoven fabrics, hence the thickness was reduced. The increase in areal density was contributed by the removal of entrapped air within the entangled fibers of the nonwoven fabrics. Studying the effect of needle punch density and compression on thickness and areal density, the effects of the same on the thermal properties of nonwoven fabrics were also studied and are discussed in the successive sections.

Figure 3.

Needle punched nonwoven fabrics of kapok, jute, and banana; single layer (top), multilayered (middle), and cross-sectional view of multilayered nonwoven fabrics (bottom).

Table 2.

Physical properties of single layer needle punched nonwoven fabrics produced with needle punch density of 120 punches/cm².

Sample ID	Fiber volume fraction	Thickness (mm)	Areal density (g/m²)	Porosity (%)
K5	0.145	5 ± 0.25	340 ± 17	85.6 ± 4.3
J5	0.096	5 ± 0.21	713 ± 36	90.4 ± 4.5
B5	0.148	5 ± 0.23	606 ± 30	85.7 ± 4.2

Figure 4.

Properties of single and multilayered needle punched nonwoven fabrics without and with compression under a load of 5 kg: (a, b) thickness and (c, d) areal density.

Thermal Properties of Needle Punched Nonwoven Fabrics

The thermal properties of needle punched nonwoven fabrics were influenced by the fiber type, fabric thickness, and areal density. At a given thickness, for example, 5 mm, the nonwoven fabric prepared with higher needle punched density had comparatively lower thickness and higher thermal conductivity. Further, for individual nonwoven fabrics, with increasing thickness (5–15 mm), the value of thermal conductivity was increased linearly. Among the three nonwoven fabrics of 5 mm thickness, the thermal conductivity of banana nonwoven fabric was highest, at 51 and 56 W/mK, when the needle punch density was 120 and 180, respectively. For kapok and jute nonwoven fabrics, the values of thermal conductivity were relatively similar. The values of heat flux were also higher for the needle punched fabrics prepared with a needle punched density of 180 punches/cm² as compared to that produced with a needle punched density of 120 punches/cm². Compaction of nonwoven fabrics under higher needle punched density was the prime reason for increased thermal conductivity and heat flux as it facilitated the conduction mode of heat transfer by elimination of entrapped air, a material with inherent poor thermal conductivity. The effect on the thermal resistance of nonwoven fabrics of varying thickness and prepared at different needle punch density was also investigated. It was observed that with increased needle punch density, for all the nonwoven fabrics the value of thermal resistance decreased. Regardless of fabric thickness, the thermal resistance of nonwoven fabrics followed the order, kapok > jute > banana. Further, with increasing needle punch density, thermal resistance was increased.

Effect of Nonwoven Fabric Thickness on Thermal Resistance

With respect to thermal insulation behavior of a material, thermal resistance is a crucial factor which depends upon the material thickness and its thermal conductivity. Thermal resistance is defined as the ratio of temperature difference across the two surfaces of the material to the rate of heat transfer per unit area. The values of thermal resistance of single and multilayered needle punched nonwoven fabrics are presented in Figure 5. Irrespective of the fiber types, the thermal resistance of needle punched nonwoven fabrics that is, kapok, jute, and banana with more thickness was higher as compared to that with less thickness. For example, the thermal resistance of nonwoven fabrics of 15 mm thickness was higher as compared to that fabric samples having thicknesses of 10 and 5 mm. The increased thermal resistance of needle punched nonwoven fabric having more thickness was associated with a greater number of fibers across per unit area. The greater number of fibers across the fabric thickness governed the entrapment of a greater volume of air between inter-fiber spaces, and better thermal resistance. Interestingly, the thermal resistance of all the multilayered needle punched nonwoven fabrics was better as compared to that of single layered nonwoven fabrics of similar thickness. For example, a single layer needle punched nonwoven kapok fabric of 10 mm thickness offered less thermal resistance than the multilayered nonwoven fabric samples of same thickness produced from a combination of two different fibers. The higher thermal resistance of multilayered nonwoven fabrics as compared to the single layered fabric with similar thickness was attributed to presence of a thin air gap between the different layers of the nonwoven fabrics. The existence of a thin air gap also contributed additional thermal resistance to nonwoven fabrics due to the inherent low thermal conductivity of air. Further, the differences in the thermal conductivity of individual fiber and areal density of nonwoven fabric samples contributed to better thermal resistance of multilayered nonwoven fabrics than that of nonwoven fabric samples prepared from individual fibers.

Figure 5.

Effect of nonwoven fabric thickness on thermal resistance: (a) single layered and (b) single and double layer.

Effect of Needle Punch Density of Nonwoven Fabrics on Thermal Resistance

During the preparation of needle punched nonwoven fabrics, needle punch density is an important parameter which has a significant effect on the structural properties of the nonwoven fabric such as thickness, areal density, fiber entanglement ratio, and strength. Hence, the effect of needle punch density on thermal resistance was investigated and the values of thermal resistance are depicted in Figure 6. The kapok fiber based needle punched nonwoven fabric prepared with needle punch of 120 punches/cm² showed the highest thermal resistance as compared to jute and banana fiber based fabrics. On increasing the needle punch density from 120 to 180 punches/cm², the thermal resistance values of all the fabric samples were decreased. On increasing the needle punch density, the decrease in thermal resistance values of nonwoven fabrics ranged between to 14% and 18%. The deceased thermal resistance of nonwoven fabrics at higher needle punch density was associated with the generation of a dense nonwoven fabric structure. The nonwoven fabric samples with dense structure eventually had fewer and smaller size pores which produced a reduced air volume accumulated within the needle punched nonwoven fabrics, eventually decreasing thermal resistance.

Figure 6.

Effect of needle punch density of nonwoven fabrics on thermal resistance.

Effect of Areal Density of Nonwoven Fabrics on Thermal Resistance

The effect of areal density on thermal resistance of needle punched nonwoven fabrics of kapok, jute, and banana was correlated through the values of thermal resistance at different areal density, as illustrated in Figure 7. The thermal resistance of nonwoven fabric samples was increased with increasing areal density. For instance, nonwoven fabric sample with 15 mm thickness showed better thermal resistance as compared to their counterparts having thickness of 10 and 5 mm. The thermal resistance of nonwoven fabric samples at higher areal density was associated with increasing fabric thickness where a greater number of entangled fibers entrapped more volume of air pockets, thus better thermal resistance. The value of R² > 0.95 was obtained for the line equations for all the needle punched nonwoven fabric samples of kapok, jute, and banana fibers. The linear regression model was fit for the thermal resistance and areal density of the nonwoven fabric. The slope of the linear regression was the highest for the kapok fiber nonwoven. It clearly indicates that as the areal density of nonwoven fabric increased the thermal resistance values increment was the highest as compared to banana and jute fiber. This is because of the fiber low density and hollow structures of the kapok fiber. Similar trends were observed in the case of banana and jute fiber nonwoven fabric.

Figure 7.

Effect of areal density of needle punched nonwoven fabrics on thermal resistance.

Effect of Compressive Load on Thermal Resistance

The effect of compressive loading on thermal resistance of multilayered nonwoven fabrics was examined in the view of compressibility of nonwoven fabrics that occurred during usage which alters the thermal insulating performance. For the purpose, a load of 5 kg was applied on the nonwoven fabric samples for 48 h and later thermal resistance values of fabric samples compared before and after compression, as shown in Figure 8. It was observed that the applied load had negligible effect on the thermal resistance behavior of needle punched nonwoven fabrics. This was attributed to the good resilience property of nonwoven fabrics and better structural integrity as well. On removing the compressive load, nonwoven fabrics recovered almost completely to their original thickness and the surface topography was also similar, hence proving good resilience or recovery ability of nonwoven fabrics from compression. This behavior of nonwoven fabric samples suggested that the selected fiber volume fraction and needle punching process parameters were well organized to produce nonwoven fabrics of good dimensional stability. The good dimensional stability of nonwoven fabrics facilitated the instant re-filling of air pockets within the inter-fiber spaces to the maximum extent as like that of before compression, hence, the thermal resistance values of nonwoven fabrics after compression were comparable to obtained before compression.

Figure 8.

Effect of compressive load on thermal resistance of needle punched nonwoven fabrics: (a) two-layered and (b) three-layered.

Effect of Fiber Properties on Thermal Resistance of Nonwoven Fabrics

The effect of fiber type on thermal resistance of needle punched nonwoven fabrics was also examined. Among the three fibers used in this study, kapok based needle punched nonwoven fabrics showed the highest thermal resistance values irrespective of the fabric thickness. For a given fabric thickness, the thermal resistance of needle punched nonwoven fabrics followed the order, kapok > jute > banana. Further, with the increasing fabric thickness, the values of thermal resistance increased in an orderly fashion. The highest thermal resistance offered by the kapok fiber based nonwoven fabrics was associated with air filled hollow fiber morphology owing to least thermal conductivity as compared to jute and banana. The air filled hollow kapok fibers ultimately contributed to large amount of air pockets within the matrix of needle punched nonwoven fabrics, hence, better thermal resistance.

Effect of Thickness of Needle Punched Nonwoven Fabrics on Heat Flux

Heat flux is another important parameter of materials to be used for thermal insulation as it reflects the instantaneous heat transfer occurring due to temperature difference between two surface in contact with each other. Hence, for the purpose of thermal insulation, materials with lower heat flux values are preferred. The effect of fabric thickness on heat flux of single and multilayered nonwoven fabric samples of kapok, jute, and banana was quantified and the values are reported Figure 9. It was observed that irrespective of the fiber used, with increasing thickness of nonwoven fabric from 5 to 15 mm, the value of heat flux was decreased marginally. In the case of single layer nonwoven fabric samples, regardless of the fabric thickness, the value of heat flux was highest for kapok based nonwoven fabrics and followed by jute and banana fabrics. The less significant effect of fabric thickness on heat flux for single layer nonwoven fabric samples was associated with instantaneous heat transfer occurring within the samples. However, significant differences in the heat flux values were observed when multilayered nonwoven fabrics were prepared by combining two different fabrics together, such as kapok–jute, kapok–banana, and jute–banana. For different fabric combinations, sample KJ had the lowest while JB had the highest heat flux values. The significant difference in the heat flux values of multilayered fabrics prepared from different fiber combinations was primarily influenced by the cross-sectional morphology of fibers which contributed to different air-entrapment levels within the matrix of nonwoven fabrics.

Figure 9.

Effect of needle punched nonwoven fabric thickness on heat flux: (a) single layer and (b) multilayered.

Effect of Nonwoven Fabric Thickness and Needle Punch Density on Thermal Conductivity

The effect of needle punched density and fabric thickness on the thermal conductivity of nonwoven fabrics were investigated, and the values are conveyed in Figure 10. The thermal conductivity of nonwoven fabrics was thickness dependent and irrespective of fiber type with increasing fabric thickness from 5 to 15 mm, the value of thermal conductivity increased relatively. The increased thermal conductivity of nonwoven fabrics with increasing thickness was dictated by the presence of a greater number of fibers within the fabric matrix which promoted the heat transfer through the conduction mode. Further, with increasing needle punch density from 120 to 180 punches/cm², the thermal conductivity of all the nonwoven fabrics was also increased due to the formation of dense fabric structure. The higher needle punch density resulted in compaction of the fabric structure which increased the areal density of nonwoven fabrics and lowered the number of air pockets, thus increasing the thermal conductivity. Among the three fibers used in this study, kapok fiber based nonwoven fabrics outperformed the others due to inherent low thermal conductivity governed by the presence of hollow fiber cross-section which entrapped more air within the nonwoven fabric matrix, and eventually lower thermal conductivity.

Figure 10.

Effect of (a) thickness and (b) needle punch density, on thermal conductivity of nonwoven fabrics.

Conclusion

In this study single and multilayered needle punched nonwoven fabrics of kapok, jute, and banana of different thicknesses to be used for the thermal insulation of buildings in cold climates were prepared by varying the needle punch density. The structural properties of nonwoven fabrics influenced the thermal properties such as heat flux, thermal resistance, and thermal conductivity. Among the three fibers used in this study, kapok based nonwoven fabrics outperformed the others due to its inherent low thermal conductivity governed by the hollow morphological structure. The improved thermal properties of multilayered nonwoven fabrics showed their superiority for thermal insulation over single layer fabrics. The better thermal insulation of multilayered nonwoven fabrics was contributed by the presence of a thin air layer between the assembled fabric layers and influenced by the fabric combinations assembled. This study confirms that the abundant availability of biodegradable natural fibers that is, kapok, jute, and banana, and their transformation into a nonwoven fabrics through needle punching offers a potential alternative to non-biodegradable synthetic fiber based thermal insulating materials. Exploration of other nonwoven fabric preparation techniques and other natural fibers or agricultural wastes to develop thermal insulating materials will be the future directions.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Anilkumar Yadav

Mukesh Bajya

Awadhesh Kumar Choudhary

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Development of Sustainable Multilayer Composite Nonwoven Fibrous Assembly for Thermal Insulation Application

Abstract

Keywords

Introduction

Materials and Methods

Preparation of Needle Punched Nonwoven Fabrics

Preparation of Multilayered Nonwoven Needle Punched Fabrics

Characterization

Results and Discussion

Needle Punched Nonwoven Fabrics

Thermal Properties of Needle Punched Nonwoven Fabrics

Effect of Nonwoven Fabric Thickness on Thermal Resistance

Effect of Needle Punch Density of Nonwoven Fabrics on Thermal Resistance

Effect of Areal Density of Nonwoven Fabrics on Thermal Resistance

Effect of Compressive Load on Thermal Resistance

Effect of Fiber Properties on Thermal Resistance of Nonwoven Fabrics

Effect of Thickness of Needle Punched Nonwoven Fabrics on Heat Flux

Effect of Nonwoven Fabric Thickness and Needle Punch Density on Thermal Conductivity

Conclusion

Footnotes

Declaration of Conflicting Interests

Funding

ORCID iDs

References