*3.5.1. Compression in wet condition*


*W W*

*W*

where WA is water absorbency in percentage, Wwet is the weight of fabric in wet condition,

Release of moisture with respect to time are determined for all samples unit they achieved the

Compression is one of the important properties to be measured to evaluate the performance of the needle-punched nonwoven jute fabric for some specific application point of view like carpet, geotextile, etc. The initial thickness, compression, thickness loss, and compression resilience can be calculated from the compression and decompression curves. For measuring

ϕ2.54 cm). The dial gauge with a least count of 0.01 mm and maximum displacement of 10.5 mm is attached to the thickness tester. The compression properties are studied under a pressure

The initial thickness of the needle-punched fabrics is observed under the pressure of 1.55 kPa. The corresponding thickness values are observed from the dial gauge for each corresponding load of 1.962 N. A delay of 30 seconds is given between the previous and next load applied. Similarly, 30 seconds delay was also allowed during the decompression cycle at every individual load of 1.962 N. These compression and recovery thickness values for correspond‐

The percentage compression, percentage thickness loss, and percentage compression resilience


*T T <sup>C</sup> T*

*T T TL T*

> *<sup>W</sup> CR W*

100

100


= ´

where C is the compression in percentage, TL is the thickness loss in percentage, CR is the compression resilience in percentage, T0 is the initial thickness, T1 is the thickness at maximum pressure, T2 is the recovered thickness, Wc is the work done during compression, and Wc′ is

The average of 10 readings from different places for each sample need to be considered. The coefficient of variation should be within 6%, if not a greater number of readings is necessary.

' 100 *<sup>C</sup> C*

(diameter =

these properties, a thickness tester is required. The pressure foot area is 5.067 cm2

ing pressure values are used to plot the compression–recovery curves.

are estimated using the following three relationships [12]:

the work done during the recovery process.

*WA*

and Wdry is the weight of the fabric in dry condition.

range between 1.55 kPa and 51.89 kPa.

constant weight.

282 Non-woven Fabrics

**3.5. Compression**

In some specific applications like geotextile, the jute and jute-based needle-punched nonwoven fabrics require special conditioning to test the fabrics under wet condition. To study the compression behaviour of needle-punched nonwoven fabric under wet condition [13-15], samples have to be cut into pieces of 25 cm x 25 cm and soaked in distilled water for a period of 24 hours before conducting the experiment. After 24 hours of soaking in distilled water the samples are passed through a pair of padding mangle with a uniform pressure exerted upon them by applying a constant load on either side of the top roller. The pressure between the padding mangles and their speed are constant. Under this condition, it can be assumed that the water pickup of the sample remained constant. Then, the sample is tested immediately for its compression property. The initial thickness, compression, thickness loss, and compression resilience were calculated from the compression and decompression curves. The compression, thickness loss, and compression resilience can be calculated from the above relationship mentioned above in Section 3.5.

#### **3.6. Compression creep**

There are some instances where the jute-based needle-punched nonwoven fabrics are used for floor mat and carpet applications. In such applications, the compression creep is one of the essential parameters required to be carried out to evaluate the compression deformation over a period of time. An instrument has been suggested as shown in Figures 2, to measure the compression creep of the needle-punched nonwoven fabrics [16-17].

**Figure 2.** Instrument for measurement of compression creep [16-17]

The instrument is capable enough to measure the compression creep for four samples at a time. The fabric samples are mounted under a known compression load with a dial gauge (D) to measure the thickness under the compression. The pressure foot (C) diameter was chosen as 25.4 mm (1 inch) for all samples. The least count of the dial gauge (D) was 0.01mm. The nonwoven sample is placed between the pressure foot (C) and anvil (I). The initial thickness can be noted without adding any additional load. The instant deformation (T0) is noted from the dial gauge after applying the compression load (H) of 25.51 N (2.6 kg) at the top of the weight pan (J) of the dial gauge (D). The selection of this pressure foot diameter of 25.4 mm and compression load of 2.6 kg is to simulate the area of the foot of a normal chair and the weight of a normal empty chair comes on the carpet surface through each leg of the chair, respectively. To study the compression creep, each sample is allowed to remain under this compression load for 168 hours (7 days). This compression creep time was selected because it was found from previous study that all the fabric's compression creep reaches equilibrium within 168 hours. The compression creep (%) is evaluated from the thickness deformation values, which are measured using the following relation:

$$CR = \frac{T\_0 - T\_t}{T\_0} \times 100$$

where CR is a compression creep in percentage, T0 is the instant thickness after applying the maximum load, and Tt is the thickness after 7 days.

The average of 10 readings from different places for each sample is considered. The coefficient of variation should be less than 6% in all the cases. The fabrics required conditioning for 72 hours in the above-mentioned condition before carrying out the experiment.

#### **3.7. Thermal resistance**

The thermal resistance of a textile material is usually defined by the ratio of the temperature difference between the two faces of the fabric material to the rate of flow of heat per unit area normal to the faces. It is analogous to the electrical resistance in case of current flow through an electrical conductor. Disc method, an application of Lee's disc apparatus to textiles, was employed to evaluate thermal resistance of polyester needle-punched nonwoven fabric samples. In this method, the material under test is held between two metal discs of which one has known thermal resistance. In steady condition, the temperature drop across the metal disc with known thermal resistance and across the material under test is measured, and from the values obtained the thermal resistance of the specimen is determined by the following techniques.

Let TRk and TRs be the thermal resistance of the known disc and the sample under test, respectively. Let t1 be the temperature registered by the lower surface of the known disc, t2 be the temperature registered by the lower surface of the sample under, and t3 be the upper surface of the sample under test. Assuming constant rate of flow of heat at steady state condition, the TRs is computed from the following formula in degrees Kelvin square metre per Watt:

Design, Development, Characterization, and Application of Jute-based Needle-Punched Nonwoven http://dx.doi.org/10.5772/61705 285

$$\frac{t\_1 - t\_2}{TR\_k} = \frac{t\_2 - t\_3}{TR\_s}, \text{or } TR\_s = TR\_k \times \frac{t\_2 - t\_3}{t\_1 - t\_2} \tag{1}$$

In this experiment, a guarded two-plate thermal resistance instrument has been used to measure the thermal resistance of jute-based needle-punched fabrics [18-19]. The thermal resistant instrument is based on a microprocessor and provides automatic results of thermal resistance value in 'tog'. The area of the test specimen used is 706.85 cm2 (diameter 30 cm). The test is non-destructive and the process of preparation of sample is free from human error. Thermal insulation of each fabric sample is measured randomly at five different places under a pressure of 0.3352 kPa. The average of five readings was considered and the coefficient of variation of readings was < 2%.

**Figure 3.** Instrument for measuring the thermal resistance of fabrics [19]

The instrument is capable enough to measure the compression creep for four samples at a time. The fabric samples are mounted under a known compression load with a dial gauge (D) to measure the thickness under the compression. The pressure foot (C) diameter was chosen as 25.4 mm (1 inch) for all samples. The least count of the dial gauge (D) was 0.01mm. The nonwoven sample is placed between the pressure foot (C) and anvil (I). The initial thickness can be noted without adding any additional load. The instant deformation (T0) is noted from the dial gauge after applying the compression load (H) of 25.51 N (2.6 kg) at the top of the weight pan (J) of the dial gauge (D). The selection of this pressure foot diameter of 25.4 mm and compression load of 2.6 kg is to simulate the area of the foot of a normal chair and the weight of a normal empty chair comes on the carpet surface through each leg of the chair, respectively. To study the compression creep, each sample is allowed to remain under this compression load for 168 hours (7 days). This compression creep time was selected because it was found from previous study that all the fabric's compression creep reaches equilibrium within 168 hours. The compression creep (%) is evaluated from the thickness deformation

> - = ´ <sup>0</sup> 0 <sup>100</sup> *<sup>t</sup> T T CR T*

where CR is a compression creep in percentage, T0 is the instant thickness after applying the

The average of 10 readings from different places for each sample is considered. The coefficient of variation should be less than 6% in all the cases. The fabrics required conditioning for 72

The thermal resistance of a textile material is usually defined by the ratio of the temperature difference between the two faces of the fabric material to the rate of flow of heat per unit area normal to the faces. It is analogous to the electrical resistance in case of current flow through an electrical conductor. Disc method, an application of Lee's disc apparatus to textiles, was employed to evaluate thermal resistance of polyester needle-punched nonwoven fabric samples. In this method, the material under test is held between two metal discs of which one has known thermal resistance. In steady condition, the temperature drop across the metal disc with known thermal resistance and across the material under test is measured, and from the values obtained the thermal resistance of the specimen is determined by the following

Let TRk and TRs be the thermal resistance of the known disc and the sample under test, respectively. Let t1 be the temperature registered by the lower surface of the known disc, t2 be the temperature registered by the lower surface of the sample under, and t3 be the upper surface of the sample under test. Assuming constant rate of flow of heat at steady state condition, the TRs is computed from the following formula in degrees Kelvin square metre per Watt:

is the thickness after 7 days.

hours in the above-mentioned condition before carrying out the experiment.

values, which are measured using the following relation:

maximum load, and Tt

284 Non-woven Fabrics

**3.7. Thermal resistance**

techniques.

The specific thermal resistance (STRs) value is used to compare the thermal resistance of different fabric samples. STRs values of all the samples are determined using the following equation:

$$\text{STR}\_{\text{S}} = \frac{\text{TR}\_{\text{S}}}{T\_0}$$

where STRs is the specific thermal resistance in K m2 /W; TRs, the thermal resistance value of fabric in K m2 /W; and T0, the mean thickness in meter at 1.55 kPa pressure of the fabric sample.

## **3.8. Evaluation of water absorbency**

The fabric samples were cut into equal size of 4 cm x 4 cm, and conditioning in the standard atmospheric condition of 65 ± 2% RH and 20 ± 2°C. The fabrics were conditioned for 24 hours in the above-mentioned atmospheric conditions and the dry weight (WD) was measured. To study the water absorbency, samples were dipped in distilled water for 24 hours to ensure uniform soaking of water and then wet samples were hung in free air for about 30 minutes to drip out the excess water absorbed by the samples. Now, the weight (WW) of wet samples was measured. The water absorbency [20] was calculated using following relationship:

$$WA(\%) = \frac{(W\_W - W\_D)}{W\_D} \times 1000$$

The average of 10 results was considered.

#### **3.9. Evaluation of soil moisture control**

The soil moisture can be efficiently controlled by the jute agro-textile. This is very essential to maintain the soil moisture for longer duration and thereby the water requirement during irrigation can be minimized. Suitable jute agro-textile can be used as mulching material. To find the efficacy of the performance of the jute-based mulching material for controlling the soil moisture, two simulated methods are recommended, namely, non-contact method and contact method. The importance of these two different methods is that during application of the agro-textile the fabrics are not assured to touch the contours of the soil surface uniform‐ ly both in lengthwise as well as widthwise directions of the fabrics. Following are the two methods recommend to measure the soil moisture control using jute needle-punched nonwoven fabrics [21].

#### *3.9.1. Non-contact method*

Some place of the mulching needle-punched nonwoven agro-textile will not come in contact with the soil surface due to the contours of the soil. To study the moisture of soil on those noncontact areas of the fabric, this method is considered [21]. In this measurement, six beakers of 100 ml are taken containing 25 ml of water in each beaker. Among them, the mouths of five beakers are tightly covered with the fabric samples and the rest are kept as control without any fabric cover. These beakers containing water and samples were weighed initially and weights were repeatedly taken at certain time interval until they reached a constant weight. This experiment is conducted under normal atmospheric conditions. At each time interval, the percentage evaporation loss is calculated from the weight difference of the individual beaker assembly at that point of time with respect to its initial weight. The results are plotted as a time versus cumulative evaporation loss to compare the performance of various agro-textile fabrics of different fabric weight.
