**3. Characterization of jute-based needle-punched nonwoven**

Unlike other fibre-based needle-punched nonwoven, jute needle-punched also requires specific tests to be evaluated to match its suitability in specific applications. This is because the jute fibre has some of the unique features which others do not have, like high moisture regain, coarseness, biodegradability, high surface roughness, etc. Following are some of the important tests to be carried out to suit its suitability in some of those application areas.

#### **3.1. Measurement of tensile property**

Tensile is one of the most important properties to be evaluated for any textile material. To evaluate this property, all the samples are tested for tensile strip test on Universal Tensile Tester (UTM) following the standard test method ASTM D1682-64 under standard atmospheric condition (65 ± 2% relative humidity and 27 ± 2 °C temperature). For needle-punched nonwo‐ ven, the sample specimen width is 25.4 mm and the gauge length is to be set at 75 mm. The strain rate has to be set in such a way that the failure of the samples occurs between a timespan of 20 ± 3 seconds, depending on the type of fabric samples. Maximum load (in terms of Newton unit) breaking extension in percentage have to be recorded. From the value of breaking load, the tenacity values are calculated by the following formula [9]:

$$T = \frac{BL}{SW \times FW} \times 100$$

where, T – fabric tenacity (cN/tex); BL – breaking load (N); SW – specimen width (mm); and FW – fabric weight (g/m2 ).

The initial modulus and secant modulus have also been calculated from the respective stress– strain curves.

#### **3.2. Measurement of air permeability**

The jute needle-punched nonwoven fabrics are porous in nature and hence they are permeable. To study the air permeability property, this test is carried out. Evaluation of air permeability nonwoven fabric samples can be done using any reliable air permeability tester (Shirley Air Permeability Tester). The results are expressed as the units of volume of air in cubic-centimetre, passed per second, through one square centimetre of fabric at a pressure difference of 10 mm or 1 cm head of water. But in some cases, the range of flow metre available in the instrument may not achieve the high flow rate required for this specific pressure difference. In such a case, superimposed layers of fabric on one another have been tested at a time and the flow rate reading for a single layer was calculated by multiplying the result by number of layers. Air permeability value was calculated by dividing the flow rate reading in cc/sec at 1 cm pressure head of water by the test area, which is in this instrument 5.07 cm2 (1 inch2 ). Sectional air permeability (SAP) value was used to compare the permeability of different fabric samples. The SAP values of all the samples were determined from the following formula [10]:

$$SAP = AP \times T\_0$$

where, SAP is the sectional air permeability in cm3 /s/cm; AP, the air permeability in cm3 /cm2 / s; and T0, the mean thickness in meter at 1.55 kPa pressure of the fabric sample. This test is recommended to carry out at 65 ± 2% relative humidity and 27 ± 2 °C temperature after conditioning the sample for 24 hrs. For each sample 10 tests were performed.
