*3.2.4. Bending property*

Fabric bending property is apparently a function of the bending property of its constituent yarns. *B* is bending rigidity, a measure of a fabric's ability to resist bending deformation. In other words, it reflects the difficulty with which a fabric can be deformed by bending.This parameter is particularly critical in the tailoring of lightweight fabrics. The higher the bend‐ ing rigidity, the higher a fabric's ability to resist when it is bent by external force like what happens during fabric manipulation in spreading and sewing.

**Type of treatment**

P 25 U.

P 50 U.

P 75 U.

E 25 U.

E 50 U.

E 75 U.

Esperase®

P: Papain, E: Esperase®

**Type of treatment**

P 25 U.

P 50 U.

P 75 U.

E 25 U.

E 50 U.

E 75 U.

Esperase®

P: Papain, E: Esperase®

8.0L

8.0L

**Bending rigidity (***B***)**

**cm2.cm-1)**

No enzyme 0.0205±0.0005 0.0117±0.0001 *0.0161* 1.80±0.02 1.60±0.01 *1.70*

g-1 fabric 0.0256±0.0007 0.0147±0.0003 *0.0202* 1.70±0.03 1.53±0.02 *1.62*

g-1 fabric 0.0356±0.0009 0.0185±0.0004 *0.0271* 1.30±0.01 1.25±0.01 *1.27*

g-1 fabric 0.0463±0.0006 0.0234±0.0002 *0.0349* 0.75±0.01 0.50±0.01 *0.63*

g-1 fabric 0.0337±0.0004 0.0126±0.0003 *0.0232* 0.85± 0.01 0.35±0.01 *0.60*

g-1 fabric 0.0321±0.0006 0.0283±0.0002 *0.0302* 0.55±0.01 0.35±0.01 *0.45*

g-1 fabric 0.0479±0.0007 0.0283±0.0005 *0.0381* 0.50±0.01 0.35±0.01 *0.43*

Marseille soap 0.0537±0.0006 0.0264±0.0003 *0.0401* 1.80±0.03 1.60±0.01 *1.70*

**Table 8.** Comparison of micromechanical properties of silk fabrics treated for 60 min with various levels of papain and

Tensile property increased when enzyme concentration increased for both protease used (Table 9). Treatment with Esperase® 8.0L and particularly with high concentrations resulted

> **Tensile (%) warp weft** *mean*

in silk fabrics more elastic compared to those treated with Marseille soap (Table 9).

No enzyme 5.15 ± 0.2 1.63 ± 0.07 *3.39*

g-1 fabric 4.09 ± 0.3 1.24 ± 0.04 *2.67*

g-1 fabric 3.97 ± 0.2 0.94 ± 0.02 *2.53*

g-1 fabric 4.53 ± 0.3 1.33 ± 0.04 *2.93*

g-1 fabric 4.51 ± 0.3 1.05 ± 0.04 *2.78*

g-1 fabric 5.37 ± 0.1 1.49 ± 0.02 *3.43*

g-1 fabric 6.32 ± 0.3 1.15 ± 0.01 *3.74*

**Table 9.** Comparison of micromechanical properties of silk fabrics treated for 60 min with various levels of papain and

Marseille soap 4.29 ± 0.2 1.42 ± 0.07 *2.86*

**Shear stiffness (***G***)**

**cm-1.degree-1)**

http://dx.doi.org/10.5772/53730

249

**(gf.**

**warp weft** *mean* **warp weft** *mean*

Physichochemical and Low Stress Mechanical Properties of Silk Fabrics Degummed by Enzymes

**(gf.**

8.0L, with reference and conventionally degummed materials

8.0L, with reference and conventionally degummed materials

Enzymatically treated silk fabrics exhibited higher *B* values compared to silk fabrics treated only with buffer solution (no enzyme) (Table 8). Bending rigidity was affected by both type of protease and enzyme concentration. Increasing enzyme concentration result‐ ed in higher *B* values, namely in more stiff fabrics. Silk fabrics treated with papain ex‐ hibited 25-116% increase in *B* values while silk fabrics treated with Esperase® 8.0L showed higher increase namely 44-137% in comparison with the buffer treated silk fab‐ rics. Enzymatically treated silk fabrics are less rigid, softer compared to conventionally degummed fabrics.

Chopra et al., [49] reported that enzyme treated silk fabrics exhibited increased bending ri‐ gidity compared to soap treated ones. In the present study, even though an increase in bend‐ ing rigidity was observed through the different experimental conditions, fabric treated with Marseille soap exhibited the highest value of this property.

#### *3.2.5. Shear property*

Shear rigidity *G* provides a measure of the resistance to rotational movement of the warp and weft threads within a fabric when subjected to low levels of shear deformation. The lower the value of *G*, the more readily the fabric will conform to three-dimensional curva‐ tures.

Enzymatically treated silk fabrics showed lower *G* values compared to untreated and con‐ ventionally treated silk fabrics. Shear rigidity (*G*) of biotreated fabrics, for a given protease, decreased, when enzyme loading was increased (Table 8). The silk fabrics treated with pa‐ pain showed 5-63% decrease in *G* values for the different enzyme activities, while the fabrics treated with Esperase® 8.0L showed a higher decrease in *G* values which ranged between 65-75%. Lower *G* values, of the enzymatically treated silk fabrics is "translated" in softer fab‐ rics with better drape (Table 8).

#### *3.2.6. Tensile property*

The tensile behaviour of fabric is closely related to the inter-fiber friction effect, the ease of crimp removal and the load-extension properties of the yarns themselves. Through the KES apparatus the EMT parameter was determined which reflects fabric's extensibility, a meas‐ ure of a fabric's ability to be stretched under tensile load. The larger the EMT, the more ex‐ tensible the fabric.


*3.2.4. Bending property*

248 Eco-Friendly Textile Dyeing and Finishing

degummed fabrics.

*3.2.5. Shear property*

rics with better drape (Table 8).

*3.2.6. Tensile property*

tensible the fabric.

tures.

Fabric bending property is apparently a function of the bending property of its constituent yarns. *B* is bending rigidity, a measure of a fabric's ability to resist bending deformation. In other words, it reflects the difficulty with which a fabric can be deformed by bending.This parameter is particularly critical in the tailoring of lightweight fabrics. The higher the bend‐ ing rigidity, the higher a fabric's ability to resist when it is bent by external force like what

Enzymatically treated silk fabrics exhibited higher *B* values compared to silk fabrics treated only with buffer solution (no enzyme) (Table 8). Bending rigidity was affected by both type of protease and enzyme concentration. Increasing enzyme concentration result‐ ed in higher *B* values, namely in more stiff fabrics. Silk fabrics treated with papain ex‐ hibited 25-116% increase in *B* values while silk fabrics treated with Esperase® 8.0L showed higher increase namely 44-137% in comparison with the buffer treated silk fab‐ rics. Enzymatically treated silk fabrics are less rigid, softer compared to conventionally

Chopra et al., [49] reported that enzyme treated silk fabrics exhibited increased bending ri‐ gidity compared to soap treated ones. In the present study, even though an increase in bend‐ ing rigidity was observed through the different experimental conditions, fabric treated with

Shear rigidity *G* provides a measure of the resistance to rotational movement of the warp and weft threads within a fabric when subjected to low levels of shear deformation. The lower the value of *G*, the more readily the fabric will conform to three-dimensional curva‐

Enzymatically treated silk fabrics showed lower *G* values compared to untreated and con‐ ventionally treated silk fabrics. Shear rigidity (*G*) of biotreated fabrics, for a given protease, decreased, when enzyme loading was increased (Table 8). The silk fabrics treated with pa‐ pain showed 5-63% decrease in *G* values for the different enzyme activities, while the fabrics treated with Esperase® 8.0L showed a higher decrease in *G* values which ranged between 65-75%. Lower *G* values, of the enzymatically treated silk fabrics is "translated" in softer fab‐

The tensile behaviour of fabric is closely related to the inter-fiber friction effect, the ease of crimp removal and the load-extension properties of the yarns themselves. Through the KES apparatus the EMT parameter was determined which reflects fabric's extensibility, a meas‐ ure of a fabric's ability to be stretched under tensile load. The larger the EMT, the more ex‐

happens during fabric manipulation in spreading and sewing.

Marseille soap exhibited the highest value of this property.

**Table 8.** Comparison of micromechanical properties of silk fabrics treated for 60 min with various levels of papain and Esperase® 8.0L, with reference and conventionally degummed materials

Tensile property increased when enzyme concentration increased for both protease used (Table 9). Treatment with Esperase® 8.0L and particularly with high concentrations resulted in silk fabrics more elastic compared to those treated with Marseille soap (Table 9).


**Table 9.** Comparison of micromechanical properties of silk fabrics treated for 60 min with various levels of papain and Esperase® 8.0L, with reference and conventionally degummed materials

## **3.3. Synergistic action of protease-lipase on silk degumming: Effect of treatment time**

lase® Ultra 50T. This combination at the highest enzyme loading used, exhibited adequate water absorbency (<1 sec) after 60 min of treatment. The mixture of papain with Lipolase® Ultra 50T did not improve the wettability of the silk fabrics compared to those treated only

Physichochemical and Low Stress Mechanical Properties of Silk Fabrics Degummed by Enzymes

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251

Crystallinity index increased with treatment time for all enzyme combination tested (Table 10). The combination of Esperase® 8.0L with lipase was more effective compared to that of papain. However, the addition of lipase did not seem to improve Crystallinity Index in any

**Treatment Wetting time (sec) Crystallinity Index (%)**

30 min 5.90 ± 0.18 62.80 ± 1.30 60 min 5.80 ± 0.12 63.20 ± 1.24 90 min 5.60 ± 0.10 63.32 ± 1.31

30 min 4.72 ± 0.20 62.90 ± 1.36 60 min 3.60 ± 0.15 63.20 ± 1.40 90 min 3.30 ± 0.30 63.32 ± 1.26

30 min 2.20 ± 0.20 64.80 ± 1.60 60 min 2.00 ± 0.19 65.00 ± 1.80 90 min 1.50 ± 0.18 65.10 ± 1.10

30 min 1.47 ± 0.09 65.20 ± 1.50 60 min <1 65.40 ± 1.40 90 min <1 66.00 ± 1.10 Marseille soap <1 66.48 ± 1.35 No enzyme 6.85 ± 0.20 63.90 ± 1.27

**Table 10.** Wetting time and Crystallinity Index of silk fabrics treated conventionally (Marseille soap) or enzymatically.

The synergistic action of protease-lipase improved the whiteness of the silk fabrics (Figure 5a). Increasing enzyme concentration and treatment time resulted in increased whiteness values. The highest whiteness values for each combination were observed at highest enzyme loading and after 90 min of treatment. Those values were 55.2 and 59.8 Berger degree for papain+ Lipolase® Ultra 50T and Esperase® 8.0L+ Lipolase® Ultra 50T, respectively. It should

g-1 fabric Lipolase® Ultra 50T

g-1 fabric Lipolase® Ultra 50T

with papain, even at higher treatment times.

50 U.

75 U.

50 U.

75 U.

g-1 fabric Papain + 50 U.

g-1 fabric Papain + 50 U.

g-1 fabric Esperase®

g-1 fabric Esperase®

8.0L + 50 U.

8.0L + 50 U.

*3.3.3. Whiteness and whiteness after bleaching with H2O2*

condition tested, compared to the action of single protease.

g-1 fabric Lipolase® Ultra 50T

g-1 fabric Lipolase® Ultra 50T

Proteases and lipases are normally used in combination for degumming and removing oth‐ ers impurities such as waxes, fats, mineral salts and pigments [49]. Waxes and fats as well as colorants and mineral components occur exclusively in silk gum layer (sericin) [66]. The combined effect of enzyme activity (expressed as Units of protease per g of silk fabric) and treatment time on physicochemical and low-stress mechanical properties of cotton fabric was investigated. Raw silk fabrics were treated with two different proteases namely papain and Esperase® 8.0L at an enzyme activity of 50 and 75 U. g-1 fabric combined with a lipase (Lipo‐ lase® Ultra 50T) at a constant activity of 50 U. g-1 fabric ic for 30, 60, 90 min. Furthermore, buffer treated and conventional degummed silk fabrics were used as controls.
