Effect of plasma sericin glutaraldehyde treatments on the low stress mechanical properties of micro denier polyester/cotton blended fabric

Tensile properties

The linearity of the load extension curve (LT), tensile energy (ET), tensile resilience (RT), and elongation (EMT) is the low-stress tensile parameters that have been assessed, as represented graphically in Figs. 1, 2, 3, 4.

Figures 1 and 2 show the extensibility and linearity of the samples. Regarding extensibility (EMT), the statistical analysis shows that there is no significant difference. Because of this, the treatments have practically no effect on extensibility. The same comments hold good linearity of the load extension curve.

Figures 3 and 4 represent the tensile energy (ET) and tensile resilience (RT) values. In the case of tensile energy values, again, there is no significant difference. However, there is a significant difference between the values concerning tensile resilience. The fabric that has been applied with plasma following treatment with sericin and glutaraldehyde exhibits a significantly lower value in comparison to the control. The fixation of the sericin/glutaraldehyde on the fabric sample represented in Fig. 4a, and the sericin-treated fabric also shows a higher tensile resilience, which is due to sericin containing random coil α-structure with less β-sheet structure. It is soluble in hot water, and when the temperature drops, the random coil β-structure of the silk is transformed to α-sheet structure, which improves the viscoelastic nature of the silk, resulting in gel formation and giving the coated material increased elasticity and durability^21,22.

Bending properties

A higher fabric bending rigidity means stiff fabric and its drape are low. Similarly, too low a value of bending rigidity means that the fabric would be too flexible or supplied. For good drapability, a certain minimum bending rigidity is required. To impart higher bending rigidity (B) and hysteresis (2HB), it is necessary to subject the fabric to finishing treatment. These treatments increase the fabric rigidity and elastic recovery from bending. A larger value of 2HB means greater fabric inelasticity.

Figures 5, 6, 7 show the values of bending rigidity, bending hysteresis and residual bending strain. Bending rigidity values do not show any significant difference between the treatments, as evidenced by the “t” test. Bending hysteresis also follow the same trend. There is no significant difference in the residual bending strain. However the treatment of plasma improves the adhesion, so MDC/P absorb more sericin glutaraldehyde on the surface of the sample (sample 5) when compared to the untreated samples, so the bending rigidity, residual bending strain value of the treated sample increased represented in Figs. 5, 6, 7. ^23,24.

Shear properties

Shear properties are considered to be important for successful draping and fabric forming qualities that are necessary for successful tailoring and garment wear. The shear properties were measured using a KES-FB instrument. The values measured are G (shear rigidity), shear hysteresis at a shear angle of 0.5 degrees (2HG) andshear angle of 5 degrees (2HG5).

Figure 8 shows the shear stiffness (G) of the fabrics. As far as the shear rigidity values are concerned, there is no evidence to show that the treatments have any effect on it. Except for the fabric treated with sericin following pre-treatment with plasma and glutaraldehyde (Sample 5), there was not much difference in other cases. This may be due to the stiffening action of the finishing agent since the combination of glutaraldehyde and sericin was used, which might have led to the stiffening of the fabric.

Figure 9 shows the shear hysteresis at a shear angle of 0.5 degrees (2HG). The shear hysteresis also follows the same trend as the shear rigidity.

Figure 10 shows the residual shear strain 2HG/G. With the exception of the sericin-glutaraldehyde-treated sample and plasma-sericin-glutaraldehyde-treated sample, the residual shear strain values are not significant. The residual shear strain 2HG/G is found to be highest in plasma- and sericin- and glutaraldehydetreated samples, which indicates that the recovery is less. This is due to the presence of sericin gum, which impedes the recovery of the fabrics from shear.

During the degumming process the random coil α-structure converted into β-pleated sheets act as the stiffening mechanism in the silk²⁵.

Figure 11 shows the hysteresis of shear at a shear angle of 5 degrees (2HG5). This follows the same trend as shear hysteresis at 0.5°. In particular, sericin and glutaraldehyde treatment show a pronounced effect with respect to shear hysteresis.

Figure 12 represents the shear recovery of the fabrics. The values are found to be significant in most of the cases. However, the plasma-treated sample was similar to the control fabric.

Compression properties

Unlike the tensile, bending, shear and surface properties, compression properties merit special consideration, as they are single values such as drapes. This type of compression refers to transverse compression.Compression properties provide an idea about the handling of the fabric. LC, CE and RC are defined in the same way as LT, ET and RT, respectively. Figures 13, 14, 15, 16 are thevalues obtained from the compression test of the fabrics. LC values are a measure of the linearity of the compression curve. CE describes fabric compressive toughness. RC indicates the rate of fabric elastic recovery. Among the three parameters that are used to represent the compression properties, CE (compression energy) is the most important parameter.

Figure 13 shows that with the exception of plasma- and sericin-glutaraldehyde-treated fabric (Sample 5), the linearity of the compression values are found to be the same for all the samples.When the compression force acts on the substrate’s surface, protrude fibers may resist the load. When the load acts on the fiber, yarns come into close contact and are flattened and straightened, at which point inter-yarn and inter-fiber friction, as well as the yarn’s bending stiffness, provide compression resistance until all fibers are in contact with one another²⁶. From the SEM image in Fig. 17d the plasma- and sericin-glutaraldehyde-treated fabric showing more uniform surface coating on the fibers, so the distribution of the loadis resisting very high when compared to other samples, and similar trend we observed in the compressional energy values represented in Fig. 14.

Figure 15 shows the compressional resilience of the treated samples. With the exception of the glutaraldehyde treated sample (sample 2), there was a significant improvement in other cases. The reason for the low compressibility may be attributed to the stiffening effect. This can be attributed to the reduction in the mechanical restraint in the polyester fabric due to sericinand glutaraldehyde finishing. Morooka et al.²⁷concluded that a combination of CE and RC can reflectthe softness of the fabric. Higher CE values accompanied by lower RC values generally lead to a softer fabric.

In Fig. 16, the percentage compression, which is a nonstandard parameter, shows a significant difference insamples 2, 3, and 5, glutaraldehydetreated sample, sericinand glutaraldehydetreated fabric and plasma- and sericinglutaraldehydetreated fabric respectively.

Surface properties

Surface properties are related to the smoothness of fabrics and are represented by MIU, MMD and SMD. MIU is the ratio of the average frictional force to the normal load. MMD (mean deviation of MIU) gives the variability in the MIU value along with the fabric. The geometrical roughness (SMD) gives the average vertical displacement of the piano wire tip with reference to the mean surface layer of the fabric.

At a magnification of 5000, Fig. 17a offers a clear image of individual fibres in a 100% cotton fabric. Figure 18, shows that the MIU value is high in the case of sericin and glutaraldehyde samples and the case of plasma and sericin cum glutaraldehyde samples shown in Fig. 17c,d when compared to control represented in Fig. 17b. The increase in friction is due to the increase in the area of contact caused by the presence of sericin and glutaraldehyde. Figure 19 shows the mean deviation of MIU (MMD) and does not show any significant difference.

The variation in fabric surface roughness is depicted in Fig. 20. With the exception of glutaraldehydetreated fabric, all the other samples show an increase in surface roughness. The surface roughness increases with the glutaraldehydetreated sample, sericin and glutaraldehyde finish and plasma finished with sericin and glutaraldehyde samples compared to the control sample.

Evaluation of fabric hand

Tables 2 and 3 shows the primary hand values (PHVs) and total hand values (THVs) for the textiles.The sensation of contact of fabric, which is relevant to the garment handle properties is the sensory comfort of garments. The subjective evaluation of textiles based on the sensation of touch has already been termed fabric handling. Fabric itchiness is determined by the diameter of fibers, fabric density at higher and lower pressures, and garment surface finish. The plasma-treated sample aids in the absorption of additional moisture, and the presence of moisture on the skin surface increases the intensity of fabric roughness sensations due to frictional changes.It is apparent that the plasma-treated sample displays a higher value, and the other values are comparable.

In Fig. 21 all the treated samples are not very much different from the control which shows that there is no measurable difference in handle following the treatments given to them. In other words, there was no deterioration in the handling of micro denierpolyester fabric due to the treatments.

ANOVA analysis of various factors

ANOVA was carried out for low-stress mechanical properties between treated and untreated fabrics. The results are given in Table 4, and it shows that there is no significant difference between various properties. However, between the treatments,there was a significant difference.