chapter 5 wicking behaviour of manmade cellulosic fibres...

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CHAPTER 5

WICKING BEHAVIOUR OF MANMADE CELLULOSIC FIBRES

LIKE VISCOSE, MODAL, TENCEL AND BAMBOO FIBRES

5.1 INTRODUCTION

This chapter is concerned with the study of properties of viscose, modal,

bamboo and tencel staple fibres and also their wicking behaviour.

5.2 MATERIALS AND METHODS

These have been already discussed in Chapter 3

5.3 RESULTS AND DISCUSSION

Table 5.1 shows the various properties of fibres together with their

variability.

Table 5.1: Fibre properties

Fibre Parameters

Fibres Viscose Modal Tencel Bamboo

Length (mm) 39.3 51.5 38.8 38.7

CV% 2.6 4.94 3 2.6

Fineness (dtex) 1.38 1.28 1.24 1.23

CV% 15.10 14.80 10.70 9.20

Tenacity (g/d) 2.66 3.72 4.22 2.64

CV% 8.10 11.70 10.80 10

Elongation (%) 18.70 15.80 10.70 18

CV% 11.20 11.40 15.90 12.60

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From Table 5.1, it is clear that the modal fibres had longer length and

higher CV% compared to other fibres. Viscose fibres showed higher fineness and

the variability was found to be higher in viscose ,modal and tencel. Tencel fibres

displayed higher tenacity compared to other fibres. This agrees with the findings

of Kreze et al., (2002). The elongation values are higher in the case of viscose and

bamboo. Tencel fibres showed greater variability. Following figures 5.1 – 5.4

illustrates the differences in their properties.

Figure 5.1: Figure 5.2:

Fibre length and CV% Fibre fineness and CV%

Figure 5.3: Figure 5.4:

Fibre tenacity and CV% Fibre elongation and CV%




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Figure 5.5: Stress strain curves of tencel, modal, bamboo and viscose fibres

Tencel Modal

Bamboo Viscose

The presence of yield point has been noticed in other fibres except tencel.




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WICKING RESULTS

Data on wicking height and time were analysed by four methods

Plotting height vs time and carrying out linear regression analysis.

Plotting height and square root of time so that the curve follows Lucas

Washburn trend. This is based on the method followed by Kamath et al.,

(1994).

Plotting H2 vs time and carrying out regression analysis as per the analysis

followed by Sharabathy et al., (2008) and Mazloompour et al., (2011).

Plotting logarithm of height vs logarithm of time and carrying out linear

regression analysis.

Figures 5.6, 5.8, 5.10 and 5.12 illustrate the wicking behaviour of fibres and

the respective tables are presented in Appendix 1.

Figure 5.6: Wicking behaviour of viscose, modal, tencel and bamboo fibres -

Height and Time




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Tables give the relevant data on slope and intercept. Table 5.2: Regression equation and correlation coefficient for various fibres

(Height and Time)

Fibres Slope(cm/min) Intercept(cm) Correlation Coefficient

(R2)

Tencel 0.143 1.4733 0.9356

Modal 0.1333 1.3467 0.9549

Bamboo 0.1279 1.1867 0.9713

Viscose 0.1055 0.86 0.9929

Figure 5.7: Slope values (Height and Time)




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Log Time and Log Height

Table 5.3: Regression equation of the form log (h)=k log t + constant and

correlation coefficient for various fibres

Fibres Slope (K) Intercept (C)

Correlation Coefficient

(R2)

Tencel 0.2989 0.3452 0.9955

Modal 0.2991 0.2619 0.9988

Bamboo 0.3064 0.1528 0.9944

Viscose 0.32 -0.1416 0.9826

Figure 5.9: Slope values versus intercept values (Log Height and Log Time)




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Square root of Time and Height

Table 5.4: Regression equation of the form H=Kt 1/2 + constant and

correlation coefficient for various fibres

Fibres Slope(cm/min1/2 ) Intercept(cm) Correlation Coefficient

(R2)

Tencel 0.6263 0.8523 0.9858

Modal 0.5803 0.7756 0.994

Bamboo 0.5528 0.6475 0.9974

Viscose 0.4494 0.4299 0.9908

Figure 5.11: Slope values (Square Root of Time and Height)




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Square of Height and Time

Table 5.5: Regression equation of the form h2/t and correlation coefficient and correlation coefficient for various fibres

Fibres Slope(cm)2/min) Intercept(cm) Correlation Coefficient

(R2)

Tencel 0.6195 1.8807 0.9736 Modal 0.5355 1.5347 0.9858 Bamboo 0.4696 1.128 0.9933 Viscose 0.3004 0.514 0.9959

Figure 5.13: Slope values (Square of Height and Time)




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In the first method of analyzing wicking, the wicking time was plotted

against the wicking height and the regression equation and correlation coefficient

were computed and shown in Table 5.2.Tencel fibres show higher values of slope

and intercept followed by modal, bamboo and viscose fibres. The correlation

between height and time was found to be good. This is due to the molecular

structure of tencel which consists of fine crystalline micro fibrils with fine pores.

The space between these micro fibrils acts like capillaries giving rise to enhanced

capillary effect. Also such crystalline arrangement of micro fibrils is uniformly

distributed in tencel unlike viscose, bamboo and modal. Hence tencel fibres

showed maximum wicking behaviour compared to other fibres In the second

method of analyzing wicking, the logarithm of wicking time was plotted against

the logarithm of wicking height. Values of the time exponent (K) and intercept

values were computed and shown in Table 5.3. Higher values of ‘C’ and lower

values of ‘K’ indicate good wickability and vice versa. Slopes and intercepts

obtained from log h –log t values were plotted to illustrate the trend as shown in

Figure 5.9. There was a negative correlation between slope K and intercept C as

suggested by Laughlin and Davies (1961) which has to be considered for

interpreting wickability. It is clear that there is an interdependency between K

and C.

In the third method , the wicking height was plotted against the square root

of time which is based on the Kamath et al.’s procedure adopted for the studies.

Table 5.4 shows the slopes and intercept values (Model assumed Kt ½ + constant,

where K is the slope) whereas the h2/t values are shown in Table 5.5. In this

method, square of height was plotted against time. In both the cases, tencel fibres

with higher values of slopes and intercepts exhibited good wickability and the

correlation was found to be good. Slope values obtained from height and time,

height and square root of time, square of height and time were plotted to illustrate

the trend as shown in Figures 5.7, 5.11 and 5.13.




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5.4 CONCLUSION

Among the fibres studied for wickability, it has been noticed that tencel

exhibits maximum wicking behaviour. The tenacity was also found to be higher

compared to other fibres.




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