Variation of thickness 61

CHAPTER 5 RESULT AND DISCUSSION 61

5.1 Variation of thickness 61

1.44 1.46 1.48 1.5 1.52 1.54 1.56 1.58 1.6 1.62 1.64

Belly Butt Shank Shoulder

Location of leather

Thickness[mm]

Chittagong Rajshahi Dhaka

Figure 5.1 Variation of thickness at different location and origin of leather

5

.2 Variations of softness

Softness is another important characteristic of leather. This characteristic depends on chemical and mechanical treatment of hides and skins to produce leather as well as natural climatic conditions where the animals live. Naturally the growth rate of fiber, degree of wave angle, compactness of fiber structure and its arrangement of an area varies on the origin of leather. In tanning process such as liming, de-liming, bating, neutralization, fat-liquoring can play an important role to increase or decrease the softness of the leather during the process. On the other hand, revolution of tanning drum, dry milling and stacking operation can also change the softness of leather.In this study the softness is measured by a softness meter using constant load at different location of leather.

The variations of softness are shown in figure 5.2. Collected data are shown in table 5.2.

Table 5.2

Variation of softness at different location of same leather with respect to geographical origin

Geographical origin Sample location Softness Softness of leather Chittagong.

Belly Butt Shank Shoulder

3.33 4.20 3.37 3.17

3.52

Rajshahi

Belly Butt Shank Shoulder

4.45 4.16 4.43 4.14

4.30

Dhaka

Belly Butt Shank Shoulder

4.15 4.16 4.03 4.26

4.15

Figure 5.2 Variation of softness at different location and origin of leather

5.3 Variation of thermal conductivity

The thermal conductivity of porous and water containing material have large dependency on their porosity and water content. Leather is considered as porous material and water molecules are present in it. The fiber compactness, hence the porosity of leather is not the same for leather produced from a specific cattle or goats.

It also has the variation over living conditions and areas. Thus the thermal conductivity of the different parts of leather and their comparison may provide important information for future application of it.

The variation of thermal conductivity of different locations and geographical origins in Bangladesh is shown in table 5.3 and fig. 5.3.

Heat can pass from one place to another only when there is a temperature difference.

Heat always moves from higher temperature to lower temperature to make an equilibrium condition. Heat transfer through the materials is mainly dependent on its thermal conductivity.Heat can pass more quickly through material of higher thermal conductivity than lower. In cold climate,the heat loss from inside shoes will be quicker if the thermal conductivity of the shoe material is high.To make shoes comfortable for cold weather, shoe materials of comparatively lower thermal conductivity are generally choosen.These materials protect the heat loss from inside the shoe in cold weather. On the other hand, in hot weather, there is not much difference between the inside and outside temperatures and consequently the heat transfer is less.

Thus,leather from Dhaka and Chittagong regions are more suitable for use in cold countries.More specifically belly and shank portion having lower thermal conductivities are better for making shoes than butt and shoulder.In case of shoes for warm countries, porous, i-e.,leather with a higher conductivity is more suitable.

Table 5.3

Thermal conductivity at different location of same leather with respect to geographical origin

Fig. 5.3 Variation of thermal conductivity graph with respect to geographical origin

Origin Location

Chattagong [k=Watt/m^° K]

Rajshahi [k=Watt/m^° K]

Dhaka [ k=Watt/m^° K ]

Belly 0.098 0.147 0.095

Butt 0.110 0.160 0.112

Shank 0.098 0.147 0.096

Shoulder 0.102 0.141 0.102

Average 0.102 0.149 0.101

CHAPTER 6

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CONCLUSION AND RECOMMENDATIONS

6.0 Conclusions

In the present investigation a modified Fitch type thermal conductivity apparatous suitable for the measurment of thermal conductivity of leather samples has been designed and manufactured.Thermal conductivity of leather originated from Rajshahi,Dhaka and Chittagong district of Bangladesh have been investigated.Thermal conductivity of butt,belly,shank and shoulder portion of each leather have also been investigated. Variation of softness with geographical origin of sample and location of each sample have also been studied.Variation in thickness of butt,belly,shank and shoulder portion of each leather have also been investigated.

Thermal conductivity of leather originated from Rajshahi district of Bangladesh has been found to be 0.149 Watt/m^º K and that of from Chittagong and Dhaka district of Bangladesh observed to be 0.102 Watt/m^º K and 0.101 Watt/m^º K respectively. The highest thermal conductivity occurs in the leather originated from Rajshahi district which may be related to it’s greater value of softness with compared to others.

Relatively, lower values of thermal conductivities in belly and shank portion has been observed as compared to butt and shoulder portion. In the present investigation, the comfort of shoes can be related to the heat flow inside the shoes and outside climate which can be finally co-related to the thermal conductivity of the leather used in manufacturing of shoes.

It is obsevved that leather from Dhaka and Chittagong regions are more suitable for use in cold countries due to their lower thermal conductivities.More specifically, belly and shank portion having lower thermal conductivites are better for manufacturing shoes than butt and shoulder.In case of shoes for warm countries like Bangladesh,leather with higher thermal conductivity is more suitable.It appeared in the present investigation that leather of Rajshahi origin is more suitable for making more comfortable shoes compared to that from Chittagong and Dhaka origin for Bangladesh and having similar climate as Bangladesh.