Chapter 4d
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Results and Discussion
4.6 OMMT: PA Composites 4.6.1 Physical properties of OMMT: PA composites 4.6.1.1 Hardness of OMMT: PA composites There is continuous increment in hardness with increase in amount of loading of nanoclay in comparison to virgin polyamide (fig 4.55). The increment in hardness is more appreciable at 4 wt % of loading in polyamide. 1 wt % loading of nanoclay in polyamide shows hardness 78, while at 4 wt % loading hardness is observed to be 90. This improvement in hardness is found to be more effective compared to virgin polyamide 73 and this is due to hard nature of polyamide with exfoliation of polymer chains in between two plates of nanoclay, which makes the surface of composite very hard due to which the indentation of the indenter is quite difficult. 90
Hardness(Shore D)
88 86 84 82 80 78 76 74 0
1
2
3
4
5
W t% o f fille r
Fig-4.55: Hardness of polyamide Nanocomposite
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
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Results and Discussion
4.6.2 Mechanical properties of OMMT: PA composites 4.6.2.1 Mechanical properties Figs 4.56 to 4.58 show the effect of OMMT on mechanical properties of polyamide nanocomposites. It is observed that tensile strength increases with increase in OMMT loading (fig 4.56). 1 wt % loading of OMMT in polyamide shows tensile strength as 109 MPa, while at 4 wt % loading of OMMT, tensile strength is observed to be 135 MPa, the tensile strength of virgin polyamide is observed as 95 MPa. The increment in Young’s modulus is found to be more appreciable at 4 wt % of loading, and it is recorded to be 4004 MPa, whereas Young’s modulus of 1 wt % loading of OMMT and virgin polyamide is found to be very less i.e. 3804 MPa and 3600 MPa respectively (fig 4.57). Likewise, tensile strength, Young’s modulus and elongation at break increase with increase in amount of clay. Elongation at break at 1 and 4 wt % loading of OMMT is recorded as 18 and 23 % respectively as shown in fig 4.58. This improvement in mechanical properties (tensile strength, Young’s modulus and elongation at break) is due to ordered exfoliation of polymer chains in between the intergallary spacing of nanoclay, which has already been discussed in this text. Moreover, the increment in elongation at break is due to reduction in viscosity of polymer during processing, which provides more strength with maximum elongation and strength. The uniform dispersion of nanoclay along with polymer chains is evidenced from SEM images (fig 4.64 to 4.65)
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 128
Results and Discussion
Fig-4.56: - Tensile strength of polyamide nanocomposites
Fig 4.57 Young’s Modulus of polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 129
Elongation @ Break
Results and Discussion
24 23 22 21 20 19 18 17 16 15 0
2 4 W t% o f f ille r
6
Fig 4.58 Elongation at break of polyamide nanocomposites 4.6.3 Flammability The flammability of polyamide nanocomposites decreases with increase in clay content (fig 4.59). At 4 wt % loadings of nanoclay, the decrement in flammability is found to be more appreciable. 1 wt % loading of nanoclay, shows flammability rate as 0.373 mm/sec, while 4 wt % loading of nanoclay in polyamide shows flammability 0.326 mm/sec. This improvement in flammability was due to formation of char layer, which is having the ability to sustain the flame for longer time.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 130
Rate of Burning [mm/sec]
Results and Discussion
0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0
1
2 3 Wt % Filler
4
5
Fig 4.59 Rate of Burning of polyamide nanocomposites 4.6.4 Vicat softening temperature (VST) The effect of clay content on vicat softening temperature of polyamide nanocomposites is shown in fig 4.60. The VST of polyamide nanocomposites increase with increase in clay content. Obviously polyamide nanocomposites are thermally stable, but incorporation of nanoclay doesn’t remarkably improve the thermal stability of polyamide nanocomposites. This increase in VST is due to uniform and ordered exfoliation of polymer chains in between the two intergallary spacing of nanoclay. 1 wt % loading of OMMT in polyamide composites results VST 240 0C, while 4 wt % loading of OMMT in polyamide composites shows 370 0
C, where as, VST of pristine polyamide recorded as 230 0C.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 131
Vicat Softning Temperature
Results and Discussion
400 350 300 250 200 150 100 50 0 0
2
4
6
Wt % of Filler
Fig 4.60 Vicat softening temperature of polyamide nanocomposites 4.6.5 Rheological properties The relationship stated from the Brabender Plasticorder is: M= CSa………………… (1) Where M is the torque, S is the rpm, and C and a are constants. The above equation resembles the power law behavior [20-22] which is given as: τ = K(γ)n…………………(2) Where τ is shear stress; K, constant; γ, shear rate and n, non-Newtonian flow index [23-38]. Based on the above two equations it can be interpreted that the torque recorded on the Brabender Plasticorder is an indirect indication of the shear stress, while rotor speed(rpm) is as indirect indication of shear rate. Thus, the viscosity that is given as the ratio of shear stress to shear rate in case of the Brabender Plasticorder and obtained from the ratio of torque to rotor speed (rpm) and is estimated as power law index (n). Fig 4.61 shows the effect of OMMT loadings on the apparent viscosity at constant shear rate of polyamide 66-OMMT nanocomposites, It is observed that two factors control the viscosity of Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 132
Results and Discussion
the polyamide 66-OMMT composites. 1) The viscosity decreases with increase in shear rate, 2) the viscosity is influenced with the blend composition. The viscosity decrease with increased shear rate indicates that the chains are easily deformed and their frictional resistance is not optimum. It is observed that at any shear rate, the higher the filler content, lower the viscosity. The decrease in viscosity is due to the increase in percentage of OMMT clay in polyamide 66. However, the effective decrease in the viscosity with increase in OMMT concentration might be due to lubrication of OMMT during processing of polyamide. The melt flow behavior of the samples can be described by power law index. Fig.4.62 illustrates the relationship between shear stress and shear rate of the polyamide/OMMT at various OMMT concentrations as log-log graphs. It is observed that shear stress decreases with increase in shear rates which strengthen the fact that the rate of increasing shear stress is affected by OMMT percentage addition. The data show that the behavior of the melts is highly nonNewtonian, according to the slope of the straight lines used to estimate the value of the non-Newtonian flow index (n). This is observed due to lubrication effect of OMMT, which is expected to improve the flow properties of the polyamide. Hence melts display a less non-Newtonian behavior with increased OMMT contents. The values of N indicate the Pseudo plastic nature of the polyamide/OMMT blends since n<1, showing that the apparent viscosity decreases as shear rate increases. The Torque Vs Wt % of Filler is shown in Fig 4.63.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 133
Results and Discussion
Viscosity [NM/rpm]
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0
1
2 3 Wt % of Filler
4
5
log shear stress
Fig 4.61 Viscosity vs shear rate of polyamide nanocomposites
1.62 1.6 1.58 1.56 1.54 1.52 1.5 1.48 1.46 1.44 1.42
y = 0.5364x + 0.6021 R2 = 0.9715
1.5
1.6
1.7 log shear rate
1.8
1.9
Fig 4.62 Log shear stress vs Log shear rate of polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 134
Results and Discussion
80
Torque[NM]
70 60 50 40 30 20 10 0 0
1
2 3 W t % o f fille r
4
5
Fig 4.63 Torque of polyamide Nanocomposites
Fig 4.64 SEM of 1 wt % of OMMT in polyamide nanocomposite
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 135
Results and Discussion
Fig 4.65 SEM of 4 wt % of OMMT in polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 136
4.6 OMMT: PA Composites 4.6.1 Physical properties of OMMT: PA composites 4.6.1.1 Hardness of OMMT: PA composites There is continuous increment in hardness with increase in amount of loading of nanoclay in comparison to virgin polyamide (fig 4.55). The increment in hardness is more appreciable at 4 wt % of loading in polyamide. 1 wt % loading of nanoclay in polyamide shows hardness 78, while at 4 wt % loading hardness is observed to be 90. This improvement in hardness is found to be more effective compared to virgin polyamide 73 and this is due to hard nature of polyamide with exfoliation of polymer chains in between two plates of nanoclay, which makes the surface of composite very hard due to which the indentation of the indenter is quite difficult. 90
Hardness(Shore D)
88 86 84 82 80 78 76 74 0
1
2
3
4
5
W t% o f fille r
Fig-4.55: Hardness of polyamide Nanocomposite
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 127
Results and Discussion
4.6.2 Mechanical properties of OMMT: PA composites 4.6.2.1 Mechanical properties Figs 4.56 to 4.58 show the effect of OMMT on mechanical properties of polyamide nanocomposites. It is observed that tensile strength increases with increase in OMMT loading (fig 4.56). 1 wt % loading of OMMT in polyamide shows tensile strength as 109 MPa, while at 4 wt % loading of OMMT, tensile strength is observed to be 135 MPa, the tensile strength of virgin polyamide is observed as 95 MPa. The increment in Young’s modulus is found to be more appreciable at 4 wt % of loading, and it is recorded to be 4004 MPa, whereas Young’s modulus of 1 wt % loading of OMMT and virgin polyamide is found to be very less i.e. 3804 MPa and 3600 MPa respectively (fig 4.57). Likewise, tensile strength, Young’s modulus and elongation at break increase with increase in amount of clay. Elongation at break at 1 and 4 wt % loading of OMMT is recorded as 18 and 23 % respectively as shown in fig 4.58. This improvement in mechanical properties (tensile strength, Young’s modulus and elongation at break) is due to ordered exfoliation of polymer chains in between the intergallary spacing of nanoclay, which has already been discussed in this text. Moreover, the increment in elongation at break is due to reduction in viscosity of polymer during processing, which provides more strength with maximum elongation and strength. The uniform dispersion of nanoclay along with polymer chains is evidenced from SEM images (fig 4.64 to 4.65)
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 128
Results and Discussion
Fig-4.56: - Tensile strength of polyamide nanocomposites
Fig 4.57 Young’s Modulus of polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 129
Elongation @ Break
Results and Discussion
24 23 22 21 20 19 18 17 16 15 0
2 4 W t% o f f ille r
6
Fig 4.58 Elongation at break of polyamide nanocomposites 4.6.3 Flammability The flammability of polyamide nanocomposites decreases with increase in clay content (fig 4.59). At 4 wt % loadings of nanoclay, the decrement in flammability is found to be more appreciable. 1 wt % loading of nanoclay, shows flammability rate as 0.373 mm/sec, while 4 wt % loading of nanoclay in polyamide shows flammability 0.326 mm/sec. This improvement in flammability was due to formation of char layer, which is having the ability to sustain the flame for longer time.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 130
Rate of Burning [mm/sec]
Results and Discussion
0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0
1
2 3 Wt % Filler
4
5
Fig 4.59 Rate of Burning of polyamide nanocomposites 4.6.4 Vicat softening temperature (VST) The effect of clay content on vicat softening temperature of polyamide nanocomposites is shown in fig 4.60. The VST of polyamide nanocomposites increase with increase in clay content. Obviously polyamide nanocomposites are thermally stable, but incorporation of nanoclay doesn’t remarkably improve the thermal stability of polyamide nanocomposites. This increase in VST is due to uniform and ordered exfoliation of polymer chains in between the two intergallary spacing of nanoclay. 1 wt % loading of OMMT in polyamide composites results VST 240 0C, while 4 wt % loading of OMMT in polyamide composites shows 370 0
C, where as, VST of pristine polyamide recorded as 230 0C.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 131
Vicat Softning Temperature
Results and Discussion
400 350 300 250 200 150 100 50 0 0
2
4
6
Wt % of Filler
Fig 4.60 Vicat softening temperature of polyamide nanocomposites 4.6.5 Rheological properties The relationship stated from the Brabender Plasticorder is: M= CSa………………… (1) Where M is the torque, S is the rpm, and C and a are constants. The above equation resembles the power law behavior [20-22] which is given as: τ = K(γ)n…………………(2) Where τ is shear stress; K, constant; γ, shear rate and n, non-Newtonian flow index [23-38]. Based on the above two equations it can be interpreted that the torque recorded on the Brabender Plasticorder is an indirect indication of the shear stress, while rotor speed(rpm) is as indirect indication of shear rate. Thus, the viscosity that is given as the ratio of shear stress to shear rate in case of the Brabender Plasticorder and obtained from the ratio of torque to rotor speed (rpm) and is estimated as power law index (n). Fig 4.61 shows the effect of OMMT loadings on the apparent viscosity at constant shear rate of polyamide 66-OMMT nanocomposites, It is observed that two factors control the viscosity of Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 132
Results and Discussion
the polyamide 66-OMMT composites. 1) The viscosity decreases with increase in shear rate, 2) the viscosity is influenced with the blend composition. The viscosity decrease with increased shear rate indicates that the chains are easily deformed and their frictional resistance is not optimum. It is observed that at any shear rate, the higher the filler content, lower the viscosity. The decrease in viscosity is due to the increase in percentage of OMMT clay in polyamide 66. However, the effective decrease in the viscosity with increase in OMMT concentration might be due to lubrication of OMMT during processing of polyamide. The melt flow behavior of the samples can be described by power law index. Fig.4.62 illustrates the relationship between shear stress and shear rate of the polyamide/OMMT at various OMMT concentrations as log-log graphs. It is observed that shear stress decreases with increase in shear rates which strengthen the fact that the rate of increasing shear stress is affected by OMMT percentage addition. The data show that the behavior of the melts is highly nonNewtonian, according to the slope of the straight lines used to estimate the value of the non-Newtonian flow index (n). This is observed due to lubrication effect of OMMT, which is expected to improve the flow properties of the polyamide. Hence melts display a less non-Newtonian behavior with increased OMMT contents. The values of N indicate the Pseudo plastic nature of the polyamide/OMMT blends since n<1, showing that the apparent viscosity decreases as shear rate increases. The Torque Vs Wt % of Filler is shown in Fig 4.63.
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 133
Results and Discussion
Viscosity [NM/rpm]
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0
1
2 3 Wt % of Filler
4
5
log shear stress
Fig 4.61 Viscosity vs shear rate of polyamide nanocomposites
1.62 1.6 1.58 1.56 1.54 1.52 1.5 1.48 1.46 1.44 1.42
y = 0.5364x + 0.6021 R2 = 0.9715
1.5
1.6
1.7 log shear rate
1.8
1.9
Fig 4.62 Log shear stress vs Log shear rate of polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 134
Results and Discussion
80
Torque[NM]
70 60 50 40 30 20 10 0 0
1
2 3 W t % o f fille r
4
5
Fig 4.63 Torque of polyamide Nanocomposites
Fig 4.64 SEM of 1 wt % of OMMT in polyamide nanocomposite
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 135
Results and Discussion
Fig 4.65 SEM of 4 wt % of OMMT in polyamide nanocomposites
Ph.D Thesis, Mr. Shriram S. Sonawane, UDCT, North Maharashtra University, Jalgaon
Page 136
