Results and Discussion
4.2 Mechanical properties of irradiated UHMWPE/MWCNTs composites and UHMWPE/ T blends
4.2.2 Mechanical properties of composites and T blends after 60 days of irradiation .1 Mechanical properties of composites
The load vs. displacement plots of composites at 25 and 100 kGy doses are shown in Figures 4.17a and 4.17b, respectively. It is observed that the trend followed by the composites was similar to that of results observed within 10 days after irradiation shown in Figure 4.13. The mechanical properties of composites after 60 days of irradiation at different doses were obtained from the load vs. displacement plots and are shown in Figures 4.18a - 4.18c. It is observed from Figure 4.18a that the work to failure of the test sample was reduced with an increase of irradiation dose but it was increased with MWCNTs concentration. The work to failure of GI25NC0.0 was 2056 mJ, which was reduced to 1595 mJ at GI100 corresponding to the reduction of 22.4 %, whereas the reduction was found to be only 17 % for NC2.0 sample when the irradiation dose was increased
Figure 4.17. Load vs. displacement plots of composites at a) 25 kGy dose b) 100 kGy dose after 60 days of irradiation
(a) (b)
0.0 0.5 1.0 1.5 2.0 1000
2000 3000 4000 5000 6000 7000 8000
Work to failure (mJ)
MWCNT wt.%
25 kGy 50 kGy 75 kGy 100 kGy
0.0 0.5 1.0 1.5 2.0
300 400 500 600 700 800
% Strain at fracture
MWCNT wt.%
25 kGy 50 kGy 75 kGy 100 kGy
0.0 0.5 1.0 1.5 2.0
15 20 25 30 35
25 kGy 50 kGy 75 kGy 100 kGy
Yield stress (MPa)
MWCNTs wt.%
Figure 4.18. Mechanical properties of composites after 60 days of irradiation a) Work to failure b) Strain at fracture c) Yield stress
from 25 to 100 kGy. It is also observed that when the concentration of MWCNTs was increased from 0 to 2 wt. % at 100 kGy irradiation dose, the work to failure of polymer was increased from 1595 to 5789 mJ corresponding to an enhancement of 263 %, whereas the enhancement was found to be 240 % at 25 kGy irradiation dose. The general trend of strain at fracture after 60 days of irradiation remained the same as that of the results obtained within 10 days after irradiation, i.e., it was increased with MWCNTs concentration but reduced with an increase of irradiation
(a) (b)
(c)
from 390 to 748 %, when the MWCNTs concentration was increased to 2 wt. % corresponding to an enhancement of 92 %. Similarly, the strain at fracture of NC0.0 and NC2.0 at 100 kGy was found to be 341 and 663 %, respectively and the enhancement was found to be 94 %. However, the strain at fracture was reduced with an increase of irradiation dose at a given concentration of MWCNTs. The strain at fracture of GI25NC2.0 was found to be 748 %, which was reduced by 11.4 % at 100 kGy dose.
The yield stress of composites tested after 60 days of irradiation is shown in Figure 4.18c, where it is observed that it was increased with MWCNTs concentration but reduced with an increase of irradiation dose. The yield stress of pure polymer was reduced from 22 to 18 MPa corresponding to 18 % reduction, when the irradiation dose was increased from 25 to 100 kGy.
In case of NC2.0 test sample, the reduction was limited to 10 % for the same condition. When the concentration of MWCNTs in UHMWPE was increased from 0 to 2.0 wt. %, the yield stress at 25 kGy was increased from 22 to 32.4 MPa corresponding to 47 % enhancement. For the same condition, the yield stress was increased by 62 % at 100 kGy irradiation dose.
4.2.2.2 Mechanical properties of T blends
The load vs. displacement plots of T blends at 25 kGy and 100 kGy irradiation dose are shown in Figures 4.19a and 4.19b, respectively, where the trend was similar to that of results observed within 10 days after irradiation but with reduced magnitude. The mechanical properties, which are derived from the load vs. displacement plots, are shown in Figures 4.20a- 4.20c. Figure 4.20a shows that the work to failure of T blends was reduced with an increase of irradiation dose at a given concentration of T but it was increased with T concentration at any given irradiation dose. The work to failure of T0.1 was reduced by 17 % upon increasing the irradiation dose from 25 to 100 kGy and it was increased by 15 % at 100kGy for T0.5
0 10 20 30 40 50 0
10 20 30 40 50 60 70 80 90
αΤ0.3 αΤ0.5
Load (N)
Dispalcement (mm)
αΤ0.1
0 10 20 30 40
0 10 20 30 40 50 60 70 80 90
αΤ0.5 αΤ0.3 αΤ0.1
Load (N)
Displacement (mm)
0.0 0.1 0.2 0.3 0.4 0.5
1500 1750 2000 2250 2500 2750 3000 3250
25 kGy 50 kGy 75 kGy 100 kGy
Work to failure (mJ)
αΤwt.%
0.0 0.1 0.2 0.3 0.4 0.5
325 350 375 400 425 450
475 25 kGy
50 kGy 75 kGy 100 kGy
% Strain at fracture
αΤwt.%
0.0 0.1 0.2 0.3 0.4 0.5
18 20 22 24
25 kGy 50 kGy 75 kGy 100 kGy
Yield stress (MPa)
αΤwt.%
Figure 4.19. Load vs. displacement plots of T blends at a) 25 kGy dose b) 100 kGy dose after 60 days of irradiation
Figure 4.20. Mechanical properties of T blends after 60 days of irradiation a) Work to failure b) Strain at fracture c) Yield stress
(a) (b)
(a)
(c)
(b)
It is observed from Figure 4.20b that the strain at fracture of T blends was reduced with an increase of irradiation dose but it was increased with T concentration. The strain at fracture at 100 kGy dose was increased from 361 to 406 %, when the T concentration was increased from 0.1 to 0.5 wt. % corresponding to an enhancement of 12.5 %. Similarly, when the irradiation dose was increased from 25 to 100 kGy, the strain at fracture of T0.1 and T0.5 sample was reduced by 16 and 11 %, respectively.
Figure 4.20c shows the yield stress of T blends, which was reduced with an increase of irradiation dose but slightly increased with T concentration. The yield stress of GI25 T0.1 was reduced from 22.8 to 20.5 MPa, i.e. ~10 %, when the irradiation dose was increased to 100 kGy.
At 100 kGy dose, the yield stress of 0.1, 0.3 and 0.5 wt. % T in UHMWPE was found to be 20.4, 22 and 22.4 MPa, respectively and the respective enhancement was found to be 10, 3.5 and 1.7 % in comparison with 100 kGy irradiated pure polymer. It is noted that the influence of irradiation dose was found to be negligible at 0.3 and 0.5 wt. % of T in UHMWPE.
4.2.3 Mechanical properties of composites and T blends after 120 days of irradiation