الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Conclusion Reviewing the discussion of the four sections the followings can be concluded: 1- The paramount level of Ts, ≈ 3.8MPa, was achieved by the composite RRP/NBR/Kaolin, 50/50/20 wt%, under conditions of 250 kGy radiation dose. The impact of radiation gave the almost value of Ts of nearly three times as much, ≈ 3MPa , the initial for NBR at the same dose, and only nearly twice as much for EPDM, ≈ 1.6MPa, at similar radiation conditions. Noticeably, the influence of radiation on the NBR feed ratio of 50% was remarkable so that the Ts values increased to nearly 300% the initial value by dose upto 250 kGy, whereas, EPDM revealed independence of dose. Such discrepancy may suggest the effect of neat polymer structure on the eventual attained Ts results. The apparent steady increase in tensile in both composites in addition to the neat NBR with radiation dose may suggest further examinations. 2- The highest level of Eb, ≈ 1500%, was recorded for the neat EPDM irradiated with 50 kGy, whereas for neat NBR it was only 10 folds. By increasing the RRP ratio, Eb of both systematically decrease with a remarkable decrease in case of NBR. Nevertheless, addition of kaolin, 10%, to a blend of RRP/EPDM, 50/50, irradiated with 50 kGy improved Eb to ≈ 500%. Similar improvement was achieved to the composite RRP/NBR, 50/50, under same conditions of irradiation. 3- The highest value of hardness, ≈ 78, was noted for the composite RRP/NBR/Kaolin, 50/50/20 wt%, under radiation conditions of 250 kGy. Generally, increasing RRP content is detrimental factor in raising up hardness of both 50/50 blends. Addition of kaolin 20% contributed to nearly 50% increasing, meanwhile irradiation upto 250 kGy further raised up hardness with additional 50%. Obviously, the impact of dose upto 50 kGy is abrupt in the case of EPDM blend and composite, suggesting effective radiation set up of crosslinking network much larger than in NBR moiety. Further, generally the increase in hardness of EPDM blend was nearly doubled by a dose of 250 kGy, whereas it’s composite reported only about 50% increase. This may be discussed on the basis of the impact of kaolin dispersion in the matrix on the radiation – induced crosslink density. However it was ensured that increasing kaolin % contributed to hardness in both composites. The ultimate hardness value reported for NBR composite can be accounted for the incremental share of hydrogen bonding settled between kaolin particles and NBR macromolecules. 4- The best thermal stability behavior was achieved by the composite RRP/NBR/Kaolin, 50/50/15 wt%, under radiation conditions of 150 kGy. Generally, increasing RRP content upto 60% led to better thermal stability for both blends (RRP/NBR), (RRP/EPDM). For both composites addition of kaolin and exposure to gamma radiation generally increased thermal stability in terms of T 0.25, T 0.50 and residual mass 5- Least oil uptakes were determined for the RRP/NBR (80/20) over the allowed time,6h, as neat NBR note oil uptake lowered 4.5 times to lesser than 1%. Meanwhile, RRP/EPDM (80/20) lowered the neat EPDM oil uptake with only two times to 14%. Brake oil uptake reported much lesser percentage in both cases due to its higher viscosity. Similar composition lessered two times the uptake in both blends down to 0.6% in the former and 2.8 in the latter. Abrupt increase in the oil uptake within the initial stage, tell one single how, was detected for the EPDM blend reflecting its higher affinity than the NBR blend which is normally used as a sealant in many applications. Interestingly, 250 kGy irradiation of 50/50 NBR and EPDM blends revealed remarkable reduction in oil uptake, predominantly in the latter, e.g. reduced to one third the pre – irradiation value, down to 7%, in motor oil. Also noticeable reduction was observed initial uptake rate, suggesting the significant radiation – induced crosslinking taking place at such dose level. The impact of irradiation on the NBR blend brake oil uptake was hardly noticed, whereas EPDM blend showed a reduction of nearly 75%. Incorporation of kaolin upto 20% in the NBR blend (50/50) showed significant decrease in oil uptakes, however comparable down to nearly half the recorded value for the pristine blend. Noticeable reduction in brake oil uptake was observed for the EPDM blend (50/50) of nearly two thirds down by introducing 20% kaolin into the blend matrix. The influence of gamma irradiation of the NBR composite 50/50/15 in the motor oil uptake was found effective as least values were given 150 kGy, whereas further irradiation upto 250 kGy was required to nearly destroy the composite brake oil uptake, as the pre – irradiation uptake value reduced to nearly one tenth, down to 0.5%. Similar EPDM composite exhibited markedly lesser tendency to oil uptake then shown for the NBR composite by irradiation. The phenomenon may reflect the more predominant impact of kaolin incorporation in the EPDM blend than in the NBR blend which was previously observed for the pre – irradiated composite specimens.