Thesis (Ph.D)-Cairo University, 2023.

Bibliography: pages 572-574.

A synthetic, ethylene-propylene- diene monomer (EPDM) rubber reinforced, with carbon-black (N-220) as filler, and other additives such as zinc oxide, stearic acid, and paraffin oil were incorporated into the EPDM rubber matrix using a laboratory two-roll mill at room temperature, The obtained master batch has been weighted and divided into equal parts and lead powder or Borax powder was added separately or together to the prepared product. The composites were cured by sulphur and mixed again using the two roll mill and vulcanized (cross-linked) by a compressive method under temperature of 153 °C and pressure 4 Mpa. The prepared composite was compressed in the form of a circular disk of diameter of 10 cm and 4 mm thick. The samples contains different concentrations of lead powder (0,25,50,75,100,200,400 and ,500 phr), were developed to be used as a radiation shielding against  - rays. Experimental studies on the influence of -radiation on the target samples were carried out using 137CS (E = 0.662 Mev) and (60Co with energies of 1.172 Mev and 1.332 Mev). Attenuation parameters such as attenuation coefficient (), and half–value layer (HVL) have been determined for all target samples. It was observed that the attenuation coefficient and HVL improved by two ways; one by increasing the concentration of lead powder at constant thickness (2 cm) and the other by increasing the thickness of the composite samples at constant concentration of lead powder. We also used composite samples containing lead powder (100, 200, 300 phr), and lead powder with 25 phr Borax, as a test for moderating fast neutron emitted from 239Pu–9Be source. The results showed good enhancement/improvement in the values of the total macroscopic cross section. As a result of using the X.com program, it was found that the values of the linear and mass attenuation coefficients were in good agreement with the experimentation values for uniform and collimated beams. However, this could not be confirmed for heterogeneous beams. Three groups of samples were prepared. The 1st group contains different phr of lead, the 2nd group contains different phr of borax, and finally the 3rd group contains 25phr borax and different phr of lead. The swelling test was carried out for all samples in the toluene. Swelling parameters such as the rubber volume fraction, crosslink density, swelling index etc. were calculated. The results showed that the crosslink density increase as the amount of lead increase and the ability of the sample to swell decrease. In contradiction, it is observed that the samples contain different phr lead and 25phr borax the crosslink density decreased, and the samples swelled to high extent. Adding Borax only to the samples had no considerable effect on the crosslink density and on the swelling behavior. Also, the swelling index has been obtained to all samples. The result showed that n ~ 0.5 which Fickian diffusion. Two models (Kraus and Cunnen – Russel) were applied to test the filler rubber interaction. The models give a good result with the experimental data. One way ANOVA statistical analysis was applied to find out more information about the effect of lead, borax and the two together on swelling behavior through the calculated coefficients. The statistical results confirmed the practical results, and the post-test Tukey was used to assess the significance of differences between pairs of group means. The composite was prepared with different borax proportions (25 and 50 phr). Thermo gravimetric analysis was performed to characterize the effect of borax on the composite's thermal stability before and after borax addition. Adding borax to the host composite rubber (EPDM composite without borax) significantly improved the thermal stability of the composite. Borax-loaded composites behaved differently at different temperatures. To investigate the kinetic-thermal analysis of the prepared samples, three different models were applied. The activation energy (Ea) and frequency factors (A) for the Horowitz - Metzger, Broido, and Coats-Redfern models were calculated. These models were compared and discussed based on their results. First-order decomposition was also found to represent the main decomposition stage.

يعتبر المطاط الصناعي الاثيلين بروبلين دايين مونومر EPDM واحد من اهم انواع المطاط الصناعي التي يتمتع بخواص فيزيائية وكميائية هائلة ,من اهمها انه من المواد العازلة كهربيا وحراريا ولذلك يتم استخدامه كعازل في الاسلاك الكهربائية كما انه يتحمل درجات حرارة عالية تصل الي 200 درجة مئوية وايضا يتحمل العوامل الخارجية مثل الرطوبة ومقاومة التأكسد ...والخ . ومن اهم مميزاته ايضا انه يحتوي علي الدايين الغير مشبع والتي يجعله يستوعب قدر كبير من الحشو بمواد اخري مالئة مثل الكربون الاسود والتي تحسن من خواصه الكهربية والميكانيكة . ونظرا لانه مادة غنية بالهيدوجين وبمساعدة الزيت الصناعي واضافة البوركس ليتم استخدامه لتعديل النيوترون السريع .moderating fast neutron
بالاضافة الي ان كل 100 جرام منه يتحمل استيعاب 500جرام من مسحوق الرصاص ,لذا يمكن استخدامه كدرع اشعاعي ضد اشاعة جاما .
تم حساب معلمات الانتفاخ مثل جزء حجم المطاط وكثافة الارتباط المتشابك ومؤشر التورم وما الي ذلك .اظهرت النتائج ان كثافة الارتباط المتشابك تزداد مع زيادة كمية الرصاص وانخفاض قدرة العينات علي الانتفاخ .علي النقيض ,لوحظ ان العينات التي تحتوي علي phr مختلفة من الرصاص مع 25 phr من البوركس ,انخفضت كثافة الارتباط المتشابك وتضخم العينات الي حد كبير .اضافة بوركس فقط الي العينات ليس له تأثير ملحوظ علي كثافة الارتباط المتشابك وعلي سلوك التورم.
تم اجراء التحليل الحراري الوزني لتوصيف تأثير البوركس علي الثبات الحراري للمركبات قبل وبعد اضافة البوركس .ادت اضافة البوركس الي المطاط الي تحسين الاستقرار الحراري للمركب بشكل كبير

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