Investigation of degradation of NBR and HNBR elastomers by light scattering rheology and molecular dynamics techniques

(2003) Investigation of degradation of NBR and HNBR elastomers by light scattering rheology and molecular dynamics techniques. Masters thesis, King Fahd University of Petroleum and Minerals.


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Arabic Abstract

في هذه الدراسة تم اختبار انحلال واندماج أنواع مختلفة من مطاط النيتريل بيوتادايين . العوامل التي تحدد نوعية المطاط تتمثل في كمية الأكريلونايترايل واللزوجة ونسبة الهيدرجة . كما تم دراسة تأثير هذه العوامل على عملية الانحلال . هدف هذه الدراسة كان لتقييم ما إذا كان الانحلال الثرموميكانيكي لهذا المطاط يحدث عند التحضير وإذا كان كذلك فسيتم دراسة طبيعته والطرق المانعة لحدوثه . لقد وجد أن المعالجة الثرموميكانيكية تؤثر على خصائص المطاط كما أن الخصائص الجزيئية تؤثر على طريقة الانحلال . تم عمل قياسات الأوزان الجزيئية بواسطة طريقة استطارة الضوء . ولإتمام دراسة الاندماج استخدمت عدة طرق منها : الرويولوجيا والكالوميتري و (المجهر الإلكتروني) والاختبارات الميكانيكية والديناميكية الجزيئية . كل الطرق أثبتت أن نوعي المطاط منسجمان ميكانيكيا بينما أن دراسات النمذجة الجزيئية أثبتت أن نوعي المطاط منسجمان ميكانيكيا وثرموديناميكيا .

English Abstract

In this study, the degradation and Miscibility of raw, uncured Nitrile Rubbers, (NBR & HNBR) has been investigated. The CAN (Acrylonitrile Content), Mooney Viscosity and % Hydrogenation are the primary criteria defining each specific brand of these rubbers. Degradation behavior as a function of these parameters was studied. The objective was to assess whether thermomechanical degradation of these rubbers is occurring during the "conditioning" process and if so, to characterize its nature and sort means to prevent it. It was found that thermomechanical treatment does affect these rubbers and that degradation is a combination of chain scission and cross-linking. Molecular parameters were found to effect selection of dominating degradation mechanism. Molecular weight measurements were carried out using light scattering technique. The rheological and light scattering results of the conditioned samples with and without antioxidants were compared to the properties of as received samples. Results were suppsorted by variations in Mw (weight-average molecular weight) by light scattering FTIR was applied as an additional complementary Investigation technique to shed some light on the different functionalities generated during the "conditioning" process. The miscibility study of the two rubbers was performed using a variety of techniques such as rheology, DSC, SEM, Mechanical testing, and Molecular Dynamics. The different techniques agreed in suggesting that the structurally similar HNBR and NBR are mechanically compatible. Molecular Simulation studies showed that these rubbers are not only mechanically but thermodynamically compatible, however due to the nature of these materials segmental miscibility is hard to achieve by conventional methods.

Item Type: Thesis (Masters)
Subjects: Chemical Engineering
Department: College of Chemicals and Materials > Chemical Engineering
Committee Advisor: Abu-Sharkh, Basel F.
Committee Members: Kahraman, Ramazan and Hussein, A. H. and Al-Mubaiyedh, Usamah A. and Amin, Mohamed B.
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 13:49
Last Modified: 01 Nov 2019 13:51