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Rheology & Solid State Properties of Polyethylene/CNT Nanocomposites: Impact of CNT Characteristics and Surface Modification.

Abbasi, Sarfraz / Initials (2010) Rheology & Solid State Properties of Polyethylene/CNT Nanocomposites: Impact of CNT Characteristics and Surface Modification. PhD thesis, King Fahd University of Petroleum and Minerals.

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Arabic Abstract

تم تجهيز مركبات نانو مكونة من البولي إيثلين المنخفض الكثافة مع أنابيب النانو الكربونية بواسطة طريقة الخلط الحراري. استخدمت انابيب نانو مختلفة (طويلة، قصيرة، وطويلة محسّنة سطحياً). تمت دراسة التحسين السطحي وطول الأنابيب على اختبارات التدفق. بشكل عام تشير النتائج إلى أن أنابيب الكربون الطويلة تقوم بدور المضافات الملّينة عندما تكون نسبتها في البوليمر أقل من 1%، وتقوم بدور المضافات المقوية عندما تكون نسبتها أكثر من 1%. الاختبارات الميكانيكية اثبتت زيادة معامل المرونة مع زيادة نسبة أنابيب الكربون في البوليمر، ولكن نسبة التمدد تناقصت عندما تكون نسبة الأنابيب 2% أو أكثر. إضافة المادة الرابطة إلى المركب لم تؤدي إلى تحسين نسبة التمدد لذلك، تم تحسين سطح انابيب الكربون أكثر من أجل إنتاج انابيب كربون مضاف إليها جزيئ C18 اثبتت اختبارات التدفق عدم تكوّن شبكة متصلة من الأنابيب داخل البوليمر. اثبتت النتائج بشكل عام أن استخدام الانابيب الطويلة المحسنة يجزيئ C18 اعطت أفضل النتائج في تحسين الخصائص الميكانيكية والتدفقية معاً لمركبات البولي ايثلين مع انابيب الكربون.

English Abstract

Nanocomposites of low density polyethylene (LDPE)/multiwall carbon nanotubes (MWCNTs) were prepared by melt blending. Different MWCNT [Long MWCNT (LCNT), Modified MWCNT (MCNT) & Short MWCNT (SCNT)] were used. The effect of surface modification and aspect ratio on dynamic, steady shear and extensional rheology were studied. In general, the rheological tools used in this study reveal a possible plasticization effect for MWCNT with high aspect ratio at low loadings (<1.0 wt%) and a filler effect at higher loadings (>1.0 wt%). The effect of COOH modification was more apparent in extensional viscosity and in N1 to some extent. Aspect ratio has influenced both viscous and elastic shear properties as well as strain hardening. Also, analysis of mechanical properties revealed that yield strength and modulus increased with increased loading of various MWCNTs. However, ultimate strength, percent elongation and toughness were reduced for 2% MWCNT loading and higher. Addition of compatibilizer improved most of the mechanical properties. However, percent elongation and toughness did not show any improvement. Thereafter, MCNT was further modified to produce C18-CNT. The addition of C18-CNT to LDPE matrix improved most mechanical properties. The use of C18 reduced dynamic viscosity and storage modulus at all loadings covered in this study. Results of phase angle suggest no presence of network. Addition of C18-CNT did not increase strain hardening, maintained extensional viscosity and time of break. On the other hand, the effect of CNT loading surface modification and aspect ratio on non isothermal crystallization kinetics reveal that presence of long MWCNT promotes initial crystallization and it impacts both the onset as well as peak crystallization temperatures. The Hoffman-Lauritzen theory showed a decrease in the activation energy with the increase in MWCNT concentration which supports the observed promotion of the initial crystallization. In summary, both the aspect ratio and C18 surface modification of CNT proved to enhance both the mechanical and rheological properties of LDPE/MWCNT nanocomposites. The selection of the proper surface modifier and its compatibility with the matrix is the key in enhancing the properties of the nanocomposites.

Item Type:Thesis (PhD)
Date:27 October 2010
Date Type:Completion
Subjects:Chemical Engineering
Divisions:College Of Engineering Sciences > Chemical Engineering Dept
Creators:Abbasi, Sarfraz / Initials
Committee Advisor:Hussein, Ibnelwaleed
Committee Members:Al- Amer, Adnan and Abu-sharkh, Basel and Al-Juhani, Abdulhadi and Hamid, Anwar
ID Code:136366
Deposited On:31 Jan 2011 13:41
Last Modified:24 Nov 2014 10:44

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