The investigation of the irradiaiton effect on Pmma/nwcnts polymer nanocomposites

Abstract

Poly (methyl methacrylate) (PMMA) is a transparent thermoplastic material that shows good mechanical properties, high resistance to abrasion and superior heat resistance. Mechanical, thermal and radiation shielding properties of PMMA can be enhanced by addition of multiwall carbon nanotubes (MWCNTs). Due to suitable structural properties of MWCNTs, PMMA is an ideal candidate for some applications such as sensor, solar cell, electronic and aerospace fields. Carbon nanotubes separate two parts which are single-wall carbon nanotubes and multi-wall carbon nanotubes. Single-wall carbon nanotubes (SWCNTs) have scale from 0.5 nm to 1.5 nm. On the other hand, multi-wall carbon nanotubes (MWCNTs) are bigger than 100 nm scale. The use of MWCNT in polymer results with higher mechanical properties than SWCNT in polymer. Besides, MWCNT in polymer gives more chemical resistance than SWCNT. MWCNT contained polymer nanocomposites can be utilized in a several industrial application areas such as automotive and aerospace due to their outstanding advantages such as high durability, high strength and light weight. PMMA is one of the thermoplastic polymers coming from the acrylate family. PMMA reinforced by carbon nanotubes has significant importance in many applications ranging from large scales to nanometer scales. It is considered as a candidate for the applications in new technologies depending on the improved mechanical, electrical, optical properties of polymer. There are three methods to produce PMMA reinforced by MWCNTs which are solution-mixing, melt compounding, in-situ polymerization. In this study, it was preffered to use Atom Transfer Radical Polymerization (ATRP) method to disperese MWCNTs in PMMA effectively. MWCNTs were selected as nanofiller to improve the mechanical and thermal properties of PMMA with the investigation of the changes in radiation shielding performance. Several analysis and tests were performed to examine the main characteristic properties of the PMMA/MWCNTs nanocomposites such as SEM, XRD, FTIR, TGA, hardness, ultrasonic test, gamma transmission technique and the behaviors of the PMMA/MWCNTs nanocomposite against neutrons. Further, PMMA/MWCNTs nanocomposite samples were irradiated at 50 kGy using Co-60 radioisotope. The irradiated polymer nanocomposite samples were characterized to examine the structural changes after irradiation treatment. The surface morphology of the PMMA/MWCNTs nanocomposite in SEM images indicated that ATRP method was efficient to get homogeneous dispersion of MWCNTs in the PMMA matrix. In addition, the results of the ultrasonic test supported the homogeneous structure of PMMA/MWCNTs nanocomposites at 2 wt.%MWCNTs. PMMA/MWCNTs nanocomposite presented three characteristic diffraction peaks in XRD analysis. The FTIR spectra of PMMA/MWCNT nanocomposites revealed the similar spectrum with pure PMMA, showing that interaction occurred between MWCNTs nanocomposites and PMMA polymer matrix. TGA results of unirradiated nanocomposite at the addition of 2 wt. % MWCNTs exhibited that the 5% weight loss temperatures shifted from ~191 °C to 243 °C with the improvement in the temperature (as ~52 °C). The thermal stability of PMMA was enhanced with the rise of the amount of the MWCNTs from (0.25 to 2 wt. %) in PMMA/MWCNTs nanocomposite. The 5 % weight loss temperatures increased after irradiation process. In the ultrasonic test, the Shear modulus, Young's modulus and Microhardness values of pure PMMA were increased with the addition of 2 wt. % MWCNTs. The improvement in Rockwell hardness values between the pure PMMA and PMMA/MWCNTs at 2 wt. % MWCNTs is ~ 11 %. The difference in Rockwell hardness values is almost ~3 % for unirradiated and irradiated states of PMMA/MWCNTs at 2 wt. % MWCNTs. The linear attenuation coefficient values for Cs-137, Co-60 radioisotopes changed slightly with the rise of the MWCNTs amount and mascroscopic cross sections for neutrons Pu-Be neutron source increased slightly.

Bu çalışmada, PMMA'daki MWCNT'lerin uygun bir şekilde dağıtılması için, Atom Transfer Radikal Polimerizasyon (ATRP) yöntemi kullanılması tercih edilmiştir. Bu tez çalışmasında, PMMA'nın mekanik, termal özelliklerini geliştirirken, radyasyon karşısındaki davranışlarını incelemek için, nanopartikül takviyesi olarak çok duvarlı karbon nanotüp (MWCNTs) seçilmiştir. Karbon nanotüp eklenmesiyle PMMA’nın karakteristik özelliklerinde oluşan değişimleri incelemek için; SEM, XRD, FTIR, TGA, setlik testi, ultrasonik test, gama ve nötron geçirgenik testleri uygulanmıştır.