Date

2013

Author

Şengör, İrem

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The aim of this dissertation was to produce shape memory polymer nanocomposites using diglycidyl ether of bisphenol A (DGEBA) epoxy resin and isophorone diamine based cyclo-aliphatic curing agent. The polymer matrix was modified with aliphatic and aromatic monomers namely, neopentyl glycol diglycidyl ether (NGDE) and resorcinol diglycidyl ether (RDE). In the formation of composites, carbon black and carbon nanotubes were used separately and also together as hybrid filler. All samples were subjected to mechanical (tensile and impact tests), thermal (DSC analysis), electrical (electrical resistivity test), morphological (SEM analysis) and shape memory characterization tests (bending test). In consequence of these characterization tests, 15 wt. % monomer containing polymers were found to have superior properties for both NGDE and RDE containing formulations. For CB loaded composites, percolation threshold was found at 1 wt. % loading and for carbon nanotube loaded composites it was found at 0.25 wt. %. In formation of hybrid composites carbon black amount was kept constant as 1 wt. % for all formulations and carbon nanotube amount was varied as 0.25 %, 0.5 % and 1 % by weight. Among these compositions, hybrid composite containing 1 % CB and 0.5 % CNT was found to have better properties for generally all characterization tests. As final composites 15 % NGDE and 15 % RDE were combined with 1 %CB, 0.5 %CNT and 1 % CB - 0.5 % CNT filler compositions. NGDE containing composites had much lower glass transition temperature compared to RDE containing ones and the composites which did not contain monomer. There was no significant difference in shape recovery values in final composites and these values were calculated in the range between 97-99 %. Same comment can be made for shape fixity property. Composites containing NGDE showed faster shape recovery than the other composites. Electrical shape memory actuation was applied for the sample containing 2 wt. % carbon nanotube only with the application of constant 100 V. Shape recovery was achieved at 49°C, whereas this value was determined as 90°C for thermal actuation. Finally, cyclic shape memory tests were applied for investigation of performance of neat epoxy and samples of E-15N, E-15N-1CB, E-15N-0.5CNT and E-15N-1CB-0.5CNT. Totally 10 consecutive cycles were applied on each sample. It was found that amount of cycles did not affect shape recovery for any sample. While percent shape fixity decreased by 2-3 % for neat epoxy and E-15N samples and did not change for the other composites. Recovery time was increased continuously for neat epoxy, but did not change for E-15N-0.5CNT and E-15N-1CB-0.5CNT samples.

Subject Keywords

Shape memory polymers., Composite materials., Carbon nanotubes.

URI

http://etd.lib.metu.edu.tr/upload/12616402/index.pdf
https://hdl.handle.net/11511/23070

Collections

Graduate School of Natural and Applied Sciences, Thesis