Browsing by Author "Acar, Oktay"

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Citation - WoS: 6
Citation - Scopus: 7
Synthesis and characterization of novel high temperature structural adhesives based on nadic end capped MDA-BTDA-ODA copolyimide
(Iop Publishing Ltd, 2018) Acar, Oktay; Varis, Serhat; Isik, Tugba; Tirkes, Seha; Demir, Mustafa M.; Demir, Mustafa
A series of novel copolyimide structural adhesives were synthesized using 4,4'-diaminodiphenyl-methane (MDA), 3,4'-oxydianiline (ODA) and 3,3',4,4'-benzophenonetetracarboxylic acid dianhy-dride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T-g) about 400 degrees C, with thermal stability up to 500 degrees C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA: ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance.
Synthesis and chracterization of polyimide derivative adhesives
(Izmir Institute of Technology, 2018-12-14) Acar, Oktay; Demir, Mustafa; Demir, Mustafa Muammer; Tirkeş, Seha
While the rapid advancement of technology is pushing the limits, today need for special advanced materials has been increased in order to obtain high-tech products with desired performance. Lightweight materials that can operate at high temperatures have critical importance in aerospace field. Between those materials, polyimides come front with their unique mechanical properties and high thermo-oxidative stabilities. They are commonly used in defense and aerospace industries as adhesives, coatings and resins in composites operating at high temperatures. PMR-15 (Polymerization of Monomeric Reactants) is considered as a state-ofthe-art high temperature resistant structural adhesive, due to its low cost, exceptional thermo-mechanical strength and thermo-oxidative resistance, up to 300 °C. However, PMR-15 has both limited processing and flexibility properties. LARC-RP46 (Langley Research Center) was developed as an alternative to PMR-15 resin. It has a higher melt flow rate to some extent. In this thesis, MDA-BTDA-ODA copolyimide adhesives with nadic end caps were synthesized. The chemical structures of the synthesized resins were verified by FTIR and 1H NMR analysis. The copolymers have thermal stabilities as high as 500 °C and Tg at around 400 °C. They showed superior adhesion performance up to 16.3 MPa. Compared to both commercial PMR-15 and LARC RP-46 polyimides, copolyimide resins showed significant processability. Kinetics of curing process of the resins was investigated by using the autocatalytic kinetic model of Kamal – Sourour. The experimental data are well-fitted with the model. The activation energies were calculated by kinetic constants derived from the model.