Epoxy resins have a wide range of applications. Their application in fabrication of fiber reinforced composites for lightweight construction has become the subject of ongoing interest in the field of polymer alloys. However due to their existence of cross-linked structure and organic nature, they have two major drawbacks - brittleness and flammability - which very often limit their usage in most applications. The aim of this thesis was to obtain and characterize new additives for epoxy-based materials, which are able to improve the toughness and flammability without any derogation of other material properties. Toughness can be improved by reducing the cross-link density of the polymer matrix or incorporation of another modifier. Recently, hyperbranched polymers have shown their promising results in the field of toughening DGEBA (diglycidyl ether of bisphenol A)-based materials. In the present work, we first examined the effect of additives and modifiers on epoxy resin used in injection process (especially in Resin Transfer Molding (RTM) process). A number of commercially available additives were tested in DGEBA-based resin formulations. However, toughness is a complex phenomenon that is influenced by many factors and meanwhile many other material properties were affected. Secondly, the results we collected in the course of the BMBF project "Innovative, modular microwave technology for the production of composite structures" are presented. Based on the previous findings from the same project, the effect of carbon-based and microwave-active fillers, such as activated carbon particles carbon black (Chezacarb® B) carbon nanotubes or graphite explored) on the homo- polymerization of the epoxy resins were investigated. In Addition, the feasibility of the microwave processing for glass fibers reinforced epoxy resin (GRP) curing was tested out. Furthermore, a series of novel oligomers like derivatives of 6H-dibenzo[c,e][1,2]- oxaphosphinin-6-oxids (DOPO, 1) and 5,5-dimethyl-1,3,2-dioxa-phosphorinan-2-one (DDPO, 2) as flame retardant additives were synthesized. The 1,3,5-tris(2-hydroxyethyl)- isocyanurate (THIC, 3)-oligomer was used as linkage molecule. These products were blended into two epoxy resin systems (DEN 438 and DGEBA, both cured with DICY and Fenuron) to obtain flame retardant thermosets. The flame retardancy and thermal properties of these epoxy resin systems were examined by UL 94-V, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. Additionally, phosphorus-containing amino compounds were also synthesized and characterized. Their reactivity with the commercial epoxy novolak was studied by means of DSC. The flammability properties of obtained compounds are also presented. Last but not least, the post-curing effect which is formed during the transesterification reaction between the free OH groups in the polymer backbone and phosphite compounds was further intensively investigated. DGEBA was used as in the majority of experiments. Various amino compounds were tested as curing agents.
|Supervisor:||Döring, Prof. Dr. Manfred|
|Date of thesis defense:||26 July 2013|
|Date Deposited:||28 Oct 2013 12:58|
|Faculties / Institutes:||Fakultät für Chemie und Geowissenschaften > Institute of Inorganic Chemistry|
|Controlled Keywords:||Epoxidharz, Verbundwerkstoffe|