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Adhesion problematics and curing kinetics in a thermosetting matrix for stitch-free non-crimp fabricKruppke, Iris, Hund, Rolf-Dieter, Cherif, Chokri 18 September 2019 (has links)
Non-crimp fabrics (NCF) have become established in the fields of the automotive, aircraft, and wind power industries, which has led to an increasing demand of fiber plastic composites. In order to utilize the known excellent load-bearing properties of NCF and also to reduce the related disadvantages such as fiber undulation caused by stitching yarn, inclusions of resin and filament breakage by the stitch-bonding process have to be addressed. Hence, an alternative manufacturing technology is presented. This technology is defined by the punctiform application of a polyester hot melt adhesive to enable different geometries of NCF and ensure the position of the high-performance fiber in the load direction. The new manufacturing process, on the one hand, demands new testing methods to investigate the adhesion between the used adhesive and highperformance fibers, while, on the other, the surface of the adherend (carbon fiber) needs to be improved. Oxyfluorination is used here for the surface modification. Different tests such as peel test, shear test and transverse tensile test were developed and evaluated with different adhesives and high-performance yarns based on glass and carbon. The influence of the used copolyester hot melt on the curing kinetics of an epoxy matrix was investigated by differential scanning calorimetry using quasi-isothermal and non-isothermal measurements. In addition, the interface between the thermoplastic epoxy resin and the copolyester hot melt was analyzed by scanning electron microscopy.
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Self-incompatible solvents with ionic groupsWang, Yana 25 February 2013 (has links)
The concept of a self-incompatible solvent is introduced as a molecule composed of two parts (compound 1 and 2) with unfavourable interactions. A third compound will be readily dissolved in this solvent to diminish this unfavourable interaction by dilution. The more incompatible compounds 1 and 2 are, the stronger this behaviour is expected to be. In this work, ionic liquids comprising non-polar carbon chain and polar ionic group are chosen to serve as a model of self-incompatible solvent. The interactions parameters k of the ionic liquids with active ingredients are investigated to examine the effect of self-incompatibility of the ionic liquid molecule.
On the other hand, phase separation between compounds 1 and 2 will reduce the positive effect of self-incompatibility. The tendency of phase separation is increasing with increasing size of the two compounds. Thus, if compounds 1 and 2 are blocks tied together into a block copolymer, one expects a decreasing ability of the block copolymer to dissolve an active ingredient with increasing block length. In this work the ability of polybutadiene-block-poly(2-vinylpyridine) (PB-b-P2VP) block copolymers to dissolve the model compound anthracene is investigated. As expected, the solubility indeed decreases with increasing block length.
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