Studies On Powder Coating Resins And Composites

Resin fibre composite is one of the most developed and matured composite. Binders that are used in fibre composites present major problems regarding solvent emissions during both manufacture and use. The harmful effects of emissions are therefore receiving serious scrutiny.In recent years powder coating has been attracting worldwide attention and interest. It is producing little pollutant while being efficient, and consumes less energy than other products.Different from solvent resin, powder coating is 100% solid, without any solvent. Using powder coating instead of liquid resins overcome potential health hazards associated with the use of liquid resins.In this thesis, several types of thermosetting powders were cured to test their dynamic properties and to calculate their crosslink density. Evaluation of these different resin systems was done to determine suitability for composite manufacture. Then powder resins were used to manufacture glass fibre composite that were tested to determine their physical and mechanical properties. This allowed comparing these components with traditional unsaturated polyester glass fibre composite panels.The contributions of this work are as follows:1. Different thermosetting resin systems were investigated: epoxy system, polyester-epoxy system, polyester system and urethane system. They were cured in a hot press at 180℃and each system contained only pure resin and its curing agent. The powders were analysed by Fourier transform infrared spectrophotometer (FTIR) in both the uncured state and in the cured state. The change of epoxide group, carboxyl group, hydroxyl group and isocyanate group, showed that reactions have occurred during the curing. Thermal properties were determined by Differential scanning calorimetry (DSC): the difference of Tg before and after reaction and the energy involved during the reaction, so the exent of reaction can be approximately determined. The measurement of the tensile storage modulus (E') was carried out by Dynamic mechanical thermal analysis (DMTA).The crosslink density calculated by the equation ve = = prove that powder can be readily crosslinked, and may replace liquid unsaturated polyester resins in fibre reinforced structural laminates. Considering results, the urethane and epoxy systems are superior to the other systems.2. Dry urethane powder and epoxy powder was coated directly onto one layer and two layers of chopped strand mat (CSM), cured in a hot press at 190℃. Unsaturated polyester glass fibre composite panel was constructed by hand layup, using the same chopped strand mat.3. Dynamic mechanical thermal analysis (DMTA) determined the properties of composite with one layer CSM, proving that adding glass fibre to the crosslinked network as reinforcement provides greatly increased strength to the resulting laminate. Tensile testing determined the mechanical properties of urethane composite and epoxy composite with two layer CSM, which were not as good as that of UPE composites. The cryo fracturing cross sections of composites were studied by Scanning electron microscope (SEM) and the micrographs showed that the glass fibre was wet by urethane resin and epoxy resin. Environment Scanning electron microscope (ESEM) was also used to observe the polished cross section of composite. Results showed that there were imperfections in the urethane and epoxy composite, which need to be improved.