Investigation of long-term water absorption behavior of polymer composites containing hydrophobic filler

In this research, affect of hydrophobic nano silica fillers on water absorption properties of epoxy and poliester based FRPCs were investigated by following chemical, physical, mechanical and thermal properties of the samples during 11 months. The changes in water uptake profile of samples are followed by changing nano silica ratio in glass and carbon fiber renforced composite materials. The main difference which distinguishes the this study form the previous ones is that this study evaluates the affect of hydrophobic nano fillers on long term water absorption behavior of composite materials by considering chemical, physical, mechanical and termal aspects at the same time. As far as we know, there isn't much study in the literature focusing on the contribution of hydrophobic nano fillers on long term water absorption properties of composite material in the sense of chemical, physical, mechanical and thermal aspects. With this study, affect of particle size distribution, filler amount, types of resin and fiber on water absoption behavior of composite materials are studied by placing the samples into distilled water for 11 months. Data that was obtained in the course of this project would make it possible to lower the water damage in composite materials and to develop new materials with extraordinary properties. In this study, two nano silicas (Aerosil R 812 and Aerosil R972) with different particle size distribution were combined with epoxy and poliester resins in different ratios and tiles in 15x15 cm dimensions are manufactured. Glass and carbon fiber reinforced composited are prepared by using compression molding technique and 20 different tiles were molded. Production was carried out in a 20x20 cm stainless steel mold by placing one layer of release film, one layer of fiber fabric and filler/resin mixture in the mold cavity. After putting one layer of fiber fabric and release film onto filler/resin mixture, a second 20x20 cm steel plate was placed over the mold cavity. Both glass and carbon fibre supported samples were moulded at 80 °C for 1 hour and two tiles from each sample were prepared. By cutting each tile in 1x7 cm dimensions, total of 48 pieces from each set of sample were obtained. Filler / resin weight ratio is increased starting from 3% up to 12% and 3-point bending strength values of the samples containing filler were compared with the filler-free sample's 3-point bending strength values. It was observed that, fillers reduce three point bending strength of poliester matrix composite materials in the presence of the carbon cloth and glass, while this effect vary with the type of fabric for epoxy matrix composites. In the glass fabric reinforced epoxy matrix composites, adding filler into the structure reduce three-point bending strength values, while 3% and 5% nanosilica addition does not have a negative effect on the mechanical properties of carbon fabric reinforced composites. Therefore, the number of analysis was limited with 3% and 5% filler containing carbon fabric reinforced epoxy matrix composite and FTIR, SEM, DSC and TGA analyzes were performed on these samples to reduce analysis cost. Since water absorption and contanct angle measurements do not require analysis fee, all samples containing 3% and 5% filler is immersed in water in a plastic container and at the end of each month mass changes and contant angles of the samples to be tested were measured. Similar experiments were repeated on 4 different filler-free carbon and glass fiber reinforced samples that were not immersed in water and affect of nano silica addition on the water absorption behavior of composite materials have tried to be understood. As a result of water absorption, the matrix structure is deteriorated and both the filler and the fibers of fabric is removed from the composite by detaching the matrix. Nano fillers to be put into the structure of carbon fabric reinforced epoxy matrix composites outside of the contribution adversely affect the mechanical properties. With the advent of the filling rate of over 5% in the carbon fabric reinforced epoxy composite, similar effect is seen and substantial reductions occur in mechanical strength values. The absence of filler and fiber separating surface is substantially the door on the evaluation of water absorption and the contact angle results. Only when we look at the mechanical strength values at the end of 11 months contribution of 3% Aerosil R972 carbon fabric reinforced epoxy composites in preventing water damage it is possible to say that for the best results.