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Kevlar/vinyl ester composites with SiC nanoparticles


Kevlar/vinyl ester composites with SiC nanoparticles were fabricated using hand lay-up.  Vacuum and mech. press were used to suppress porosity, increase the fiber vol. fraction and assist infiltration.  The SiC nanoparticles were examd. using TEM and TGA, and were vacuum-baked at 200° to remove adsorbed moisture, as per TGA measurement.  γ-Methacryloyloxypropyltrimethoxysilane (MPS) was used as the coupling agent and its dosage was calcd. to achieve monolayer coverage.  Both mixing routes with (1) the nanoparticles pretreated with a dil. MPS soln. in an acid 5% (vol./vol.) water-ethanol mixt. and (2) the MPS sonicated as an integral blend with the filled vinyl ester, were attempted.  FTIR was used to study the silanol condensation between MPS and the SiC nanoparticles.  X-ray inspection and x-sectioning were performed on the nanocomposite panels.  The modulus from 3-point bend tests showed an increase for both mixing routes, whereas strength increased for route (2) but decreased for route (1).  The increases in modulus and strength are likely due to the better dispersion quality as obsd. under the optical microscope and AFM, lower resin viscosity, lower porosity, and a stronger coupling/bonding between the SiC nanoparticles and vinyl ester resin as a result of the MPS addn.  The decrease in strength in route (1) was likely caused by the siloxane layer between the SiC nanoparticles assocd. with the three reactive silanols per mol. of MPS.  A 19% increase in tensile strength was found in route (2) with 1 vol.% SiC addn., which confirmed the high potential of nanoparticles in enhancing the mech. properties of structural composites.

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