Addition Of Hollow Microspheres Research Articles

Shrinkage stress of thermal cured epoxy resin reduced by addition of functional hollow microspheres

The shrinkage stress of thermal cured epoxy resin developed during curing process can cause low film adhesion strength, low dimensional accuracy and even coating films warping which severely reduce service lifetime of the coating. Therefore, there is growing interest in developing effective means to reduce the shrinkage stress. In this paper, we report the use of hollow microspheres prepared from Pickering emulsion droplets in the thermal cured epoxy resin formulations and the shrinkage stress due to resin solidification is monitored in real time to reveal the effect of hollow microspheres upon shrinkage stress of the resin. Epoxy group functionalized silica nanoparticles from the Stöber method are used as Pickering emulsion stabilizer and the emulsion droplets are polymerized to obtain hollow microspheres with controllable mechanical properties and surface morphologies. Due to the reactivity of the hollow microspheres, they can be incorporated into the epoxy resin coatings and the shrinkage stress is thus reduced with the addition of hollow microspheres. It is revealed that the shrinkage stress is reduced from 195.79 kPa to 140. 40 kPa with the addition of 12 wt% hollow microspheres and polydisperse hollow microspheres are more effective in shrinkage stress reduction. As the modulus of the hollow microspheres is reduced and elasticity is increased, the shrinkage stress of the coating film is also reduced from 181. 37 kPa to 157.42 kPa which is not achieved by hollow glass microspheres. The hollow microspheres are well dispersed in the resin matrices which doesn't undermine the basic mechanical properties of the coating such as adhesion and surface hardness.

Effects of different control methods on the mechanical and thermal properties of ultra-light foamed concrete

Porosity and pore structure are the critical factors affecting the properties of ultra-light foamed concrete. In this study, four different measures were adopted to control the performance of ultra-light foamed concrete. Specifically, by changing foam content, water-cement ratio (W/C), and hydroxypropyl methylcellulose ether content, different ultra-light foamed concrete specimens were prepared and their properties were studied. At the same time, hollow microspheres were incorporated into cement slurry to optimize the properties of the ultra-light foamed concrete further. The results reveal that when the foam content reached 30 wt% (by weight of cement), the dry density of foamed concrete was lower than 300 kg/m3. When the W/C reached 0.42, the volumetric water absorption, compressive strength and thermal conductivity of the foamed concrete were 31.9%, 0.499 MPa, 0.0857 W/(m·K), respectively. At W/C of 0.42, adding 1 wt% hydroxypropyl methylcellulose ether could lead to increase in compressive strength by about 24%. Hollow microspheres can effectively improve the pore structure of ultra-light foamed concrete and significantly reduce its thermal conductivity. With the addition of hollow microspheres at 6.5 wt%, the volumetric water absorption and thermal conductivity were 20.1% and 0.0456 W/(m·K), reduced by 37% and 95%, respectively.

Method and apparatus for a non-oil-filled towed array with a novel hydrophone design and uniform buoyancy technique

A structure and method for constructing a non-oil-filled towed array providing a single cable entry point for each channel irregardless of the number of hydrophones used to make up a hydrophone group or array is described. The method and apparatus enables uniform buoyancy of the hydrophone array and the primary cable around which the hydrophone array is wound. Uniform buoyancy is achieved through the addition of hollow micro-spheres into a Reaction Injection Molded (RIM) polyurethane material used to mold the hydrophones. Additional buoyancy may be desired adjacent heavier cable sections where connectors and telemetry modules are located. An embodiment enables precise adjustment of hydrophone cable buoyancy by providing precise adjustment of the concentration of hollow glass micro-spheres in areas where more or less buoyancy is desired.