UTILIZATION OF MICROGRAVITY AND HIGH GRAVITY TO PREPARE MATERIALS WITH CONTROLLED PROPERTIES

摘要

The most promising way to extend the scope of properties of known materials is to increase the number of controlled external factors involved in the manufacturing process. These factors include gravitational and centrifugal forces. In particular, in polymer processing many advantages can be gained from changing the level of the mass forces. This conclusion relies on the fact that the density of the reaction mixture during polymerization varies due to heat liberation and to conversion of a monomer to a polymer. The more predictable gravitational effect is convection in a liquid monomer in the early stages of reaction. Convection stirs the reaction mixture, leading to a more uniform temperature and a more uniform degree of conversion. While participating in convective motion, the mixture continues polymerizing and may lose fluidity before homogenization is complete. The gradients of temperature and degree of conversion leads to a variation in the reaction rate and, as a result, to an inhomogeneous polymeric microstructure and a nonuniform distribution of properties in finished products.