Accession Number : ADP006429

Title :   PMMA - Impregnated Silica Gels: Synthesis and Characterization,

Corporate Author : RUTGERS - THE STATE UNIV PISCATAWAY NJ

Personal Author(s) : Abramoff, B. ; Klein, L. C.

Report Date : MAR 1992

Pagination or Media Count : 8

Abstract : Shaped microporous silica has been prepared by a sol-gel process. The resulting silicas have 50% open porosity. The open porosity is filled by immersing the shapes in methyl methacrylate (MMA) and polymerizing with ultraviolet radiation. The fully impregnated silica is recovered in net shape. The outstanding feature of the PMMA-impregnated silica is its transparency. There is little loss from scattering because of the nanometer scale of the microstructure and the similarity in index of refraction for silica and PMMA. The flexure strength of the silica-PMMA composite has been measured in 4-point bending. The strength increases at slower strain rates because the PMMA provides crack blunting. The composites can withstand thermal shocks up to about 150 deg C without losing strength. The thermal expansion coefficient for the range 0 to 150 deg C follows a mixing rule for 50% silica - 50% PMMA. While the mechanical behavior of the composite largely follows that of bulk PMMA, the microhardness is 3 to 5 times greater than for bulk PMMA.

Descriptors :   *GELS, *THERMAL EXPANSION, *OPTICS, BEHAVIOR, BENDING, COEFFICIENTS, CRACKS, EXPANSION, INDEXES, MICROHARDNESS, MICROSTRUCTURE, MIXING, NETS, POROSITY, RADIATION, RATES, REFRACTION, SCALE, SCATTERING, SHAPE, STRAIN RATE, THERMAL SHOCK, TRANSPARENCIES, ULTRAVIOLET RADIATION.

Subject Categories : Optics
      Organic Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE