Epoxy resin quartz filler

Table 15.13 Epoxy Resin-Quartz Filler—Electrical Properties versus Silane...

Figure 1.10 Effect of various particulate fillers on the interlaminar shear strength of glass fabric reinforced epoxy resin laminates (23]. A, no filler B, BOixm glass beads, untreated C, same but silane treated D, 7 i,m glass beads, untreated E, same but silane treated F, 15p.m glass flakes G, 8 i,m calcium carbonate H, 15p.m quartz I, 15p.m alumina trihydrate, fire retardant J, 20p.m mica K, 60p.m thin-walled hollow-glass microspheres...

Fig. 3. Dielectric permittivities of a non-filled Bisphenol-A based epoxy resin (C) and its composite filled with 60 wt% wollastonite (C/W, left) and of a non-filled cycloaliphatic epoxy resin (B) and its composites filled with 60 wt% wollastonite (B/W) and quartz (B/Q, right). The high-temperature, low frequency polarization process is most probably due to the matrix/electrode interface in the case of resin C, while it is related to the matrix/filler interface in the case of resin B. (After Ref. [6]).

Silica glass, formed by fusing high grade quartz sand, is ball-milled o produce a fine powder. GP-31, of which 99% is finer than 30 /tm and 21% less than 1 ftm. -Obviously, a sol of colloidal amorphous silica could be made from the fines fractions (489). As a filler in epoxy resin, it greatly reduces the thermal expansion. 

Figure 5.25. Spectra of relaxation times of specimens containing epoxy resin with quartz filler at concentrations 1-0, 2-0.04, 3-0.31, 4-0.44.

Composites used in Dentistry were developed in 1962 by combining dimethacrylates (epoxy resin and methacrylic acid) with silanized quartz powder [49]. Modem restorative composites are comprised of synthetic monomers, typically dimethacrylates, reinforcing fillers, typically made from radiopaque glass, quartz or silica, chemicals which promote or modify the polymerization reaction, and silane coupling agents which bond the reinforcing fillers to the polymer matrix [26]. 

Electrical properties of filled resin systems are also improved by filler treatment. Filler particles are naturally hydrophilic via their metal hydroxide surfaces, and the particles naturally seek to agglomerate with each other, and so transport electrical charges through resin composite. Treatment with silane-coupling agent alters the chemistry of the filler surface, allow better dispersion of the filler throughout the resin matrix, and imparts improved electrical properties to the composite. Table 15.13 indicates the improved electrical properties of a quartz-fiUed epoxy resin system with 0.3% silane admixed into the formulation. Improved insulation values, including reduced dielectric constant and reduced dissipation factor, are also denoted. 

Skudelny D, Quartz and Fused silica Fillers for Epoxy Cast Resins. Quartzwerke GmbH, Frechen, Germany. 

Quartz was used as a filler in the manufacture of optical devices from epoxy in a UV-curable system. Figure 6.22 shows that addition of a filler can substantially reduce curing shrinkage which is highly desirable in the precise manufacture of these materials. Reduced shrinkage is the result of a low thermal expansion coefficient of quartz in comparison with the resin. 

The second, obvious application is studying polvmer-filler interactions in filled and reinforced composites. Some data are presented for wollastonite and quartz filled Bisphenol-A based and cycloaliphatic epoxies [6]. These data show, that Tg shifts observed by different relaxation methods (dielectric spectroscopy, DSC, thermomechanical measurements) are not necessarily the same (Table 1.), they depend on the effective frequency, changes in activation energy have also to be taken into account. Correlations between Tg shift and polymer adsorption can be understood using Lipatov s theory [7]. Positive Tg shift usually indicates strong adhesion, while negative Tg shift can be explained by the fact that the adsorbed polymer layer forms a looser structure than that of the bulk material. If both the neat resins and their composites are studied dielectrically, the origin of the low-... 

---