Page 452 - Book Hosokawa Nanoparticle Technology Handbook

APPLICATIONS 1 DISPERSION OF FINE SILICA PARTICLES
chromate treatment. In the field of liquid crystal display, elasticity of urethane. Urethane is a typical rubber
consumption of the hybrid material has increased as the material having a structure with solid hard segment
sealing material due to its high heat-resistance and domains (HS) dispersed in the liquid phase of soft
adhesiveness onto glass substrate and is being investi- segment domains (SS).
gated for use as the protection coating for color filters. As shown in Fig. 1.6, it was contrived to form the
Furthermore, three-phase hybrid consisting of hybrid domain with silica generated only in the HS
epoxy resin, silica hybrid and liquid polymer phases phase in the urethane-silica hybrid. The silica contributes
has also been developed by this method and commer- to give the heat-resistance to the HS domain and does
cialized as adhesives for flexible printed boards with not affect its flexibility by the existence of the SS phase.
high heat-resistance, adhesiveness and flexibility. We previously demonstrated the structure of the
The water absorption, electric property and mechan- molecular hybrid from the photoluminescence spec-
ical strength are controlled by adjusting tetram- trum of colorimetric substrate on the silica surface
ethoxysilane and alkyltrimethoxysilane as raw silane and reported the interaction between the domains
compound. In addition, bisphenol and novolac for using SALS [8, 9]. This material has an expanded
epoxy resin are also in the product line to meet diverse range of uses as a coating material for flexible boards,
customer requirements. fiberscopes, elastic paints and sealants.

4. Tough resin: hybrid of the phenol resin system 6. Cheap engineering plastics in place for imide:
hybrid of the amideimide system
When the novolac phenol resin used as a hardening
agent for epoxy resin is combined with silica, it devel- Amideimide is hardly used in the advanced elec-
ops mechanical toughness as well as disappearance of tronic industries because of its low flexibility, high
Tg as the epoxy system by the introduction of silica, dielectric constant and high water absorption, in
although it is not superior to the epoxy system in spite of its low monomer cost of less than a fifth
terms of the low rate of thermal expansion and the compared with imide. Although the ductility of the
decomposition temperature [7]. material cannot be increased by the addition of sil-
These phenol-system hybrids are commercialized ica, water absorption and dielectric constant similar
as the material for loudspeakers, taking advantage of to those of polyimide were obtained whilst main-
its heat-resistance, flame retardancy and mechanical taining the original flexibility of polyamideimide
strength. limiting the influence of silica to the bridge of mol-
ecules by introducing polymethoxysiloxane at only
5. Soft silica hybrid: hybrid of the urethane system the edge of the molecules as shown in Fig. 1.7 [10].
A hybrid of the amideimide system is being com-
The specified orientation of the silica site is essential mercialized as a material for super heat-resistant
for making a hybrid of silica making use of the rubber enamel wire, sliding parts and belts for printers.

HS SS Silica
Segment polyurethane chain

Polyurethane Hybrid
SS Phase

HS
domain

Hybrid
domain

Figure 1.6
Model of urethane–silica hybrid.

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