Page 310 - Handbook of Adhesives and Sealants

274 Chapter Seven

nantly to modify the viscosity of filled systems. 17 It has been shown
that a small percentage of titanate in a heavily filled resin system can
reduce the viscosity significantly. Thus, titanate adhesion promoters
allow higher fillings of particulate matter to either improve properties
or lower the cost of the system without having a negative effect on the
viscosity of the system. Improved bond strength to halocarbon sub-
strates and improved hydrolytic stability are also claimed. 34
The titanate structure may be tailored to provide desired properties
through the six functionalities on the basic (RO) -Ti-(O-X-R -Y) n
2
m
structure. The (RO) is the hydrolyzable portion that attaches to the
m
inorganic substrate (Fig. 7.6). It also controls dispersion, adhesion,
viscosity, and hydrophobicity. The X group enhances corrosion protec-
tion and acid resistance and may provide antioxidant effects, depend-
ing on chemistry. The R provides entanglements with long hydrocar-
2
bon chains and bonding via van der Waals forces. The Y group
provides thermoset reactivity, chemically bonding the filler to polymer.
Examples of titanate coupling agents are shown in Table 7.9. New
neoalkoxy technology allows liquid, powder and pellet titanate cou-
pling agents to be processed like color concentrates without pretreat-

Figure 7.6 Titanate condensation on a hydroxyl containing
surface. 36