Page 475 - Handbook of Adhesives and Sealants

Adhesives Families 411

ature and set by loss of water through a porous substrate and by a
certain degree of chemical conversion. Thus, mixed casein adhesives
have a finite pot life. They are used for paper labels, woodworking,
and other interior applications. They cannot be used outdoors al-
though they are resistant to dry heat up to 158 F. Resistance to or-
ganic solvents is generally good. Certain casein glues are used to bond
high voltage paper insulation. Casein has a unique property in that
it can be impregnated with insulating oil and thus provide excellent
insulation characteristics.
Blood albumen adhesives (blood glues) are used in much the same
way as casein glues. The blood proteins can be hardened by hot press-
ing as well as by loss of water. Porous materials require only several
minutes at 176 F to set. These adhesives are used to a limited degree
to make softwood plywood. The major applications are bonding porous
materials such as paper, cork, leather, and textiles.
Animal glues are made from bone and hide byproducts. These glues
are supplied as liquids, jellies, or solids in the form of flakes, cubes,
granules, etc. for reconstitution with water. They are used primarily
for furniture woodworking, but are also used for leather, paper and
textiles. These glues set at temperatures in the range of 176–194 F
or they may set in longer times at room temperature. The bond
strength usually exceeds the strength of wood and fibrous substrates.
Fish glues are by-products of fish skins, usually cod. They have
properties similar to animal glues. Fish glues were the forerunners of
all household glues. Fish glue is usually used in cold setting liquid
form. These glues may be exposed to repeated freezing and thawing
cycles without adverse effects. Initial tack is excellent on remoisten-
ing. Fish glues bond well to glass, ceramics, metals, wood, cork, paper,
and leather. The main uses are in the preparation of gummed tapes.

10.4.3.2 Inorganic adhesives and cements. Adhesives based on inor-
ganic compounds generally have low cost and high temperature prop-
erties. They are usually applied as water based adhesives. These ma-
terials form strong bonds in applications where at least one substrate
is porous. The advent of synthetic organic polymer adhesives has led
to a decline in the use of many of these adhesives except for specialty
applications. The most common inorganic adhesives are sodium sili-
cate, phosphate cement, litharge cement, and sulfur cement.

10.4.3.2.1 Sodium silicate. Commonly know as water-glass, this color-
less low cost inorganic material is usually supplied as a viscous water
solution. These adhesives display little tack, and holding pressure
must be applied until the bond is sufficiently dry. The dry adhesive is
brittle and water sensitive. In fact the adhesive may be re-dissolved