Page 469 - Handbook of Adhesives and Sealants

Adhesives Families 405

TABLE 10.21 Advantages and Disadvantages of Thermoplastic Adhesive Forms 39
Form Advantages Disadvantages
Water base ..... Lower cost Poorer water resistance
Nonflammable Subject to freezing
Nontoxic solvent Shrinks fabrics
Wide range of solids content Wrinkles or curls paper
Wide range of viscosity Can be contaminated by some
metals used for storage and
High concentration of high-
molecular-weight material application
can be used Corrosive to some metals
Penetration and wetting Slow drying
can be varied
Poorer electrical properties
Solvent base .... Water-resistant Fire and explosive hazard
Wide range of drying rates Health hazard
and open times
Special explosion proof and
Develop high early bond ventilating equipment needed
strength
Easily wets some difficult
surfaces
Hot melt ....... Lower package and Special applicating equipment
shipping cost per pound of needed
solid material
Limited strength because of
Will not freeze viscosity and temperature
limitations
Drying and equipment for
drying are unnecessary Degrades on continuous
heating
Impervious surfaces easily
bonded Poorer coating weight control
Fast bond-strength Preheating of adherends may
development be necessary
Good storage stability
Provides continuous water-
vapor impermeable and
water-resistant adhesive
film

Products of this type are good adhesives for applications where at
least one substrate is porous. Paper, plastics, metal foil, leather, and
cloth can be bonded with polyvinyl acetate emulsions. The major use
is in packaging. Polyvinyl acetates are also used in hot-melt adhesive
formulations. In this form they are commonly used for bookbinding
and lamination of foils. Organic solvent solutions are also used, al-
though not as much as the latex.