Page 265 - Mechanical Engineer's Data Handbook

ENGINEERING MATERIALS 253

Polyacr ylates 6.16.4 Thermoset adhesives

These are generally used for textiles and the pressure- These adhesives set as a result of the build-up of
sensitive types are used for labels. Water-based acrylic molecular chain length to give rigid cross-linked
sealants are available. matrices. They include epoxy resins, which are some of
the most widely used adhesives.
Polyester acrylics
Phenolic formaldehyde (PF) resins
These cure in the absence of air (anaerobic) and give an
extremely strong bond for metals, glass, ceramic and These are widely used in woodworking especially for
many other materials. The shear strength may be as plywood, and have excellent resistance to water, oils,
high as 14MNm-’. solvents, etc. They will bond fluorocarbons, nylons
and epoxy resin. Engineering adhesives are based on
Acrylic solvent cement mixtures with other resins.
This consists of polymethyl methacrylate (PMMA) Phenolic neoprene
dissolved in methyl chloride and is used for bonding
PMMA to itself and to cellulosics, styrene, polycar- This is a heat-curing adhesive good for bonding metal
bonate and rigid PVC. The shear strength is about to metal and metal to wood with a strength of
7MNm-’ at 38°C. 20 MN m-’.

Cyanoacrylates Phenolic nitrile

These set in the presence of moisture (from the This is a hot-curing adhesive with a shear strength of
adherents) in several seconds to give an extremely high 28 MN m-’ at a service temperature of 175 “C. It is
strength (up to 20MNm-’). They are used for the used for metal to non-metal joints such as car brake
rapid assembly of small components, metal to metal, linings.
and metal to non-metal joints, but not for porous
materials since voids are not filled.
Phenolic polyamides
Silicone resins
These are usually available as a thermoplastic poly-
These will bond fluorocarbons. They have low amide film and phenolic resin solution. The shear
strength but a high service temperature. They can be strength is up to 35 NM m-’.
formulated with other adhesives to give higher
strength . Phenolic vinyls

Polyamides These have a high strength (up to 35 NM m- ‘), but are
not very useful above 100°C. They are used for
These are applied hot and set on cooling. They bond bonding honeycomb sandwich constructions, metal to
metals, wood, plastics, leather and laminates. The metal and rubber to metal.
chemical resistance is the same as that for nylon.
Resorcinol formaldehydes (RF)
Acrylic acid diesters
These are used for wood and have superior strength,
These are anaerobic adhesives used for e.g. nut locking water resistance and temperature resistance compared
and as a gasket cement. Their performance is satisfac- with PF adhesives. They bond acrylics, nylons, phen-
tory up to 150°C. olics and urea plastics.