Page 264 - Mechanical Engineer's Data Handbook

252 MECHANICAL ENGINEER'S DATA HANDBOOK

Natural rubbers Polyurethane adhesives

Solvent-type natural rubber adhesives have service These are used for many plastics including PVC,
temperatures up to 60 "C, and hot-curing types are polystyrene, and melamine. They have good strength
serviceable up to 90 "C. The former may incorporate at room temperature, excellent resistance to oils, acids,
resin for improved strength (see later). Resistance to alkalis and many solvents, but poor resistance to
water is good, but resistance to oils and solvents is water. They give a flexible bond suitable for resisting
poor. Adherents include: natural rubber; some plastics shock and vibration.
such as acrylics and PTFE; expanded natural rubber,
polystyrene and polyurethane; aluminium alloy, iron Polysulphide rubber adhesives
and steel; fabrics, card, leather, paper, wood; and glass
and ceramics. Solutions are used for car upholstery, These have outstanding resistance to oils, solvents,
paper, fabric-backed PVC to hardboard, and floor light, air and heat, and will bond steel, aluminium,
coverings. The latex type is also used to adhere paper glass, concrete, ceramics and wood. Uses include
to plastics and metal. Reclaim rubber adhesives are sealants for fuel tanks, aircraft pressure cabins and
used for car sound-proofing, draught excluding and windscreens, lights and pipe joints. With epoxy resins
undersealing. Pressure-sensitive adhesive is used for they are used for filling and sealing aluminium roof
tapes, labels and gluing polythene sheet to metals. panels and car body panels.
Polychloroprenes (neoprene) Silicone rubber adhesives

These synthetic-rubber-based adhesives have good These vulcanize at room temperature and bond a wide
resistance to water, oils and solvents and are either range of materials, including silicone rubber. The
solvent setting or vulcanizing by heat curing or shear strength is up to 1.4MNm-' at the maximum
catalyst with or without resin modifiers. They are used service temperature of 316 "C. Although the strength is
for bonding metal, wood, leather, synthetic leather and not high, they have excellent resistance to high tem-
plastics (except PVC) with applications in car, aircraft peratures. Formulation with epoxy resin gives good
and ship-building industries. strength up to 340°C.
Acrylonitride butadienes (nitrile) 6.16.3 Thermoplastic adhesives

These adhesives are similar to neoprene types and are In general, these have a low shear strength and suffer
supplied in the form of solutions for joining rubber to from creep at high loading. They are therefore used in
rubber, unbacked PVC to itself, and metal, wood, low-stress conditions. Resistance is good to oils and
leather and PVC sheet to metals. The latex type is used poor to good for water.
for PVC film to paper, textiles, aluminium foil to
plastics, paper and wood, etc. The shear strength is up Polyvinyl acetate (PVA)
to 7 MN m-2.
Butyl rubber adhesives This is the well-known 'white glue' used for wood-
working. It also bonds metals, glass, ceramics, leather
These are used in the car and building industries and and many plastics. The shear strength is good and the
are applied by gun or tape. Resistance to water is good, resistance high to oils and mould, but poor to heat and
but that to oils is poor. limited to water. Emulsion types are used for ceramic
tiles. A fast-setting type is available.
Styrene butadiene rubber adhesives
Polyvinyl alcohol (P VA)
These are based on the synthetic rubber used for car
tyres and are used in the car industry for bonding felt This is made from PVA and is similar to it. It is used for
carpets and for gluing metal to rubber trims. The paper in a re-sealable form. Resistance to oils and
pressure-sensitive type is used for tapes and labels. greases is good, but poor to water.