28 adhesives

WOOD MATERIALS TECHNOLOGY

4th Edition

Chapter 28Adhesives

AdhesivesShelf life

– Best before date – how long the glue will keep in its container or packaging

Pot life– The time that the glue remains usable in a pot– Also known as open assembly time

Closed assembly time– The time you have to adjust and cramp the pieces before

the glue starts to set

How a glue works

Specific adhesion– The holding power of

the glue itself

Mechanical adhesion– The grip it has on the

material, e.g. cracks, crevices, pores

Types of adhesive

Scotch glue/pearl gluePVA glueCasein glueContact/impact glueFormaldehyde glueEpoxy resinsAliphatic (yellow) glueSuperglueHot melt glue

Scotch glue/pearl glue

Scotch/pearl/animal glueWater soluble – dissolves in

waterStrong smellNot heat resistantLong shelf lifeMust be prepared in glue

potUsed for veneering

PVA glue

PolyVinyl Acetate (PVA) – Water soluble– Water-resistant types

available– Ready to use from container– Strong bond– Requires cramps– Sets in 4 – 12 hours– Mainly used for bonding wood

Epoxy resin

Expensive Glue and hardener – 2 partVery strong glueBonds different materialsQuick setting

Impact/contact glue

Used for veneering Solvent-based Harmful if inhaledStrong smellAvoid skin contact

Fixing veneer or laminate to wooden base

Using contact glue

Superglue

Very strong bond Quick-setting Expensive – only for small jobsWater-resistant glueBonds many different materialsAvoid skin contact – harmful

Hot melt glue

Glue sticks are melted in the hot gun

Hot liquid glue is squeezed out with the trigger

Glue sets quickly

Applying glueMethods

Fit joints without glue and check

Apply glue to pieces Assemble joints carefullyCramp pieces lightly and

firmlyWipe off all excess glue with

a clean damp clothCheck for square

Assembly

Quiz

What do the letters PVA stand for?

– PolyVinyl Acetate

Name the tool and state its use

• Hot melt glue gun− An electrically heated gun

used for heating and applying hot melt glue

Which glue might be used to bond two metals together?

– Epoxy resin glue– Superglue

Where might you use animal glue?

• Scotch/animal/pearl glue− Usually used for

veneering

Suggest a suitable adhesive to be used when forming the laminated piece of this project

– PVA glue– Casein glue

Suggest a suitable adhesive for bonding the veneer to the base

A suitable glue might be– Contact glue– Scotch/animal glue