The engineer will be concerned with the behaviour and performance of the selected adhesive from the time he first purchases it from the manufacturer, through the mixing, application and curing phases to its properties in the hardened state within a joint over the intended design life. Thus the properties of interest in approximate chronological order are likely to include:
(1) Unmixed — shelf life
(2) Freshly mixed — viscosity
usable life wetting ability joint open time
(3) During cure — rate of strength development
(4) Hardened — strength and stress/strain characteristics
fracture toughness temperature resistance moisture resistance creep fatigue
To a large extent the performance of the hardened adhesive within a joint will be discussed in considerable detail in Chapters 3 and 4. Thus, the purpose of the review which follows is to compare the basic properties of bulk adhesive from the time of mixing to the hardened state.