Short Epoxy Glossary
Temperature, Curing. The
temperature to which an adhesive or an assembly is
subjected to cure the adhesive. Note-The temperature attained by the adhesive in the process of setting it may differ from the temperature of the atmosphere surrounding the assembly.
Tensile Strength. The pulling force necessary to break a given specimen divided by the cross sectional area. Units given in lbs./in/2 (P.S.I.). It measures the resistance of a material to stretching without rupture. Normally is not used with reference to elastic materials which recover after elongation.
Thermal Shock Resistance. The ability of a cured system to resist cracking or
crazing under conditions of rapid and continuous thermal change. The 1/4 inch
Olyphant Washer test is cycled over a temperature range of -55°C to +125°C, this temperature is normally used as the test condition unless otherwise stated.
Thermosetting. Describes the property of an epoxy, to set or become rigid and
non-meltable when heated with or without pressure.
Thixotropy. False body. The property of a paste or fluid to thicken or set up to a
paste or semi-gel when allowed to stand. Agitation breaks it down but further
standing will again permit a viscosity rise.
Time, Curing. The period of time during which an assembly or part may be
subjected to heat or pressure, to cure the epoxy. It is the time between the
addition of curing agent to the resin, and completed polymerization.
Viscosity. The property of resistance to flow exhibited within the body of a fluid.
Usually measured in centipoise.
1 cps = Water
400 cps = #10 Motor Oil
1,000 cps = Castor Oil
3,500 cps = Karo Syrup
25,000 cps = Hersheys Chocolate Syrup
Volume Resistivity. The ratio of the electrical resistance through a cross section
A divided by the length through which the current flows. Measured in ohms-cm.
Volume Shrinkage (%)
Amount of dimensional change during cure. Water Absorption (%)
% by weight water absorbed by material in 24 Hours @ RT
Wetting. The thorough impregnation of a material by a liquid. The more viscous a fluid, and the higher its surface tension, the more difficult it is for the liquid to "wet" materials. Certain additives, for example, water softeners, reduce surface tension, or viscosity and improve wetting properties, allowing the material to flow out more.
Working life. The period of time during which an epoxy after mixing with a curing
agent, remains workable and suitable for use.
Yield Strength. The load in pounds per square inch where the material under test begins to change dimensions and will not completely recover when the load is removed. Yield strength will normally be lower than ultimate strength. Generally speaking, the more rigid a material is, the closer will be yield and ultimate strengths. Furthermore, the more resilient a material is, the greater the spread between yield and ultimate strengths.