Also known commonly as glue. A substance in a liquid or semi-liquid state that adheres or bonds materials together through surface attachment. Adhesives usually require a controlled temperature for curing.
Useful accessories used for different working steps for a variety of product applications. Examples include; squeeze bottles, wax sheets, needles, syringes, adhesives, meter mix equipment, release agents, sealers, fillers and glass fabrics.
An intermediate stage in the reaction of thermosetting resins in which the material softens when heated and swells when in contact with certain liquids, but may not entirely fuse or dissolve. The resin in an uncured thermosetting system is usually in this stage.
The scale of temperature which features 0° and 100° as the freezing and boiling point of water respectively. To convert Centigrade to Fahrenheit multiply by 1.8 and add 32, e.g. (100° x 1.8) +32 = 212°F.
The state in which the particles of a single substance are held together by primary or secondary valence forces observed in the tendency of the substance to stick to itself. As used in the adhesive field, the state in which the particles of the adhesive (or the adhered) are held together.
Tying together large molecules and hence changing the physical properties of a material. Cross-linking usually involves formation of three-dimensional molecular network and is customarily associated with thermosetting resins.
Separation of a tool and a model after the material has cured. If Demoulding is difficult, this can be due to small sections or in the worst case, total model/tool bonding. To ensure easy demoulding ensure all surfaces are completely sealed and released. On difficult-to-draw models, consider incorporating demoulding aids such as jackscrews and air fittings directly into the tool.
The property of materials whereby they tend to recover their original size and shape after deformation. Note – if the strain is proportional to the applied stress, the material is said to exhibit ideal elasticity.
A material which at room temperature can be stretched repeatedly to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.
The ability of an epoxy system to resist combustion or burning. Some materials tend to extinguish themselves when subjected to a flame. Such materials are classified as self-extinguishing. ASTM D790-63.
The temperature at which a material softens enough to distort under a given load. It is not usually considered to be beyond the maximum usable temperature, but is an indication of the maximum usable temperature when the material is load bearing at a given load. As the load decreases, the maximum usable temperature will increase. Measured in °C.
The ratio of the amount of moisture contained in the atmosphere to the amount of moisture that can be carried in the atmosphere at a given temperature. Relative humidity is expressed in percent, e.g. 75% R.H. at a given temperature means that the air is 75% saturated with moisture.
A measure of the brittleness of a material. Brittle materials will have low Izod impact values (0.15 for example). Tough materials will have high Izod impact strengths (0.60 for example). Units of measure are usually ft-lb/in. This different to Impact Strength (Charpy) which is expressed as kJ/m2 (ISO 179).
Having some resistance to high humidity. A moisture resistant adhesive will not be easily affected by moisture. Will not easily change its chemical and physical properties due to moisture. Should not be confused with “water-proof”.
The length of working time of a two component reactive system from the time of the addition of the curing agent in a specific mass (i.e. 100 grams), remains workable and suitable for use. It is expressed in minutes or hours.
Temperature of the working environment e.g. a laboratory or working area. Shop temperature should be held between 21-25°C. Cold inhibits curing, whereas higher temperatures may cause an undesirable exothermic reaction.
A materials hardness measured on a durometer, the scale of which is 0-100, used on elastomers and other flexible materials. Consists of a pin point depression into the material, the material being at least 100 mils thick. A Shore A reading of 80 equals a Shore D reading of 30.
The materials hardness measured on a durometer similar to the Shore A durometer, the scale of which is 0-100, used on rigid and semi-rigid materials. Consists of a pin point depression into the material.(DIN 53505).
Soft spots are small bubbles or streaks detected in a tool. They may appear in the tooling surface or throughout the tool laminate or casting. They can range from a slightly softer than normal section to a liquid-like totally unreacted tool mass.
The ratio of the weight of any volume of a mass or substance to the weight of an equal volume of water at given temperature. The specific gravity of a substance times the density of water equals the density of the substance.
An applied force or pressure, as tension or shear, exerted on a body which produces a resultant strain on the material. The ability of the material to withstand a stress depends on the strength of its cohesive force or molecular structure.
The property of a liquid which causes the surface to pull into the smallest area for a maximum volume, hence drops are spherical. The fact that water drops on a wax surface do not spread out due to surface tension. If a wetting agent were added to the water the round droplet would spread out into a film because of the lowered surface tension.
The pulling force necessary to break a given specimen divided by the cross sectional area. Units of measure are lbs/in2 or MPa. It measures the resistance of a material to stretching without rupture. Normally is not used with reference to elastic materials which recover after elongation.
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.
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. It is expressed in minutes or hours.
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.
The load in lbs/in2 or MPa 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 the yield and ultimate strengths. Furthermore, the more resilient a material is, the greater the spread between the yield and ultimate strengths.