Venus Hot Melt Glues are made from 100% solid adhesive. Because they are not solvent based they are friendly to the environment and will not taint foods or other packaged items. Also because they are solvent and water free there is no wastage and no glue odours when set. Venus Hot Melt Glues have an almost unlimited shelf life and are far easier to use and store than messy cans and tubes.
Hot Melt Formulation
All Venus Hot Melt Glues are composed of a basic POLYMER such as EVA (ethyl vinyl alcohol), PP, ethylene or poyamide mixed with a natural or oil derived TACKIFIER resin which holds the elements together and also determines the adhesive strength. A high tackifier content gives lower viscosity and a stronger bond. RESIN gives the adhesive its tackiness. Paraffin or polythene WAX is used as a viscosity modifier: a higher wax content produces faster setting and a crisper bond.
Other ingredients include ANTI- OXIDENTS to stabilise the colour, RUBBER to increase resilience and reduce brittleness, PLASTICISERS and OILS to extend the open time. Where substrates might be exposed to temperature extremes and where impact resistance is required at low temperatures it is necessary to consider the more expensive polyamide glues such as Venus 9901.
Hot Melt Terminology
Viscosity is the liquidity of the adhesive in its hot state and is generally quoted in centipoise (CPS) at a given temperature. The lower the CPS value the thinner the liquid. Water has a value of 1 CPS. Viscosity is quoted in a fairly wide range (ie 7000 to 10000 CPS) as chemical companies only manufacture to a +-2% variation on softening point specification. Therefore viscosity varies from batch to batch.
Open Time is the maximum working time before the adhesive cools to a point at which only marginal bonding can take place. It is based on adhesive formulation and rate of heat loss. Temperature Resistance is the resistance of the bond to heat and cold. Important to electronic component assembly, deep freeze packaging etc. The Venus range of EVA polymer glues includes temperature resistances from -20°C to +80°C and polyamides from -20°C to + 149°C.