FOSPAT hotmelt adhesives are completely solid, non-toxic adhesives that contain no solvents or water.  They are manufactured in rigid stick, slug or cartridge form to exacting standards in our own modern factories.  The adhesives are easily loaded into glue guns and flow when the trigger is gradually squeezed.  The solid adhesive is pushed into a heated chamber, and comes out of the nozzle as molten adhesive.

Hotmelt adhesives provide instant, permanent bonding on a wide range of materials whilst avoiding the use of harmful solvents.  They are ideal for quick, repetitive bonding applications.

Melted adhesive is applied by a hand held glue gun to one surface, then the parts are pressed together and a bond is made instantly.  The adhesives are easy to store and have practically unlimited shelf life.  With a choice of over 25 varieties to choose from, there is a solution for all of your applications.

Here are some of the advantages of using a shaped hotmelt system for industrial applications:

• Reliable Instant Bonding
• Economical and Easy to Use
• Suitable for a Wide Range of Substrates
• Non Toxic and Solvent Free

Fospat hotmelt adhesives have a wide range of applications including:

• Packaging
• Potting and Encapsulation (e.g. electronics)
• Sealing and Reinforcing
• Coating and Insulating
• Vibration Reduction & Component Cushioning
• Anti-slip (e.g. for stabilising pallets)
• Repair Assembly
• Decorate and Create

Adhesive Application Methods:

There are two methods of application, bead (or dot) and spray:

Bead/Dot:

A continuous bead of molten adhesive is produced by the glue gun, giving the user complete control over the spread, pattern and volume of glue. 

Spray:

The molten adhesive is sprayed from the applicator nozzle of the glue gun using our pneumatic spray tool.  This method has certain advantages for some applications:

• It is more economical because less adhesive is used.
• The adhesive is spread over a wider area and is suitable for heat sensitive materials that can be damaged by bead application.

Hotmelt adhesives are thermoplastic and, therfore, their performance changes with temperature.  One of the more prominent changes is the reduction of bond strength with increasing temperature.

Heat resistance is a measure of bond strength for hotmelt adhesives, relating to the temperature (in ‘degrees C’) at which a standardised sample fails (when subjected to a constant load).

A Ring and Ball Softening Point (the point at which the adhesive becomes liquid – usually a higher value than the heat resistance figure for any given adhesive) is often quoted for hotmelt adhesives, and this is sometimes misinterpreted as a measure of heat resistance.

Adhesive bond strength can be influenced by various other factors (such as type of adhesive, length of time exposed to higher temperature, the amount and direction of the load imposed on the bond line, and the nature of the substrates being bonded). Therefore,  the quoted heat resistance figures of FOSPAT hotmelts should only be used as an approximate guide when comparing different adhesives.  It shouldn’t be assumed that the adhesives will be able to withstand the quoted temperatures in all cases.

The user should conduct their own tests to determine the suitability of an adhesive for a particular application.

Hotmelt adhesives are thermoplastic. This means that they become liquid at higher temperatures, returning to a solid state at lower temperatures.  When liquid, a measure of the ease with which adhesive flows is its viscosity, and this decreases as the temperature rises.  The viscosity of an adhesive is measured using a viscometer and is usually quoted in ‘Poise’ or ‘Centipoise’ (cps).

A lower viscosity adhesive will flow easily, increase glue gun output, reduce stringing, and form stronger bonds.  However, they are unsuitable for very porous surfaces, such as foams and fabrics.

A higher viscosity adhesive will be suitable for bonding coarse or uneven surfaces, and for applications where good gap filling and low sag properties are needed.  However, higher viscosity adhesives can reduce the output of glue guns, so a more powerful glue gun may need to be specified.

FOSPAT adhesives are designed to run at different temperatures, so we can broadly classify the viscosity as High, Medium or Low, as follows:

The open time of an adhesive is the duration of time available to make a bond after the hotmelt adhesive has been applied.

This may be as little as a couple of seconds with a fast setting packaging adhesive, or up to several minutes for some product assembly adhesives.

The maximum open time of a hotmelt adhesive depends on the temperature of application, the amount of the adhesive applied, the type of substrate, the temperature, and the ambient conditions.

For the highest bond strength it is important to get the parts together as soon as possible after the adhesive has been applied.

As a result of the different factors that can influence open times, it is not simple to quote exact open times for hotmelt adhesives.

The open times of FOSPAT hotmelt adhesives are broadly classified into 3 groups:

Hotmelt Adhesives can be formulated using several different base polymers.

The choice of polymer influences the adhesion, temperature resistance, chemical resistance and the cost.

FOSPAT use several different polymers which enable us to formulate a large range of useful properties into FOSPAT hotmelt adhesives.

Ethylene Vinyl Acetate (EVA)

This is one of the most popular base polymers for hotmelt adhesives, and is used in both packaging and product assembly formulations.  It is economical and provides service temperatures of -30ºC to 80ºC.

Polyamide (PA)

A higher performance polymer that is used to formulate adhesives with better resistance to temperature extremes; typically -60ºC to 130ºC.  These adhesives are more chemical resistant but tend to be slightly less sticky than adhesives that are based on EVA.

Polypropylene (PP)

These are used to formulate adhesives with specific adhesion properties and delayed setting time.  They are often used for spray formulations.  Service temperatures are -30º to 110ºC depending on the formulation.

Polyurethane (PUR)

FOSPAT Polyurethane Reactive Hotmelt can be applied, and initially sets, like a normal Hotmelt Adhesive by losing heat and becoming solid.  The PUR absorbs a small amount of moisture from the surrounding materials or atmosphere and cross links.

This is a permanent chemical change that takes several days and increases heat and chemical resistance.

A small amount of moisture is required for this reaction to take place. Therefore, it is better if at least one substrate is porous.  If moisture is only available from the edge of the bond then cross linking will be slow and unreliable.

More water shouldn’t be applied to a surface before bonding as this will overwhelm the reactive component of the adhesive and stop cross linking.

FOSPAT PUR is packed in individual foil packs and comes with a shelf life of at least 6 months.

Recently, progress in hotmelt adhesives has allowed many product assembly applications to benefit from the efficiencies of hotmelts.

Although performance bonds are now possible on many substrates, it should be noted that bond strength will vary depending upon the following factors:

1. Temperature resistance

Hotmelts are thermoplastic and, therefore, become more brittle at low temperatures and softer at higher temperatures.  The technical data sheets provide heat resistance and glass transition figures (tg), but it must be recognised that these are laboratory tests and that the results are only a guide.  As a result of the thermoplastic nature of hotmelts, the strength of a bond will vary with both the amount and rate of load at different temperatures.

1. Amount of adhesive applied

The strength of a bond varies with the amount of adhesive applied.  Larger amounts of adhesive cover a greater area and increase overall bond strength.  Also, larger amounts of adhesive conserve heat and the adhesive tends to be a higher temperature when parts are brought together and increases bond strength.

1. Time taken to assemble

Once the hotmelt adhesive is applied, it starts to cool.  If the assembly is not finished fast enough, then the bond strength will reduce as the adhesive will have cooled to a point where a strong bond cannot be achieved.  This is known as a cold bond and although early results look acceptable, the bond can deteriorate over a 24-hour period to an unacceptable level.

In general, potential users of hotmelt adhesive for applications that require semi-structural bonds should perform their own tests to satisfy themselves that the adhesive will meet their requirements in the various conditions the finished product may encounter.  They should also ensure adequate controls are in place to ensure that the amount of adhesive and time taken for assembly is adequately controlled.

Fospat Industrial will be pleased to make recommendations and offer guidance, but because we cannot control the application, the quantity of adhesive or variations in substrates, it is not possible for us to provide specific performance guarantees.  In all cases we would urge the user to conduct their own tests to ensure that the recommended adhesive meets their requirements.

• Hotmelts are thermoplastic polymer-based materials that are 100% solid; they contain no water or solvent and are simply melted by heat so they can be applied as a liquid.
• Hotmelt adhesive is applied in molten form to one surface.  Once the parts being bonded are pressed together the heat in the adhesive is quickly dissipated into these parts and the adhesive solidifies forming an almost instant bond.
• Most materials can be bonded with hotmelt adhesives,  providing the parts can be assembled while the adhesive is still molten.
• Adhesives are available with application temperatures of between 120ºC and 215ºC depending on the heat sensitivity of the materials being bonded.
• Working times also vary from just a few seconds to several minutes.