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A hot melt adhesive, also known as a hot glue, is the name given to a polymer-based glue which is solid at room temperature and is applied in a molten state.

There are three main stages to the process of a hot melt adhesive bonding together materials. Firstly, the solid adhesive is heated until it reaches its softening point, at which stage it will turn to liquid. The molten adhesive is then applied and wets the substrate. The period available to make the bond between applying the thermoplastic adhesive and bringing in the secondary material is called the open time. Lastly, cooling time will then occur. This typically varies from just a few seconds to up to 5 minutes, and during which the hot melt will solidify and very quickly build up strength and stability. This fast turn around allows for a quick processing time and rapid assembly.

 

Main Components of Hot Melt Adhesives:

Polymers: These help to give the adhesive strength and flexibility, as well as heat and impact resistance.

Resins: Control the wetting of the adhesive (how long it remains a liquid whilst in contact with the substrate).

Wax: Primarily controls the open time, and how long the bond takes to form. It also helps thin the adhesive for application. The higher the wax content present within a hot melt, the higher viscosity and greater flexibility the bond will have. High levels of wax also allow for a quicker bond.

Antioxidants: These are used primarily to help preserve the material during its shelf life.

 

 

Equipment required for hot melt adhesives:

The equipment which accompanies the hot melt glue is just as important as the adhesive itself, since without the glue gun there is no way of heating the adhesive to the correct application temperature. The glue gun also allows for accurate and precise application onto the substrate. Each gun is specifically made to suit a different need, such as the 3M Hot Melt Low Temperature Applicator LT which maintains a temperature of 129ºC making it an ideal choice for heat sensitive surfaces such as foam and plastics. If a higher temperature is required, the 3M Hot Melt Touch Control Adhesive Applicator TC dispenses up to 196 ºC and is great for more detailed work.

 

 

Advantages of Hot Melt Adhesives:

Good for hard to reach areas:  As the adhesive is applied in a purely liquid form, it allows for easy application to more obscure places or surfaces which other glue or adhesive products cannot do as well. Many glue guns and nozzles are manufactured to distribute the glue into these small complex places ensuring the entire chosen surface is reachable and covered which in turn, allows for stronger bonds.

Speed and ease: As the whole process of using hot melt adhesives is quick, this lowers assembly time and allows for optimum productivity with a fast turnaround.

Bonds variety of substrates: Hot melt adhesives are specially formulated for specific tasks. A wide variety of materials can be bonded, such as wood or corrugated cardboard. Heat sensitive materials such as foam or even some plastics and metal can also be bonded using hot melt adhesive when dispensed at a lower temperature. They can also bond both porous and non-porous surfaces.

Neat Application: The bond which forms from a hot melt adhesive is practically invisible which gives an overall pleasing aesthetic. This is particularly useful when used for items such as signs, displays or even furniture.

Long shelf life: Hot melt adhesives have excellent moisture resistance and do not need refrigeration meaning they remain firmly bonded for an extensive period. 

Challenges of hot melt adhesives:

As with most adhesive products, alongside the benefits, hot melt adhesives have a few limitations. The temperature at which hot melt adhesives are set at is crucial to the application process.

• Once molten, the adhesive must be hot enough for assembly. If the adhesive is not hot enough at this stage, a weak bond may be formed which is also known as a cold bond.
• However, if the hot melt adhesive is applied in a molten state at too high a temperature, it will remain in a liquid state for too long and result in a soft bond being formed. Any stress or weight on this bond will cause a weakening which could fail immediately.
• Unlike other adhesives, if hot melts bonds are re-heated to their softening point temperature, the previous adhesion caused by the cooling process can be reversed. Although this does make hot melt adhesives more flexible and easier to repeatedly change, it can cause a hindrance should this be applied to a substrate which will undergo or survive in an environment with higher temperatures. However, many hot melts are now being manufactured with higher levels of heat resistance to combat this.

 

Common Industries:

Packaging Industry	Electronic Industry
Automotive Industry	Bookbinding Industry
Furniture/Woodwork Industry	Retail Industry

Shop our range of Hot Melt Adhesives here. 

Additional links:

At Ellsworth Adhesives, we supply a wide range of hot melt adhesives and glue guns from leading brands Henkel Loctite and 3M. View our complete range of hot melt adhesives here. 

Unsure if hot melt adhesives are right for you? Our Glue Doctor is available to answer any technical questions you may have. Simply fill out our enquiry form.

UV curing adhesives, also known as light curing adhesive, use UV light or other radiation sources to initiate the curing process. A permanent bond then forms without application of heat by a means of free-radical chemistry.

UV curing adhesives are available in a range of viscosities and several different chemical systems, most of which are polymer based. These include acrylics, epoxies, polyurethanes, polyesters and silicones.

UV curing adhesives can bond to a wide range of substrates, even those which are dissimilar, and provide a tough clear bond making them a highly popular choice.

In this blog post, we’ve highlighted 10 of the most popular uses for UV Curing Adhesives and the reasons why they work so well for these applications…

1. GLASS BONDING 

With high transparency and excellent stability, UV curing adhesives are well suited to glass bonding since the nature of the adhesive allows it to perform under tough environmental conditions such as humidity and sunlight. This works particularly well for bevel bonding and stained-glass windows.

 

We recommend: Dymax 429 Lightweld Adhesive

2. ARCHITECTURAL BONDING

Architectural bonding benefits from UV curing adhesive on items such as glass balconies and staircases. The light treated curing resists yellowing, vibration and thermal shock and can be used for large area bonding.

We recommend: Dymax 425 Lightweld Adhesive

3. PLASTIC BONDING

Plastic bonding for point of sale display items or signs is made much easier by using a UV curing adhesive as it allows for full coverage and clear, bubble free bond lines. The highly resilient adhesive gives rapid adhesion to plastic making it a great choice for point of sale signs.

 

We recommend: Dymax 3099

4. AUTOMOTIVE ASSEMBLY

Light-curing adhesives are particularly effective for large volume manufacturing or assembly processes where fast curing and high quality are required. In the automotive industry, safety critical devices such as headlamps and seat belt monitoring switches are increasingly being treated using this method thanks to these benefits.

We recommend: Dymax Adhesives 3030

 

5. DISPOSABLE MEDICAL DEVICES

Medical device manufacturers worldwide are rapidly seeking the use of light cure technology in their industry, as it offers a rapid cure and a vast product range.  Henkel Loctite UV light adhesives meet SO-10993 biocompatibility requirements, the same test standard used in the licensing of medical devices.

 We recommend: Henkel Loctite 4305

6. ENCAPSULATION OF PRINTED SURFACE BOARDS

 

UV curing conformal coatings can be applied over the entire surface area of a printed surface board or in a discreet, shadowed areas to provide full protection from external environments. This quick-curing process means there is no need to dry the board after application, unlike traditional time consuming thermal-cure coatings.

We recommend: Dymax Adhesives 9481-E

7. SHOWER DOORS, HANDLES & CABINETS 

Fast and highly durable bonding between glass to acrylic, such as those within bathroom cabinets and doors, can be achieved with the use of UV curing adhesives. The low stress bonder resists yellowing in the sun and can cure through UV blocked and tinted glass or plastic. It also offers a good performance during thermal cycling.

We recommend: Dymax 4-20418

 

 

8. FLAT PANEL DISPLAYS, TOUCH SCREENS & LAMINATION

Light-curable optical digital bonding adhesives are specifically formulated for when durable, invisible bonds are required. Their fast, on demand cure and superior workability mean substrates can be repositioned continuously until they are ready to be cured. They are non-yellowing allowing for increased light transmission and optical clarity on touch and LCD screens such as phones or tablets and offer an easy flow for flat panel lamination.

We recommend: Dymax Adhesives 9701

 

9. MANUFACTURING OF RESPIRATORY SUPPORT DEVICES

As UV curing adhesives work well under testing environmental conditions, it makes them a perfect fit for the bonding of products such as facemasks and breathing circuits. The attributes of the bond allow flexibility and contain no non-reactive solvents. The ability to cure in seconds allows maximum speed and high-quality performance for the assembly of the medical device.

We recommend: Dymax Adhesives 110-MSK

 

10. SHOP FITTINGS

The bonding of display cases and shelves can be achieved almost instantly using a light curing adhesive. Any excess can be removed easily after adjustment, which is aided by the precise and easily dispensed application of the adhesive. The bonds which are formed generally exceed the strength of the substrates.

We recommend: Dymax Adhesives 3094-GEL-REV-A

 

 

Shop our full range of UV Curing Adhesives

 

Additional links:

Want to know more about UV light curing? Check out our ‘Guide to UV Curing Blog‘ which explains the advantages of UV Curing technology and the key UV curing systems and  materials you need to know about.

Ellsworth Adhesives supplies an extensive range of UV Curing products – you can view our full UV Curing range here.

Our Glue Doctor is available to answer any technical questions you may have regarding UV curing materials or UV Curing equipment. Simply fill out our enquiry form.