The hot melt market place is highly competitive – and with a significant number of regional and world players employing many highly qualified technologists, it is no surprise that product innovation is alive and well.

As a result, the substrates (whether pervious or impervious) that can be bonded with hot melt have grown year on year and include plastics, rubbers, metals, composites, glass, ceramics, fibreboard, fabrics, wood, leather, foams, paper and board.

Depending upon formulation, hot melts can create an instant bond or have a longer open time to allow bonding down the production line.  As coatings, they can be self-adhesive or they can be reactivated by heat, if that suits the production requirement.  According to need, they can be selected to give strong and permanent bonds or weak and peelable bonds or something in between.

Hot melts are neither hazardous, toxic nor flammable and do not contain solvents, making their handling, storage, transportation and use easy, safe and reliable without harming the environment.  They are available in a variety of forms: from glue sticks for DIY to bulk adhesives for industrial use, which is our focus here.

But to compete against alternative fixing methods, hot melts have to make a business case.  Here are seven key reasons to use hot melt adhesive technology:

1.  To drive innovation
Adhesives free the designer to create new products and new methods of manufacturing without the constraints of mechanical fixings.  Hot melt adhesives aid this process by allowing high speed production with the flexibility to bond a wide range of substrates.

2.  To improve product appearance
Hot melts can replace mechanical fixings to make smoother, cleaner, more aesthetically pleasing products.  They can fill voids, encapsulate or seal; individual components or complete products can be made tamper proof or tamper evident.

3.  To build in toughness
Hot melts maintain their strength and flexibility throughout the life of a product.  They eliminate weak points created by mechanical fixings or welding.  Their bond strength is spread evenly across the application area without distorting the substrate.  In impact and tensile strength tests, hot melts score highly.

4.  To simplify manufacturing processes
Hot melt application can be automated or manual to suit production needs and costs – and one adhesive may well be suitable for a variety of uses.  There is no pick and placing, as with threaded fixings, or dirt and danger implications, as with welding.

5.  To lower costs
A simplified product can help to drive down costs through reduced component inventory, with easier and faster assembly as fabrication time is reduced and labour costs are lowered.

Hot melts can bring other economies too – unlike many adhesives, no curing, drying or extraction equipment is required, giving space saving and flexibility in production line engineering.  There is virtually no waste.

6.  To keep ahead of competitors
To be at the forefront, you need to keep ahead of your competitors – by designing hot melt adhesives into your products and processes, you are much closer to achieving this.

7.  To address end-of-life strategies
End-of-life strategies will need to be addressed for many products – the use of hot melt adhesives in assembly assists in their ultimate dis-assembly and subsequent recycling of the different materials.  This can have a positive impact on the product life cycle analysis.

Hot melts in use

Thousands of companies have made hot melt adhesives an integral part of their product or manufacturing process – whether to create a permanent bond or to hold components in place temporarily.  Examples include:

• Automotive  Adhering recycled fabric to LDPE for automotive insulation; bonding and sealing rear lamp assemblies where the hot melt prevents the ingress of water and withstands typical automotive temperature and ageing tests.  Other applications include bonding sound deadening materials, carpets, head liners and many individual components.
• Industrial products  Tracer cable encapsulation and bonding backings to sanding disks – where heat resistance and high cohesive strength are critical properties.
• Filter manufacture  From the complete fabrication of air filters to using a hot melt to seal the holes created by sewing threads.
• Domestic appliances  Forming a gasket on an ABS vacuum cleaner cover and in refrigerator and freezer production, where manufacturers use temporary bonds to locate components and seal holes with a hot melt prior to the injection of polyurethane foam.
• Electronics  Uses include bonding computer disks to their central cores and embedding copper wire circuits and attaching them to high pressure laminate boards.
• Construction  Bonding foam to steel for applications as diverse as window construction and making moulds for reinforced concrete floor panels.  Other uses include bonding foams, metals, plastics and paper, either on their own or in combination, in the fabrication of insulation panels, cavity closures and the anti-heave honeycomb panels used at Heathrow Terminal 5 featured in FAST, January 2008.
• Furniture and furnishings  Hot melt adhesives have replaced solvents and other fastening systems for foam and fabric bonding in the bedding and furniture industries as well as for automotive seats.
• Glass and ceramics  There are applications where the purpose of the adhesive is not to form a strong, permanent bond but to create a spacer to protect a surface finish during transportation – now common in the high-end ceramic tile industry.  This concept is also used to separate panes of glass with a very thin swirl of hot melt – sufficient to stop them sticking together when stored (because of the vacuum effect of glass on glass).  In both applications, the hot melt is easily removed without leaving a mark.
• Plastics  There are hot melts with high heat resistance – in excess of 125°C – and others that remain flexible and give good adhesion down to -60°C.  We have developed thermoplastic, non-reactive hot melt adhesives with ambient shear strength capabilities of over 1,000 N/25 mm2.

Versatility

All these examples demonstrate that hot melt adhesives, whether for producing temporary or permanent bonds, are highly versatile.  So too are the methods of applying them – manually with hand guns or through fully automated systems that apply precise amounts of adhesive and use slot, roller, jet or spray nozzles to suit the adhesive and the application.

Hot melt adhesives are used globally – but as with all specialist solutions, talking to companies that have a deep understanding and a focus on hot melts is vital.

This is particularly so if there’s a solution to an application you didn’t know existed!

E-mail: stuart.wetherell@beardowadams.com

For a TXT copy of this release and photographs please contact Peter Mann at Buzz Associates on 01767 651115 or e-mail peter@buzzassociates.co.uk

For a pdf of release click here