Sticky solutions for fixing signage

Nobody knows when the first sign was glued together and hung above a door, but you can guarantee everybody commented when it fell down. Keeping a sign in place means using a safe and secure fixing system because if the fixture fails (and God forbid it falls on someone’s head) the whole world will quickly know about it. Screws, nuts and bolts are the first method, but in this feature, I’ll explore the world of tapes and adhesives which make up so much of the sign-maker’s armoury.

Adhesives

First, I turned to Simon Dearing, the managing director of Eurobond Adhesives based in Kent for his opinion. The firm began life back in 1984 supplying the manufacturing and signage industries. Its products include one and two-part structural adhesives, acrylic tapes, MS Polymer adhesives, UV light curing adhesives, electrically conductive adhesives and tapes and instant adhesives. So, the question for the Eurobond man was which of the products are of most use for sign-makers?

Dearing replies: “Let’s look at tapes first. Typically, the most popular in sign-making fall into three categories: acrylic foamed tape, single-sided polyethylene tapes and double-sided polyethylene tapes. Acrylic tapes are generally used for structural bonding where applications include bonding sign channel/rail to the back of sign faces, bonding PVC or acrylic sheet behind fret cut letters, bonding flat cut letters to vertical surfaces and a host of other applications. Acrylic tape is actually 100 percent liquid adhesive that’s been partially cured to flexible solid, extruded into the shape of a tape and wound onto a roll ready for use. The acrylic formulation is pressure sensitive and will give an immediate bond on contact with another surface. By applying pressure along the length of tape, the material wets out and starts to flow (microscopically) into every deformation, scratch or groove in the substrate surface.”

In Lancashire, Innova Solutions supplies the trade with a variety of products including tapes. Liam Dunleavey of the firm says: “Generally speaking, we can subcategorise our core range of tapes into foamed acrylics, double sided tapes/filmic tapes and foam tapes. The foamed acrylics are used for permanent bonds between dissimilar substrates, both internally and externally. We can tailor these to adhere better to certain substrates that the sign-maker may find troublesome. For example, we now have tapes that will bond metals prior to powdercoat temperatures of up to 220ºC, and we also have a tape that will adhere to the painted powdercoat surface.”

Taped

Tapes are one way to bond materials while adhesives, says Eurobond’s Dearing, are the other option with the most popular chemistries ones being toughened acrylic adhesives, MS Polymer (hybrid) adhesives and solvent weld adhesives. He says: “The most common and widely used toughened acrylic adhesive is Penloc. It is a very strong, very reliable and very fast two-part structural adhesive used to bond many different material combinations. It can replace welding, riveting and mechanically fixing of different metals, Dibond composites, wood, glass, plastics, Corian, marble, stone and many other materials. This type of adhesive is rubber toughened and contains nano-sized rubber spheres in the formulation giving it flexible properties to cope with differing material coefficients of thermal expansion, resistance to vibration, impact and shock.”

Dunleavey comments: “In terms of adhesives, we can subcategorise these into two-part structural adhesives, single component adhesives and solvent adhesives. Two-part structural adhesives can be used for a wide range of substrates for permanent bonds. As mixing the two components initiates the curing process, we can modify the speeds to suit different applications where cure speed is crucial. Adhesive technology is advancing, and we are able to modify adhesives to perform better in all situations. We are able to improve the clarity and flexibility of adhesives, and we can increase the temperature tolerance to allow it to go through a powdercoat oven.”

Locators

The problem of expanding and contracting due to heat is something that all bonding materials must take into account. Some adhesives have a flexible rubberised content which allows for it to expand or contract to the same degree as the material it is bonding. However, compared to metal fixings such as screws and bolts adhesives can allow for the expansion and contraction without tearing, breaking of failing. And their other advantage is that unlike metallic fixings they spread the load allowing potentially greater strength in keeping a sign in place.

When it comes to locators, Innova says plastic locators can be subcategorised into acrylic and plastic blend locators. The firm comments: “Originally sign-makers would use either clear acrylic locators or white nylon locators, however, we have found that locators have recently been formed using a blend of many low surface energy plastics, which makes them notoriously tough to bond. Acrylic locators (typically clear) have a high surface energy, which allows our Acrylic based two-part methacrylates to adhere with ease. Depending on the substrate you are bonding to, you would select the adhesive based on the following criteria: colour (aesthetics of the sign, will the glue be seen at all); material; transparency of material; heat reaction (witness marks), and the weight of the sign.”

Resin

Many adhesives feature resin as part of their make-up or use an artificial resin. Resins have been used to stick things together since the Stone Age when pine resin was used to help glue flint axe heads to wood handles. Since then fish extract, animal fats and vegetable extracts have been combined and still feature in some adhesives although they are usually referred to as bio-resins and are not as strong as their artificial cousins. Considerable research has been undertaken in adhesives in order to create new types to cater for the growing number of materials. Eurobond says for sign-makers there are quite a few different types of adhesive. They say that by far the most popular chemistries are toughened acrylic adhesives, MS Polymer (hybrid) adhesives and solvent weld adhesives.

Eurobond says: “MS Polymer (Hybrid) adhesives are flexible, moisture curing adhesives that offer many benefits to sign- makers. Typically, they will fully cure over a 24-hour period at room temperature, however they can’t be applied in temperatures at or below 5°C as the catalyst in the formulation crystallises and prevents the adhesive crosslinking to a cured state. This type of adhesive usually offers a high grab and a reasonably long open/working time allowing the sign-maker to apply the adhesive to large surface areas. MS Polymers can bond signs to wet or damp surfaces, have a very good chemical and weathering resistance and in general do not contain any hazardous chemicals. It is always advisable to check the label or the material safety datasheet. Eurobond Multi Seal is grey in colour and is guaranteed for 25 years. Eurobond Solo is white, offers very high initial grab and exhibits very high bond strength. Of course, when bonding clear plastics or glass Eurobond Clear Fix can be used as it will not leave a shadowed area along the bond line.”

O Factoid: Resins have been used to stick things together since the Stone Age when pine resin was used to help glue flint axe heads to wood handles.O

Dearing of Eurobond continues: “Solvent weld type adhesives are used to cold weld certain plastics together. The strongest of the organic solvent adhesives will dissolve materials, effectively welding them together as the glue dries. Many organic solvents are designed to work with specific materials, due to the molecular structure of the adhesive compound. For example, a PVC cement will only work when applied to PVC. The adhesive is made up of a solvent liquid carrier that contains an adhesive suspended in the formulation. This type of bonding can often stress the plastics being bonded causing stress unsightly fractures along the bond line.”

Advice

When it comes to buying adhesives there is one golden rule: ask the seller for advice. James Carpenter at Dorotape has had years of experience in the market and knows his tapes from his adhesives and can give advice on applications and products with an in-depth knowledge of the industry. He says: “Adhesives used for the manufacture of self-adhesive films have advanced leaps and bounds since I joined Doro tape over many years ago.  Originally sign-makers used plain coloured self-adhesive vinyl films for applying graphics to vehicles or to boards for building facia signs.  To a certain degree the advances in adhesives have gone hand in hand with the advent of the large format printer.

“We at Doro Tape now supply high tack films that sticks direct to carpets, floors, walls, whether inside or out.  There are also ultra-low tack films that can be applied to interior walls without fear of causing damage.  Applying graphics to glass now could not be easier with the availability of crystal clear self-adhesive printable films. These advances allow sign-makers and graphic designers the opportunity to offer their clients a much greater variety of marketing and promotional opportunities.  In turn this has opened up new markets for the sign industry into retail, hospitality, leisure and even the home market. However, the sheer choice of self-adhesive films available can lead to much confusion. It is therefore imperative that sign-makers and graphic designers go to the exhibitions, read the trade press and, most importantly, talk to their suppliers.”

Another aspect of adhesives and tape is to follow the instructions carefully says Carpenter. He says that it is one thing to buy the right product but without following the manufacturer’s directions for application the adhesive can fail. Also buying a cheaper unknown brand may lead to an expensive future problem as if the adhesive fails and the sign begins to fall down the sign-maker will have to repair it at their own expense with the resulting loss of reputation. Health and safety is something not to be taken lightly. Dunleavey comments: “It’s important to remember that an adhesive is manufactured using a combination of chemicals. These chemicals all come with health and safety warnings, and handling instructions, that must be adhered to, as per the REACH and RoHS guidelines.”

Dos and don’ts

There is more advice on using adhesives from Innova Solutions’ Liam Dunleavey who says it is vital to assess the application as there is not one adhesive that suits every application. And as for don’ts he says don’t use the adhesive that you have to hand but always check before you go ahead that it is suitable. He says: “Don’t apply the adhesive sparingly, depending on the application a consistent bead size, applied in a snaking motion, will sufficiently secure the pieces together. Don’t assume all adhesives will fill the same gap, all adhesives have different viscosities and apertures to dispense from. Don’t press locators too far into the adhesive—this will disperse what is underneath and lack the ability to grab the locator. Don’t leave the nozzle on the cartridge once the job is completed—the adhesive will cure down the nozzle and potentially cure the adhesive within the cartridge. As for dos, maintain a minimum of 0.7mm of adhesive between two surfaces to ensure there’s a sufficient amount of adhesive to cope with the forces that will be applied. Expel a small amount of adhesive prior to putting the nozzle on, this will ensure both chambers are dispensing, and the chemical reaction can take place. Once the nozzle has been attached—dispense at least one nozzle’s worth of adhesive to ensure the correct ratio of part A and B has been mixed. Leave the adhesive for 24 hours to full cure.”

Future trends

The technology behind the development of adhesives continues to expand. The ability of adhesives and tapes to resist extreme heat and cold as well as the rigours of the elements or water has revolutionised the sign-making industry in the last decades. Developments that have seen new products with properties that sign-makers in the early 20th century could only dream of—let alone those Stone Age hunters who glued their flint axe heads with pine resin to the wooden handles.