How To Optomise Glue Adhesion.
Cleanliness is next to optimum bond strength!
As the leading industrial glue manufacturer and supplier in Ireland, our technologists constantly advise an exceptionally wide range of industrial manufacturers on the optimum glue to use for their specific applications, and the optimum way to use it.
Surface treatment, it is a term which we constantly use when we are working with customers, either through carrying out lab work using their materials, or carrying out on-site training within their manufacturing plants. But what is the meaning of ‘surface treatment’.
Before we glue anything together, we need to check the materials and using a practical laboratory test, determine if the glue can be applied directly to the part being glued, or if the parts need to be modified in order to achieve the strongest bond possible. Since glues bond to the surface of metals, composites and plastics, we need to be sure that the surface is optimised to accept the glue. If not, the surface may need to be modified and to enable this, surface treatment may need to be carried out.
There five main forms of surface treatment and below, I have listed them in order of ease of use in the industrial environment.
1. Degreasing. This process removes oils and grease. We manufacture a range of degreasing agents which are designed for both metal and plastic/composite materials.
2. Primers. Primers are applied to either one or both sides of the materials being bonded. Most of them are solvent based. When the solvent evaporates, what is left behind is a reactive layer (reactive groups). This later makes the surface very receptive to a film of glue. Mechanical Treatment.
3. Mechanical Treatment. This class encompasses surface roughening through manual or mechanical sanding and also sand blasting. This process is great for removing surface oxidation from metals. It also increases the surface area of bond area and presents a very active surface just wanting to be glued. Mechanical treatment needs very little in the way of expensive equipment. Manual roughening is suggested for plastics and composites.
Care is needed in sanding composite materials, since the fibre matrix may be damaged with over zealous sanding. Sand blasting tends to be used in more critical applications such as bonding rubber to steel. One critical point to remember…….since the surface of the metal is very active after sand blasting, it will start to oxidise quite quickly. Glue immediately after sand blasting!
4. Chemical Treatment. This process tends to be used on very inert materials which do not lend themselves to manual treatment. Materials include plastics such as High-Density Polyethylene, Polypropylene, EPDM, and Polyethylene etc.
5. Corona or Plasma Treatments. These are reasonably new processes in which much work is continuing in Ireland. They are both rapid and reliable process which activate the surface of really difficult to bond to materials such as polyolefin types. In particular, plasma treatment does need to be carried out in a specific environment and the parts once treated, stay active for approximately twenty-four to thirty-six hours.
Remember, good bonding is the result of a number of factors. The correct joint design, correct adhesive and method of application and possibly most important of all, proper surface preparation.
In any gluing job, we can offer you the optimum glue for your application, plus the full services of our laboratories, which will guide you through the optimum gluing process.