Blooming marvellous? Working towards a bloom-free manufacturing process
01 September 2020
‘Blooming’, for those who use cyanoacrylate-based adhesives, has been the talk of the manufacturing industry for many years. It is the white staining of parts near where the adhesive is applied that detracts from the overall appearance of the assembled parts.
In some cases, blooming is not an issue as assembled parts may be subsequently painted or finished. In other cases, such as in the manufacture of high-end goods, aesthetic is everything. Clearly, staining on expensive fashion accessories or equally costly consumer electronics is not acceptable; it supports neither the quality of the product or its brand.
So, what causes blooming? From a technical perspective, blooming occurs because, depending on their composition, fast-reacting cyanoacrylate adhesives may comprise volatile ingredients, i.e. they have significant ‘vapour pressure’. The types with volatility generate staining when volatiles condense on part surfaces. This is particularly noticeable on black or shiny parts, and on optically transparent parts – for example, lipstick cases, lenses and glass covers, high-end writing instruments, perfume bottles and such like.
Instant adhesive types
Within the world of instant adhesives, there are two principal types, so-called ‘Ethyl Cyanoacrylate’ and ‘Methoxyethyl Cyanoacrylate’, abbreviated as ‘ECA’ and ‘MECA’. ECA-based adhesive products are well accepted and well utilised. They are generally inexpensive to produce and have become the mainstay of the adhesives industry, as they are convenient and easy to use, and also provide strong and instant adhesion. Nonetheless, they suffer two major disadvantages, both associated with their volatility: they create blooming, and they have an acrid odour and must be used in a proper environment.
Read the full article in the September issue of DPA.
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