Coating PMMA (polymethylmethacrylate) is an extremely delicate operation: manufacturers of items made of this material must ensure that the finished product is not only aesthetically pleasing, but also – regardless of its intended use – resistant over time. This is especially true for thin sheets of PMMA - among the most versatile, most in demand items in the marketplace.
What are, then, the best techniques to manage the finishing process of this material, and what technological solutions are available today to help the most demanding manufacturers?
Before going through the range of possible solutions, it is helpful to analyse the main finishes that can be obtained by coating PMMA. Since PMMA sheets are generally used to cover panels, a glossy (or mirror) finish is often required. For specific applications, however, these sheets can also be used with different finishes: from satin to deep matt going through embossed and metallic.
High-gloss and mirror effects are more aesthetically appealing, but over time they are more prone to scratches and chipping. Conversely, satin and matt finishes in particular are better at “hiding” any signs of ageing.
Regardless of the type of finishing chosen, however, the surface of PMMA sheets leaving the factory must be of high quality, resistant and totally free from defects.
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Although PMMA is generally associated with paint coating, finishing techniques for this material also include printing and lamination.
Mainly used in the furniture industry, lamination turns sheets of polymethylmethacrylate into thin plates that create a surface effect reminding of bright glazed surfaces.
As for the digital printing process, it allows the back of PMMA sheets to be printed with any desired image which, thanks to the transparency of the material, appears perfectly visible with a charming reflective effect. This technique is often used to give the same visual impression as shiny marble or inlaid wooden floors.
In order to choose one approach or the other, therefore, a number of factors should be taken into account: aesthetics, durability and budget are primary considerations. Choosing the finishing technique for thin PMMA sheets that best suits your needs means finding each time the right mix of these factors and aiming for solutions that guarantee the right degree of flexibility to always obtain the best possible result in different use conditions.
Created to provide a lasting finish and an appealing surface effect, thin extruded PMMA sheets are, as we mentioned above, semi-processed items particularly delicate when it comes to coating them. This prompted Cefla Finishing to develop a specifically tailored process, which is based on a roller coating machine operating in a controlled and dust-free environment.
Prior to PMMA coating, thorough surface cleaning operations are performed to ensure spotless finishes.
Once this phase has been completed, the sheets are fed into the machine. More specifically, the application unit consists of two rollers (a top roller for coating application, and another roller below the sheets to provide physical support) which firmly act on the PMMA sheets leaving no space for sheet warping. A scraper blade which removes excess lacquer from the lower application roller also contributes to optimising the coating process of such thin sheets.
When a deep matt finish is required, excimer matting technologies not only ensure the best possible result, but are also a “green” option, as they use less nitrogen than standard solutions.
In addition to the specially developed roller coating equipment, the line can be completed with pressurised booths including air filtration and conditioning systems to avoid dust pollution and guarantee a controlled processing environment.
After the coating stages, the PMMA sheets can be dried in different ovens. Our UV-I inert curing solution maximises physical resistance and also dramatically reduces the need for photoinitiators, making the process more sustainable and reducing the related costs.
Exydry is a good example: it is an oven designed to process flat surfaces and will ensure a fingerprint -proof, soft-touch, deep matt finish, even on slightly raised panels.
H2 – Tailor-made solutions: which machines are used for PMMA coating?
Cefla Finishing - which has the widest available range of finishing technologies and machines designed to carry out specific processes such as PMMA coating - is now able to offer its customers the first roller coating solution specifically designed to process thin sheets. This is a dedicated line integrating a combined upper application roller and a lower support roller that work in synergy, as well as a cleaning system and a working environment designed to prevent dust pollution.
More specifically, the machinery that can be integrated into an advanced line for PMMA coating includes:
Each machine has specific features for completing the PMMA coating process and can be configured to meet actual requests from customers. However, in the event of even more challenging specific requirements, with tailor-made details to be expected or processing steps that imply customer-specific variables in terms of types of lacquer, production volumes or available space, feel free to visit our Cefla Finishing LAB in Imola or one of our satellite laboratories in China and the United States to identify possible solutions with our Cefla experts.
Contact us to arrange an appointment with Cefla Finishing specialists or run a live test.
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