Humidity control in laminated safety glass manufacturing

Laminated glass manufacture requires exceptionally clean and dry conditions to ensure a high-quality product. The process of manufacturing uses a film of highly hygroscopic transparent plastic, which works as an adhesive, sandwiched between two pieces of glass.

Polyvinyl butyral (PVB) is a clear, colourless, amorphous thermoplastic obtained by condensation reaction of polyvinyl alcohol and butyraldehyde. The resin is known for its excellent flexibility, film-forming and good adhesion properties as well as outstanding UV resistance.

One of the major uses of PVB film is safety glass. Due to its good adhesion to glass, most of the splinters of fractured glass will adhere to the surface of the PVB film and thus, prevent personal injury by large and sharp glass fragments. PVB laminated glass also offers an improved sound barrier, good impact resistance, and almost 100% absorption of UV light. The latter is important for the protection of interiors from fading due to UV exposure.

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The manufacturing process is highly susceptible to fluctuations in RH and maintaining a stable low RH environment is key. If this lamination process is carried out in an uncontrolled humid environment, the film will contain excess moisture. Failure to maintain this environment will result in imperfections in the final product and in some cases lead to catastrophic failures. The second part of the process involves heat and pressure. The moisture trapped in the film can boil during the process and create steam bubbles which are trapped inside the laminated glass. Maintaining 18.0°Cdb, <25% RH is classed as an ideal condition for PVB lamination to take place.

Advantages of Dehumidification Systems for the Manufacture of Laminated Safety Glass

Utilisation of desiccant sorption dehumidification systems are ideally suited to this application, as they provide a means of maintaining a continuous stable RH within the lamination area.

Fisair design and manufacture desiccant rotor dehumidifier systems to maintain manufacturing and PVB storage areas at low dewpoints and stable temperatures (15-20°C, 25%RH), this prevents moisture issues from impacting production. This ensures consistent production during seasonal changes and significantly reduces products failing inspection due to bubbles.

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