IMPROVED PROCESS CONTROL THROUGH REALTIME MONITORING OF BONDING ENVIRONMENTS FOR AEROSOL CONTAMINANTS

Bonding, coating, painting, and sealing operations are well known to be extremely sensitive to the substrate surface composition prior to adhesive, sealant, or coating application. Predictable product performance requires controlled surface chemical composition. One way surface composition can change is through contamination. This can occur via contact with contaminated surfaces (e.g. fixtures used for storage, human skin) or via aerosol routes. Simply depending on process protocols to protect surfaces from contamination are insufficient: there are multiple documented cases of silicone contamination occurring in facilities where all silicones are banned. Procedures and equipment for detection of aerosol contaminants in a manufacturing facility are uncommon and generally based on continual spectroscopic monitoring of air composition, a complicated and expensive approach. This paper discusses an alternative approach involving regular monitoring of the wettability of inexpensive witness surfaces that have been strategically placed in the facility of interest, typically in a bond or paint shop, or in a zone dedicated to preparation or storage of structures prior to bonding, coating, and sealing. Wettability (as measured via contact angles) can be more sensitive than surface analysis techniques such as FTIR or X-ray photoelectron spectroscopy (XPS) to low surface energy detrimental contaminants such as silicones. Real-life examples are presented which show the utility of using rapid, cloud-based collection of realtime water contact angle measurements of witness surfaces as a ‘canary in the coalmine’ to monitor facility hygiene and warn of the presence of potentially detrimental (and unintended) environmental conditions in a manufacturing facility. This approach allows issues to be corrected before substandard product is produced and shipped.