Greener cleaning formulations are often not as effective as traditional harsher chemistries. However, consumers are demanding products with similar performance.
Several long-term studies (e.g. for cleaning buses and trains) have shown the performance of industrial cleaners can be much improved by adding hydroxyproline rich proteins (HRPs) to their formulations. Furthermore, the environmental impact of these industrial operations could be significantly reduced, as the HRPs allowed for a reduction in the formulation’s alkalinity.
This work investigated the surface behavior of these proteins and their application as additives in hard-surface cleaning formulations. Quartz crystal microbalance analysis and contact angle measurements have found that dilute solutions of HRPs form net hydrophilic layers, a few nanometers thick, on different surfaces. These layers are protective and support surfactants, thus preventing soil materials from directly contacting the surface and allowing for easier sequential cleanings.
The effectiveness of several cleaning formulations, with and without HRPs, were evaluated using a scrub abrasion and washability tester. Surfaces were cleaned once with their respective formulation, soiled, and then cleaned again. These experiments found that formulations with HRPs outperformed the same control formulations without HRPs. This improved performance has the potential to provide a similar or better degree of cleaning, albeit with less aggressive, more environmentally friendly chemistries.
Surface tension experiments evaluating the interactions of HRPs with a series of common surfactants were also investigated. While several surfactant classes show little interaction with the HRPs, glucamine based surfactants were found to exhibit a synergistic effect with regards to their surface tensions.