KRAKOW, Poland—The growing drive to replace petrochemical-derived substrates with bio-based alternatives has led to a wide range of potential crop and agricultural waste sources being investigated. Now, a group at the Cracow University of Technology has been investigating another potential source for biopolyols to make polyurethanes—cherry seeds.
As an inedible waste product, they do not compete with the food chain. The seeds account for about 15% of the weight of the cherry, with about 0.225MT of cherry seed waste being produced every year. Methods to turn them into products such as bioethanol, biodiesel, concrete fillers and activated carbon have already been investigated, but what about polyols?
That’s what the Cracow team set out to discover. They took cold-pressed cherry seed oil, and used a transesterification reaction to create a polyol, both including and without nanosilver particles as an antimicrobial agent. Nine different sets of reaction conditions were tried, and they found the presence of nanosilver made no difference to the results of the polyol-forming reaction.
Each of the nine polyols were then used to produce open-cell polyurethane foams with pMDI, with no other polyol included in the mix. All nine foams had similar apparent densities and thermal conductivity coefficients, and these were typical of standard open-cell PU foams.
However, there were significant differences in the proportion of closed cells and the compressive strength, influenced by the composition of the reaction mixtures—higher proportions of monoglycerides and monoesters in the polyols led to an increase in both.
They also looked at the antimicrobial properties of the foam, which is important if it is going to be used as insulation in attics. This was the reason for including nanosilver in some of the polyol-forming reactions.
The growth of the fungus Candida albicans was addressed on and around the foams. Regardless of silver content, all inhibited fungal growth on the foam itself, and two of those containing silver nanoparticles inhibited fungal growth away from the foams. One of these had the highest silver content; both had low cell density, giving better access to the antimicrobial agent.
The work has been published in the journal Clean Technologies and Environmental Policy.
