Maringá, Brazil – Scientists at the State University of Maringá in Brazil have been investigating the potential of replacing poly(ethylene glycol) with corn cob fibres in PU foam. The aim was to make a more sustainable foam, with the fibres modifying the foam’s mechanical strength and, potentially, enhancing its biodegradability. They also looked at incorporating antibacterial silver nanoparticles into the foam.
They selected corn cobs as the fibre source because they are abundant in Brazil, and have high strength and stiffness while being lightweight. The foam was made using MDI, while the corn cobs were sourced from a local farmer.
The corn cobs were treated to expose hydroxyl groups to react with the isocyanate. First, they were cleaned and oven-dried, then ground in a knife mill and sieved. The resulting fibres were soaked in NaOH solution for half an hour, before washing with deionised water and dried at 60°C for 24h. They then deposited the silver nanoparticles on the fibre surface by heating the two components in water at reflux for an hour, before filtering, washing with more water, and finally air dried.
Foams were made by mixing the fibres with polyethylene glycol, and then adding to MDI plus tin octanoate as catalyst. This was then stirred vigorously until a foam was formed. The maximum amount of fibres that still foamed with 25% by weight without the silver nanoparticles, and 35% with. Below 20% fibre content the foam largely maintained the properties of fibre-less foam, with viscoelastic behaviour seen at 15% and 20% content. They therefore suggested the foam could have applications mattresses and upholstery. Above 20%, the higher fibre content made the foams more tough, and would be more appropriate for insulation, acoustic and thermal foams.
They also assessed the antimicrobial properties of the foam containing silver nanoparticles against four common bacteria. For S. aureus and P. aeruginosa, it had a microbiostatic action, but it was also microbicidal against E. coli and C. albicans.
The work has been published in the journal ACS Omega.
