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There is a need for
safe and sustainable alternatives in the coating
industry. Bio-based coatings are interesting in this perspective.
Although various oils and waxes have been used as traditional wood
coatings, they often lack sufficient durability. Lignin is an abundant
natural polyphenol that can be used to cure epoxies, but its poor
water solubility has impeded the use of unmodified lignin in coatings
in the past. To address this issue, water-dispersible colloidal lignin
particles (CLPs) and an epoxy compound, glycerol diglycidyl ether
(GDE), were used to prepare multiprotective bio-based surface coatings.
With the GDE/CLP ratios of 0.65 and 0.52 g/g, the cured CLP–GDE
films became highly resistant to abrasion and heat. When applied as
a coating on wooden substrates, the particulate morphology enabled
effective protection against water, stains, and sunlight with very
thin layers (less than half the weight of commercial coatings) while
retaining the wood’s breathability excellently. Optimal hydrophobicity
was reached with a coat weight of 6.9 g(CLP)/m
2
, resulting
in water contact angle values of up to 120°. Due to their spherical
shape and chemical structure, the CLPs acted as both a hardener and
a particulate component in the coating, which removed the need for
an underlying binding polymer matrix. Light interferometry measurements
showed that while commercial polymeric film-forming coatings smoothened
the substrate noticeably, the particulate morphology retained the
substrate’s roughness in lightweight coatings, allowing for
a high water contact angle. This work presents new strategies for
lignin applications in durable particulate coatings and their advantages
compared to both currently used synthetic and bio-based coatings.
Wood is increasingly replacing concrete to reduce CO2 emissions in buildings, but fossil-based adhesives are still being used in wood panels. Epoxidized lignin adhesives could be a potential replacement, but...
The design of antimicrobial
surfaces as integral parts of advanced
biomaterials is nowadays a high research priority, as the accumulation
of microorganisms on surfaces inflicts substantial costs on the health
and industry sectors. At present, there is a growing interest in designing
functional materials from polymers abundant in nature, such as cellulose,
that combine sustainability with outstanding mechanical properties
and economic production. There is also the need to find suitable replacements
for antimicrobial silver-based agents due to environmental toxicity
and spread of resistance to metal antimicrobials. Herein we report
the unprecedented decoration of cellulose nanofibril (CNF) films with
dehydroabietylamine 1 (CNF-CMC-1), to give
an innovative contact-active surface active against Gram-positive
and Gram-negative bacteria including the methicillin-resistant S. aureus MRSA14TK301, with low potential to spread
resistance and good biocompatibility, all achieved with low surface
coverage. CNF-CMC-1 was particularly effective against S. aureus ATCC12528, causing virtually complete reduction
of the total cells from 105 colony forming units (CFU)/mL
bacterial suspensions, after 24 h of contact. This gentle chemical
modification of the surface of CNF fully retained the beneficial properties
of the original film, including moisture buffering and strength, relevant
in many potential applications. Our originally designed surface represents
a new class of ecofriendly biomaterials that optimizes the performance
of CNF by adding antimicrobial properties without the need for environmentally
toxic silver.
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