| dc.description.abstract | Lignosulphonate nanoparticles/Phytic acid bio-flame retardant for PLA is a novel and
environmentally friendly flame retardant that has the potential to revolutionize the fire safety
industry. This research paper provides a comprehensive overview of the background, possible
applications, process conditions, key results, and novelty of this innovative bio-flame retardant.
The background of this dissertation stems from the growing concern over the use of traditional
flame retardants, which often contain harmful chemicals that can pose serious health and
environmental risks. In response to this, researchers have been exploring alternative, sustainable
flame-retardant materials, and the combination of lignosulphonate nanoparticles and phytic acid
has emerged as a promising candidate.
Polylactic acid (PLA) is a biodegradable polymer with applications in engineering, electronics,
transportation, and aerospace due to its excellent properties; however, because it has an organic
matrix, its thermal and fire retardancy needs improvement. Lignin has a high aromatic content
and therefore offers a chance to use bio-based materials as nanoscale intumescent flame
retardants. However, because of its structural heterogeneity, lignin requires modification with a
material that has flame-retardant qualities. It has already been proven that combining lignin and
PLA causes the matrix of a polymer to degrade during melt-processing. Phosphorous
functionalized lignin nanoparticles, on the other hand, appear to reduce PLA degradation during
melt-processing. Our goal was to create a high-functionality, bio-based phosphorus-containing
flame-retardant that could be reactively incorporated into the PLA matrix to enhance flame
retardant efficacy in a way that is sustainable. Through the combination of phytic acid and
lignosulfonate, bio-based flame retardant was formulated. Functionalized lignin nanoparticles
were synthesized by first combining lignosulfonate with phytic acid at 80ºC for 4hrs with magnetic
stirring, followed by 1 hour of ultrasonication at a frequency of 20Hz with a cavitation probe of
3.175 mm, to give a nanoparticle dispersion, LNP-PA. The LNP-PA dispersion was spray-frozen
on aluminium plate cooled with liquid nitrogen and kept frozen at -80ºC, followed by lyophilization.
Key results presented in this paper demonstrate the successful synthesis of functionalized
lignosulphonate nanoparticles, superior flame-retardant properties of the lignosulfonate/Phytic
acid bio-flame retardant compared to traditional flame retardants. The bio-flame retardant exhibits
excellent fire resistance, low toxicity, and minimal environmental impact, making it a highly
desirable alternative for various applications.X-ray powder diffraction (XRPD) spectrum showed
that the pristine lignin and the functionalized NPs both have an amorphous structure, and the
broadening of the spectra of the phosphorylated lignin after sonication shows the formation of
nanoparticles, whose sizes were confirmed by dynamic light scattering (DLS). According to the
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DLS measurements, the average particle diameter was 238 nm. However, scanning electron
microscopy (SEM), revealed that there was agglomeration of particles after freeze drying but a
significant particle size reduction of lignin was observed. Fourier transform infra-red spectroscopy
(FTIR) spectrum showed a reduced intensity due to the loss of hydroxyl functional groups
resulting from homolytic cleavage during ultrasonication, and phosphorylation. This was
confirmed by 31P-NMR, which shows the loss of hydroxyl functional groups, indicating that they
reacted with the phosphate groups in PA. The appearance of peaks in LNP-PA's FTIR spectrum
corresponding to P=O and P-O-R ester bonds proved that phytic acid had been chemically and
successfully linked to lignosulfonate. The fire-retardant effect of the bio-flame retardant
formulation was examined using a modified UL-94 tests. The control sample, pristine PLA burned
more vigorously in the vertical method. Melting drips were observed in pristine PLA, PLA/LNP,
and PLA/5LNP-PA, all of which were classified as V-2.PLA/10LNP-PA and PLA/15LNP-PA
samples that had higher weight percentages of the bio-flame retardant additive demonstrated
better fire behaviour and were classified as V-1 and V-0 respectively. All samples were classified
as HB in the horizontal mode, and as the loading ratio of LNP-PA additives increased, the rate of
burning decreased. The results are credited to the presence of lignosulfonate whose highly
aromatic composition forms a carbon-based char layer which inhibits the diffusion of oxygen to
the combustion site. Phytic acid also forms a char layer when it degrades due to the six phosphate
groups within its structure, that produce phosphoric acid. This forms a protective layer which
reduces the amount of fuel needed to sustain the combustion process and restricts heat flow in
the material.
The novelty of this research lies in the development of a sustainable and effective bio-flame
retardant that addresses the shortcomings of conventional flame retardants. Previously published
research on this subject has reported on the use of pristine or phosphorous based macro-scale
lignin to synthesize bio-flame retardants, and there has been few reports involving lignin
nanoparticles or their combination with phytic acid. The combination of lignosulfonate and phytic
acid offers a unique and innovative solution to fire safety concerns, paving the way for a more
sustainable and eco-friendly approach to flame retardancy. Possible applications of lignosulfonate
nanoparticle/Phytic acid bio-flame retardant include its use in various industries such as
construction, textiles, and electronics, where fire safety is of utmost importance. | en_US |
