Lightweight Biobased Polyurethane Composites Derived from Liquefied Polyol Reinforced by Biomass Sources with High Mechanical Property and Enhanced Fire-Resistance Performance.

Lightweight biobased insulation polyurethane (BPU) composite foams with high fire-resistance efficiency are interested in building effective energy and low environmental impact today. This study focuses on manufacturing lightweight BPU from liquefied bamboo polyols and biomass resources, including rice husk and wood flour. Then, they are combined with three flame retardant (FR) additives, such as aluminum diethyl phosphinate, aluminum trihydroxide, and diammonium phosphate, to improve their fire resistance performance. The physicochemical properties, microstructure, thermal stability, mechanical properties, and flame-retardant properties of the BPU composites are characterized to optimize their compromise properties. The results showed that composites with optimized FRs achieved UL94 V-0 and those with nonoptimized FRs reached UL94 HB. The limiting oxygen index exhibited that the fire resistance of BPU composites could increase up to 21-37% within FR additives. In addition, the thermal stability of BPU composites was significantly improved in a temperature range of 300-700 °C and the compressive strength of the BPU composites was also enhanced with the presence of FRs. The scanning electron microscopy observation showed an influence of FRs on the morphology and cell size of the BPU composites. The bio-PU-derived samples in this study showed significantly low thermal conductivity values, demonstrating their remarkable thermal insulation effectiveness.

Novel films of pectin extracted from ambarella fruit peel and jackfruit seed slimy sheath: Effect of ionic crosslinking on the properties of pectin film.

Here, we prepared ionically crosslinked films using pectin extracted from agro-wastes, specifically ambarella peels (AFP) and jackfruit seed slimy sheath (JFS). Physiochemical properties of pectins, including moisture content, molecular weight (Mw), degree of esterification (DE), and galacturonic acid (GA), were analyzed. Optimal extraction was determined, i.e., citric acid concentration 0.3 M, time 60 min, solid/liquid ratio 1:25, and temperature 90 °C for AFP or 85 °C for JFS. Pectin yields under these conditions were 29.67 % ± 0.35 % and 29.93 ± 0.49 %, respectively. AFP pectin revealed Mw, DE, and GA values of 533.20 kDa, 67.08 % ± 0.68 %, and 75.39 ± 0.82 %, while JFS pectin exhibited values of 859.94 kDa, 63.04 % ± 0.47 %, and 78.63 % ± 0.71 %, respectively. The pectin films crosslinked with Ca2+, Cu2+, Fe3+, or Zn2+ exhibited enhanced tensile strength and Young's modulus, along with reduced elongation at break, moisture content, water solubility, water vapor permeability, and oxygen permeability. Structural analyses indicated metal ions were effectively crosslinked with carboxyl groups of pectin. Notably, the Cu2+-crosslinked film demonstrated superior water resistance, mechanical properties, and exhibited the highest antioxidant and antibacterial activities among all tested films. Therefore, the pectin films represent a promising avenue to produce eco-friendly food packaging materials with excellent properties.

Sustainable Lignin-Based Nano Hybrid Biomaterials with High-Performance Antifungal Activity.

Aspergillus flavus (A. flavus) and Aspergillus niger (A. niger) mainly spread through airborne fungal spores. An effective control to impede the dissemination of the spores of Aspergillus in the air affecting the environment and food was carried out. This study focuses on the sustainable rice husk-extracted lignin, nanolignin, lignin/n-lignin capped silver nanoparticles used for fungal growth inhibition. These biomaterials inhibit the growth of fungi by altering the permeability of cell membranes and influencing intracellular biosynthesis. The antifungal indexes for A. flavus and A. niger on day 5 at a concentration of 2000 µg/100 µL are 50.8 and 43.6%, respectively. The results demonstrate that the hybrid biomaterials effectively prevent the growth or generation of fungal spores. The findings of this research hold significant implications for future investigations focused on mitigating the dissemination of Aspergillus during the cultivation of agricultural products or in the process of assuring agricultural product management, such as peanuts and onions.

Novel Thiosemicarbazone Quantum Dots in the Treatment of Alzheimer's Disease Combining In Silico Models Using Fingerprints and Physicochemical Descriptors.

Searching for thiosemicarbazone derivatives with the potential to inhibit acetylcholinesterase for the treatment of Alzheimer's disease (AD) is an important current goal. The QSARKPLS, QSARANN, and QSARSVR models were constructed using binary fingerprints and physicochemical (PC) descriptors of 129 thiosemicarbazone compounds screened from a database of 3791 derivatives. The R 2 and Q 2 values for the QSARKPLS, QSARANN, and QSARSVR models are greater than 0.925 and 0.713 using dendritic fingerprint (DF) and PC descriptors, respectively. The in vitro pIC50 activities of four new design-oriented compounds N1, N2, N3, and N4, from the QSARKPLS model using DFs, are consistent with the experimental results and those from the QSARANN and QSARSVR models. The designed compounds N1, N2, N3, and N4 do not violate Lipinski-5 and Veber rules using the ADME and BoiLED-Egg methods. The binding energy, kcal mol-1, of the novel compounds to the 1ACJ-PDB protein receptor of the AChE enzyme was also obtained by molecular docking and dynamics simulations consistent with those predicted from the QSARANN and QSARSVR models. New compounds N1, N2, N3, and N4 were synthesized, and the experimental in vitro pIC50 activity was determined in agreement with those obtained from in silico models. The newly synthesized thiosemicarbazones N1, N2, N3, and N4 can inhibit 1ACJ-PDB, which is predicted to be able to cross the barrier. The DFT B3LYP/def-SV(P)-ECP quantization calculation method was used to calculate E HOMO and E LUMO to account for the activities of compounds N1, N2, N3, and N4. The quantum calculation results explained are consistent with those obtained in in silico models. The successful results here may contribute to the search for new drugs for the treatment of AD.

Natural sourced and non-toxic hybrid materials for boosting the growth of lettuce in a hydroponic system.

Nanostructured hybrid materials, fabricated by combining nanosilica (n-S) obtained from rice husk and oligochitosan (OC) obtained from the shrimp shell, are environmentally friendly substances that can applied in green agriculture. In this study, 50 mg/L of nanostructured hybrid materials were applied on lettuce (Lactuca sativa L. var. longifolia) at different stages of its growth. Most of the hybrid-material-treated lettuce plants showed better growth than that of the control. The most suitable ages for applying the hybrid material to the lettuce are the ages of three weeks (H3W1) and four weeks (H4W1) to stimulate their growth. The longest leaf of the H3W1-treated lettuce increased by 7.14%, its fresh weight by 8.51%, the numbers of leaves by 4.67%, and the content of total chlorophyll by 24.89% compared with those of the control lettuce. The longest leaf of H4W1 increased by 9.52%, its fresh weight by 26.27%, the number of leaves by 9.52%, and the total chlorophyll content by 52.87% compared with those of the control lettuce. Hence, the hybrid material could be used as a green agrochemical with a great potential in modern agriculture. It can help replace and reduce the use of toxic chemical fertilizers and plant-protection products currently used on the market.

Ag/SiO2 nanoparticles stabilization with lignin derived from rice husk for antifungal and antibacterial activities.

Antibacterial materials have been developed for a long time but bacteria adapt very quickly and become resistant to these materials. This study focuses on the synthesis of a hybrid material system from lignin and silver/silica nanoparticles (Lig@Ag/SiO2 NPs) which were used against bacteria including Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and inhibited the growth of the fungal Aspergillus flavus (A. flavus). The results showed that the spherical diameter of Lig@Ag/SiO2 NPs has narrow Gaussian distribution with a range from 15 nm to 40 nm in diameter. Moreover, there was no growth of E. coli in samples containing Lig@Ag/SiO2 NPs during 72-h incubation while colonies of S. aureus were only observed at high concentrations (106 CFU/mL) although both species of bacteria were able to thrive even at low bacterial concentration when they were exposed to Ag/SiO2 or lignin. For fungal resistance results, Lig@Ag/SiO2 NPs not only reduced mycelial growth but also inhibited sporulation in A. flavus, leading to decreasing the spreading of spores into the environment. This result represents a highly effective fungal growth inhibition of Lig@Ag/SiO2 NPs compared to lignin or Ag/SiO2, which could not inhibit the growth of sporulation.

Acidolysis of Poly(ethylene terephthalate) Waste Using Succinic Acid under Microwave Irradiation as a New Chemical Upcycling Method.

A novel method of chemical upcycling of used poly(ethylene terephthalate) (PET) bottles by acidolysis with succinic acid (SA) was performed under microwave irradiation. The long polyester chain of PET was efficiently fragmented into small molecules and oligomers, such as terephthalic acid and α,ω-dicarboxylic acid oligo(ethylene succinate-co-terephthalate) (OEST). Various input molar ratios of SA/PET from 1.0 to 2.5 were used, and the product mixtures were separated successfully. The recovered terephthalic acid can be reused as a basic chemical. The α,ω-dicarboxylic acid OEST was used as a curing agent for epoxy resin. The recovered SA can be reused for further PET acidolysis. Structures of OEST were identified by Fourier transform infrared (FTIR) spectroscopy, 1H NMR spectroscopy, and electrospray ionization-mass spectrometry (ESI-MS). The presence of succinic anhydride as a side product was confirmed by FTIR and ESI-MS analyses. The evaporation of SA and the formation of volatile succinic anhydride compete with the acidolysis of PET. The minimum SA/PET ratio of 1.0 was selected so that the acidolysis was effective and without the SA recovery step by MEK treatment. OEST-1.0 was used for curing diglycidyl ether of bisphenol A. The structures and thermal properties of cured adducts were confirmed by FTIR and differential scanning calorimetry (DSC). This chemical upcycling method of PET is eco-friendly without the use of a solvent and a catalyst for the reaction, and all materials were recovered and they could be reused for novel polymer preparation.

Three-dimensional pore characterization of poly(lactic)acid/bamboo biodegradable panels.

In the context of novel environmental and energy regulations in construction (RE2020), biocomposites derived from bamboo fibers, bamboo powders, and biodegradable poly(lactic)acid polymer, all of which are renewable resources, have been investigated to meet the criteria of the novel regulations. In this work, the biocomposites were manufactured by twin-screw internal mixing at 170 °C for 5 min with a rotation speed of 60 rpm. The composites sheets were then shaped on a hydraulic press at 185 °C. Pore characterization including pore volume fraction, 3D-pore structure and morphology, and pore distribution of these materials were investigated using X-ray tomography combined with image processing (Avizo). The results show that when the bamboo fibers content is increased, an augmentation in the pore volume fraction and the number of large-volume pores could be observed. In turn, the bamboo powder-containing sheet had a significant increase in pore volume fraction, while a higher quantity of smaller pores, with uniform size, could be observed. The water absorption capacity of these composite increases with the increase of the amount of pore distribution, pore connection, and pore volume fraction. In addition, the orientation of the fibers in 3D observation, flexural mechanical properties, and thermal stability of the biocomposites are also reported in this study.

Nanocellulose and Graphene Oxide Aerogels for Adsorption and Removal Methylene Blue from an Aqueous Environment.

The characteristics of aerogel materials such as the low density and large surface area enable them to adsorb large amounts of substances, so they show great potential for application in industrial wastewater treatment. Herein, using a combination of completely environmentally friendly materials such as cellulose nanofibers (CNFs) extracted from the petioles of the nipa palm tree and graphene oxide (GO) fabricated by simple solvent evaporation, a composite aerogel was prepared by a freeze-drying method. The obtained aerogel possessed a light density of 0.0264 g/cm3 and a porosity of more than 98.2%. It was able to withstand a weight as much as 2500 times with the maximum force (1479.5 N) to break up 0.2 g of an aerogel by compression strength testing and was stable in the aquatic environment, enabling it to be reused five times with an adsorption capacity over 90%. The CNF/GO aerogel can recover higher than 85% after 30 consecutive compression recovery cycles, which is convenient for the reusability of this material in wastewater treatments. The obtained aerogel also showed a good interaction between the component phases, a high thermal stability, a 3D network structure combined with thin walls and pores with a large specific surface area. In addition, the aerogel also exhibited a fast adsorption rate for methylene blue (MB) adsorption, a type of waste from the textile industry that pollutes water sources, and it can adsorb more than 99% MB in water in less than 20 min. The excellent adsorption of MB onto the CNF/GO aerogel was driven by electrostatic interactions, which agreed with the pseudo-second-order kinetic model with a correlation coefficient R 2 = 0.9978. The initial results show that the CNF/GO aerogel is a highly durable "green" light material that might be applied in the treatment of domestic organic waste water and is completely recoverable and reusable.

Advancement of Microwave-Assisted Biosynthesis for Preparing Au Nanoparticles Using Ganoderma lucidum Extract and Evaluation of Their Catalytic Reduction of 4-Nitrophenol.

This study describes the biosynthesis of gold nanoparticles (AuNPs) using the extract of Ganoderma lucidum in the buffer zone of Bach Ma National Park, Vietnam, as a reducing and protecting agent using microwave-assisted synthesis. The as-synthesized AuNPs were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Compared to the conventional method, the proposed microwave-assisted method produced AuNPs having a small size of 22.07 ± 8.11 nm in a short synthesis time period. In excess NaBH4, the as-prepared AuNPs demonstrated good catalytic activity for reducing 4-nitrophenol to 4-aminophenol. Furthermore, AuNPs demonstrated improved reusability after four cycles. The pseudo-first-order apparent rate constant was estimated to be 0.086 min-1 at 303 K. Both the catalytic mechanism and reaction path of reduction were proposed. Moreover, activation energy and thermodynamic parameters, including activation enthalpy and entropy, were examined.

Highly Functional Materials Based on Nano-Lignin, Lignin, and Lignin/Silica Hybrid Capped Silver Nanoparticles with Antibacterial Activities.

Rice husk is one of the most abundant biomass resources in the world, yet it is not effectively used. This study focuses on the sustainably rice-husk-extracted lignin, nano-lignin (n-Lignin), lignin-capped silver nanoparticles (LCSN), n-Lignin-capped silver nanoparticles (n-LCSN), and lignin-capped silica-silver nanoparticles (LCSSN), and using them for antibacterial activities. The final n-Lignin-based products had a sphere-like structure, of which the size varied between 50 and 80 nm. We found that while n-Lignin and lignin were less effective against Escherichia coli than against Staphylococcus aureus, n-Lignin/lignin-based hybrid materials, i.e., n-LCSN, LCSN, and LCSSN, were better against E. coli than against S. aureus. Interestingly, the antimicrobial behaviors of n-LCSNs could be further improved by decreasing the size of n-Lignin. Considering the facile, sustainable, and eco-friendly method that we have developed here, it is promising to use n-Lignin/lignin-based materials as highly efficient antimicrobials without environmental concerns.

Synthesis of Novel Thermostable Polyamideimides from Bis(2-aminoethyl)terephthalamide and Dianhydrides.

Bis(2-aminoethyl)terephthalamide, an amide-containing diamine, was obtained from the aminolysis of waste poly(ethylene terephthalate) bottles. This diamine reacts with various aromatic dianhydrides to form novel polyamideimides (PAIs). The formation of amic acid or ammonium carboxylate salt intermediates depends strongly on the substituents of the dianhydrides. The electron-withdrawing substituents promote the creation of an ammonium carboxylate salt, whereas the electron donors assist with the amic acid intermediate formation. These salts and amic acids were further converted into polyimides by thermal treatment. The structures of the intermediates and PAIs were characterized by Fourier transform infrared, 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopies, and their thermal properties were determined by differential scanning calorimetry and thermogravimetry. X-ray diffraction patterns and inherent viscosity values of these PAIs were also reported. By using these chemical transformations, waste poly(ethylene terephthalate) bottles were converted into high-performance PAIs. These PAIs can be used as membrane-modifying agents for industrial separation applications.

Comprehensive Investigation of the Behavior of Polyurethane Foams Based on Conventional Polyol and Oligo-Ester-Ether-Diol from Waste Poly(ethylene terephthalate): Fireproof Performances, Thermal Stabilities, and Physicomechanical Properties.

The chemical recycling of postconsumer poly(ethylene terephthalate) (PET) bottles to produce highly thermally stable polyurethane foam (r-PUF) with excellent flame-retardant (FR) performance could be applied on an industrial scale to create a sustainable recycling industry. The advantage of oligo-ester-ether-diol obtained from waste PET glycolysis is its application in r-PUF, generating a durable foam with excellent fire resistance at rather low loadings of phosphorus-nitrogen FRs (P-N FRs), especially in high moisture environments. Compared to polyurethane foam from commercial polyol (c-PUF), r-PUF is notably more thermally stable and efficient in terms of flame retardancy, even without adding FRs. By incorporating 15 php diammonium phosphate (DAP) as a P-N FR, r-PUF/DAP self-extinguished 5 s after the removal of the 2nd flame application with a limited oxygen index value of 24%. However, for c-PUF, a much higher DAP (30 php) loading did not exhibit any rating in the vertical burning test. The aromatic moiety in the oligo-ester-ether-diol structure strongly enhanced the compressive strength and thermal stability. The positive outcomes of this study also confirmed that the r-PUF/DAP prepared from oligo-ester-ether-diol not only satisfied the fire safety requirements of polymer applications but also contained a high percentage of postconsumer PET, which could help reduce the amount of recycled polymer materials and improve waste management.

Novel Nitrogen-Phosphorus Flame Retardant Based on Phosphonamidate: Thermal Stability and Flame Retardancy.

A novel nitrogen-phosphorus flame retardant (P-N FR) based on phosphonamidate, dimethyl N,N'-1,3-phenylenebis(P-methylphosphonamidate) (DMPMP), was successfully synthesized and its flame-retarding performances and thermal degradation were compared with those of other P-N FRs and a phosphorus-based FR such as resorcinol bis(diphenyl phosphate) (RDP). DMPMP was applied to acrylonitrile-butadiene-styrene (ABS) and ethylene-vinyl acetate (EVA) to investigate the factors governing the flame-retarding behaviors of P-N FRs which would make them efficient for noncharrable polymers. V-0 ratings were achieved at 20 wt % loading of DMPMP for ABS and at a much lesser amount of DMPMP loading (10 wt %) for EVA. Meanwhile, no rating and V-2 were achieved even at 20-30 wt % loading of other P-N FRs or RDP for ABS and EVA, respectively. The results from thermogravimetric analysis, Fourier transform infrared, and UL-94V indicated that DMPMP is a highly efficient FR and acts mainly in a gas-phase flame-retarding mode of action. The condensed phase of DMPMP also contributed to the flame retardancy property through -NH- groups which tendentiously generate a nitrogen-phosphorus-rich residue because of the intermolecular coupling transesterification reaction. These results demonstrated the assumption that DMPMP has a high P content and good hydrostability, which exhibits good flame retardancy for noncharrable polymers such as ABS and EVA.

Excellent Fireproof Characteristics and High Thermal Stability of Rice Husk-Filled Polyurethane with Halogen-Free Flame Retardant.

The thermal stabilities, flame retardancies, and physico-mechanical properties of rice husk-reinforced polyurethane (PU-RH) foams with and without flame retardants (FRs) were evaluated. Their flammability performances were studied by UL94, LOI, and cone calorimetry tests. The obtained results combined with FTIR, TGA, SEM, and XPS characterizations were used to evaluate the fire behaviors of the PU-RH samples. The PU-RH samples with a quite low loading (7 wt%) of aluminum diethylphosphinate (OP) and 32 wt% loading of aluminum hydroxide (ATH) had high thermal stabilities, excellent flame retardancies, UL94 V-0 ratings, and LOIs of 22%-23%. PU-RH did not pass the UL94 HB standard test and completely burned to the holder clamp with a low LOI (19%). The cone calorimetry results indicated that the fireproof characteristics of the PU foam composites were considerably improved by the addition of the FRs. The proposed flame retardancy mechanism and cone calorimetry results are consistent. The comprehensive FTIR spectroscopy, TG, SEM, and XPS analyses revealed that the addition of ATH generated white solid particles, which dispersed and covered the residue surface. The pyrolysis products of OP would self-condense or react with other volatiles generated by the decomposition of PU-RH to form stable, continuous, and thick phosphorus/aluminum-rich residual chars inhibiting the transfer of heat and oxygen. The PU-RH samples with and without the FRs exhibited the normal isothermal sorption hysteresis effect at relative humidities higher than 20%. At lower values, during the desorption, this effect was not observed, probably because of the biodegradation of organic components in the RH. The findings of this study not only contribute to the improvement in combustibility of PU-RH composites and reduce the smoke or toxic fume generation, but also solve the problem of RHs, which are abundant waste resources of agriculture materials leading to the waste disposal management problems.

Novel Oligo-Ester-Ether-Diol Prepared by Waste Poly(ethylene terephthalate) Glycolysis and Its Use in Preparing Thermally Stable and Flame Retardant Polyurethane Foam.

Rigid polyurethane foam (PUF) was successfully prepared from a novel oligo-ester-ether-diol obtained from the glycolysis of waste poly(ethylene terephthalate) (PET) bottles via reaction with diethylene glycol (DEG) in the presence of ZnSO4·7H2O. The LC-MS analysis of the oligodiol enabled us to identify 67 chemical homologous structures that were composed of zero to four terephthalate (T) ester units and two to twelve monoethylene glycol (M) ether units. The flame retardant, morphological, compression, and thermal properties of rigid PUFs with and without triphenyl phosphate (TPP) were determined. The Tg values showed that TPP played a role of not only being a flame retardant, but also a plasticizer. PUF with a rather low TPP loading had an excellent flame retardancy and high thermal stability. A loading of 10 wt % TPP not only achieved a UL-94 V-0 rating, but also obtained an LOI value of 21%. Meanwhile, the PUF without a flame retardant did not achieve a UL-94 HB rating; the sample completely burned to the holder clamp and yielded a low LOI value (17%). The fire properties measured with the cone calorimeter were also discussed, and the results further proved that the flame retardancy of the PUF with the addition of TPP was improved significantly. The polymeric material meets the demands of density and compression strength for commercial PUF, as well as the needs of environmental development. The current study may help overcome the drawback of intrinsic high flammability and enlarge the fire safety applications of materials with a high percentage of recycled PET.

Functional Nanostructured Oligochitosan⁻Silica/ Carboxymethyl Cellulose Hybrid Materials: Synthesis and Investigation of Their Antifungal Abilities.

Functional hybrid materials were successfully synthesized from low-cost waste products, such as oligochitosan (OCS) obtained from chitosan (one of the main components in crab shells) and nanosilica (nSiO2) obtained from rice husk, in a 1:1 ratio (w/w), and their dispersion in the presence of carboxymethyl cellulose at pH 7 was stable for over one month without aggregation. The molecular weights, chemical structures, morphologies, and crystallinities of the obtained materials were characterized by GPC, FTIR, TEM, and XRD, respectively. The antifungal effects of OCS, nSiO2, and the OCS/nSiO2 hybrid materials were investigated via a disk-diffusion method. The results showed that the nanohybrid materials had better resistance to Phytophthora infestans fungus than the individual components, and a concentration of the OCS2/nSiO2 hybrid material of 800 mg L-¹ was the lowest concentration where the material completely inhibited Phytophthora infestans growth, as measured via an agar dilution method. This study not only creates a novel environmentally friendly material with unique synergistic effects that can replace current toxic agrochemicals but also can be considered a new platform for further research in green agricultural applications.