Resin Acids Research Articles

Adhesion durability of dual-cure resin cements and acid–base resistant zone formation on human dentin

ObjectivesBond durability and resistance to acid-base challenge of dentin with dual-cure resin cement have been rarely investigated. The purpose of this study was to evaluate dentin bond strength and observe the adhesive-dentin interface after acid-base challenge using three different dual-cure resin cements. MethodsThirty dentin surfaces from caries-free human premolars were ground and bonded with one of three dual-cure resin cements: PANAVIA V5 (V5), ESTECEM II (E II) and Rely X Ultimate (RXU) and thermocycled for 0, 5,000 and 10,000 cycles. A microtensile bond strength (μTBS) test was undertaken and the interface of the bonded specimens after acid-base challenge was examined by SEM. ResultsThe μTBS of V5 exhibited a stable bond strength despite thermal cycling while the bond of EII and RXU after 10,000 cycles dropped significantly among all thermal cycle periods (p<0.05). An acid-base resistant zone (ABRZ) was observed in all groups, however, the morphology of the bonded interface differed among the tested cements. ConclusionBonding durability to dentin and ABRZ morphologies differed among the cements evaluated. PANAVIA V5 cement system with tooth primer provided the most reliable bond strength and was best able to resist the acid–base challenge.

Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd–acrylic resins

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. Therefore, the goal of this work was to prepare and evaluate various properties of HAAR. These materials were obtained by miniemulsion polymerization from a hyperbranched alkyd resin (HAR), methyl methacrylate (MMA), butyl acrylate (BA), and acrylic acid (AA). The proportions of HAR:acrylic monomers were as follow: 50:50 (HAAR1), 40:60 (HAAR2), 30:70 (HAAR3), and 20:80 (HAAR4). The particle size increased with the content of HAR, but the colloidal stability, critical deformation, zeta potential, thermal stability, and hardness followed an opposite behavior. The order of colloidal stability of the HAAR miniemulsions was HAAR4 > HAAR3 > HAAR2 > HAAR1. The particle morphology of the HAAR was mainly core–shell, but acrylic and alkyd particles were also observed. In addition, all HAAR initially exhibited a reduction in complex viscosity (η*) with the increase in angular frequency. The thermal stability of the HAR was lower than that of the HAAR. The HAAR showed better resistance against a 0.10 M sodium hydroxide (NaOH) solution than HAR.

Membrane-free electrodeionization using phosphonic acid resin for nickel containing wastewater purification

Membrane-free elctrodeionization (MFEDI) is a technology in which ion exchange resins can be electrically regenerated in situ. It allows the purification of nickel containing wastewater, as well as the production of concentrated nickel solution, which could be recycled. However, proper choice of packed ion exchange resins is crucial to MFEDI. In this study, emphasis was placed on improving the performance of MFEDI by the introduction of phosphonic acid resin. Much of this information was obtained by analyzing the characteristic of phosphonic acid resin, the stack configuration of packed ion exchange resin and the mechanism of electrical regeneration. The layered hybrid resin bed filled with both phosphonic acid resin and weak acid resin was found to be the most effective stack configuration for the adjustment of concentrate pH. The purification study demonstrated that, pure water with conductivity below 0.3 μS/cm was produced. The electrical regeneration study showed that, the average concentrate nickel concentration was over 95 mg/L, the concentrate pH was around 7.4, thus precipitation of nickel hydroxide was prevented. Moreover, in comparison to previous study, in which MFEDI was packed with hybrid strong acid and weak base resin and hybrid weak acid and strong base resin, the water recovery ratio was increased from 88.0% to 89.5%, the energy consumption was decreased from 5.6 to 4.1 kWh/m3 wastewater. The regeneration mechanism study revealed that, more than 72% of resin regeneration was attributed to the water splitting, and less than 28% of resin regeneration was contributed by the water electrolysis.

Matching the Activity of Homogeneous Sulfonic Acids: The Fructose-to-HMF Conversion Catalyzed by Hierarchically Porous Sulfonic-Acid-Functionalized Porous Organic Polymer (POP) Catalysts

Three HO3S-functionalized porous organic polymers (HO3S-POPs) with high surface areas (500–700 m2/g) and a broad range of porosity profiles were synthesized and tested against homogeneous-acid analogs and commercially available acid resins to evaluate their relative catalytic activities in the acid-catalyzed conversion of fructose to HMF. Comparison of fructose conversions and HMF yields demonstrates that the sulfonated POPs with hierarchical porosity can achieve catalytic activities that rival those of their homogeneous counterparts. The associated HMF selectivities represent optimized values that increase with higher temperature and faster heating, both of which can reduce the reaction time and limit product decomposition. Due to their intrinsically high mesoporosity and number of accessible acid sites, these HO3S-POPs also outperform the commercially available Amberlyst 15 resin catalyst and its crushed variant.

Polymer conjugation optimizes EDTA as a calcium-chelating agent that exclusively removes extrafibrillar minerals from mineralized collagen

During development of mineralized collagenous tissues, intrafibrillar mineralization is achieved by preventing mineralization precursor inhibitors that are larger than 40 kDa from entering the collagen fibrils. Such a property is incorporated in the design of a calcium chelator for dentin bonding in the etch-and-rinse technique that selectively demineralizes extrafibrillar apatite while leaving the intrafibrillar minerals intact. This strategy prevents complete demineralization of collagen fibrils, avoids collapse of collagen that blocks resin infiltration after air-drying, and protects the completely demineralized fibrils from bacteria colonization and degradation by endogenous proteases after resin bonding. In the present study, a water-soluble glycol chitosan-EDTA (GCE) conditioner was synthesized by conjugation of EDTA, an effective calcium chelator, to high molecular weight glycol chitosan, which exhibits weak chelation property. The GCE conjugate was purified, characterized by FTIR, 1H NMR, isothermal titration calorimetry and ICP-AES, and subjected to size exclusion dialysis to recover molecules that are >40 kDa. The optimal concentration and application time for etching dentin were determined by bond strength testing to ensure that the dentin bonding results were comparable to phosphoric acid etching, and maintained equivalent bond strength after air-drying of the conditioned collagen matrix. Extrafibrillar demineralization was validated with transmission electron microscopy. Inhibition of endogenous dentin proteases was confirmed using in-situ zymography. The water-soluble GCE dentin conditioner was non-cytotoxic and possessed antibacterial activities against planktonic and single-species biofilms, supporting its ongoing development as a dentin conditioner with air-drying, anti-proteolytic and antibacterial properties to enhance the durability of bonds created using the etch-and-rinse bonding technique. Statement of SignificanceThe current state-of-the-art techniques for filling decayed teeth with plastic tooth-colored materials require conditioning the mineralized, biofilm-covered, decayed dentin with acids or acid resin monomers to create a surface layer of completely- or partially-demineralized collagen matrix for the infiltration of adhesive resin monomers. Nevertheless, fillings prepared using these strategies are not as durable as consumers have anticipated. Conjugation of polymeric glycol chitosan with EDTA produces a new conditioner for dentin bonding that demineralizes only extrafibrillar dentin, reduces endogenous protease activities and kills biofilm bacteria. The high molecular weight glycol chitosan-EDTA is non-cytotoxic to the key regenerative players within the dentin-pulp complex. This advance permits dry bonding and the use of hydrophobic resins.

Rosin Product Review

Rosin is the non-volatile exudate of pine resin with hydrophobic characteristics that are widely used and modified as a precursor for many industrial applications such as paints, inks and adhesives. The review paper discusses the rosin, its nature, processing, production material development for green science. The composite materials have been designed and tailored with respect to desired applications to offer a potential replacement of petrochemical use. Rosin consists of different resin acids that can undergo isomerisation at elevated temperatures and interchange its form, which, can be used as a rigid building block to manipulate their mechanical properties and crystallisation behaviours. Modified rosin epoxy binders have been recognised as materials with resistance to a wide variety of chemical conditions that can be used to fabricate a variety of reinforced constructions. Rosin has been employed in foam making in addition to composite material, depicting its ability as a crosslinker.

Induced antimicrobial activity in heat‐treated woodchips inhibits the activity of the invasive plant pathogen Phytophthora ramorum

The antimicrobial activity of heat‐treated woodchips of three woody host species against the invasive oomycete plant pathogen Phytophthora ramorum was investigated to assess the potential of heated woodchips to suppress disease. Results demonstrated that heat‐treated woodchips of pine (Pinus sylvestris), Japanese larch (Larix kaempferi) and rhododendron (Rhododendron ponticum) inhibited recovery of P. ramorum spores and mycelium compared with similar material that had only been air‐dried. Effects were most evident with pine and larch; inhibition was maintained even when larch woodchips were diluted with soil. In vitro assays using methanol crude extracts from woodchips of the three species showed they all had an inhibitory effect on P. ramorum zoospores and reduced chlamydospore germination compared with air‐dried wood extracts. Chemical analysis of the extracts revealed several induced compounds were present but in different concentrations for each species. Coniferaldehyde was the most active inhibitor against spores and mycelium, while the dominant resin acids, dehydroabietic and abietic acid, decreased the minimum inhibitory concentration of phenolic compounds tested against P. ramorum but were ineffective when used alone. An array of compounds, including dehydroabietic acid, methyl abietate, α‐pinene and 3‐carene, occurred at elevated levels in the living tissue of Japanese larch bark attacked by P. ramorum. These compounds may be part of the induced resistance response of larch to P. ramorum. Results of a field trial using heat‐treated and air‐dried woodchips were consistent with the crude extract bioassay results, suggesting that heat‐treated woody materials have potential to reduce the survival of P. ramorum under natural conditions.

Hydroconversion of abietic acid into value-added fuel components over sulfided NiMo catalysts with varying support acidity

The hydroconversion of abietic-type rosin acids, with a tri-ring structure into mono-ring structure hydrocarbons, was investigated. The reactions were performed at 380 °C under 7500 kPa of H2 pressure over sulfided NiMo catalysts supported on alumina, USY-zeolite and mixed alumina/USY-zeolite. The NiMo supported catalysts were characterized using N2-physisorption, ethylamine-temperature programmed desorption (ethylamine-TPD), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and temperature programmed oxidation (TPO). The sulfided NiMo supported on only USY-zeolite showed the highest selectivity towards production of the mono-ring hydrocarbons such as methyl cyclopentane due to the strong Brønsted acid character of USY-zeolite. Whereas, the sulfided NiMo supported on alumina with weaker Brønsted acidity showed strong selectivity towards the di and tri-ring hydrocarbons such as dimethyl tetralins and retene. Moreover, the selectivities towards the mono-ring hydrocarbons over the NiMo catalysts with mixed supports were lower with a higher alumina content. Finally, the results show that the sulfided NiMo catalyst supported on alumina/USY-zeolite support with 50 wt% zeolite achieved a good level of deoxygenation, ring opening and cracking of the rosin acid while avoiding excessive coke formation.

Dehydroabietic Acid Suppresses Inflammatory Response Via Suppression of Src-, Syk-, and TAK1-Mediated Pathways.

Dehydroabietic acid (DAA) is a naturally occurring diterpene resin acid derived from coniferous plants such as Pinus and Picea. Various bioactive effects of DAA have been studied including antibacterial, antifungal, and anticancer activities. However, the anti-inflammatory mechanism of DAA remains unclear. We evaluated the anti-inflammatory effect of DAA in macrophage cell lines. Dehydroabietic acid clearly reduced nitric oxide (NO) production and inflammatory gene expression decreased according to RT-PCR results. Dehydroabietic acid displayed anti-inflammatory activity at the transcriptional level in results from NF-κB- or AP-1-mediated luciferase assays. To identify the DAA target protein, we investigated NF-κB and AP-1 pathways by Western blotting analysis. Dehydroabietic acid suppressed the activity of proto-oncogene tyrosine protein kinase (Src) and spleen tyrosine kinase (Syk) in the NF-κB cascade and transforming growth factor beta-activated kinase 1 (TAK1) in the AP-1 cascade. Using overexpression strategies, we confirmed that DAA targeted these kinases. Our findings demonstrate the anti-inflammatory effects and molecular mechanism of DAA. This suggests that DAA has potential as a drug or supplement to ameliorate inflammation.

The impact of sulfate ions on the ion exchange of rare earth elements

The influence of sulfate versus chloride media on the adsorption of rare earth elements (REE) by strong acid and iminodiacetic acid resins was investigated. For the strong acid resin, Lewatit MonoPlus SP 112, the adsorption constants recorded for La, Sm and Er from MgSO4 solution were much lower compared to the values recorded from MgCl2 solution. The adsorption isotherms constructed for Sm from 0.5 M MgSO4 and 0.5 M MgCl2 solution also showed a substantial decrease in the equilibrium resin capacity that could be attained from sulfate solution. In addition, it was determined that the extraction strength of Sm from 0.5 M MgSO4 solution was unaffected by a change in solution pH from 1 to 3, despite the significant change in the aqueous speciation of SO42− and Sm3+ over this range. For the iminodiacetic acid resin, Purolite S930Plus, a similarly large decrease in the La adsorption constants was recorded from MgSO4 solution compared to MgCl2 solution which resulted in a large shift in the extraction curve to higher pH (pH50 = 1.9 in 1 M MgCl2 solution and 2.8 in 1 M MgSO4 solution). For both resins the decreased adsorption strength of the REE in sulfate solution also resulted in a decreased selectivity for the REE over key impurity ions. For instance the selectivity of the strong acid resin for Sm over Al was more than halved in MgSO4 versus MgCl2 solution, whereas the selectivity of the iminodiacetic acid resin for La over Mg decreased by an order of magnitude in MgSO4 versus MgCl2 solution (pH 4).

Removal of hexavalent chromium in soil by lignin-based weakly acidic cation exchange resin

Abstract The adsorption of Cr(VI) from soil onto lignin-based weakly acidic cation exchange resin (LBR) has been investigated. Lignin is a three-dimensional amorphous polymer composed of methoxylated phenylpropane units. The unique structure and chemical properties render the lignin suitable for the remediation of hexavalent chromium in the soil. Soil column leaching experiments were conducted to optimize the adsorption conditions. The effects of contact time, pH, adsorbent dosage and temperature on the adsorption of Cr(VI) onto the LBR have been investigated. Experiment data were then correlated with Freundlich and Langmuir isotherms. The Langmuir isotherm model fits the experimental data better than the Freundlich isotherm. It was found that the LBR has a high adsorption capability for Cr(VI) (3.95 mg·g−1) with a removal rate of 91.9%. Thus, LBR can serve as a good absorbent for the reduction of the concentration of Cr(VI) in soil.

Identification of Toxicants from a Highly C10–C40‐Contaminated Sediment Influenced by the Wood Industry: Petroleum Hydrocarbons or Biogenic Organic Compounds?

Sediment from a log pond located in south Finland contained 15 000 to 50 000 mg/kg dry weight of C10 -C40 hydrocarbons. It was unclear whether they originated from the hydraulic fluid of the log hoist or the wood extractives. In the present study, methods of effect-directed analysis were used for the identification of toxicants. A combination of fractionation, biotesting, and chemical analyses revealed that the key toxicant of log pond sediment was retene, a dialkyl-substituted phenanthrene derived from wood resin acids. In addition, the most toxic fraction included 3 other wood-originated diterpenic compounds. Typical wood extractives such as sesquiterpenes and odd-carbon number alkanes in the range C21 -C33 were identified in the fraction, which showed minor genotoxic potency. The most polar fraction contained triterpenes and showed estrogenic activity. No evidence for the presence of hydraulic fluid in sediment was found. The study also indicated that in cases where the organic matter content of sediment or soil is high, using the results of standard mineral oil analysis in risk management can lead to incorrect actions because standard methods do not differentiate petroleum hydrocarbons from biogenic hydrocarbons. Environ Toxicol Chem 2019;9999:1-11. © 2019 SETAC.

Selective recovery of polyphenols from MDF process waters by adsorption on a macroporous, cross-linked pyrrolidone-based resin

AbstractA scalable, fixed-bed adsorption system for the removal and selective recovery of polyphenols (lignans and stilbenes) from medium-density fiberboard (MDF) process waters was developed. Before adsorption, fibers and non-colloidal substances were removed from process water by centrifugation, while colloidal fatty and resin acids were removed by filtration through a 30-kDa cut-off membrane. Polyphenols were then isothermally adsorbed on a medium-pressure liquid chromatography (MPLC) column packed with Divergan® RS, a regenerable macroporous, cross-linked pyrrolidone-based [polyvinylpolypyrrolidone (PVPP)] resin. Loading at acidic pH and subsequent gradient elution of polyphenols with methanol were monitored at 280 nm, and elution conditions for selective polyphenol recovery were optimized based on gas chromatography/mass spectrometry (GC/MS) analyses of the obtained fractions. Lignans were eluted in successive fractions containing the individual lignans in different proportions, followed by pinosylvin in a separate fraction. The capacity of the PVPP for hydroxymatairesinol (HMR) as a model lignan was determined to be 37.4 mg g−1 at 1% breakthrough. Highly polar substances such as sugars and sugar alcohols, however, were not retained on the column and remained in the flow-through. The results revealed the benefits of PVPP for the recovery of potentially valuable polyphenols from MDF process waters while reducing carbon load and toxicity for subsequent biological treatment.

Sustainable elastomers derived from cellulose, rosin and fatty acid by a combination of "graft from" RAFT and isocyanate chemistry.

Utilization of natural sustainable feedstock to fabricate polymers has attracted remarkable attention. In this work, we reported a strategy to prepare a series of grafted copolymers from rosin, fatty acids and ethyl cellulose. The process involved the preparation of EC-based macro-RAFT agent through a simple esterification reaction, followed by a "grafting from" reversible addition-fragmentation chain transfer polymerization (RAFT) of DAGMA (derived from rosin) and LMA (derived from fatty acid) to achieve a class of EC-g-P(DAGMA-co-LMA) graft copolymers with a tunable Tg tuned by the DAGMA/LMA molar ratio. Then, hexamethylene diisocyanate (HDI) was used to crosslink these graft copolymers. The mechanical and dynamic thermo-mechanical properties of tests showed that elastic recovery values of copolymers were enhanced to 90%, as compared to the un-crosslinked samples. Additionally, all these polymers showed an excellent UV absorption performance. This study provides a facile way to fabricate biobased elastomeric materials with improved mechanical properties.

New nitrogen-containing polymer with strengthening and hydrophobizing effect on paper and cardboard

A new nitrogen-containing product based on tall oil rosin, adipic acid and diethylenetriamine is capable of simultaneously exerting a strengthening and hydrophobizing effect on paper and cardboard made both from primary (cellulose) and secondary (waste paper) fibers. The strengthening effect is due to the presence in its structure of nitrogen-containing groups –NH 2 and –NH– capable of forming additional interfiber bonds with negatively charged hydroxyl groups of cellulose macromolecules. Hydrophobizing effect is provided by resin acids included in the product. Preparation of the product with preset physicochemical properties (acid number not more than 40 mg KOH/g, solubility in water, cationic character and thermal stability at a temperature of at least 135 °C) was carried out in three stages. The first stage is the tall oil resin acids modification with diethylenetriamine; the second stage is the polycondensation of the resin acid amides obtained in the first stage with adipic acid and diethylenetriamine; the final stage is water dilution of the product formed in the second stage, to a solids content of 10–12 %. In paper masses containing primary and secondary fibers glued with alkylketene dimers (Fennosize KD 225 YP), the replacement of the import strengthening agent (cationic starch Hi-Cat) with a new nitrogen-containing product allows us, first, to increase the dry strength of paper and cardboard and improve hydrophobicity and, secondly, to prevent undesirable process of “sticking” when storing paper samples (elementary layers of cardboard).

Anti-inflammatory activity and accelerated stability studies of crude extract syrup of &lt;i&gt;Cannabis sativa&lt;/i&gt;

Purpose: To formulate Cannabis sativa-based syrup and investigate its anti-inflammatory potential and the stability of the formulation under stress conditions.Methods: The syrup was prepared using different combinations of crude C. sativa resin, propylene glycol, aspartame, sucrose, sodium metabisulphite (SMBs) and ethylenediaminetetraacetic acid (EDTA). The stability of the formulations was determined under accelerated temperature conditions. The anti-inflammatory activity of the resin and different formulations were evaluated by the egg albumin induced paw edema model in rats. Biochemical assay was determined by Reitman and Frankel colorimetric assay method while hematological assay was evaluated by standard protocols.Results: EDTA-containing syrup (CE) was the most stable with estimated shelf-life of 2204 days (K25ºC, 4.78 x 10-5/day). Higher propylene glycol levels significantly improved anti-inflammatory activity compared to those containing a lower amount. All the formulations showed anti-inflammatory activity higher than the crude resin with a dose-dependent inhibition of paw edema compared with the control. There was no significant difference (p &lt; 0.05) between the serum glutamate-oxaloacetate transaminase (SGOT, 13.821 ± 0.190 - 16.008 ± 1.012), serum glutamate-pyruvate transaminase (SGPT, 19.241 ± 1.027 - 22.901 ± 1.093) and urea (9.812 ± 0.252 - 10.054 ± 0.252) levels of the treated and 16.856 ± 1.053, 24.960 ± 0.101 and 10.654 ± 0.925 units/L of the control animals respectively. With the exception of eosinophil that disappeared from the blood in the third week, all the hematological parameters showed a gradual increase in lymphocytes, neutrophils, monocytes, packed cell volume (PCV), white and red blood cell counts in the third week compared to control.Conclusion: Formulation of C. sativa as syrup using efficient carriers improves the pharmacological activity of the crude extract. SMBs and EDTA significantly enhance the stability of the syrup with no observable biochemical and hematological changes in treated animalsKeywords: Cannabis sativa, Syrup, Anti-inflammatory, Stability, Hematological

Molecular characterization of organic aerosols in the Kathmandu Valley, Nepal: insights into primary and secondary sources

Abstract. Organic atmospheric aerosols in the Hindu Kush–Himalayas–Tibetan Plateau region are still poorly characterized. To better understand the chemical characteristics and sources of organic aerosols in the foothill region of the central Himalaya, the atmospheric aerosol samples were collected in Bode, a suburban site of the Kathmandu Valley (KV) over a 1-year period from April 2013 to April 2014. Various molecular tracers from specific sources of primary organic aerosols (POAs) and secondary organic aerosols (SOAs) were determined. Tracer-based estimation methods were employed to apportion contributions from each source. The concentrations of organic carbon (OC) and elemental carbon (EC) increased during winter with a maximum monthly average in January. Levoglucosan (a molecular tracer for biomass burning, BB) was observed as the dominant species among all the analyzed organic tracers and its annual average concentration was 788±685 ng m−3 (ranging from 58.8 to 3079 ng m−3). Isoprene-SOA (I-SOA) represented a high concentration among biogenic-SOA tracers. For the seasonality, anhydrosugars, phenolic compounds, resin acid, and aromatic SOA tracer showed similar seasonal variations with OC and EC while monosaccharides, sugar alcohols, and I-SOA tracers showed lower levels during winter. BB contributed a significant fraction to OC, averaging 24.9 %±10.4 % during the whole year, and up to 36.3 %±10.4 % in the post-monsoon season. On an annual average basis, anthropogenic toluene-derived secondary OC accounted for 8.8 % and biogenic secondary OC contributed 6.2 % to total OC. The annual contribution of fungal spores to OC was 3.2 % with a maximum during the monsoon season (5.9 %). For plant debris, it accounted for 1.4 % of OC during the monsoon. Therefore, OC is mainly associated with BB and other anthropogenic activity in the KV. Our findings are conducive to designing effective measures to mitigate the heavy air pollution and its impacts in the KV and surrounding area.

Synthesis of a novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano zinc oxide and its application in poly (lactic acid) resin

A novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano ZnO (A4‐d‐ZnO) was synthesized and applied in poly (lactic acid) (PLA). Fourier transform infrared (FTIR), solid state nuclear magnetic resonance (SSNMR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS) were used to confirm the chemical structure of A4‐d‐ZnO. The thermal stability and the flame‐retardant properties of the PLA composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI), vertical burning test (UL‐94), and micro combustion calorimeter (MCC) test. The results of XPS showed that A4‐d‐ZnO has been synthesized, and the doping ratio of ZnO was 7.2% in flame‐retardant A4‐d‐ZnO. TGA results revealed that A4‐d‐ZnO had good char forming ability (40 wt% at 600°C). The results of LOI, vertical burning test, and MCC showed that PLA/5%A4‐d‐ZnO composite acquired a higher LOI value (24%), higher UL94 rating, and lower pk‐HRR (501 kW/m2) comparing with that of pure PLA. It indicated that a small amount of flame‐retardant A4‐d‐ZnO could achieve great flame‐retardant performance in PLA composites. The catalytic chain scission effect of A4‐d‐ZnO could make PLA composites drip with flame and go out during combustion, which was the reason for the good flame‐retardant property. Moreover, after the addition of A4‐d‐ZnO, the impaired mechanical properties of PLA composites are minimal enough.

Production of HMF from glucose using an Al3+-promoted acidic phenol-formaldehyde resin catalyst

An Al3+-modified formaldehyde-p-hydroxybenzenesulfonic acid resin catalyst (Al-SPFR) was synthesized through a hydrothermal method. N2 adsorption–desorption experiment and acid–base titration revealed that the Al-SPFR catalyst had better texture properties and higher strong acid content than the previously prepared unmodified SPFR. The effects of reaction time and temperature, catalyst loading, and water content in water/GVL mixture were investigated for glucose dehydration using Al-SPFR as the catalyst. An HMF yield of 47.4% was obtained at 170 °C for 2 h in the biphasic GVL/H2O medium. Further performing a five-cycle experiment, the HMF yield initially decreased and then remained fairly constant, and the recyclability of the Al-SPFR was reasonable.

Topochemical engineering of composite hybrid fibers using layered double hydroxides and abietic acid.

Topochemical engineering of hybrid materials is an efficient way of synthesizing hydrophobic and highly tensile fiber composites by utilizing the intermolecular hydrogen bonds in natural materials. These materials include wood pulp fibers, abietic acid (resin acid) and inexpensive metal salts. In this work, a hybrid composite was created using bleached and unbleached kraft pulp fibers as cellulose platform. In situ co-precipitation of layered double hydroxide (LDH) was performed to grow LDH crystals on the surface of the cellulose fibers, followed by the immobilization of abietic acid (AA) on LDH-grafted cellulose. Here we aimed to benefit from the hydrogen bonding between –OH groups of cellulose and LDH, and the –COOH groups of AA to obtain charge-directed assembly of one material on the other material. Thus, composite hybrid fibers (C-HF) were produced and then characterized by optical (CAM), spectroscopic (XRD, IR) and microscopic techniques (SEM) to determine their average length and distribution, structure and purity, bonding, and morphology. These fibers further were tested for water contact angle (hydrophobicity), oil absorption (lipophilicity), tensile strength and ISO brightness measurements. The performance of C-HF was compared with unmodified reference fibers (REF), fibers composed with only AA (C-F) and LDH-hybridized fibers (HF). The results revealed a variety of correlations between materials and their properties due to characteristic surface morphology, functional groups, hydrogen bonding and natural co-materials such as lignin and hemicelluloses. Attractive and repulsive van der Waals forces between material entities play a crucial role in the resulting properties.