Tung oil-based waterborne UV-curable coatings via cellulose nanofibril stabilized Pickering emulsions for self-healing and anticorrosion application.

In this study, waterborne UV-curable coatings with self-healing properties based on transesterification were prepared using renewable biomass resources for anti-corrosion application. Tung oil (TO)-based oligomer (TMHT) was synthesized through Diels-Alder reaction of TO with maleic anhydride, subsequent ring opening reaction with hydroxyethyl acrylate (HEA), and final neutralize reaction with triethylamine. A series of waterborne UV-curable coatings were prepared from cellulose nanofibrils (CNF) stabilized TMHT-based Pickering emulsions after drying and UV light-curing processes. It is suggested that CNF significantly improved the storage stability of Pickering emulsions. The obtained waterborne UV-curable coatings with CNF of 1-3 wt% exhibited remarking coating and mechanical performance (pencil hardness up to 5 H, adhesion up to 2 grade, flexibility of 2 mm, tensile strength up to 11.6 MPa, etc.), great transmittance (82.3 %-80.8 %) and great corrosion resistance (|Z|0.01Hz up to 5.4 × 106 Ω·cm2). Because of the presence of the dynamic ester bonds in TMHT, the coatings exhibited excellent self-healing performance (78.05 %-56.34 %) at 150 °C without catalyst and external force. More importantly, the |Z|0.01Hz of the self-healing coating was higher than that of the scratched coating, indicating that the self-healing performance could extend the service life of the coating in corrosion resistant application.

Tough and strong sustainable thermoplastic elastomers nanocomposite with self-assembly of SI-ATRP modified cellulose nanofibers.

The ingenious design of sustainable thermoplastic elastomers (STPEs) is of great significance for the goal of the sustainable development. However, the preparation of STPEs with good mechanical performance is still complicated and challenging. Herein, to achieve a simple preparation of STPEs with strong mechanical properties, two biobased monomers (tetrahydrofurfuryl methacrylate (THFMA) and lauryl methacrylate (LMA)) were copolymerized into poly (THFMA-co-LMA) (PTL) and grafted onto TEMPO oxidized cellulose nanofiber (TOCN) via one-pot surface-initiated atom transfer radical polymerization (SI ATRP). The grafting modified TOCN could be self-assembled into nano-enhanced phases in STPEs, which are conducive to the double enhancement of the strength and toughness of the STPEs, and the size of nano-enhanced phases is mainly affected by TOCN fiber length and molecular weight of grafting chains. Especially, with the addition of 7 wt% TOCN, tensile strength, tensile strain, toughness, and glass transition temperature (Tg) of TOCN based STPEs (TOCN@PTL) exhibited 140 %, 36 %, 215 %, and 6.8 °C increase respectively, which confirmed the leading level in the field of bio-based elastomers. In general, this work constitutes a proof for the chemical modification and self-assembly behavior of TOCN by one-pot SI ATRP, and provides an alternative strategy for the preparation of high-performance STPEs.

Wood-Derived Polymers from Olefin-Functionalized Lignin and Ethyl Cellulose via Thiol-Ene Click Chemistry.

Lignin and cellulose derivatives have vast potential to be applied in polymer materials. The preparation of cellulose and lignin derivatives through esterification modification is an important method to endow cellulose and lignin with good reactivity, processability and functionality. In this study, ethyl cellulose and lignin are modified via esterification to prepare olefin-functionalized ethyl cellulose and lignin, which are further used to prepare cellulose and lignin cross-linker polymers via thiol-ene click chemistry. The results show that the olefin group concentration in olefin-functionalized ethyl cellulose and lignin reached 2.8096 mmol/g and 3.7000 mmol/g. The tensile stress at break of the cellulose cross-linked polymers reached 23.59 MPa. The gradual enhancement in mechanical properties is positively correlated with the olefin group concentration. The existence of ester groups in the cross-linked polymers and degradation products makes them more thermally stable. In addition, the microstructure and pyrolysis gas composition are also investigated in this paper. This research is of vast significance to the chemical modification and practical application of lignin and cellulose.

Recent Advances in Degradation of Polymer Plastics by Insects Inhabiting Microorganisms.

Plastic pollution endangers all natural ecosystems and living creatures on earth. Excessive reliance on plastic products and excessive production of plastic packaging are extremely dangerous for humans because plastic waste has polluted almost the entire world, whether it is in the sea or on the land. This review introduces the examination of pollution brought by non-degradable plastics, the classification and application of degradable materials, and the current situation and strategy to address plastic pollution and plastic degradation by insects, which mainly include Galleria mellonella, Zophobas atratus, Tenebrio molitor, and other insects. The efficiency of plastic degradation by insects, biodegradation mechanism of plastic waste, and the structure and composition of degradable products are reviewed. The development direction of degradable plastics in the future and plastic degradation by insects are prospected. This review provides effective ways to solve plastic pollution.

Lignin Degradation via Chlorine Dioxide at Room Temperature: Chemical Groups and Structural Characterization.

Lignin degradation is an effective means of achieving the high-value application of lignin, but degradation usually requires the use of high temperatures and harsh reaction-conditions. This study describes a green, mild approach for the degradation of lignin, in which chlorine dioxide (ClO2) was used for the oxidative degradation of lignin (IL) in an acidic aqueous suspension at room temperature. The optimal process conditions were: 30 mL of ClO2 solution (2.5 mg·L-1), pH 4.5 and 3 h. The FT-IR, NMR (1H NMR, 2D-HSQC and 31P NMR), XPS and GPC analyses indicated that lignin could be degraded by ClO2 relatively well at room temperature, to form quinones and muconic acids. Additionally, DIL was reduced to substances with a high phenolic-hydroxyl (OH) content (RDIL) under the presence of NaBH4, which further confirmed the composition of DIL and which can be applied to the development of lignin-based phenolic resins, providing a reference for the further modification as well as the utilization of DIL.

Utilization of different wood-based microfibril cellulose for the preparation of reinforced hydrophobic polymer composite films via Pickering emulsion: A comparative study.

Pickering emulsion is a promising strategy for the preparation of hydrophobic polymer composite using hydrophilic nanocellulose. Herein, two types of microfibril cellulose, pure mechanical pretreated microfibril cellulose (P-MFC) and Deep eutectic solvents pretreated microfibril cellulose (DES-MFC), were used to fabricate reinforced hydrophobic polystyrene (PS) composites (MFC/PS) with the aid of Pickering emulsion. The results showed that both oil/water ratio and the content as well as surface hydrophilicity of MFC were playing an important role in emulsifying capacity. 8 % MFC/PS emulsion showed the smallest and most uniform emulsion droplets which is similar to nanofibril cellulose (NFC)/PS at the oil/water ratio of 3:1. The mechanical performance of MFC/PS composites verified that the reinforcement effect was closely related to the emulsifying capacity of MFC. Specially, when the content of P-MFC was 8 wt%, the composite exhibited the best mechanical properties with the tensile strength of 44.7 ± 4.4 MPa and toughness of 1162 ± 52.8 kJ/m3 and Young's modulus of 13.5 ± 0.8 GPa, which was comparable to NFC/PS composite. Moreover, the effective enhancement role of P-MFC in hydrophobic polymethyl methacrylate and polycarbonate composites were also realized via Pickering emulsion strategy. Overall, this work constituted a proof of concept of the potential application of P-MFC in nano-reinforced hydrophobic composite.

Self-Plasticized PVC Prepared by Introducing Fatty Acid to the PVC with Triglycidyl Isocyanurate as an Intermediate Bridge.

The phthalate-free self-plasticization of poly(vinyl chloride) (PVC) conforms to the concept of green chemistry. In this work, phthalate-free, biocontaining, self-plasticized PVC with nonmigration (4-an-TG-X-PVC; X = R, P, or O) was prepared by covalent attachment of ricinoleic acid, palmitic acid, and oleic acid, respectively, to the PVC matrix with 4-aminothiophenol and triglycidyl isocyanurate (TGIC) as intermediate bridges. 4-Aminothiophenol and TGIC acted as the nucleophilic reagent and the thermally stable substance, respectively. The 4-an-TG-X-PVC was observed by diverse characterization methods. Specifically, Fourier transform infrared spectra, 1H nuclear magnetic resonance, gel permeation chromatography, and migration stability tests proved the successful synthesis of 4-an-TG-X-PVC. Compared to the neat PVC, the mechanical property of 4-an-TG-X-PVC is better. The glass transition temperature (T g) of PVC is 81.24 °C, while that of 4-an-TG-X-PVC decreased to 41.88, 31.49, and 46.91 °C. The 4-an-TG-X-PVC showed higher elongation at break and lower tensile strength than neat PVC. Simultaneously, the thermal property of 4-an-TG-X-PVC got a boost. Thermogravimetry-infrared and thermogravimetry-mass spectrometry showed that 4-an-TG-X-PVC released less HCl than neat PVC in a thermal environment. Discoloration experiments demonstrated that 4-an-TG-P-PVC had better heat stabilization and better color than 4-an-TG-O-PVC and 4-an-TG-R-PVC. This work provides a viable solution to the dependence on phthalates, reduced human health and ecological risks, and endowed PVC with improved thermal stability and nonmigration performance.

Cardanol derived P, Si and N based precursors to develop flame retardant phenolic foam.

A novel eco-friendly halogen-free cardanol-based flame retardant with P, Si, and N on the chain backbone (PSNCFR) was synthesized and incorporated into phenolic foams (PFs). PSNCFR was comprehensively investigated via Fourier transform infrared spectroscopy and nuclear magnetic resonance. PSNCFR endowed PFs with flame retardancy, contributed to generating a composite char defense against flames, and efficiently prevented smoking from PFs. PSNCFR introduction improved the flexural strength of the PFs to approximately 155% of that of pristine PF. PSNCFR-modified PFs displayed a high limiting oxygen index value of 41.9%. The results of cone calorimeter show that the mean heat release rate, mean effective heat of combustion, and total heat release of the PSNCFR-modified PFs reduced by 26.92%, 35.71%, and 31.25%, respectively. In particular, the total smoke production of the PSNCFR-modified PFs decreased by 64.55%, indicating excellent smoke inhibition. As for the mechanism, the condensation and gas phases during pyrolysis were responsible for the synergistic flame retardancy in the modified PFs. The findings demonstrate that PSNCFR can be used in PF preparation to overcome their drawbacks of internal brittleness and flammability.

High-Performance Flocculants for Purification: Solving the Problem of Waste Incineration Bottom Ash and Unpurified Water.

The silicon-aluminum-iron flocculant (PAFSi) combines the most abundant resources of waste incineration bottom ash and unpurified water, being regarded as one of the most promising approaches toward water purification. Herein, in this research, waste incineration bottom ash was employed to produce a cost-effective and highly efficient flocculant. PAFSi with a particle size of 214 nm and a zeta potential of 8.63 mV reached the optimum performance using a dosage of 2 mL/50 mL at pH from 8 to 11. The results with the copolymer exhibited the following: (1) a good flocculation efficiency over a wide pH range, (2) superior flocculation performance compared to those of polyaluminum chloride and polyferric sulfate, (3) three-dimensional branching structure of PAFSi micelles with a high aggregation degree, (4) charge neutralization and bridging as the main flocculation mechanism, and (5) recycling the floc. Thus, this work provides an attractive solution to the pressing global clean water shortage problem.

Preparation of Biomass-Based Ester End-Capped Hyperbranched Poly(ether)s via Facile One-Pot Reaction and Their Performance as Non-Toxic Plasticizers.

The aim of this study was to develop a facile one-pot reaction for the synthesis of biomass-based hyperbranched poly(ether)s end-capped as acetate esters (BHE) for use as a sustainable, safe and feasible plasticizer for flexible poly(vinyl chloride) (PVC) materials. BHE is completely miscible with PVC but shows weaker plasticizing effect than dioctyl phthalate (DOP) (EΔTg value of BHE reaches 64.8%). PVC plasticized with BHE displays greater thermal stability than that of PVC or PVC plasticized with DOP materials. BHE improves the thermal stability and flexibility of PVC materials. As a plasticizer, BHE displays lower solvent extractability and greater volatilization resistance than DOP. Acute oral toxicity indicates that BHE has toxic doses of 5 g/kg, suggesting that BHE is non-toxic.

Properties of Rigid Polyurethane Foam Modified by Tung Oil-Based Polyol and Flame-Retardant Particles.

Although tung oil is renewable, with an abundant production and low price in China, and it is used to synthesize different polyols for rigid polyurethane foam (RPUF), it remains a challenge to improve the properties of RPUF by redesigning the formula. Therefore, we propose four novel compounds to strengthen the properties of RPUF, such as the catalyst-free synthesis of tung oil-based polyol (PTOK), aluminum phosphate micro-capsule (AM), silica micro-capsule (SiM), and grafted epoxidized monoglyceride of tung oil on the surface of SiO2 (SiE), which were designed and introduced into the RPUF. Because of the PTOK with a catalytic function, the foaming process of some RPUF samples was catalyst-free. The results show that the incorporation of AM, SiM, and SiE, respectively, endow RPUF with a better thermal stability at a high temperature, and the T5%, Tmax1, and Tmax2 of RPUF appeared to be reduced, however, the Tmax3 and residue rate at 800 °C were improved, which may have a positive effect on the extension of the rescue time in case of fire, and the limiting oxygen index (LOI) value was increased to 22.6%. The formula, containing 25% PTOK made the RPUF environment-friendly. The results were obtained by comparing the pore size and mechanical properties of the RPUF-the AM had a better dispersion in the foam, and the foam obtained a better mechanical, thermal, and flame retardancy.

Designing Rosin-Based Plasticizers: Effect of Differently Branched Chains on Plasticization Performance and Solvent Resistance of Flexible Poly(vinyl chloride) Films.

In the present study, we report a strategy to prepare rosin-based plasticizers with differently branched chains, which have the same benzene ring and similar alkane structure compared to phthalate plasticizers. Castor oil methyl ester, cardanol, and triethyl citrate were reacted with the chemical structure of rosin-based plasticizers. Rosin-based plasticizers with differently branched chains as alternative plasticizers for preparing phthalate-free flexible poly(vinyl chloride) films. All rosin-based plasticizers exhibited more excellent solvent extraction performance than phthalate plasticizers in four different solvents. The plasticizing efficiency of rosin-based plasticizers containing triethyl citrate groups reached 85.5%. The relationships between plasticizing efficiency, thermal stability, solvent resistance, tensile properties, and relative molecular mass of the branched chains of rosin-based plasticizers were investigated.

Synthesis and Properties of UV-Curable Polyfunctional Polyurethane Acrylate Resins from Cardanol.

A novel UV-curable polyurethane acrylate (PUA) oligomer was synthesized by modifying cardanol with a polyfunctional acrylate precursor obtained through reacting pentaerythritol triacrylate with isophoronediisocyanate. Chemical structures of the obtained cardanol-based PUA (C-PUA) oligomer were confirmed by Fourier transform infrared and 1H NMR. Subsequently, viscosity and gel content of the C-PUA resins containing different quantities of hydroxymethyl methacrylate (HEMA) were characterized. The C-PUA oligomer possessed a viscosity of 8360 mPa s, which reduced to 115 mPa s when 40% of the HEMA diluent was added. Furthermore, thermal, mechanical, coating, and swelling properties of the resulting UV-cured C-PUA/HEMA materials were investigated. The ultimate biomaterials showed excellent performance, including a glass transition temperature (T g) of 74-123 °C, maximum thermal degradation temperature of 437-441 °C, tensile strength of 12.4-32.0 MPa, tensile modulus of 107.2-782.7 MPa, and coating adhesion of 1-2. In conclusion, the developed C-PUA resins show great potential to be applied in UV-curable materials like coatings.

Synthesis and Properties of Tung Oil-Based Unsaturated Co-Ester Resins Bearing Steric Hindrance.

New tung oil (TO)-based, unsaturated, co-ester (Co-UE) macromonomers bearing steric hindrance were synthesized by modifying a TO-based maleate (TOPERMA) monomer with an anhydride structure with hydroxyethyl methacrylate (HEMA) and methallyl alcohol (MAA), respectively. The obtained Co-UE monomers (TOPERMA-HEMA and TOPERMA-MAA) were then characterized by 1 H NMR and gel permeation chromatography (GPC). For comparison, hydroxyethyl acrylate (HEA)-modified TOPERMA (TOPERMA-HEA) was also synthesized and characterized. Subsequently, the obtained Co-UEs were thermally cured with styrene, and the ultimate properties of the resulting materials were studied. It was found that by introducing the structure of steric hindrance into the TO-based Co-UE monomer, the tensile strength and Young's modulus of the resulting materials were improved. Furthermore, by reducing the length of the flexible chain in the Co-UE monomer, the tensile strength, Young's modulus, and glass transition temperature (Tg) of the resultant materials were also improved. The TOPERMA-MAA resin gave the best performance in these TO-based Co-UE resins, which showed a tensile strength of 32.2 MPa, Young's modulus of 2.38 GPa, and Tg of 130.3 °C. The developed ecofriendly materials show promise in structural plastic applications.

Flexible PVC materials grafted with castor oil derivative containing synergistic flame retardant groups of nitrogen and phosphorus.

Internally plasticized PVC by replacement of chlorine with castor oil derivative containing synergistic flame retardant groups of nitrogen and phosphorus, that is, castor oil derivative grafted onto PVC matrix, is reported. Low glass transition temperature (Tg) of modified PVC was produced although thermal stability was reduced. However, the migration was completely suppressed. The combination of castor oil derivative containing synergistic flame retardant groups of nitrogen and phosphorus with PVC matrix through modifying PVC materials with click reaction prepared flexible PVC materials with zero migration and enhanced flame retardant property.

Bio-inspired hydrophobic modification of cellulose nanocrystals with castor oil.

This work presents an efficient and environmentally friendly approach to generate hydrophobic cellulose nanocrystals (CNC) using thiol-containing castor oil (CO-SH) as a renewable hydrophobe with the assist of bio-inspired dopamine at room temperature. The modification process included the formation of the polydopamine (PDA) buffer layer on CNC surfaces and the Michael addition reaction between the catechol moieties of PDA coating and thiol groups of CO-SH. The morphology, crystalline structure, surface chemistry, thermal stability and hydrophobicity of the modified CNC were charactered by TEM, XRD, FT-IR, solid-state 13C NMR, XPS, TGA and contact angle analysis. The modified CNC preserved cellulose crystallinity, displayed higher thermal stability than unmodified CNC, and was highly hydrophobic with a water contact angle of 95.6°. The simplicity and versatility of the surface modification strategy inspired by adhesive protein of mussel may promote rapid development of hydrophobic bio-based nanomaterials for various applications.

A Strategy for Nonmigrating Plasticized PVC Modified with Mannich base of Waste Cooking Oil Methyl Ester.

The waste cooking oil (WCO) production from the catering industry and food processing industry causes serious environmental, economic and social problems. However, WCO can be used for the preparation of fine chemicals such as internal plasticizer. With this aim, this work is focused on preparing internal plasticizer by using WCO and determining technical viability of non-migration poly (vinyl chloride) (PVC) materials. The mannich base of waste cooking oil methyl ester (WCOME) was synthesized from WCO via esterification, interesterification and mannich reaction, which was used to produce self-plasticization PVC materials as an internal plasticizer. The results showed that the PVC was plasticized effectively. Self-plasticization PVC films showed no migration in n-hexane, but 15.7% of dioctyl phthalate (DOP) leached from DOP/PVC(50/50) system into n-hexane. These findings transformed the traditional plastic processing technology and obtained cleaner production of no migration plasticizer from WCO.

Effects of Tung Oil-Based Polyols on the Thermal Stability, Flame Retardancy, and Mechanical Properties of Rigid Polyurethane Foam.

A phosphorus-containing tung oil-based polyol (PTOP) and a silicon-containing tung oil-based polyol (PTOSi) were each efficiently prepared by attaching 9,10-dihydro-9-oxa-10-phosphaphenanthrene (DOPO) and dihydroxydiphenylsilane (DPSD) directly, respectively, to the epoxidized monoglyceride of tung oil (EGTO) through a ring-opening reaction. The two new polyols were used in the formation of rigid polyurethane foam (RPUF), which displayed great thermal stability and excellent flame retardancy performance. The limiting oxygen index (LOI) value of RPUF containing 80 wt % PTOP and 80 wt % PTOSi was 24.0% and 23.4%, respectively. Fourier transfer infrared (FTIR), Nuclear Magnetic Resonance (NMR) and thermogravimetric (TG) analysis revealed that DOPO and DPSD are linked to EGTO by a covalent bond. Interestingly, PTOP and PTOSi had opposite effects on Tg and the compressive strength of RPUF, where, with the appropriate loading, the compressive strengths were 0.82 MPa and 0.25 MPa, respectively. At a higher loading of PTOP and PTOSi, the thermal conductivity of RPUF increased while the RPUF density decreased. The scanning electron microscope (SEM) micrographs showed that the size and closed areas of the RPUF cells were regular. SEM micrographs of the char after combustion showed that the char layer was compact and dense. The enhanced flame retardancy of RPUF resulted from the barrier effect of the char layer, which was covered with incombustible substance.

Plasticizers Derived from Biomass Resources: A Short Review.

With rising environmental concerns and depletion of petrochemical resources, biomass-based chemicals have been paid more attention. Polyvinyl chloride (PVC) plasticizers derived from biomass resources (vegetable oil, cardanol, vegetable fatty acid, glycerol and citric acid) have been widely studied to replace petroleum-based o-phthalate plasticizers. These bio-based plasticizers mainly include epoxidized plasticizer, polyester plasticizer, macromolecular plasticizer, flame retardant plasticizer, citric acid ester plasticizer, glyceryl ester plasticizer and internal plasticizer. Bio-based plasticizers with the advantages of renewability, degradability, hypotoxicity, excellent solvent resistant extraction and plasticizing performances make them potential to replace o-phthalate plasticizers partially or totally. In this review, we classify different types of bio-based plasticizers according to their chemical structure and function, and highlight recent advances in multifunctional applications of bio-based plasticizers in PVC products. This study will increase the interest of researchers in bio-based plasticizers and the development of new ideas in this field.

Cardanol Groups Grafted on Poly(vinyl chloride)-Synthesis, Performance and Plasticization Mechanism.

Internally plasticized poly(vinyl chloride) (PVC) materials are investigated via grafting of propargyl ether cardanol (PEC). The chemical structure of the materials was studied by FT-IR and ¹H NMR. The performace of the obtained internally plasticized PVC materials was also investigated with TGA, DSC and leaching tests. The results showed that grafting of propargyl ether cardanol (PEC) on PVC increased the free volume and distance of PVC chains, which efficiently decreased the glass transition temperature (Tg). No migration was found in the leaching tests for internally plasticized PVC films compared with plasticized PVC materials with commercial plasticizer dioctyl phthalate (DOP). The internal plasticization mechanism was also disscussed according to lubrication theory and free volume theory. This work provides a meaningful strategy for designing no-migration PVC materials by introducing cardanol groups as branched chains.