Initial Decomposition Temperature Research Articles

Enhancement of mechanical properties in reactive polyurethane film via in-situ assembly of embedded cellulose nanocrystals.

Comparing to the solvent-based and waterborne polyurethanes (PU), the solvent-free reactive PU (RPU) is prepared via in-situ polymerization and film-formation of isocyanate-capped prepolymers and macromolecular polyols in solvent-free system. Thus, the carbon emissions and environmental pollutions are significantly reduced. However, the rapid polymerization also challenges the well control of structure and properties, especially the ordered microstructures. In this work, an efficient approach is applied to enhance the mechanical property of RPU via chemically bonding cellulose nanocrystals (CNCs) with isocyanates in a solvent-free system. The well distributed spot-like structure in the RPU film is realized and significantly improve the mechanical property due to the synergistic effect of hydrogen bonds and urethane bonding. Only adding 1 wt% of CNCs, the tensile strength and elongation at break are profoundly increased to 25.4 ± 1.5 MPa and 748 ± 50.0 %, respectively. Both values are 490 % and 16 % better than that without CNCs. Additionally, the thermal stability is also improved. The initial decomposition temperature is 29 °C higher than that without CNCs. This approach provides a simple method for developing bio-based RPU with well-ordered structures, showing great potential in applications such as environmentally friendly materials and high-performance polymers.

Molecular dynamic simulation study on the influence of heating rate on the thermal decomposition process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).

To clarify the effect of heating rate on the thermal decomposition process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), this study employs molecular dynamic simulations to investigate the thermal decomposition of TATB at heating rates of 20, 40, 60, and 80K/ps. The initial temperature is uniformly set to 300K, while the final temperature is set to 3000K. Results indicate that within the temperature range of 300-3000K, the thermal decomposition rate of TATB decreases with increasing heating rate, whereas the initial decomposition temperature of TATB increases, consistent with the experimental pattern. Within the studied temperature range, a lower heating rate results in a higher number of decomposition fragments, leading to more effective collision between active fragments, facilitating more effective collisions between active species, and leading to the formation of more stable products such as H₂O, CO₂, and N₂. Conversely, higher heating rates reduce the quantities of these stable products. This study enhances the understanding of TATB's thermal decomposition mechanism, providing valuable insights for its safe handling and application. METHODS: The Gaussian09 software was used to calculate the BDEs of TATB molecules, while the MD simulation using the ReaxFF-lg force field was performed by the LAMMPS package. Visualization and postprocessing were conducted using the OVITO software, and a custom script was developed to analyze the reaction products and frequencies.

Synergistic effects of thermoplastic starch and nanofibrillated cellulose on the mechanical, thermal, and micromorphological properties of polylactic acid composites

AbstractFilling and reinforcing highly brittle and costly polylactic acid (PLA) with nanocellulose and starch has been found to be a promising approach for practical applications. However, the strong tendency of nanocellulose to agglomerate significantly affects the overall performance of the resulting composites. This study employed ball‐milling method to incorporate nanofibrillated cellulose (NFC) into starch, innovatively producing reinforced thermoplastic starch (TPS), which is then used to enhance the mechanical properties and reduce costs of PLA without compromising biodegradability. The effects of the ratio of PLA to TPS and the amount of NFC added were thoroughly investigated. Notably, the inclusion of NFC and TPS not only enhanced tensile strength but also improved toughness. At a PLA:TPS ratio of 70:30 with 4 wt% NFC, the composites achieved maximum toughness of 10.73 kJ/m3, a 973% increase over pure PLA. Furthermore, adding 7 wt% NFC significantly boosted tensile strength and elastic modulus, increasing by 14.7% and 29% respectively compared with NFC‐free composites, reaching 37.11 and 710.94 MPa. Additionally, NFC and TPS addition enhanced PLA crystallization and thermal stability. Thermal decomposition of PLA typically occurred at approximately 250°C. However, blending raised the initial thermal decomposition temperature of PLA/TPS/NFC composites to 290°C, indicating enhanced thermal stability. These findings enhance the application potential of PLA‐based composites, extending to environmentally friendly packaging and furniture industrial applications.Highlights NFC dispersion in TPS composites was enhanced through ball milling treatment. Composites with 4 wt% NFC showed a 973% toughness increase over pure PLA. The developed composites achieved maximum tensile strength (37.11 MPa). TPS imparted toughness to PLA, which reduced its brittleness. The thermal decomposition temperature of the composites rose to 290°C.

Thermal stability, flame retardancy and mechanical properties of casein-based rigid polyurethane foam with starch and sepiolite as fillers

Casein-based rigid polyurethane foam (RPUF) with different ratios of starch and sepiolite were prepared by a one-step process. Thermogravimetric analysis, CONE analysis, scanning electron microscopy analysis, limiting oxygen index (LOI) analysis, vertical combustion analysis, and mechanical property analysis were used to explore the thermal stability, flame retardancy, and compressive properties of the modified RPUFs, respectively. The results showed that the initial decomposition temperature and activation energy (E) of RPUF-C5ST2SE3 (5 g casein, 2 g starch, and 3 g sepiolite) were the highest. Under the condition of radiant flux of 50 kW/m2, the peak heat release rate (PHRR), total heat release (THR), peak smoke production rate (PSPR), and total smoke release (TSR) were reduced by 35.92%, 10.83%, 36.67%, and 18.20%, respectively, compared with the RPUF without flame retardant. By analyzing the carbon residue, it was found that RPUF-C5ST2SE3 had the highest carbon residue and its carbon residue morphology was relatively intact. In addition, the RPUF-C5ST2SE3 had the highest LOI and a UL-94 rating of V-0. At the same time, it also had the best mechanical property. The present experimental results can provide a useful reference for future RPUF flame retardant studies.

Extraction of cellulose nanocrystals from date seeds using transition metal complex-assisted hydrochloric acid hydrolysis.

In this study, the role of a transition metal complex in improving hydrolysis efficiency during nanocellulose production was analysed. Cellulose nanocrystals (CNCs) were extracted from date seeds by incorporating a copper metal complex during HCl hydrolysis. In contrast to traditional HCl hydrolysis at moderate conditions, which yielded only microcrystalline cellulose (MCC), this approach resulted in the extraction of CNCs with a 10% improved yield compared to MCC. Morphological analysis using scanning electron microscopy revealed semi-spherical shaped particles, while transmission electron microscopy showed CNCs with a particle size ranging from 70 to 80nm. Dynamic light scattering analysis indicated a significant reduction in average particle size from 900nm to 121nm, highlighting the remarkable efficiency of using the copper metal complex in combination with HCl to improve yield and particle size. Energy dispersive X-ray spectroscopy analysis confirmed the purity of the CNCs, with no residual copper detected. Thermal analysis demonstrated the high stability of the CNCs, with an initial decomposition temperature (Tonset) of 274.02°C and an activation energy (Ea) of 219.90kJ/mol. X-ray diffraction analysis revealed that the CNCs exhibited high degree of crystallinity (Crl=72.03%). Disseminating these research findings will significantly impact the CNCs production industry, facilitating improved yields and the production of nano-sized fibers through the utilization of transition metal complexes alongside hydrolysis solvents.

Rapid and well-controlled degradation of polylactic acid materials with bio-based GEL(pectin/α-cellulose/SiO2/CaCl2).

Polylactic acid (PLA) has been a subject of considerable interest as a degradable polymer. However, the degradation process is slow and uncontrollable. In this work, controlled degradable PLA/bio-based GEL (pectin/α-cellulose/SiO2/CaCl2) hydrophilic plasticizer composite material was successfully prepared by solution blending process. The bio-based GEL was proven to have strong water absorption properties and the ability to improve and regulate the degradation performance of PLA. The results declared that the addition of 5% GEL and 15% polyethylene glycol (PEG) to the PLA composites resulted in a degradation degree of 83% within 12h in an alkaline solution. And the rate represents a 21.2-fold increase in speed compared to pure PLA material. Under neutral and acidic conditions, the degradation degree of the modified composites was approximately 169 times faster than that of pure PLA. Meanwhile, the tensile strength of PLA composites decreased from 44.8MPa to 16.7MPa, but the elongation at break increased from 5.8% to 172% compared to pure PLA. Furthermore, the initial decomposition temperature and maximum thermal decomposition rate temperature of PLA composites were found to be reduced. The controlled degradation of PLA composites was accomplished through the regulation of GEL content. The hydrolysis degradation process under different pH laid a foundation for the pretreatment process of soil microbial degradation of PLA. The mechanism suggested that the GEL created a large number of pores on the surface and inside the material within an extremely short period of time, providing ample opportunities for soil microorganisms to invade.

Improving the performance of polylactic acid/polypropylene/cotton stalk fiber composites with epoxidized soybean oil as a high efficiency plasticizer.

Polylactic acid (PLA) can serve as a biodegradable alternative to traditional petroleum-based plastics, but its poor impact resistance and high production costs limit its applications. In this study, different contents of epoxidized epoxy soybean oil (ESO) were added as plasticizer to melt blend with polylactic acid (PLA), polypropylene (PP) and cotton stalk fiber (CSF), examining its impact on the mechanical properties, thermal stability, microstructure, and crystallization behavior of the blends. The results indicated that ESO reacted with PLA and CSF to form branched polymers and microgels. With increasing ESO content, the blends exhibited increased initial thermal decomposition temperature, impact strength, and elongation at break, while stiffness, maximum decomposition rate, and crystallinity decreased. When the mass ratio of CSF to ESO was 2:1, the notch impact strength and elongation at break of PLA/PP/CSF/ESO blends were 1.63 times and 1.98 times higher than those of PLA/PP/CSF blends, respectively. Moreover, a reduction in surface grooves of CSF and formation of a gel layer were observed. Importantly, this study opens an effective new pathway for the utilization of waste natural fibers and the widespread application of biodegradable composite materials, contributing to environmental protection, resource conservation, and cost reduction.

Thermal decomposition behaviors and reaction mechanism of emulsion explosive with the addition of TiH2 powders

To explore compatibility and thermal stability of the emulsion explosive added with TiH2 powders, the actions of TiH2 powders on the thermal decomposition properties, reaction product compositions of the emulsion explosives were researched by TGA-FTIR, TG-DSC, XRD and XPS. The results manifested that the adding of 7.6 μm TiH2 powders in the range of 2–8 mass% could reduce the initial decomposition temperature of the emulsion explosive and promote the thermal decomposition reaction. The apparent activation energies of pure emulsion explosive sample were 110.5 and 107.05 kJ/mol, respectively. When the addition of 7.6 μm TiH2 powders to emulsion explosive was 2 mass%, the apparent activation energy decreased to the minimum value, which were 100.1 and 95.9 kJ/mol, respectively. While the initial decomposition temperatures and the activation energies of explosive samples added with TiH2 powders with particle sizes of 33.7, 50.1 and 120.0 μm both continued to rise. Furthermore, based on the experimental results, the thermolysis mechanism of emulsion explosive added with TiH2 powders was proposed. This study is helpful to further understand the thermolysis properties and reaction mechanism of emulsion explosives containing TiH2 powders, and offer theoretic direction for the formulation optimization as well as industrial production of high-energetic emulsion explosives.

Fabrication and Performance Investigation of Flame Retardant Flexible Polyurethane Composites via Polyethyleneimine/Phytic Acid LBL Self‐Assembly Coatings

ABSTRACTTo bolster the fire resistance of flexible polyurethane foam (FPUF), and a series of FPUF/polyethylenimine/phytic acid (FPUF/PEI/PA) composites were prepared by layer‐by‐layer self‐assembly strategy. Furthermore, the thermal stability, flame retardancy, combustion properties, and char layer were comprehensively evaluated via thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical combustion test, microcalorimetry (MCC), scanning electron microscopy (SEM), Raman spectroscopy, and tensile testing. TG analysis revealed that the PEI/PA coatings markedly diminished the initial decomposition temperature (T‐5wt%) and char residue at 800°C. FPUF‐6 extended the burning duration by 20 s, a 80% improvement compared with unmodified FPUF, with an LOI value increased to 19.2 vol%. SEM and Raman analyses of the char residues indicated that the PEI/PA coating promoted graphitization degree of the char layer. This work offered novel insights for the development of high‐performance FPUF composites.

New Insights into the Effect of Cellulose-Based Separators on Electrode-Electrolyte Interface in Lithium Metal Batteries

With a surging demand for electrification, lithium-ion batteries (LIBs) featuring higher energy and power densities have become indispensable. Copious research is being conducted on various components of LIBs to achieve cells with superior performance. Among these components, the separator plays a crucial role as it serves as insulation between the positive and negative electrodes while providing mechanical and thermal stability to the cells, thereby ensuring battery safety. In the pursuit of enhancing separators, a sufficient and controllable porosity and increased electrolyte wettability have gained prominence in separator research for high-performance LIBs, reflected in a large increase in research publications on separator technology in the past decade1.Currently, polyethylene (PE)/polypropylene (PP) membranes, known for their desirable electrochemical stability, have been the favored material for separators. However, these membranes have poor thermal stability, particularly at higher temperatures associated with fast charging rates. This thermal vulnerability can culminate in the decomposition of the separator, introducing a major hazard in the form of electrical shorts that may discharge the battery and lead to battery fires. Thus, separator materials that offer superior safety benefits are needed to ensure safe application of LIBs in next-generation applications2.Among the proposed materials for next-generation separators, there is a notably strong interest in cellulose-based separators (CBS). The primary advantage of cellulose compared to PE/PP membranes is greater thermal stability, as demonstrated by an initial decomposition temperature of 270°C. This greatly increases the safety of the battery since the risk of battery fires stemming from separator decomposition is reduced significantly. Along with increased thermal stability, several reports have shown enhanced energy density, and longevity in LIBs using CBS because of its desirable electrochemical stability, wettability, and water scavenging capability3,4,5.In this work, we study the CBS in a Li-metal battery with inherently higher energy density, thus, intensified challenges. While the majority of reports discuss the advantages of CBS, herein, we present new insights into possible drawbacks of CBS and its suitability for highly concentrated Li-based batteries. We investigated a commercial CBS with Li metal anode and NMC cathode materials. The compatibility and performance of CBS in Li metal-based coin cells (symmetrical and asymmetrical) are studied through electrochemical measurement techniques including cyclic voltammetry (CV), pre- and post-cycling electrochemical impedance spectroscopy (EIS) and cycling test. Similar measurements are carried out on cells with conventional PE/PP separator. Surface and morphological characterizations are conducted on the CBS, Li metal anode, and cathode to provide a more comprehensive view of the CBS interaction with Li metal and NMC cathode. It was observed that while CBS results in a more stable and uniform solid electrolyte interphase (SEI) on Li metal, it is incompetent in impeding Li dendrites. A potential method to reach a clearer understanding of the underlying mechanisms, involving the introduction of oxide coatings to the CBS separator, is explored. It is expected that this study will provide a fundamental understanding of the effects of cellulose on Li metal battery and further clarify its potential for next generation LIBs.

Adjusting the Coordination Configuration by Changing Electrostatic Potential: Introducing N/O/S Heteroatoms Based on the Electronic Effect.

Energetic coordination compounds (ECCs) have demonstrated unique advantages in regulating the physicochemical properties of energetic materials through the design of organic ligands. The fundamental approach involves altering the electron cloud density distribution of organic ligands to modify the characteristics of coordination sites and, thus, achieve new coordination configurations. In this study, Mulliken charge distribution and surface electrostatic potential analysis were used to elucidate the effects of pyridinic N, pyrrolic N, oxazolic O, and thiazolic S on the electron cloud density of carbohydrazide groups through the induction effect and conjugate effect. Furthermore, three AgClO4-based ECCs were synthesized based on 1H-imidazole-4-carbohydrazide, oxazole-4-carbohydrazide, and thiazole-4-carbohydrazide. Single-crystal X-ray diffraction analysis revealed that [Ag(IZ-4-CA)ClO4]n has a one-dimensional (1D) chain structure, while Ag2(OZCA)2(ClO4)2 and Ag2(SZCA)2(ClO4)2 exhibit zero-dimensional structures. The 1D structure, with good planarity, results in [Ag(IZ-4-CA)ClO4]n having lower mechanical sensitivity (IS = 21 J, FS = 80 N). The introduction of oxazolic O enhances oxygen balance (OB), leading to a higher predicted detonation velocity and pressure for Ag2(OZCA)2(ClO4)2 (D = 6.4 km s-1, P = 23.6 GPa). Although the introduction of thiazolic S is unfavorable for improving oxygen balance, Ag2(SZCA)2(ClO4)2 exhibits the highest initial decomposition temperature among the three, at 232 °C. Additionally, initiation tests demonstrated that three ECCs can successfully detonate cyclotrimethylenetrinitramine (RDX), indicating good initiation capabilities.

Impact of encapsulation conditions on V-type granular starch-curcumin complexes

V-type granular starch (VGS) could be a potential carrier of active substances according to previous research. Its hydrophobic cavity is capable of encapsulating and accommodating guest molecules with hydrophobicity. This study investigates the impact of various encapsulation conditions on curcumin payload capacity, encapsulation efficiency, and composite index, revealing that the optimal conditions for curcumin encapsulation using VGS were an encapsulation temperature of 60 °C, a curcumin addition ratio of 20% (w/w), a reaction duration of 1 h, and an ethanol solution volume of 40% (v/v). This observation is attributed to the hydrophobic capacity of VGS and the environmental sensitivity of curcumin. Furthermore, the initial temperature of thermal decomposition and the maximum weight loss rate temperature occurs for the complex are higher than those of VGS, curcumin, and the physical blend. In the enzymatic resistance experiments, the resistant starch content in the complex increased from 10.38% to 35.12%, while the rapidly digestible starch (RDS) content decreased from 72.77% to 40.62%. Collectively, these findings underscore the immense potential of VGS as a carrier for the transport of sensitive actives.

A Bio-Based Polybenzoxazine Derived from Diphenolic Acid with Intrinsic Flame Retardancy, High Glass Transition Temperature and Dielectric Properties.

A bio-based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME-HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non-isothermal differential scanning calorimetry (DSC). The activation energies of DPME-HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME-HFBz) presented an ultra-high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME-HFBz) was as high as 38%. Poly(DPME-HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME-HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low-dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties.

Novel functional copolymer: Design, synthesis, click chemistry modification, and evaluation of dielectric and thermal properties

In this study, the modification of new polymers carrying dipeptide side groups with chalcone and their electrical properties were investigated. Therefore, initially, the phenylalanine dipeptide (Tyr(Boc)-Phe–OCH3) was synthesized. The ester group in the structure of this compound was converted to carboxylic acid to obtain the Boc-Tyrosine Phenylalanine-OH (Tyr(Boc)-Phe-OH) compound. This compound reacted with propargyl amine (PA) to synthesize (Tyr(Boc)-Phe-PA), which subsequently reacted with methacryloyl chloride to produce the methacrylate monomer (MA-Tyr(Boc)-Phe-PA). The polymerization of the prepared methacrylate monomer was carried out using the free radical polymerization method. In the final step, the active alkyne-terminated homopolymer reacted with the azide-terminated (4-Cl-CF3 N3-Chalcone) under copper catalysis through a click reaction, resulting in the synthesis of poly(MA-Tyr(Boc)-Phe-click-chalcone). The thermal behaviors of the polymers were determined using DSC and TGA thermal analysis methods. The initial decomposition temperature of the polymer was found to be 207.05 °C, whereas this value was 188.53 °C for the P(MA-Tyr(Boc)-Phe-click-chalcone) polymer. Additionally, the temperatures corresponding to a 50 % mass loss were 383.79 °C for the P(MA-Tyr(Boc)-Phe-PA) polymer and 394.78 °C for the P(MA-Tyr(Boc)-Phe-click-chalcone) polymer. The dielectric constant of the P(MA-Tyr(Boc)-Phe-PA) polymer was calculated to be 8.98, while the dielectric constant of the modified polymer obtained after click modification was calculated to be 13.87. The increase in the dielectric constant is thought to be due to the greater polarization of the triazole ring formed by the click reaction under an electric field. Furthermore, the AC conductivities of the compounds were calculated to be 5.00 × 10−9 S/cm and 1.11 × 10−9 S/cm at 1 kHz. When the dielectric properties of these two compounds are compared, the second polymer exhibits better polarization in an electric field, indicating its potential use as an electronic circuit element.

Ultra-lightweight asymmetric hierarchical porous structure for high-efficiency absorption-dominated electromagnetic interference shielding

In this work, ultra-lightweight composite aerogels with a hierarchical pore structure consisting of hollow Fe3O4 microspheres (∼250 nm), hollow MXene microspheres (∼580 nm) and pores (10–40 μm) in polyimide (PI) aerogel are developed through directional freezing, followed by freeze drying and thermal annealing. The composite aerogels exhibit a distinct asymmetric structure, with a top Fe3O4/PI aerogel layer designed for impedance matching and a bottom MXene/PI aerogel layer aimed at enhancing attenuation. This deliberate structure design not only reduces the density of the composite aerogels but also greatly enhances their absorption of electromagnetic waves. The composite aerogel demonstrates an impressive X-band EMI SE of 69.7 dB, a remarkable absorption coefficient (A) of 0.73, and an excellent surface-specific SE (SE divided by material density and thickness) of 13352 dB cm2 g−1, achieved at a density of just 0.034 g/cm³. Moreover, the composite aerogel exhibits outstanding stability in compression and shielding performance. Following 100 cycles of compression, the compressive strength remains at 94.9 % of the initial compressive strength (98 kPa), and its EMI SE maintains 68.5 dB with a retention rate of 98.2 %. Additionally, the composite aerogel presents outstanding thermal insulation (0.046 W m−1 K−1) and thermal resistance (initial decomposition temperature > 500 °C). This work provides novel insights into the design and fabrication of ultra-lightweight and absorption-dominated EMI shielding materials.

Synthesis and Characterization of Schiff Base Compounds Containing Mono and Disulfonic Groups

Aromatic mono- or diamine compounds containing sulfonic groups are extensively utilized in the production of textiles, dyes, and polymers. Schiff base compounds are synthesized through the condensation reactions of these types of compounds with aromatic aldehydes or ketones. Due to their multifunctional nature, these Schiff base compounds serve as precursors in the synthesis of poly(ester)s, poly(ether)s, poly(urethane)s, and poly(azomethine)s. The Schiff base compounds were 2,5-bis((E)-(2-hydroxybenzylidene)amino)benzene sulfonic acid (SCH1) and 4,4'-bis((E)-(2-hydroxybenzylidene)amino)-[1,1'-biphenyl]-2,2'-disulfonic acid (SCH2). The yields of SCH1 and SCH2 were calculated to be 85% and 80%, respectively. Structural confirmation was achieved using FT-IR, UV-Vis, 1H NMR and 13C NMR measurements. Further characterization through fluorescence spectroscopy (PL), thermogravimetric analysis (TGA) and cyclic voltammetry (CV) revealed high thermal stability of the compounds, attributed to the phenyl groups in their structures. TGA measurements indicated the initial decomposition temperatures for SCH1 and SCH2 at 298°C and 347 °C, respectively, with the residual masses of 34.64% and 41.24% at 1000 °C.

Multiphase Biopolymers Enriched with Suberin Extraction Waste: Impact on Properties and Sustainable Development.

This manuscript explores the development of sustainable biopolymer composites using suberin extraction waste, specifically suberinic acid residues (SAR), as a 10% (w/w) reinforcing additive in polylactide (PLA) and thermoplastic starch-polylactide blends (M30). The materials were subjected to a detailed analysis using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) to assess their thermal, mechanical, and structural properties. The study confirmed the amorphous nature of the biopolymers and highlighted how SAR significantly influences their degradation behavior and thermal stability. M30 exhibited a multi-step degradation process with an initial decomposition temperature (T5%) of 207.2 °C, while PLA showed a higher thermal resistance with decomposition starting at 263.1 °C. Mechanical performance was assessed through storage modulus (E') measurements, showing reductions with increasing temperature for both materials. The research provides insights into the potential application of SAR-enriched biopolymers in sustainable material development, aligning with circular economy principles. These findings not only suggest that SAR incorporation could enhance the mechanical and thermal properties of biopolymers, but also confirm the effectiveness of the research in reassurance of the audience.

Enhanced thermal and mechanical properties of flame-retardant expandable graphite modified silk fibroin-based rigid polyurethane foam

At present, in order to reduce the environmental pollution caused by the use of petrochemical products, the preparation of flame-retardant polyurethane foam (PUF) using green raw materials is increasingly attracting widespread attention. A biomass protein-based green flame-retardant rigid PUF (RPUF) with expandable graphite (EG) and silk fibroin (SF) was prepared in a one-step process. Thermal stability, combustion characteristics and compression properties of modified RPUFs were investigated by thermogravimetric analysis, cone test, limiting oxygen index (LOI) test, UL-94 vertical burning test and mechanical compression test. The RPUF with 10 wt% EG (RPUF-SF/EG10) exhibited superior heat resistance, with the highest initial decomposition temperature (Ti), integral programmed decomposition temperatures (IPDT) and activation energy (E). And RPUF-SF/EG10 had the lowest peak heat release rate (PHRR) and total heat release (THR), and it also showed the highest LOI and had a flammability rating of V-0. In Addition, the apparent density and compressive strength of RPUF-SF/EG10 were the largest among the four EG-added materials. The results indicated that RPUF-SF/EG10 had excellent thermal stability, flame retardancy and compression resistance, which was attributed to the synergistic effect of SF and EG in the system. This provided a valuable reference for the development of new, environmentally friendly and high-performance RPUFs.

Increase of bridge length by ingenious grafting of ester chains, imparting epoxy resins superb thermal, smoke suppression, gas-phase flame retardancy, and mechanical properties

While bifunctional synergistic flame retardants have demonstrated efficacy in enhancing the fire safety of epoxy resins (EPs), the grafting of specific functional monomers into flame retardant molecules, elucidating their mechanisms of action through comparative analysis, and concurrently achieving a delicate balance among flame retardancy, heat resistance, and mechanical toughness remains a significant challenge. Herein, this research present an innovative strategy to derive a novel sulfur-based bifunctional flame retardant, DSTA, based on the structure of the original flame retardant, DST, by grafting the ester chains to increase the bridge length of the molecular structure. As expected, the addition of flexible ester chains enabled DSTA to have a very high initial decomposition temperature and the heat-resistance index. DSTA can be used in low dosage compared to DST, enabling EP to achieve UL-94 V-0 rating. Combustion behavior showed that DSTA had the best ability to heat and smoke suppression for EP, and had faster response speed and higher fire growth index. Notably, pyrolysis volatiles tested on DSTA revealed that the ester chains can pyrolysis to release large amounts of CO2, which occurs in the early stages of pyrolysis and works together with other N-containing inert gases and P-containing radicals in the gas-phase to efficiently extinguish flames. Meanwhile, DSTA improves all mechanical properties of EP, which was attributed to the presence of ester chains. In summary, this work presents a new strategy for examining the impact of specific functional groups on the flame retardant mechanisms of EP.

Ultra-high toughness and strength polylactic acid/bio-polyamide 11 blend induced by dendritic structure of hyperbranched polyester with microcrystalline cellulose as the core

The development and use of bio-based materials instead of traditional petroleum-based materials is an effective way to conserve fossil resources and reduce carbon emissions. Polylactic acid (PLA) has considerable potential as a bio-based material for industrial purposes. However, its limited toughness restricts its widespread application. In this study, a hyperbranched polyester with microcrystalline cellulose as the core (MCC-EHBP) was designed, synthesized, and used to upgrade the compatibility of a PLA/bio-based polyamide 11 (PA11) blend by synchronously enhancing the toughness and strength of PLA. Owing to the excellent reactivity of the epoxy group, MCC-EHBP forms a block-like dendritic polymer structure with the molecular chain of PLA/PA11, which observably improves the compatibility of the two phases of the blend. The prepared PLA/PA11/MCC-EHBP blend has tensile strength of 67.37 MPa, impact strength of 38.75 kJ m−2, and an elongation at break of 30.3 %, which are 36.9 %, 241.7 %, and 300.1 % higher than those of PLA, respectively. Moreover, the initial decomposition temperature and activation energy of PLA are increased by 5 °C and 17.3 %, respectively. The proposed simple, efficient, and environmentally friendly method for preparing PLA with ultra-high toughness, strength, and heat resistance is expected to broaden the industrial applications of this polyacid.