Initial Decomposition Temperature Research Articles

Study on the thermal stability of NG/NC/RDX triple-base gun propellants modified by oligomer GAP (Mn = 330)

The thermal stability of gun propellants is related to significant safety issues in their development, production, storage, or transportation. Therefore, the study of improving the thermal stability of propellants has urgent and important practical significance. In this work, glycidyl azide polymer (GAP) with a relative molecular weight of 330 was added to the gun propellant to prepare modified NG-NC-RDX gun propellants containing different contents of oligomeric GAP. The ability of the propellant to cause discoloration of methyl violet test paper due to thermal decomposition, as well as the thermal weight loss and adiabatic decomposition behavior of the propellant, were characterized. And the differential charge density of GAP and NG, as well as the free volume and microstructure of GAP/NC and NG/NC blends, were compared, and the mechanism by which GAP improves the thermal stability of the propellant was discussed. When the content of GAP in the propellant changes from 0% to 16%, the time for the methyl violet test paper to change from purple to orange is prolonged from 87 minutes to 98 minutes. The initial decomposition temperature of thermal weight loss increased from 164.7 °C to 176.4 °C. The maximum temperature rise rate during adiabatic decomposition decreased from 0.95 °C·min−1 to 0.12 °C·min−1. According to MS simulation calculations, GAP provides a larger free volume and improves the uniformity of the mesoscopic phase structure of the propellant. The covalent effect of bond C-N3 in GAP molecules is stronger than that of bond O-NO2 in NG molecules. The thermal stability of the NG-NC-RDX propellant increases with the addition of GAP, and it increases with the increase of GAP content in the propellant. This work provides a scheme for improving the thermal stability of the gun propellant and offers a way to reduce the risk of thermal stimulation.

Enabling simultaneous reprocessability and fire protection via incorporation of phosphine oxide monomer in epoxy vitrimer

The conception of epoxy thermosets with both reprocessability and flame retardancy delineates a new horizon in polymer science, offering a material solution that is not only superior in fire safety but is also environment friendly. Herein, a flame-retardant epoxy vitrimer (EV) was prepared using partially bio-based IADPPO (diphenylphosphine oxide itaconic anhydride) and citric acid as curing reagents via a solvent-free process. Their incorporation created covalent adaptable networks (CANs) in the matrix which promote reprocessability and recyclability. The EV exhibits excellent thermal stability with high initial decomposition temperature (T-5wt% ∼308 °C) and high glass transition temperature (Tg ∼107 °C), similar to the blank EV (115 °C). The flame retardancy, mechanical properties, transesterification-based reprocessability, and flame-retardant mechanism were investigated. The EV containing 3 wt% phosphorus (EV IADPPO 3P) achieved UL-94 V0 classification with a limiting oxygen index (LOI) of 27%, while the virgin sample Blank EV (without phosphorus) burned completely. Additionally, increased flexural strength of 79% was observed for EV IADPPO 3P compared to Blank EV. Furthermore, the flame-retardant EV showed high malleability and reparability that could be thermomechanically reprocessed without sacrificing the thermal, mechanical, and flame-retardant properties. Thus, the newly developed epoxy vitrimer is not only fire-safe but fulfills the sustainability goals of today’s society.

Effect of Fluoroalcohol Chain Extension Modified HTPB Binder on the Combustion Performance of Aluminized Propellants

To enhance both the mechanical properties of hydroxyl-terminated polybutadiene (HTPB) binder and the combustion efficiency of aluminized propellants, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (OFHD) was employed as a chain extender to impart mechanical regulation to the HTPB binder. Mechanical testing showed that the mechanical properties of fluoride-modified HTPB polyurethane (FPU) were significantly improved: the peak tensile strength of the optimized samples reached 1.99 MPa, and the elongation at break attained 486%. The structural characterization of the FPUs was conducted using Fourier transform infrared (FTIR) spectroscopy. Thermogravimetry-mass spectrometer (TG-MS) analysis revealed that the initial thermal decomposition temperature of the FPU shifted from 170 °C to 162 °C, accompanied by the release of fluorine-containing fragments during decomposition. Analysis of the combustion residue indicated that the addition of OFHD can reduce the agglomeration of aluminum (Al) powder in aluminized propellants. Dynamic pressure characteristics results showed an augmented pressurization rate under argon and oxygen atmospheres, increased by 18.67% and 37.29%, respectively. Heat release tests indicated that the aluminized propellants with the addition of OFHD had a higher combustion heat, being increased by 6.57%. The binder system is expected to be applied in aluminized propellants to improve the mechanical properties and combustion efficiency of Al powder.

Novel four-in-one intumescent flame retardants for polypropylene: Synthesis, characterization and properties

To address the shortcomings of traditional intumescent flame retardants (IFRs), a novel four-in-one IFR (M [APP/NiCo2O4]) was constructed for the first time. It integrates acid source, gas source, carbon source (crosslinking β-CD), and synergistic agent (NiCo2O4 nanoparticles) into a single entity by a co-encapsulation technology. Under the loading of 20 wt%, its flame retardant performance was significantly better than that of simple mixed flame retardants, and it could increase the limiting oxygen index of polypropylene (PP) from 18 to 30.2 and pass the UL-94 V-0 rating. At the same time, it could reduce the peak of heat release rate, total heat release, and peak of CO production of PP by 77%, 22%, and 80%, respectively, showing excellent flame retardant performance. The excellent flame retardant performance is mainly because the synergist NiCo2O4 nanoparticles in the four-in-one flame retardant can easily combine and efficiently interact with the acid source, carbon source, and gas source in the intumescent flame retardant to form a more stable protective char residue. In addition, the crosslinking β-CD shell enhances both the water resistance and initial thermal decomposition temperature of PP containing the four-in-one IFR compared to PP with simple mixed control samples. After 72 h of water resistance test, it can still maintain the UL-94 V-0 rating. The presence of the crosslinking β-CD shell also improves the compatibility of the four-in-one flame retardant in PP, and its adverse effects on the mechanical properties of PP are also significantly smaller than those of the mixed control sample.

Study on Thermomechanical Properties and Morphology of an Epoxy Resin Thermally Conductive Adhesive under Different Curing Conditions.

An epoxy resin thermally conductive adhesive is a type of thermosetting polymer encapsulation material that exhibits comprehensive performance, and the thermomechanical properties of this adhesive vary significantly under different curing conditions. In this paper, spherical alumina was used as a filler for thermal conductivity to prepare an epoxy resin thermal conductivity adhesive using a multistage freezing mixing method. The effects of various curing conditions on the thermal-mechanical properties and fracture morphology of the epoxy resin thermal conductivity adhesive were studied. The results showed that the curing condition of 150 °C/2.5 h significantly improved the performance of the epoxy resin thermally conductive adhesive. Through the shear test of the composite material, the influence of the curing agent on the adhesion of the thermally conductive adhesive under fixed conditions was explored. It was found that the curing agent with a superbranched structure exhibited latent properties and greatly enhanced the toughness of the cured epoxy resin product. Altering the curing conditions increases the shear strength by up to 307%. With the increase in curing temperature and the extension of curing temperature, the glass transition temperature gradually increased from 103.9 to 159.8 °C. The initial decomposition temperature TIDT gradually increased from 295.4 to 310.1 °C, and the temperature at which the fastest decomposition rate occurs (Tmax) gradually increased from 312.48 to 330.33 °C. The thermal stability of the substance increased with both temperature and time. The curing time and curing temperature were increased, and the morphology of the fracture of the epoxy resin thermally conductive adhesive cured sample gradually showed a ductile fracture from a typical brittle fracture. The research results reveal the influence of curing conditions on the thermal conductivity and thermal stability of the epoxy resin thermally conductive adhesive, which has a specific reference value for improving the performance of the epoxy resin thermally conductive adhesive, optimizing its usage conditions, and improving production efficiency.

Enhancing fuel characteristics and combustion performance of cellulose-rich straws through CO2-assisted torrefaction

Cellulose-rich straws of corn and rice were torrefied under carbon dioxide, and the fuel characteristics and combustion performance of the obtained biochar were investigated. A high severity resulted in surface collapse, greater pore volume, elimination of oxygen, elevated calorific value, and improved hydrophobicity in biochar. Following carbon dioxide torrefaction, the cellulose content in solid biochar experienced a slight decrease when the temperature was raised to 220 °C for longer residence durations. At 300 °C, the cellulose content in the biochar was nearly eliminated, while the relative proportion of non-sugar organic matter in corn stover and rice straw increased to 87.40 % and 77.27 %, respectively. The maximum calorific values for biochar from corn and rice straws were 22.38 ± 0.03 MJ/kg and 18.72 ± 0.05 MJ/kg. The comprehensive combustion indexes of rice and corn straw samples decreased to 1.06 × 10−7 and 1.31 × 10−7 after torrefaction at 300 °C, respectively. In addition, the initial decomposition temperatures increased by 38 °C and 45 °C, while the ultimate combustion temperatures rose by 13 °C and 16 °C for corn and rice straws, respectively. These results imply an extended combustion timeframe for the torrefied samples.

Design of near-infrared responsive self-healing photocured polyurethane materials with thiourethane bonds

In this work, a photopolymerizable polyurethane oligomer (PETU) with thiourethane bonds was designed and synthesized. Afterwards, the near-infrared responsive self-healing polyurethane films (PETU-HI-X) were fabricated by photopolymerization using homemade PETU, polydopamine (PDA), and commercially available isobornyl acrylate (IBOA) and 2-hydroxyethyl acrylate (HEA). PETU-HI-X have good photopolymerization and photothermal conversion performance. The as-prepared near-infrared responsive self-healing polyurethane polymer PETU-HI-1.0 exhibited a tensile stress of 1.06 MPa, strain of 1021 %, initial decomposition temperature of 290 °C. In addition, the temperature of the material can rise to more than 100 °C after irradiation with near-infrared light for 3 min, showing excellent photothermal conversion performance, based on which the material shows more than 90 % self-healing efficiency after irradiation with near-infrared light for 30 min. More importantly, the near-infrared responsive self-healing polyurethane polymer PETU-HI-1.0 also has an excellent degradation property. The self-healing polyurethane films have also been used to prepare the flexible electronic device that can be healed and fully restored their conductivity after getting damaged.

Effects of two antioxidants with different degrees of steric hindrance on the thermal‐oxidative aging properties of ABS resin

AbstractABS resin is easily oxidized and deteriorated during use or processing. The addition of antioxidants is an effective method for improving ABS oxidation. The hindered phenol antioxidant DBHMIE and the asymmetrically hindered 245 were added separately or together to ABS; the oxidation induction temperature of ABS increased by 10.6, 12.1 and 14°C, with the addition of DBHMIE, 245 and their combination, respectively, and the initial decomposition temperature T3% increased by 29.7, 16.2 and 51.3°C, respectively. The addition of these two antioxidants to ABS did not greatly affect the mechanical properties of the material, but the impact strength increased by 2.24 kJ/m2 when both antioxidants were added together. During the thermal aging test, the decomposition temperature of the ABS splines prepared with the combined antioxidants increased during the first few cycles. The impact strength of the splines prepared with the combined antioxidants was the highest, with the smallest decrease of only 5.18%. The yellow index of the spline prepared with the combined antioxidants was between those of splines prepared with the antioxidants added alone. The combination of DBHMIE and 245 induced synergistic effects, improved thermal‐oxidative aging resistance, and improved and protected the toughness of ABS resin.

Improved thermal stability and flame‐retardant performance of rigid polyurethane foam modified by hydrolyzed keratin‐modified polyol and aluminium hypophosphite

AbstractRigid polyurethane foam (RPUF) was prepared using hydrolyzed keratin‐modified polyol and aluminium hypophosphite as flame retardants. The effects of aluminium hypophosphite on the thermal stability and flame‐retardant properties of hydrolyzed keratin‐modified RPUFs were studied by limiting oxygen index (LOI) method, thermogravimetric analysis, pyrolysis kinetic analysis, cone analysis and smoke density analysis. The results showed that RPUF added with 7.5 wt% aluminium hypophosphite (RPUF‐HK5‐7.5AL) had the highest LOI, which was 26.1%. RPUF‐HK5‐7.5AL had the highest initial decomposition temperature, the highest T5% at a heating rate of 10 °C min−1 and the highest activation energy. In addition, RPUF‐HK5‐7.5AL possessed the lowest heat release rate at 50 kW m−2 of 125.10 kW m−2, and the lowest total heat release rate of 5.30 MJ m−2. Results indicated that RPUF‐HK5‐7.5AL had the best thermal stability and flame‐retardant properties. Scanning electron microscopy showed that hydrolyzed keratin and aluminium hypophosphite had a synergistic effect on the flame retardancy of the RPUFs. The current research results provide a useful reference for the preparation of RPUFs with good flame‐retardant properties by bio‐based modification. © 2024 Society of Industrial Chemistry.

Fabrication and characterization of poly(lactic acid-trimethylene carbonate) based biodegradable composite films

Two biobased composite films have been prepared with poly (lactic acid-trimethylene carbonate), polylactic acid and Laponite by solvent evaporation method. The 1H NMR and FTIR spectrums illustrate that P (LA-TMC) polymer is successfully synthesized and designed composite films are produced. Morphometric analyses demonstrate that the roughnesses of the film's surface and cross-section are on the increase with higher PLA and Laponite content. Mechanical performances reveal that the rise in tensile strength and modulus while maintaining excellent elongation at break is mainly due to the increase in the content of polylactic acid and Laponite. By utilizing the nano effect of Laponite, the maximum tensile strength of the composite film reaches 34.59 MPa. Thermal property results illustrate that the Tg and initial decomposition temperature are on the growth with the increase of PLA content. However, it is not significant on the effect of Laponite on the initial decomposition temperature. The water vapor permeability measurements prove that the barrier property of P(LA-TMC)/PLA/Laponite composite film is on the ascent with the Laponite addition. Hydrolytic degradation tests indicate that PLA and Laponite play avital part in accelerating the degradation rate of composite films and alkaline media is superior acidic and neutral conditions.

Enhancing Flame Retardancy and Thermal Insulation Performance of Silicone Rubber Composites Using Silicon Carbide

This study focuses on modifying silicone rubber using silicon carbide (SiC) to enhance the flame retardancy and thermal insulation properties of the composites. The study characterizes the thermal stability, mechanical properties, and flame retardancy of the composite materials. The results demonstrate the effective improvement in thermal stability achieved by incorporating SiC into the silicone rubber composites. At a SiC addition level of 6 wt.%, the composite material shows optimal thermal stability with an initial decomposition temperature of 487°C, which is 84°C higher compared to the pure matrix. Additionally, the SiC/SR composites system exhibits a char yield of 72.13% at 900°C, representing an approximately 9% increase compared to the pure SR matrix. Simultaneously, the incorporation of SiC significantly enhances the flame retardancy of silicone rubber. At a SiC addition level of 10 wt.%, the LOI (Limiting Oxygen Index) value increases by 10.5% to reach 30.4%, surpassing the non-additive sample. Moreover, the UL-94 classification of the composite material is V-0, meeting the standard for flame retardant materials.

Effect of Starch Plasticization on Morphological, Mechanical, Crystalline, Thermal, and Optical Behavior of Poly(butylene adipate-co-terephthalate)/Thermoplastic Starch Composite Films.

Starches plasticized with glycerol/citric acid/stearic acid and tributyl 2-acetylcitrate (ATBC), respectively, were processed with poly (butylene adipate-Co-terephthalate (PBAT) via extrusion and a film-blown process. All the composite films were determined for morphology, mechanical, thermal stability, crystalline, and optical properties. Results show that the most improved morphology was in the 30% glycerol plasticized PBAT/thermoplastic starch (TPS) composite films, characterized by the smallest and narrowest distribution of TPS particle sizes and a more uniform dispersion of TPS particles. However, the water absorption of PBAT/TPS composite films plasticized with glycerol surpassed that observed with ATBC as a plasticizer. Mechanical properties indicated insufficient plasticization of the starch crystal structure when using 10% ATBC, 20% ATBC, and 20% glycerol as plasticizers, leading to poor compatibility between PBAT and TPS. This resulted in stress concentration points under external forces, adversely affecting the mechanical properties of the composites. All PBAT/TPS composite films exhibited a negative impact on the initial thermal decomposition temperature compared to PBAT. Additionally, the haze value of PBAT/TPS composite films exceeded 96%, while pure PBAT had a haze value of 47.42%. Films plasticized with 10% ATBC, 20% ATBC, and 20% glycerol displayed lower transmittance values in the visible light region. The increased transmittance of films plasticized with 30% glycerol further demonstrated their superior plasticizing effect compared to other PBAT/TPS composite films. This study provides a simple and feasible method for preparing low-cost PBAT composites, and their extensions are expected to further replace general-purpose plastics in daily applications.

Design of reactive linear polyphosphazene to improve the dielectric properties and fire safety of bismaleimide composites

The high-frequency transmission of 5th-Generation Mobile Communication Technology (5G) and more integrated mobile terminals pose a challenge to the safety and dielectric properties of existing electronic packaging materials. This work innovatively designs a linear polyphosphazene compound (PABN) with benzonitrile as the reactive side group. The prepared bismaleimide (BMI)/PABN is an excellent dielectric composite material, breaking the technical barrier of balancing fire safety and dielectric performance. With only 1 wt% PABN, the UL94 rating of BMI composite reaches V0, and the impact strength increases by 48.5 %, demonstrating excellent fire safety and toughness. Specifically, the dielectric constant (Dk) of the composite containing 4 wt% PABN is as low as 2.67, far meeting the requirements of 5G. In addition, the glass transition temperature (Tg) of all BMI/PABN composites is around 290 °C, and the initial decomposition temperature exceeds 400 °C, indicating potential applications in the integration and miniaturization of microelectronic devices.

Enhancing RDX Thermal Decomposition in Al@RDX Composites with Co Transition Metal Interfacial Layer

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g−1, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N2O, CH2O, CO2 and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH2 and –NO2 within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (Ea) of 115.6 kJ·cm−3. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models.

A facile method to prepare biobased flexible polydimethylsiloxane − Benzoxazine resin: Dielectric properties and high heat resistance

For the benefit of meet the industrial demand of integrated circuits for low dielectric constant (k) and the environmental requirements of sustainable development, it is important to prepare biobased benzoxazine resin with low k and high heat resistance by solvent-free method. In this paper, the biobased monomer V-fa containing aldehyde group was synthesized by biobased raw materials furfurylamine and vanillin, and then reacted with amino-terminated polydimethylsiloxane (PDMS) to prepare benzoxazine monomer V-fa-pdms containing schiff base structure by a solvent-free method. Then, the monomer was cured to obtain biobased benzoxazine resin poly(V-fa-pdms), and the heat resistance, mechanical and dielectric properties of poly(V-fa-pdms) were studied. The results indicate that the resin exhibits excellent thermal stability and toughness by combining benzoxazine and PDMS reasonably. The initial thermal decomposition temperature (Tdi, 5% thermogravimetric loss) is 387 °C, and the material also exhibits excellent dielectric properties. When the frequency increases from 1 Hz to 1 MHz, the k of the material decreases from 2.71 to 2.60, and the fluctuation range of dielectric loss is 0.0051–0.0049. With the increase of frequency, both k and dielectric loss show a downward trend. At the same time, the material shows good corrosion resistance in commonly used solvents. These excellent properties of poly(V-fa-pdms) are due to the existence of a high cross-linked network structure formed by multiple cross-linking sites in the polymer network and the combined effect of low k and high heat-resistant PDMS components.

Synthesis, UV-curing behaviors and general properties of acrylate-urethane resins prepared from castor oil-based polyols

Castor oil-based polyols with high OH values are synthesized through the low odor thiol-ene reaction and then are used for preparing UV-curable acrylate-urethane resins (AUCORs). The structure of the AUCORs is confirmed by 1H NMR and IR. The AUCORs based resins containing diluents can rapidly form cured films under UV light irradiation in air, with a very high gel ratio of over 95 %. The UV-curing dynamics shows that polymerization rate and final acrylate conversion under the N2 atmosphere both depend on CC bond content, but they are reduced under air due to oxygen inhibition effect. All the cured films have good heat stability with an initial decomposition temperature over 300 °C. The cured films can display different Tg within the region of 55–85 °C depending on the crosslink density tuned by the acrylate/urethane content. The urethane content/diluter can affect some general properties of the coating films, for instance water absorption ability, wettability, hardness and adhesion force. Interestingly, the cured films have a very good light transmittance in the visible light region, as high as that of glass slides.

Thermal decomposition and combustion performance of the organic-inorganic hybrid crystal structure oxidant DAN-2

In this paper, we investigated the potential use of a new organic-inorganic hybrid crystal structure based on KNO3 in ignition compositions. H2dabco[K(NO3)3] (DAN-2) with organic-inorganic hybrid crystal structure is synthesized through intermolecular assembly technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to detect the crystal morphology, structure and molecular structure of DAN-2, which has a regular cubic structure. Experimental data were obtained using thermogravimetric/differential scanning calorimetry (TG-DSC), closed bomb test and high-speed photography, which were then used to study and analyze the thermal decomposition properties and combustion properties of DAN-2. The initial thermal decomposition temperature of DAN-2 was low (194 °C) and the activation energy of the thermal decomposition was 154 kJ/mol. Possible thermal decomposition mechanisms are further discussed and proposed. This research pushed forward the application of organic-inorganic hybrid crystal structure oxidant DAN-2 in ignition system.

Excellent catalytic effect of V2C MXene on dehydrogenation performance of α-AlH3

Lowering the dehydrogenation temperature and maintaining high dehydrogenation capacity are greatly hindering the practical application of α-AlH3 for the hydrogen fuel cell industry. Herein, the layered accordion-like V2C MXene is synthesized and doped into α-AlH3 by mild ball milling. The 1 wt.% V2C-catalyzed α-AlH3 possesses excellent dehydrogenation performance with a low initial decomposition temperature of 70.5 °C and a high hydrogen release capacity of 8.1 wt.%. Furthermore, 7.8 wt.% of hydrogen could be quickly released from α-AlH3-1 wt.% V2C composite within 15 min at 120 °C, with a lower activation energy of 69.5 kJ/mol than that of as-received sample. The excellent dehydrogenation performance is attributed to the high activity of the zero valence V catalyst which is transformed from the multivalent V during ball milling and to promote dissociation and reorganization of hydrogen. This effective approach significantly enhances the dehydrogenation of α-AlH3, providing a hopeful approach for modifying metal hydrides.

Effects of tannin acid impregnated pretreatment on dimensional stability and chemical composition of heat-treated Chinese fir

Abstract Thermal treatment is an effective method for improving the dimensional stability of wood; however, it typically requires high temperatures. To achieve low-temperature heat treatment, this study employed wood samples impregnated with 10 % tannin acid (TA) and examined their changes in dimensional stability and chemical components after heat treatment at various initial moisture content levels. The results revealed that the TA-10 %-HT group exhibited enhanced dimensional stability. Specifically, both the tangential and radial moisture swelling decreased by 21.7 % and 11.8 %, respectively. FTIR and XRD analysis indicated that the presence of tannin acid catalytically facilitated the degradation of hemicellulose. Moreover, an increase in moisture content resulted in the ionization of TA, amplifying acidity and further affecting cellulose degradation. TGA demonstrated that TA impacted the thermal stability of heat-treated materials by lowering the initial decomposition temperature of wood components and increasing the residual weight of wood. Overall, pretreatment with TA impregnation and moisture content significantly improved the dimensional stability of Chinese fir wood and altered its chemical composition. This approach holds considerable potential for enhancing wood properties through a low-energy consumption method during the heat treatment process, expanding the practical application of wood.

A novel macromolecular phosphorus-nitrogen containing flame retardant for polycarbonate

In this paper, an innovative macromolecular phosphorus-nitrogen containing flame retardant (PDPSB) was successfully designed and synthesized to investigate its impact on the flame retardancy, burning behavior, thermal stability, mechanical properties of polycarbonate (PC) composites. Furthermore, an in-depth exploration of the potential flame-retardant mechanism was conducted. The combustion results indicated that PC-3 with 3 wt% PDPSB reached V-0 rating in UL-94 test and showed a high limiting oxygen index (LOI) of 33.0 %. Compared to pure PC, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of PC-3 were decreased by 37.9 %, 11.1 % and 4.9 %, respectively. It was noteworthy that the amount of char residue for PC-3 was raised from 7.4 % for pure PC to 15.8 % with increasing 113.5 %. The thermogravimetric analysis (TGA) results under N2 atmosphere revealed that PDPSB possessed preferable thermal stability with initial decomposition temperature (Tinitial) of 342.6 °C and higher char residue yield of 48.4 %. With increasing the amount of PDPSB, the maximum mass loss rate (Rpeak) was reduced and the char residue yield was increased for PC/PDPSB composites. In addition, the mechanical properties of PC/PDPSB composites were well maintained due to the good compatibility and dispersion between PDPSB and PC matrix. The tensile, flexural and izod impact strength of PC-3 were weakened by 4.3 %, 1.7 % and 16.8 % in comparison of pure PC, respectively. Based on the investigation into the flame-retardant mechanism of PDPSB, the excellent flame retardance of PC/PDPSB composites has been validated. In gaseous, the release of pyrolysis gases was suppressed and active radicals were captured by generated phosphorus free radicals. In condensed phase, the stable char residue with phosphorus and nitrogen elements acted as a barrier to hinder heat, flame and oxygen. This high-efficient single-component multifunctional additive presented a novel approach to the development of fire-resistant polymers with enhanced performance characteristics.